ASTM A29 Steel: Grades, Properties, Composition & Equivalent Materials

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Posted on May 02, 2024 at 01:00 PM

What is ASTM A29 Steel?

ASTM A29 is a specification published by ASTM International that defines the general requirements for hot-wrought steel bars, covering carbon steel, alloy steel and stainless steel. Officially titled "Standard Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought", it is one of the most widely referenced standards in industrial steel procurement. 

The standard is also available as ASTM A29/A29M (metric version of the same standard). Both refer to the same document, A29 is in inch-pound units and A29M is in SI (metric) units. If you are ordering steel bars overseas, you may find that you have to order from either designation, but they are equivalent.

ASTM A29 does not define a single steel grade. Rather, it establishes general manufacturing, testing, quality and standard requirements that are applicable to all a broad range of steel bar grades referred to by other more product-specific standards (such as ASTM A108 for cold-finished bars) that rely on and build upon this specification. 

ASTM A29 Specification Overview

ASTM A29 covers four primary product forms:

• Hot Rolled Carbon Steel Bars
• Cold Finished Carbon Steel Bars
• Hot Rolled Alloy Steel Bars
• Cold Finished Alloy Steel Bars

Available Forms and Shapes

Material Certifications Available

• Raw Materials Certificate: EN 10204/3.1B
• 100% Radiography Test Report
• Third Party Inspection Reports
• Mill Test Certificates (MTC)

ASTM A29 Steel Grades

ASTM A29 Chemical Composition

Grade 4140 (Most Widely Used)

Standard	Grade	C	Mn	P (max)	S (max)	Si	Cr	Mo
ASTM A29	4140	0.38–0.43	0.75–1.00	0.035	0.040	0.15–0.35	0.80–1.10	0.15–0.25
SAE/AISI	4140	0.38–0.43	0.75–1.00	0.035	0.040	0.15–0.35	0.80–1.10	0.15–0.25
EN 10250	42CrMo4	0.38–0.45	0.60–0.90	0.035	0.035	0.40	0.90–1.20	0.15–0.30
JIS G4105	SCM440	0.38–0.43	0.60–0.85	0.030	0.030	0.15–0.35	0.90–1.20	0.15–0.30

For a detailed breakdown of AISI 4140 alloy steel properties and applications, refer to our dedicated guide. 

Carbon Steel Grades (1020, 1045, 1050)

Grade	C	Mn	P (max)	S (max)
1020	0.18–0.23	0.30–0.60	0.040	0.050
1045	0.43–0.50	0.60–0.90	0.040	0.050
1050	0.48–0.55	0.60–0.90	0.040	0.050

Learn more about SAE 1045 steel properties and industrial use cases in our detailed blog post.

ASTM A29 Mechanical Properties

Note: Mechanical properties vary significantly based on heat treatment condition (annealed, normalized, quenched & tempered). Always specify the required condition when ordering.

ASTM A29 Equivalent Materials

International Equivalents

ASTM A29 Grade	ASTM	SAE/AISI	EN/DIN	JIS
1020	A108	1020	C22 / 1.0402	S20C
1045	A108	1045	C45 / 1.0503	S45C
1050	A108	1050	C50 / 1.0540	S50C
4140	A108	4140	42CrMo4 / 1.7225	SCM440
4340	A108	4340	36NiCrMo16 / 1.6565	SNCM439
5140	A108	5140	41Cr4 / 1.7035	SCr440

ASTM A29 Indian Standard (IS) Equivalents

For buyers in India, the following IS grades are commonly considered equivalent:

ASTM A29 Grade	IS Equivalent	IS Standard
1020	C20	IS 1570 Part 2
1045	C45	IS 1570 Part 2
1050	C50	IS 1570 Part 2
4140	40Cr4Mo3	IS 1570 Part 4
4340	40Ni14Cr18Mo3	IS 1570 Part 4
5140	40Cr13	IS 1570 Part 4

Disclaimer: These equivalents are approximate and based on similar chemical composition ranges. Always verify with your metallurgist or testing laboratory before substitution in critical applications.

ASTM A29 Heat Treatment

ASTM A29 sets out general requirements but does not prescribe fixed heat treatment procedures — these are determined by the specific grade and intended application. The standard heat treatment sequence for ASTM A29 alloy steel bars is as follows:

1. Annealing

Steel bars are heated to above the critical transformation temperature, soaked uniformly, then cooled slowly (typically in the furnace). This softens the material, relieves internal stress, and improves machinability.

2. Normalizing

Bars are heated above the transformation range and cooled in still air. Normalizing refines the grain structure and produces more uniform mechanical properties than the as-rolled condition.

3. Hardening

• Preheat to 815°C–900°C (1,500°F–1,650°F) depending on grade
• Soak at temperature to ensure uniform transformation
• Quench in oil, water, or polymer solution — choice depends on grade and section thickness
• Quenching produces a martensitic microstructure, achieving high hardness

4. Tempering

After quenching, tempering reduces brittleness and internal stress:

• Reheat to 150°C–600°C (300°F–1,100°F)
• Hold for a specified time, then cool
• Higher tempering temperatures yield better toughness at some cost to hardness

For a deeper understanding of these processes, read our article on the difference between annealing and tempering. 

Typical Hardness After Heat Treatment (Grade 4140)

Condition	Hardness
Annealed	~197 HB
Normalized	~217 HB
Quenched & Tempered (mid-range)	28–34 HRC
Supplied hardened condition	18–22 HRC

ASTM A29 Application Industries

ASTM A29 steel bars are used across a wide range of industries:

Automotive

Crankshafts, axles, gears, transmission components, and steering parts benefit from the high strength and wear resistance of grades like 4140 and 4340.

Oil & Gas

Drill collars, valve bodies, pump shafts, and wellhead components require the combination of high toughness and corrosion resistance found in ASTM A29 alloy grades.

Aerospace & Defense

Landing gear components, engine shafts, and structural airframe parts use 4340 and similar high-strength grades for their excellent fatigue resistance and strength-to-weight ratio.

Construction & Infrastructure

Structural fasteners, reinforcement components, and anchor bolts in buildings, bridges, and infrastructure projects commonly use carbon steel grades from ASTM A29.

Power Generation

Turbine shafts, generator components, and high-temperature fittings rely on alloy grades for thermal resistance and long service life.

Railways

Rail couplings, brake components, and wheel axles use ASTM A29 bars for their toughness under cyclic loading and impact.

Mining & Heavy Equipment

Bucket pins, hydraulic cylinder rods, crusher shafts, and drilling equipment components are manufactured from ASTM A29 grades for resistance to impact and abrasion.

General Manufacturing

Tooling, dies, machine spindles, and industrial fasteners are produced from ASTM A29 bars for their machinability and versatile heat treatment response.

Condition	Hardness
Annealed	~197 HB
Normalized	~217 HB
Quenched & Tempered (mid-range)	28–34 HRC
Supplied hardened condition	18–22 HRC

ASTM A29 Steel Properties Summary

For quick reference, here is a consolidated overview of ASTM A29 steel properties across the most common grades:

Grade	Type	Tensile Strength	Yield Strength	Hardness	Machinability
1020	Carbon	395 MPa	295 MPa	111 HB	72%
1045	Carbon	570 MPa	310 MPa	163 HB	57%
1050	Carbon	620 MPa	340 MPa	179 HB	54%
4140	Alloy	655 MPa	415 MPa	197 HB	65%
4340	Alloy	745 MPa	470 MPa	217 HB	50%
5140	Alloy	570 MPa	435 MPa	167 HB	60%

Values shown are for annealed/normalized condition. Quenched and tempered conditions will yield significantly higher tensile and yield strength values.

ASTM A29 Yield Strength — What You Need to Know

The yield strength of ASTM A29 steel varies considerably by grade and heat treatment condition. For Grade 4140 in the annealed condition, yield strength is 415 MPa (60,200 psi). After quenching and tempering to full hardness, yield strength can exceed 900 MPa, making it suitable for high-stress structural and mechanical applications. When specifying ASTM A29 steel, always state the required yield strength alongside the grade and condition to ensure the correct material is supplied.

ASTM A29 PDF — Standard Document

The official ASTM A29 standard PDF is a paid publication available directly from ASTM International at astm.org. It is not legally available as a free download. If you have encountered free versions online, be aware these may be outdated editions that do not reflect the current revision.

For technical data on specific grades — including chemical composition tables, mechanical property requirements, and testing methods — our team can provide material test certificates (MTC) and grade-specific datasheets with every order at no additional cost.

Why Choose Amardeep Steel for ASTM A29 Steel Bars?

• Huge ready stock across Grade 4140, Grade 4340, 1045, 1020 and more
• Custom cutting to length, diameter, and finish requirements
• Mill test certificates and third-party inspection available
• Fast dispatch from Mumbai with pan-India and export delivery
• Expert technical support to help you select the right grade and condition