Short answer: The four grades buyers ask for most – 4130, 4140, 4340, and 8620 – share a chromium-molybdenum base but split on nickel, carbon, and heat treatment. This guide explains what each does best so you can specify with confidence.
At a Glance
Why These Four?
They are the AISI/SAE grades specified across automotive, oil & gas, and machinery. They share chromium-molybdenum hardenability but differ in carbon and nickel, which shifts them from weldable tubing to ultra-tough aircraft parts.
Grade-by-Grade
The chart summarizes them. 4130 is weldable and used for tubing and frames. 4140 is the general-purpose hardenable grade for shafts and forgings. 4340 adds nickel for maximum toughness. 8620 carburizes for hard wear surfaces. See our alloy steel supply page.
Choosing by Duty
Match the grade to load and heat treatment: 4130 for welded structures, 4140 for through-hardened machine parts, 4340 for fatigue-critical parts, 8620 for carburized gears and pins. See our strength comparison for the numbers.
Standards and Certification
Specify by AISI/SAE or EN (e.g. 42CrMo4 for 4140) and request heat-treatment and mill-test certificates. See our steel standards guide.
Get a Quote
Tell HXSCO the grade, form, and quantity and we will quote with certification and lead time.
Veelgestelde vragen
General-purpose hardened shafts, gears, forgings, and machine parts needing good strength and toughness.
4130 is lower-carbon and more weldable for tubing/frames; 4140 is higher-carbon and hardens to higher strength for machine parts.
High-toughness, fatigue-critical parts in aircraft, oil & gas, and heavy equipment where impact resistance matters most.
A carburizing grade that develops a hard wear surface over a tough core for gears, pins, and bearings.
State the load, heat treatment, and environment; HXSCO will recommend 4130/4140/4340/8620 or an EN equivalent.
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Send us the grade, form, dimensions, quantity, and any certification or test requirements. HXSCO replies with a competitive quote, lead time, and mill-test options.
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