Here are the key things to know about the ASTM A108 specification for carbon steel bars and rods:
ASTM A108 sets compositional, mechanical property, and testing requirements for carbon steel rods that will be heat treated for applications requiring hardness.
Chemical composition limits are defined, most commonly specifying a carbon content between 0.15-0.35% for 1040. Alloying element content is also regulated.
Based on rod diameter, minimum tensile strength and impact testing requirements are established that materials must meet. For example, 5/8" 1040 rod needs a 58 ksi minimum yield strength.
Dimensional tolerances are provided to ensure consistent diameters and straightness within defined ranges. Surface finish is also called out.
Inspection and testing procedures are outlined, like checking longitudinal defects through ultrasonic testing.
Identification and marking of test samples to certified labs are described for chemical and mechanical verification.
Requiring 1040 rod adhere to A108 allows you to be confident in consistent and reliable material properties no matter the heat or supplier. Let me know if any part of this standard specification needs more explanation!