Volume 01 - Properties and Selection Irons, Steels, and High-Performance Alloys Part 5 potx

and take their chances on occasional difficulties. In conventional practice, depth of machining for hot-rolled bars is 1.6
mm (
1
16
in.) for bars 38 to 76 mm (1
1
2
to 3 in.) in diameter, and 3.2 mm (
1
8
in.) for bars over 76 mm (3 in.) in diameter.

Reference cited in this section
1.

Alloy, Carbon and High Strength Low Alloy Steels: Semifinished for Forging; Hot Rolled Bars, Cold
Finished Bars; Hot Rolled Deformed and Plain Concrete Reinforcing Bars,
AISI Steel Products Manual,
American Iron and Steel Institute, 1986
Surface Treatment
It is uncommon for hot-rolled steel bars and shapes to be descaled by the producer or protected from the weather during
transit. Most cleaning and coating operations are done either by the customer or by an intermediate processor.
Descaling of hot-rolled bars and shapes is generally done by either pickling or blasting, depending on the end use. There
are several subsequent coatings that can be used. Oil is both the simplest and the least expensive to use and acts as a
temporary rust preventive. Lime, in addition to serving as a rust preventive, can serve as a carrier for lubricants used
during cold drawing or cold forging. A more sophisticated system includes descaling, followed by a zinc phosphate
coating, coupled with a dry lubricant. This system provides some rust protection and serves as a lubricant for cold-
forming operations.
Heat Treatment
Hot-rolled low-carbon and medium-carbon steel bars and shapes are often used in the as-rolled condition, but hot-rolled
bars of higher-carbon steel and most hot-rolled alloy steel bars must be heat treated in order to attain the hardness and

microstructure best suited for the final product or to make them suitable for processing. Such heat treatment consists of
one or more of the following: some form of annealing, stress relieving, normalizing, quenching, and tempering.
Ordinary annealing is the term generally applied to heat treatment used to soften steel. The steel is heated to a suitable
temperature, held there for some period of time, and then cooled; specific times, temperatures, and cooling rates vary.
Maximum hardness compatible with common practice can be specified.
Annealing for specified microstructures can be performed to obtain improved machinability or cold-forming
characteristics. The structures produced may consist of lamellar pearlite or spheroidized carbides. Special control of the
time and temperature cycles is necessary. A compatible maximum hardness can be specified.
Stress relieving involves heating to a sub-critical temperature and then cooling. For hot-rolled bars, the principal
reason for stress relieving is to minimize distortion in subsequent machining. It is used to relieve the stresses resulting
from cold-working operations, such as special machine straightening.
Normalizing involves heating to a temperature above the critical temperature range and then cooling in air. A
compatible maximum hardness can be specified.
Hardening by quenching consists of heating steel to the correct austenitizing temperature, holding at that temperature
for a sufficient time to produce homogeneous austenite, and quenching in a suitable medium (water, oil, synthetic oil or
polymer, molten salts, or low-melting metals) depending on chemical composition and section thickness.
Tempering is an operation performed on normalized or quenched steel bars. In this technique, the bars are reheated to a
predetermined temperature below the critical range and then cooled under suitable conditions.
When a hardness requirement is specified for normalized and tempered bars, the bars are ordinarily produced to a range
of hardnesses equivalent to a 0.4 mm range of Brinell impression diameters. Quenched and tempered bars are ordinarily
produced to a 0.3 mm range of Brinell impression diameters. Quenched and tempered bars can also be produced to
minimum mechanical property requirements.
Product Requirements
Hot-rolled steel bars and shapes can be produced to chemical composition ranges or limits, mechanical property
requirements, or both. The mechanical testing of hot-rolled steel bars and shapes can include tensile, Brinell or Rockwell
hardness, bend, Charpy impact, fracture toughness, and short-time elevated-temperature tests, as well as test for elastic
limit, proportional limit, and offset yield strength, which require the use of an extensometer or plotting of a stress-strain
curve. These tests are covered by ASTM A 370 and other ASTM standards.
Other tests sometimes required include the measurement of grain size and hardenability. Austenitic grain size is
determined by the McQuaid-Ehn test, which is described in ASTM E 112. This test involves metallographic examination

of a carburized specimen to observe prior austenitic grain boundaries. Hardenability can be measured by several methods,
the most common beingthe Jominy end-quench test, as described in ASTM A 255 (see the article "Hardenability of
Carbon and Low-Alloy Steels" in this Volume).
Soundness and homogeneity can be evaluated by fracturing. The fracture test is commonly applied only to high-carbon
bearing quality steel. Location of samples, number of tests, details of testing technique, and acceptance limits based on
the test should be established in each instance.
Testing for nonmetallic inclusions consists of careful microscopic examination (at 100×) of prepared and polished
specimens. The specimens should be taken on a longitudinal plane midway between the center and surface of the product.
Location of specimens, number of tests, and interpretation of results should be established in each instance. Typical
testing procedures are described in ASTM E 45. Nonmetallic inclusion content can also be measured on the macroscopic
scale by magnetic particle tests such as those described in AMS 2300 and 2301. These tests involve the measurement of
inclusion frequency and severity in a sampling scheme that represents the interior of the material.
Surface and subsurface nonuniformities are revealed by magnetic particle testing. This test was developed for, and is used
on, fully machined or ground surfaces of finished parts. When the magnetic particle test is to be applied to bar stock,
short-length samples should be heat treated and completely machined or ground.
Tensile and hardness tests are the most common mechanical tests performed on hot-rolled steel bars and shapes.
Hardness is a relatively simple property to measure, and it is closely related to tensile strength, as shown in Fig. 1. When
Fig. 2 is used together with Fig. 1, a simple hardness test can give an estimate of yield strength and elongation, as well as
tensile strength.

Fig. 1
Relationship between hardness and tensile strength of steel. Range up to 300 HB is applicable to the
hot-finished steel discussed in this article. Source: Ref. 2

Fig. 2 Relation of tensile properties for hot-rolled carbon steel
It is not practicable to set definite limitations on tensile strength or hardness for carbon or alloy steel bars in the as-rolled
condition. For mill-annealed steel bars, there is a maximum tensile strength or a maximum hardness (Table 2) that can be
expected for each grade of steel. For steel bars in the normalized condition, maximum hardness, maximum tensile
strength, minimum hardness, or minimum tensile strength can be specified. For normalized and tempered bars and for
quenched and tempered bars, either maximum and minimum hardness or maximum and minimum tensile strength can be

specified; for either property, the range that can be specified varies with tensile strength and is equivalent to a 0.4 mm
range of Brinell indentation diameters at any specified location for normalized and tempered bars and to a 0.3 mm range
for quenched and tempered bars.
Table 2 Lowest maximum hardness that can be expected for hot-
rolled steel bars, billets, and slabs with
ordinary mill annealing
Maximum hardness, HB
(a)

Steel grade

Straightened

Nonstraightened

Carbon steels
1141 201
192
1144 207
197
1151 207
201
1541 207
197
1548 212
207
1552 212
207
15B41 207
197

15B48 212
207
Alloy steels
1330 187
179
1335 197
187
1340 201
192
1345 212
201
4012 149
143
4023 156
149
4024 156
149
4027 170
163
4028 170
163
4037 192
183
4047 212
201
4118 170
163
4130 183
174
4137 201

192
4140 207
197
4142 212
201
4145 217
207
4147 223
212
4150 235
223
4161 241
229
4320 207
197
4340 235
223
4419 170
163
4615 174
167
4620 179
170
4621 179
170
4626 187
179
4718 179
170
4720 170

163
4815 223
192
4817 229
197
4820 229
197
5015 156
149
50B44 207
197
50B46 217
201
50B50 217
201
50B60 229
217
5120 170
163
5130 183
174
5132 187
179
5135 192
183
5140 197
187
5145 229
197
5147 217

207
5150 212
201
5155 229
217
5160 235
223
51B60 235
223
6118 163
156
6150 217
207
81B45 201
192
8615 163
156
8617 163
156
8620 170
163
8622 179
170
8625 179
170
8627 183
174
8630 187
179
8637 201

192
8640 207
197
8642 212
201
8645 217
207
8655 235
223
8720 170
163
8740 212
201
8822 187
179
9254 241
229
9255 241
229
9260 248
235
94B17 156
149
94B30 183 174

(a)

Specific microstructure requirements may necessitate modification of these hardness numbers.

It is essential that the purchaser specify the positions at which hardness readings are to be taken. When both hardness and

tensile strength are specified at the same position, the limits should be consistent with each other. When hardness limits
are specified as surface values, they may be inconsistent with tensile-test values, which of necessity are properties of the
bulk metal; the inconsistency will vary according to the size of the bar and the hardenability of the steel. The purchaser
should specify limits that take this inconsistency into account.
If the locations of hardness readings are not specified on the purchaser's order or specification, the hardness values are
applicable to the bar surface after removal of decarburization. Hardness correction factors for bars of various diameters as
described in ASTM E 18 should be employed if a flat area is not available on the bar tested.
Generally, yield strength, elongation, and reduction in area are specified as minimums for steel only in the quenched and
tempered or the normalized and tempered condition, and they should be consistent with ultimate tensile strength or
hardness. When quenched and tempered bars are cold worked by cold straightening, stress relieving may be required to
restore elastic properties and to improve ductility.

Reference cited in this section
2.

Materials, Vol 1, 1989 SAE Handbook, Society of Automotive Engineers, 1989

Product Categories
Hot-rolled carbon steel bars are produced to two primary quality levels: merchant quality and special quality. Merchant
quality is the lower quality level and is not suitable for any operation in which internal soundness or freedom from surface
imperfections is of primary importance. Special, quality includes all bar categories with end-use-related and restrictive
quality requirements.
The mechanical properties of hot-rolled carbon steel bars in the as-rolled condition are influenced by:
• Chemical composition
• Thickness or cross-sectional area
• Variables in mill design and mill practice
Carbon content is the dominant factor. The minimum expected mechanical properties of commonly used grades of hot-
rolled carbon steel bars are shown in Fig. 3.

Fig. 3 Estimated minimum tensile properties of selected hot-rolled carbon steel bars

Quality descriptors for hot-rolled alloy steel bars are related to suitability for specific applications. Characteristics
considered include inclusion content, uniformity of chemical composition, and freedom from surface imperfections.
Carbon steel and alloy steel structural shapes and special shapes do not have specific quality descriptors but are covered
by several ASTM specifications (Table 3). In most cases, these same specifications also cover structural quality steel bars.
The ASTM specifications covering other qualities of hot-rolled bars are listed in Table 4. The various categories of hot-
rolled steel bar products and their characteristics are described in the following sections.
Table 3 Typical ASTM specifications for structural quality steel bars and steel structural shapes
Covered in ASTM A 6
Specification

Steel type and condition
Carbon steels
A 36
(a)(b)

Carbon steel plates, bars, and shapes
A 131
(c)

Carbon and HSLA steel plates, bars, shapes, and rivets for ships
A 529
Carbon steel plates, bars, shapes, and sheet piling with minimum yield strength of 290 MPa (42 ksi)

A 709
Carbon, alloy, and HSLA steel plates, bars, and shapes for bridges
Alloy steel
A 710
Age-hardening low-carbon Ni-Cu-Cr-Mo-Nb and Ni-Cu-Nb alloy steel plates, bars, and shapes
High-strength low-alloy (HSLA) steels
A 131

(c)

See above under Carbon Steel
A 242
HSLA steel plates, bars, and shapes
A 572
Nb-V HSLA steel plates, bars, shapes, and sheet piling
A 588
HSLA steel plates, bars, and shapes with minimum yield point of 345 MPa (50 Ksi)
A 633
Normalized HSLA steel plates, bars, and shapes
A 690 HSLA steel H-piles and sheet piling for use in marine environments

(a)

This ASTM specification is also published by the American Society of Mechanical Engineers, which adds an S in front of the A.
(b)

See also Canadian Standards Association (CSA) specification G40.8.
(c)

See also Section 39 of the ABS specifications.

Table 4 Typical ASTM specifications for hot-rolled steel bars
See Table 3 for ASTM specifications for structural quality bars and structural shapes.
Specification

Steel type and condition
Carbon steels
A 321

(a)

Quenched and tempered carbon steel bars
A 575
(a)

Merchant quality carbon steel bars
A 576
(a)

Special quality carbon steel bars
A 663
(a)

Merchant quality carbon steel bars subject to mechanical property requirements
A 675
(a)

Special quality carbon steel bars subject to mechanical property requirements
Alloy steels
A 295
Bearing quality high-carbon chromium steel billets, forgings, tube rounds, bars, rods, and tubes
A 304
(a)

Alloy steel bars subject to end-quench hardenability requirements
A 322
(a)

Alloy steel bars for regular constructional applications

A 434
(a)

Quenched and tempered alloy steel bars, hot rolled or cold finished
A 485
Bearing quality high-carbon chromium steel billets, tube rounds, bars, and tubes modified for high hardenability

A 534
Carburizing alloy steel billets, tube rounds, bars, rods, wire, and tubes of bearing quality
A 535 Special quality alloy steel billets, bars, tube rounds, rods, and tubes for the manufacture of antifriction bearings

(a)

Covered in ASTM A 29

Merchant Quality Bars
Merchant quality is the least restrictive descriptor for hot-rolled carbon steel bars. Merchant quality bars are used in the
production of noncritical parts of bridges, buildings, ships, agricultural implements, road-building equipment, railway
equipment, and general machinery. These applications require only mild cold bending, mild hot forming, punching, and
welding. Mild cold bending is bending in which a generous bend radius is used and in which the axis of the bend is at
right angles to the direction of rolling.
Merchant quality bars should be free from visible pipe; however, they may contain pronounced chemical segregation, and
for this reason, product analysis tolerances are not appropriate. Internal porosity, surface seams, and other surface
irregularities may be present and are generally expected in bars of this quality. Consequently, merchant quality bars are
not suitable for applications that involve forging, heat treating, or other operations in which internal soundness or freedom
from surface imperfections is of primary importance.
Grades. Merchant quality bars can be produced to meet both chemical composition (heat analysis only) and mechanical
properties. These steels can be supplied to chemical compositions within the ranges of 0.50% C (max), 0.60% Mn (max),
0.04% P (max), and 0.05% S (max), but are not produced to meet any specific silicon content, grain size, or any other
requirement that would dictate the type of steel produced.

Merchant quality steel bars do not require the chemical ranges typical of standard steels. They are produced to wider
carbon and manganese ranges and are designated by the prefix "M."
When ordering merchant quality bars to meet mechanical properties, the following strength ranges are to be used up to a
maximum of 655 MPa (95 ksi):
• 70 MPa (10 ksi) for minimums up to but not including 415 MPa (60 ksi)
• 80 MPa (12 ksi) for minimums from 415 MPa (60 ksi) up to but not including 460 MPa (67 ksi)
• 100 MPa (15 ksi) for minimums from 460 to 550 MPa (67 to 80 ksi)
Specification ASTM A 663 defines the requirements for hot-wrought merchant quality carbon steel bars and bar-size
shapes intended for noncritical constructional applications.
Sizes. Merchant quality steel rounds are not produced in diameters greater than 76 mm (3 in.).
Special Quality Bars
Special quality bars are employed when end use, method of fabrication, or subsequent processing treatment requires
characteristics not available in merchant quality bars. Typical applications, including many structural uses, require hot
forging, heat treating, cold drawing, cold forming, and machining.
Special quality bars are required to be free from visible pipe and excessive chemical segregation. Also, they are rolled
from billets that have been inspected and conditioned, as necessary, to minimize surface imperfections. Frequency and
degree of surface imperfections are influenced by chemical composition, type of steel, and bar size. Resulfurized grades,
certain low-carbon killed steels, and boron-treated steels are most susceptible to surface imperfections.
Some end uses or fabricating procedures can necessitate one or more extra requirements. These requirements include
special hardenability, internal soundness, nonmetallic inclusion rating, and surface condition and are described in the
AISI manual covering hot-rolled bars. The quality descriptorfor bars to which only one of these special requirements is
applied is Restrictive Requirement Quality A. When a single special restriction other than the four mentioned above is
applied, the quality descriptor is Restrictive Requirement Quality B. Multiple Restrictive Requirement Quality bars are
those to which two or more restrictive requirements are applied.
Special quality steel bars can be produced using rimmed, capped, semikilled, or killed deoxidation practice. The
appropriate type is dependent on chemical composition, quality, and customer specifications. Killed steels can be
produced to coarse or fine austenitic grain size.
Special quality steel bars are produced to product chemical composition tolerances and can be purchased on the basis of
heat composition. Special quality steel bars can also be produced to meet mechanical property requirements. The tensile
strength ranges are identical to those presented in the section "Merchant Quality Bars" in this article. Additional

information on mechanical property requirements and test frequencies is available in the appropriate ASTM
specifications.
Sizes. Special quality steel bars are commonly produced in the following sizes:
• Rounds: 6.4 to 254 mm (
1
4
to 10 in.)
• Squares: 6.4 to 154 mm (
1
4
to 6
1
16
in.)
• Round-cornered squares: 9.5 to 203 mm (
3
8
to 8 in.)
• Hexagons: 9.5 to 103 mm (
3
8
to 4
1
16
in.)
• Flats
: greater than 5.16 mm (0.203 in.) in thickness and 152 mm (6 in.) and less in width, or 5.84 mm
(0.230 in.) and greater in thickness and 203 mm (8 in.) and less in width
Common size ranges have not been established for special quality bars of other shapes, including bar-size shapes, ovals,
half-ovals, half-rounds, octagons, and special bar-size shapes.

Carbon Steel Bars for Specific Applications
Cold-working quality is the descriptor (replacing the older terminology of scrapless nut, cold forging, cold heading,
and cold extrusion qualities) for hot-rolled bars used in the production of solid or hollow shapes by means of severe cold
plastic deformation, such as (but not limited to) upsetting, heading, forging, and forward or backward extrusion involving
movement of metal by expansion and/or compression. Such processing normally involves special inspection standards
and requires sound steel of special surface quality and uniform chemical composition. If steel of the type or chemical
composition specified does not have adequate cold-forming characteristics in the as-rolled condition, a suitable heat
treatment, such as annealing or spheroidize annealing, may be necessary.
Axle Shaft Quality. Bars of axle shaft quality are produced for the manufacture of power-driven axle shafts for cars,
trucks, and other vehicles. Because of their design or method of manufacture, these axles either are not machined all over
or undergo less than the recommended amount of stock removal for proper cleanup of normal surface imperfections.
Therefore, it is necessary to minimize the presence of injurious surface imperfections in bars of axle shaft quality through
the use of special rolling practices, special billet and bar conditioning, and selective inspection.
Cold-Shearing Quality. There are limits to the sizes of hot-rolled steel bars that can normally be cold sheared without
specially controlled production procedures. When the cold shearing of larger bars is desirable, it is recommended that
cold-shearing quality bars be ordered. Bars of this quality have characteristics that prevent cracking even in these larger
sizes. Cold-shearing quality bars are not produced to specific requirements such as hardness, microstructure, shear life, or
productivity. Maximum size (cross-sectional area) limitations for the cold shearing of hot-rolled steel bars without the
specially controlled production procedures, and of cold-shearing quality bars, are given in the AISI manual that covers
hot-rolled bars. If even larger bars are to be cold sheared, cold-shearing behavior can be further improved by suitable
prior heat treatment.
Structural quality is the descriptor for hot-rolled bars used in the construction of bridges and buildings by riveting,
bolting, or welding and for general structural purposes. The general requirements for bars of this quality are given in
ASTM A 6; individual ASTM specifications are listed in Table 3.
Additional qualities of carbon steel bars are available for specific requirements. Such qualities are related to
application and processing. They include:
• File quality
• Gun barrel quality
• Gun receiver quality
• Shell steel quality A

• Shell steel quality B
• Shell steel quality C
• Shell steel quality D
Alloy Steel Bars
Hot-rolled alloy steel bars are commonly produced in the same size as special quality steel bars. Common size ranges
have not been established for other shapes of hot-rolled alloy steel bar, including bar-size shapes, ovals, half-ovals, half-
rounds, octagons, and special bar-size shapes.
Hot-rolled alloy steel bars are covered by several ASTM specifications (Tables 3 and 4). Many of the alloys covered in
these specifications are standard AISI-SAE grades (Table 5).
Table 5 AISI-SAE grades of hot-rolled alloy steel bars in ASTM specifications
ASTM
specification
AISI-SAE grades
A 295
52100, 51100, 50100
A 304
All H grades except 4626H and 86B30H
A 322
All standard grades except 4032, 4042, 4135, 4422, 4427, 4617, 50B40, 5046, 5060, 5115, 5117, 50100, 8115,
86B45, 8650, 8660, 9310, and 94B15
A 434
By agreement
A 534
4023, 4118, 4320, 4620, 4720, 5120, 8620, E-3310, E-9310
A 535 3310, 4320, 4620, 4720, 4820, 52100, 52100 Mod. 1, 52100 Mod. 2, 52100 Mod. 3, 52100 Mod. 4, 8620, 9310

Hot-rolled alloy steel bars are also covered by several quality descriptors, which are discussed below. As with all quality
descriptors, these descriptors differentiate bars on the basis of characteristic properties required to meet the particular
conditions encountered during fabrication or use.
Regular quality is the basic or standard quality for hot-rolled alloy steel bars, such as those covered by ASTM A 322.

Steel for this quality are killed, are usually produced to fine grain size, and are melted to chemical composition limits.
Bars of this quality are inspected, conditioned, and tested to meet the normal requirements for regular construction
applications for which alloy steel is used.
Axle Shaft Quality. Alloy steel bars of axle shaft quality are similar to carbon steel bars of the same quality (see the
discussion of axle shaft quality bars in the section "Carbon Steel Bars for Specific Applications" in this article).
Ball and roller bearing quality and bearing quality apply to alloy steel bars intended for antifriction bearings.
These bars are usually made from steels of the AISI-SAE standard alloy carburizing grades and the AISI-SAE high-
carbon chromium series. These steels can be produced in accordance with ASTM A 534, A 535, A 295, or A 485 (Table
4). Bearing quality steel bars require restricted melting and special teeming, heating, rolling, cooling, and conditioning
practices to meet rigid quality standards. Steelmaking practices may include vacuum treatment. The foregoing
requirements include thorough examination for internal imperfections by one or more of the following methods:
macroetch testing, microscopic examination for nonmetallic inclusions, ultrasonic inspection, and fracture testing.
It is not practical to furnish bearing quality steel bars in sizes exceeding 64,500 mm
2
(100 in.
2
) in cross-sectional area to
the same rigid requirements as those for bars in smaller sizes because of insufficient hot working in the larger bars.
Usually, bars over 102 mm (4 in.) in thickness are forged to 102 mm (4 in.) square or smaller for testing.
Cold-Shearing Quality. Alloy steel bars of cold-shearing quality are similar to carbon steel bars of the same quality
(see the discussion of cold-shearing quality bars in the section "Carbon Steel Bars for Specific Applications" in this
article).
Cold-working quality, which replaces the older terminologies cold-heading quality and special cold-heading quality,
is the descriptor for hot-rolled bars used in the production of solid or hollow shapes by means of severe cold plastic
deformation, such as (but not limited to) upsetting, heading, forging, and forward or backward extrusion involving
movement of metal by expansion and/or compression. Such processing normally involves special inspection standards
and requires sound steel of special surface quality and uniform chemical composition. If steel of the type or chemical
composition specified does not have adequate cold-forming characteristics in the as-rolled condition, a suitable heat
treatment, such as annealing or spheroidize annealing, may be necessary.
Aircraft quality and magnaflux quality are the descriptors used for alloy steel bars for critical or highly stressed

parts of aircraft and for other similar or corresponding purposes involving additional stringent requirements such as
magnetic particle inspection, additional discard, macroetch tests, and hardenability control. To meet these requirements,
exacting steelmaking, rolling, and testing practices must be employed. These practices are designed to minimize
detrimental inclusions and porosity. Phosphorus and sulfur are usually limited to 0.025% maximum each.
Many parts for aircraft, missiles, and rockets require aircraft quality alloy steel bars. Magnetic particle testing as in AMS
2301 is sometimes specified for such applications. Some very critical aircraft, missile, and rocket applications require
alloy steel bars of a quality attained only by vacuum melting or by an equivalent process. The requirements of AMS 2300
are sometimes specified for such applications.
Aircraft quality alloy steel bars are ordinarily made to Aerospace Material Specifications published by the Society of
Automotive Engineers. Typical examples of parts for aircraft engines and airframes made from bars covered by AMS
specifications are given in Table 6.
Table 6 Specifications and grades of alloy steel bars for aircraft parts

Part AMS
specification

AISI-SAE grade

or approximate

grade
Aileron, rudder, and, and elevator hinge pins

6415
E4340
6370
4130
6280
8630
6382

4140
6322
8740
Airframe parts (tubing, fittings, and braces)
6415
E4340
Bearings 6440
E52100
Bolts, studs, and nuts 6322
8740
Connecting rods 6415
E4340
6342
9840
6382
4140
Crankcases
6322
8740
Crankshafts 6415
E4340
6415
E4340
6448
6150
Gears and shafts
6274
8620
6322
8740

6382
4140
Landing gears
6415
E4340
Propellers, spiders, hubs, and barrels 6415
E4340
Springs 6450 6150

Structural quality is the descriptor for hot-rolled bars used in the construction of bridges and buildings by riveting,
bolting, or welding and for general structural purposes. The general requirements for bars of this quality are given in
ASTM A 6; the only individual ASTM specification referred to in A 6 that pertains to alloy steel bars is A 710.
Additional Qualities. The quality designations shown below apply to alloy steel bars intended for rifles, guns, shell,
shot, and similar applications. They may involve requirements for amount of discard, macroetch testing, surface quality,
or magnetic particle testing, as indicated in the product specification:
• AP shot quality
• AP shot magnaflux quality
• Gun quality
• Rifle barrel quality
• Shell quality
• Shell magnaflux quality
High-Strength Low-Alloy Steel Bars
In addition to the carbon steel and alloy steel bars of structural quality discussed in preceding sections of this article,
ASTM A 6 also lists several specifications covering high-strength low-alloy (HSLA) steel bars of structural quality
(Table 3). High-strength low-alloy steel bars are also covered in SAE J 1442.
Bars of these steels offer higher strength than that of carbon steel bars and are frequently selected for applications in
which weight saving is important. They also offer increased durability, and many offer increased resistance to
atmospheric corrosion. Additional information on HSLA steels is available in the articles "High-Strength Structural and
High-Strength Low-Alloy Steels," "High-Strength Low-Alloy Steel Forgings" and "Bulk Formability of Steels" in this
Volume.

Microalloyed steel bars constitute a class of special quality carbon steels to which small amounts of alloying
elements such as vanadium, niobium, or titanium have been added. Microalloyed steels in the as-hot-rolled condition are
capable of developing strengths higher than those of the base carbon grades through precipitation hardening. In some
cases, strength properties comparable to those of the quenched and tempered base grade can be attained. These steels are
finding increased application in shafting and automotive forgings.
Concrete-Reinforcing Bars
Concrete-reinforcing bars are available as either plain rounds or deformed rounds. Deformed reinforcing bars are used
almost exclusively in the construction industry to furnish tensile strength to concrete structures. The surface of the
deformed bar is provided with lugs, or protrusions, which inhibit longitudinal movement relative to the surrounding
concrete. The lugs are hot formed in the final roll pass by passing the bars between rolls into which patterns have been
cut. Plain reinforcing bars are used more often for dowels, spirals, structural ties, and supports than as substitutes for
deformed bars. Concrete-reinforcing bars are supplied either straight and cut to proper length, or bent or curved in
accordance with plans and specifications.
Grades. Deformed and plain concrete-reinforcing bars rolled from billet steel are produced to the requirements of
ASTM A 615 or A 706. For special applications that require deformed bars with a combination of strength, weldability,
ductility, and improved bending properties, ASTM A 706 is specified, which is an HSLA steel. Deformed and plain
concrete-reinforcing bars are also available rolled from railroad rails (ASTM A 616) and from axles for railroad cars
(ASTM A 617), Specification ASTM A 722 covers deformed and plain uncoated high-strength steel bars for prestressing
concrete structures.
Sizes. Numbers indicating sizes of reinforcing bars correspond to nominal bar diameter in eighths of an inch for sizes 3
through 8; this relationship is approximate for sizes 9, 10, 11, 14, and 18. The nominal values for bar diameter, cross-
sectional area, and weight per unit length corresponding to these size numbers are given in Table 7. The nominal cross-
sectional area and the nominal diameter of a deformed bar are the same as those of a plain bar of equal weight per foot.
Table 7 Dimensions of deformed and plain concrete-reinforcing bars of standard sizes

Nominal
diameter
Cross-
sectional area

Nominal weight

Bar

size

mm in. mm
2
in.
2
kg/m
lb/ft
3 9.52 0.375

71 0.11 0.560
0.376

4 12.70

0.500

129 0.20 0.994
0.668

5 15.88

0.625

200 0.31 1.552
1.043

6 19.05

0.750

284 0.44 2.235
1.502

7 22.22

0.875

387 0.60 3.042
2.044

8 25.40

1.000

510 0.79 3.973
2.670

9 28.65

1.128

645 1.00 5.059
3.400

10 32.26

1.270

819 1.27 6.403
4.303

11 35.81

1.410

1006 1.56 7.906
5.313

14 43.00

1.693

1452 2.25 11.384

7.65
18 57.33

2.257

2581 4.00 20.238

13.60


Structural Shapes

Structural shapes, as stated previously, are flanged shapes 76 mm (3 in.) and greater in at least one cross-sectional
dimension (smaller shapes are referred to as bar-size shapes) and are used in the construction of structures such as
bridges, buildings, ships, and railroad cars. Included in this product category are regular structural shapes (see ASTM A
6), such as standard beams, wide-flange beams, columns, light beams, joists, stanchions and bearing piles, and certain
tees, along with special structural shapes, which are those designed for specialized applications and that have dimensions
and/or values of weight per foot that do not conform to regular shapes. Bar-size structural shapes (angles, channels, tees,
and zees with greatest cross-sectional dimension less than 76 mm, or 3 in.) are considered to be in the merchant quality
bar category rather than the structural shape category.
The common method of designating sizes of structural shapes is as follows:
• Beams and channels: By depth of cross section and weight per foot.
• Angles: By length of legs and thickness in fractions of an inch or, more commonly, by
length of legs and
weight per foot. The longer leg of an unequal angle is commonly stated first
• Tees: By width of flange, overall depth of stem, and weight per foot, in that order
• Zees: By depth, width of flanges, and thickness in fractions of an inch o
r by depth, flange width, and
weight per foot
• Wide-flange shapes: By depth, width across flange, and weight per foot, in that order
Most structural shapes are produced to meet specific standard specifications, such as those listed in Table 3. Structural
shapes are generally furnished to chemical composition limits and mechanical property requirements.
Special requirements are sometimes specified for structural shapes to adapt them to conditions they will encounter during
fabrication or service. These requirements may include specific deoxidation practices, additional mechanical tests, or
nondestructive testing.
Special Shapes
Special shapes are hot-rolled steel shapes made with cross-sectional configurations uniquely suited to specific
applications. Examples of custom-designed shapes are track shoes for tractors or tanks and sign-post standards.
The only type of standard shape in high production that falls in this classification is rail. Railroad rails of the standard
American tee rail shape are produced from carbon steel to the dimensional, chemical, and other requirements of the
American Railway Engineering Association (AREA). The sizes of railroad rails are designated in pounds per yard of
length; rails are furnished in 40 to 64 kg (90 to 140 lb) sizes. The most common sizes are 52, 60, 62, and 64 kg (115, 132,

136, and 140 lb). The ordinary length of railroad rails is 12 m (39ft). Carbon steel tee rails for railway track are covered
by ASTM A 1; rail-joint bars and tie plates are covered in ASTM A 3, A 4, A 5, A 49, A 67, and A 241.
Light rails are available for light duty, such as in mines and amusement park rides, in sizes from 6.8 to 39 kg (15 to 85 lb).
Light rails are covered by specifications of the American Society of Civil Engineers (ASCE).
Crane rails generally have heavier heads and webs than those of railroad rails in order to withstand the heavy loads
imposed on them in service. Crane rails in sizes from 18 to 79 kg (40 to 175 lb) are furnished to ASCE, ASTM, and
producers' specifications.
References
1.

Alloy, Carbon and High Strength Low Alloy Steels: Semifinished for Forging; Hot Rolled Bars, Cold
Finished Bars; Hot Rolled Deformed and Plain Concrete Reinforcing Bars,
AISI Steel Products Manual,
American Iron and Steel Institute, 1986
2.

Materials, Vol 1, 1989 SAE Handbook, Society of Automotive Engineers, 1989
Cold-Finished Steel Bars
Revised by the ASM Committee on Cold-Finished Bars
*


Introduction
COLD-FINISHED STEEL BARS are carbon and alloy steel bar products (round, square, hexagonal, flat, or special
shapes) that are produced by cold finishing previous hot-wrought bars by means of cold drawing, cold forming, turning,
grinding, or polishing (singly or in combination) to yield straight lengths or coils that are uniform throughout their length.
Not covered in this article are flat-rolled products such as sheet, strip, or plate, which are normally cold finished by cold
rolling, or cold-drawn tubular products.
Cold-finished bars fall into five classifications:
• Cold-drawn bars

• Turned and polished (after cold drawn or hot roll) bars
• Cold-drawn, ground, and polished (after cold draw) bars
• Turned, ground, and polished bars
• Cold-drawn, turned, ground, and polished bars
Cold-drawn bars represent the largest tonnage production and are widely used in the mass production of machined and
other parts. They have attractive combinations of mechanical and dimensional properties.
Turned and polished bars have the mechanical properties of hot-rolled products but have greatly improved surface finish
and dimensional accuracy. These bars are available in sizes lager than those that can be cold drawn. Turned bars are
defect and decarb free.
Cold-drawn, ground, and polished bars have the increased machinability, tensile strength, and yield strength of cold-
drawn bars together with very close size tolerances. However, cold-drawn, ground, and polished bars are not guaranteed
to be defect free.
Turned, ground, and polished bars have superior surface finish, dimensional accuracy, and straightness. These bars find
application in precision shafting and in plating, where such factors are of primary importance.
Cold-drawn, turned, ground, and polished bars have improved mechanical properties, close size tolerances, and a surface
free of imperfections.

Note
*

K. M. Shupe, Bliss & Laughlin Steel Company; Richard B. Smith, Stanadyne Western Steel; Steve Slavonic,
Teledyne Columbia-
Summerill; B. F. Leighton, Canadian Drawn Steel Company; W. Gismondi, Union
Drawn Steel Company, Ltd.; John R Stubbles, LTV Steel
Company; Kurt W. Boehm, Nucor Steel; Donald
M. Keane, LaSalle Steel Company
Bar Sizes
Cold-finished steel bars are available in a wide variety of sizes and cross-sectional shapes. Normally, they are furnished in
straight lengths, but in some sizes and cross sections they may be furnished in coils. Cold-finished steel bars are available
with nominal dimensions designated in either inches or millimeters. Cold-finished product is available in standard size

increments, which vary by size range. Special sizes can be negotiated depending on hot mill increments and cold-finish
tooling. The sizes in which they are commonly available in bar and coil form are given in Table 1.
Table 1 Common commercially available sizes of cold-finished steel bars and coils
Bars
(a)

Minimum
thickness or diameter
Maximum
thickness or
diameter
Size increments Normal length
Coils
(b)
, sizes
Configuration

mm in. mm in. mm in. m ft mm
in.
Round 3.2 0.125 305 12 0.8-
25
1.6-
75
3.2-
152
32nds to 1 in.,
16ths to 3 in., 8ths
to 6 in.
3.0-3.7
or 6.1-

7.3
10-12
or 20-
24
≤
25
≤
1
Square 3.2 0.125 152 6 1.6-
38
3.2-
70
16ths to 1
1
2
in.,
8ths to 2
3
4
in.
3.0-3.7 10-12
≤
16
≤
5
8

Hexagonal 3.2 0.125 102 4 1.6-
50
6.4-

102
16ths to 2 in., 4ths
to 4 in.
3.0-3.7 10-12
≤
16
≤
5
8

Flat 3.2 thick
× 6.4
wide
0.125
thick ×
0.25 wide
76 ×
371
3 thick ×
14
5
8

wide
1.6-
17
3.2-
44
6.4-
76

16ths to
11
16
in.,
8ths to 1
3
4
in.,
3.0-3.7 10-12
≤
14.3 ×
15.9
(c)

≤
9
16
×
5
8
(c)

(a)

Ref 1.
(b)

Ref 2.
(c)

Or other sections having cross-sectional areas
≤
194 mm
2
(
≤
0.30 in.
2
)


References cited in this section
1.

J.G. Bralla, Handbook of Product Design for Manufacturing, McGraw-Hill, 1986
2.

Alloy, Carbon, and High Strength Low Alloy Steels, Semifinished for Forging; Hot Rolled Bars; Cold
Finished Steel Bars; Hot Rolled Deformed and Plain Concrete Reinforcing Bars,
AISI Steel Products
Manual, American Iron and Steel Institute, 1986
Product Types
In the manufacture of cold-finished bars, the steel is first hot rolled oversize to appropriate shape and is then subjected to
mechanical operations (other than those intended primarily for scale removal) that affect is machinability, straightness,
and end-cut properties. The two common methods of cold finishing bars are:
• Removal of surface material by turning or grinding, singly or in combination
• Drawing the material through a die of suitable configuration
Pickling or blasting to remove scale may precede turning or grinding and must always precede drawing. For bar products,
cold rolling has been almost superseded by cold drawing. Nevertheless, cold-finished bars and special shapes are
sometimes incorrectly described as cold rolled.

Commercial Grades. Any grade of carbon or alloy steel that can be hot rolled can also be cold finished. The choice of
grade is based on the attainable cold-finished and/or hardenability and tempering characteristics necessary to obtain the
required mechanical properties.
Production methods vary widely among cold-finished cold-drawn suppliers. For example, one supplier currently anneals
and cold draws grades 1070, 1090, and 5160, and in the future plans to do the same with grade 9254. Grade 1070 is a
high-volume item, and cold drawing is required for precision sizing and subsequent nondestructive testing of the bar,
using a rotating-probe eddy current device (see the articles "Eddy Current Inspection," "Remote-Field Eddy Current
Inspection," and "Steel Bar, Wire, and Billets" in Nondestructive Evaluation and Quality Control, Volume 17 of ASM
Handbook, formerly 9th Edition Metals Handbook) for detecting surface seams. Cold drawing is also necessary because
the smallest hot-rolled size typically available for some applications is not small enough for customer use. Thus, a
supplier whose smallest hot-rolled bar size is 11.1 mm (0.437 in.) cold draws this diameter to as small as 9.98 mm (0.393
in.).
Carbon steels containing more than 0.55% C must be annealed prior to being cold drawn so that the hardness will be
sufficiently low to facilitate the cold-drawing operation. For carbon steels containing up to 0.65% C, this will normally be
a lamellar pearlitic anneal; for carbon steels containing more than 0.65% C, a spheroidize anneal is required. The type of
structure required is normally reached by agreement between the steel producer and the customer.
Alloy steels containing more than 0.38% C are usually annealed before cold drawing.
Machined Bars. Bar products that are cold finished by stock removal can be:
• Turned and polished
• Turned, ground, and polished
• Cold drawn, ground, and polished
• Cold drawn, turned, and polished
• Cold drawn, turned, ground, and polished
Turning is done in special machines with cutting tools mounted in rotating heads, thus eliminating the problem of having
to support long bars as in a lathe. Grinding is done in centerless machines. Polishing can be done in a roll straightener of
the crossed-axis (Medart) type with polished rolls to provide a smooth finish. Polishing by grinding with an organic wheel
or with a belt is of increasing interest (see the article "Grinding Equipment and Processes" in Machining, Volume 16 of
ASM Handbook, formerly 9th Edition Metals Handbook) because it is cost effective to grind and polish the bars on the
same machine simply by using grinding wheels or belts of different grit size. Grinding produces a smoother finish than
turning; polishing improves the surface produced by either technique. Turned, ground, and polished rounds represent the

highest degree of overall accuracy, concentricity, straightness, and surface perfection attainable in commercial practice
(Ref 3).
The surface finish desired is specified by using the process names given above because the industry has not developed
standard numerical values for roughness, such as microinch or root mean square (rms) numbers. However, surface finish
with respect to rms (root mean square deviation from the mean surface) as determined with a profilometer can be
negotiated between the producer and a customer. This could be done for such critical-finish applications as turned and
polished bars used to produce shafting as well as stock used to produce machined parts of which a superior finish is
required on surfaces not machined.
The published range of diameters both for turned and for turned and ground bars is 13 to 229 mm (
1
2
to 9 in.) inclusive;
for cold-drawn and ground bars, it is 3.2 to 102 mm (
1
8
to 4 in.) inclusive. These are composites of size ranges throughout
the industry; an individual producer may be unable to furnish a full range of sizes.
For example, one well-known producer supplies turned rounds from 13 to 229 mm (
1
2
to 9 in.), another from 29 to 203
mm (1
1
8
to 8 in.) all finished sizes. Yet another producer supplies sizes up to and including 152 mm (6 in.) that are
turned on special turning machines and ground on centerless grinders; larger sizes are lathe turned and ground on centers.
Because turning and grinding do not alter the mechanical properties of the hot-rolled bar, this product can be machined
asymmetrically with practically no danger of warpage (Ref 3).
Stock removal is usually dependent on American Iron and Steel Institute (AISI) seam allowances (Ref 2). Stock removal
in turning, or turning and grinding, measured on the diameter, is normally 1.6 mm (

1
16
in.) for sizes up to 38 mm (1
1
2

in.), 3.2 mm (
1
8
in.) for the 38 to 76 mm (1
1
2
to 3 in.) range, 4.8 mm (
3
16
in.) for the 76 to 127 mm (3 to 5 in.) range, and
6.4 mm (
1
4
in.) for 127 mm (5 in.) diameter and larger.
Cold-drawn round bars are available in a range of diameters from 3.2 to 152 mm (
1
8
to 6 in.). The maximum
diameters available from individual producers, however, may vary from 76 to 152 mm (3 to 6 in.). The reduction in
diameter in cold drawing, called draft, is commonly 0.79 mm (
1
32
in.) for finished sizes up to 9.5 mm (
3

8
in.) and 1.6 mm
(
1
16
in.) for sizes over 9.5 mm (
3
8
in.). Some special processes use heavier drafts followed by stress relieving. One
producer employs heavy drafting at elevated temperature. With this exception, drawing operations are begun with the
material at room temperature to start, and the only elevated temperature involved is that developed in the bar as a result of
drawing; this temperature rise is small and of little significance.
Originally, cold finishing, whether by turning or by cold rolling, was employed only for sizing to produce a bar with
closer dimensional tolerances and a smoother surface. As cold-finished bar products were developed and improved,
increased attention was paid to the substantial enhancement of mechanical properties that could be obtained by cold
working. This additional advantage is now more fully appreciated, as evidenced by the fact that increased mechanical
properties are an important consideration in about 40% of the applications. In approximately half of these applications, or
20% of the total, cold drawing is used only to increase strength; in the other 20%, close tolerances and better surface
finish are desired in addition to increased strength.
As-rolled microalloyed high-strength low-alloy (HSLA) steels or microalloyed HSLA steels in various combinations of
controlled drafting and furnace treatment provide an extension of property attainment. A high percentage of free-
machining steels are cold drawn for the combination of size accuracy and improved machinability. Recent developments
in microalloyed steels provide hot-rolled turned bars, under certain circumstances, having mechanical properties similar
to cold-drawn nonmicroalloyed steels.
An appreciable fraction of all applications of cold finishing to carbon steel bars utilizes cold drawing to improve
mechanical properties. For alloy steel, however, cold finishing is commonly used to improve surface finish and
dimensional accuracy, and not for additional mechanical strength. When additional mechanical strength is desired, alloy
steel bars may be heat treated (quenched and tempered) and then cold drawn and stress relieved. Elevated-temperature or
warm-drawn steels are also available with increased mechanical strength and improved machinability.
Heavily drafted and strain-tempered carbon and alloy steels subjected to induction hardening of the surface provide many

additional property combinations. The extra cost of using alloy steel in cold-finished bars can be justified only when heat
treatment (quenching and tempering) is necessary for meeting the required strength level. Because work-hardening effects
are removed during heating prior to quenching, the benefit of increased mechanical strength due to cold finishing is
eliminated from the finished product.
Turning Versus Cold Drawing. Basic differences exist between bars finished by turning and those finished by cold
drawing. First, it is obvious that turning and centerless grinding are applicable only to round bars, while drawing can be
applied to a variety of shapes. Drawing, therefore, is more versatile than turning.
Second, there is a difference in the number and severity of the surface imperfections that may be present. Because stock is
removed in turning and grinding, shallow surface imperfections and decarburization may be completely eliminated. When
material is drawn, stock is only displaced, and surface imperfections are only reduced in depth (in the ratio of the change
in bar diameter or section thickness). The length of these imperfections may be slightly increased because in the drawing
operation an increase in length accompanies the reduction in cross section.
Cold-drawn bars can approach the freedom from surface imperfections obtained in turned or turned and ground bars if the
hot-rolled bars from which they are produced are rolled from specially conditioned billets. Quality conditions such as
cold-working quality are available from producers of hot-rolled bars. The depth limits of the surface imperfections are as
agreed to between the producer and the customer. However, if maximum freedom from surface imperfections is the
controlling factor, turned bars have an advantage.
Different size tolerances are applicable to cold-finished products, depending on shape, carbon content, and heat treatment.
Listed in Tables 2, 3, and 4 are the tolerances for cold-finished carbon and alloy steel bars published in ASTM A 29.
These tables include cold-drawn bars; turned and polished rounds; cold-drawn, ground, and polished rounds; and turned,
ground, and polished rounds. From the data in Tables 2, 3, and 4, certain generalizations can be stated. The tolerances for
cold-drawn and for turned and polished rounds, for example, are the same for sizes up to and including 102 mm (4 in.).
There are differences, however, between the tolerances that apply to carbon steel and those that apply to alloy steels.
Tolerances for several finishes also vary with certain levels of carbon content. Broader tolerances are applicable to bars
that have been heat treated before cold finishing. In contrast, tolerances are closer when bars are ground, and these
tolerances are independent of carbon content.
Table 2 Size tolerances for cold-finished carbon steel bars, cold drawn or turned and polished
This table includes tolerances for bars that have been annealed, spheroidize annealed, normalized, normalized and tempered, or
quenched and tempered before cold finishing. This table does not include tolerances for bars that are annealed, spheroidize annealed,
normalized, normalized and tempered, or quenched and tempered after cold finishing; the producer should be consulted for tolerances

for such bars.
Size tolerance
Maximum carbon (C) range, %
Size
C
≤
0.28
0.28 < C
≤
0.55
C
≤
0.55
including stress
relief or annealed

after cold
finishing
C > 0.55
All grades
quenched and
tempered
or normalized
before cold finishing
mm in. mm in. mm in. mm in. mm in. mm
in.
Rounds cold drawn (to 102 mm, or 4 in., in size) or turned and polished
To 38 inclusive
To 1
1

2
inclusive
-
0.05
-
0.002
-0.08

-0.003 -0.10 -0.004 -
0.13
-
0.005
-0.13
-0.005
>38-64 inclusive
>1
1
2
-2
1
2

inclusive
-
0.08
-
0.003
-0.10

-0.004 -0.13 -0.005 -

0.15
-
0.006
-0.15
-0.006
>64-102
inclusive
>2
1
2
-4 inclusive
-
0.10
-
0.004
-0.13

-0.005 -0.15 -0.006 -
0.18
-
0.007
-0.18
-0.007
>102-152
inclusive
>4-6 inclusive -
0.13
-
0.005
-0.15

-0.006 -0.18 -0.007 -
0.20
-
0.008
-0.20
-0.008
>152-203
inclusive
>6-8 inclusive -
0.15
-
0.006
-0.18

-0.007 -0.20 -0.008 -
0.23
-
0.009
-0.23
-0.009
>203-229
inclusive
>8-9 inclusive -
0.18
-
0.007
-0.20

-0.008 -0.23 -0.009 -

0.25
-
0.010
-0.25
-0.010
Hexagons cold drawn
To 19 inclusive
To
3
4
inclusive
-
0.05
-
0.002
-0.08

-0.003 -0.10 -0.004 -
0.15
-
0.006
-0.15
-0.006
>19-38 inclusive
>
3
4
-1
1
2

inclusive

-
0.08
-
0.003
-0.10

-0.004 -0.13 -0.005 -
0.18
-
0.007
-0.18
-0.007
>38-64 inclusive
>1
1
2
-2
1
2

inclusive
-
0.10
-
0.004
-0.13

-0.005 -0.15 -0.006 -

0.20
-
0.008
-0.20
-0.008