Short answer: AISI 4340 is a nickel-chromium-molybdenum alloy steel that reaches tensile strengths above 1000 MPa after quench and temper while keeping excellent toughness, so it serves heavily loaded shafts, crankshafts, gears and aircraft parts where 4140 would be marginal, supplied in the heat-treated condition with mill certificate and verified by the strength and hardness comparisons.
At a Glance
What 4340 Is
4340 is a deeper-hardening relative of 4140, with the basis in our Alloy Steel Supplier and strength notes in our Metal Strength Comparison; hardness detail is in our Hardness Comparison.
Strength and Use
4340 serves tough, fatigue-loaded parts, with fatigue notes in our Metal Fatigue Guide and the automotive context in our Automotive Guide; the aerospace context is in our Aerospace Guide.
Fabrication and Heat Treat
4340 needs preheat and post-weld heat treatment, with the method in our Heat Treatment Guide and machining in our Machining Guide; finish is in our Surface Treatment Guide.
Quality and Sourcing
Alloy stock is checked by inspection, with methods in our Quality Inspection Guide; buyers confirm condition via our Mill Test Certificate Guide and pack per our Export Packing Guide.
Get a Quote
Tell HXSCO your requirements and we will respond with a competitive quote and lead time.
Domande frequenti
A Ni-Cr-Mo alloy steel for high strength and toughness.
Tensile above 1000 MPa after quench and temper.
Yes – nickel gives it much better toughness.
Aircraft parts, crankshafts, gears and shafts.
Confirm condition and certificate, then pack for export.
Specify 4340 Steel with HXSCO
HXSCO supplies 4340 bar, tube and plate in annealed or quench-tempered condition with mill certificate. Send sizes and condition for a quote.