ASTM A574 Standard Specification for Alloy Steel Socket Head Cap Screws

Get Certified ASTM A574 for Uncompromising Quality and Project Success

High-strength socket-head cap screws see substantial mechanical stress in structural, mechanical, and load-bearing assemblies, and a fastener that falls short of its specified strength can compromise the entire assembly it holds together. ASTM A574 provides manufacturers with requirements for a socket-head cap screw that can demonstrate that a fastener meets its material and mechanical requirements

The scope of ASTM A574 includes:

• Material type: Quenched and tempered alloy steel, manufactured to fine-grain practice.
• Purpose: Establishing chemical composition and mechanical property requirements for high-strength socket-head cap screws.
• Properties evaluated: Tensile or wedge load, proof load, yield strength, elongation, Rockwell and Vickers hardness.
• Testing Requirements: Manufacturers verify finished screws against the specified chemical composition and applicable mechanical property requirements. 
• Results: Pass or fail against the specified chemical composition limits and mechanical property minimums for the selected grade.
• Test limitations: ASTM A574 applies only to the inch-pound diameter range of 0.060 through 4 in.; the metric companion specification for this fastener type has been withdrawn.
• Use conditions: Finished screws are inspected and tested according to the specified alloy grade before acceptance.
• Applications: Structural assemblies, machinery, and other high-strength bolted connections requiring alloy steel socket-head cap screws.

What are the Uses of ASTM A574?

ASTM A574 gives manufacturers and purchasers a documented way to verify that alloy steel socket-head cap screws meet the chemical composition and mechanical strength a high-strength application demands. The specification-

• Confirms chemical composition against the specified alloy grade.
• Verifies tensile or wedge strength against the minimum requirement for the grade.
• Checks applicable proof-load and yield-strength requirements before a fastener enters service.
• Measures elongation to confirm that the minimum ductility requirements for the selected grade are met.
• Determines Rockwell and Vickers hardness to verify that the screw meets the heat treatment requirements for the selected grade.
• Supports quality control and acceptance testing of high-strength fastener production.

Which Materials Can Be Tested Under ASTM A574?

ASTM A574 applies to alloy steel socket-head cap screws manufactured from fine grain alloy steel complying with the chemical composition requirements of this specification. When Supplementary Requirement S1 is specified, additional alloy grades, including 4137, 4142, 4145, 4340, and 8740, with their respective chemical compositions, may be employed. Technicians can select the appropriate alloy steel grade and diameter in accordance with the purchase order requirements and application.

Why is ASTM A574 Important?

Socket-head cap screws that do not meet the minimum tensile strength or hardness requirements can fail mechanical assemblies under load. ASTM A574 provides purchasers with chemical composition and mechanical property requirements that establish a baseline for a socket-head cap screw that can be relied on to perform its designed function without failure in high-strength service.

ASTM A574 Testing Process and Data Collection

A technician selects representative socket-head cap screws from the batch and confirms that the product falls within the specification’s 0.060 through 4 in. diameter range. The technician performs mechanical and hardness testing in accordance with the applicable screw size, product length, and test requirements. The analyst enters the test results against the applicable mechanical and hardness testing requirements for the tested grade and prepares the test report that summarizes the findings.

Common Challenges and Troubleshooting

Accurate ASTM A574 testing requires identifying the correct alloy grade and using calibrated tension-testing and hardness equipment. Testing a fastener against the wrong grade’s requirements can lead to erroneous pass/fail results. Technicians mitigate this risk by confirming the specified grade and ensuring that tension, proof-load, and hardness testing equipment are calibrated.

• The technician reports the tensile or wedge load strength in Ksi and compares it to the applicable minimum tensile strength requirement for the tested grade and size.
• The proof-load stress and yield strength are expressed in Ksi in Table 1. In addition, screw tensile tables also specify the proof load in lbf.
• The technician reports the obtained screw elongation as a percentage to confirm that the minimum ductility requirements for the tested grade are met.
• The engineer reports the Rockwell and Vickers hardness values and compares them to the applicable minimum and maximum hardness requirements for the tested grade.

Link to ASTM A574