Project Description

AISI 4140 steel Manufacturer and Exporter,supplied with round,square,flat,block,and shaft etc.AISI 4140 is defined as a low alloy steel which has 1% Cr-Mo as strengthening alloy elements.Compared with AISI 4130, it has a higher carbon content with good balance of strength, toughness ,abrasion and impact resistance and heat treatment capabilities,but poor in weldability characteristics.AISI 4140 is generally supplied in quenched and tempered condition with hardness 28-32HRC.AISI 4140 steel round bar

1.Supply Form & Size & Tolerance

Supply FormSize(mm)ProcessTolerance

Φ6-Φ100Cold DrawnBright/Black Best H11


Hot Rolled
Peeled/ground Best H11


Hot Forged
Rough Turned-0/+3mm

Thickness :120-800
Hot Forged
Rough Machined-0/+3mm

Remark:Tolerance can be customized as per requests

2.Chemical Composition

ASTM A2941400.38-0.430.15-0.350.75-1.00≤ 0.035≤ 0.040.8-1.10.15-0.25


≤ 0.4


≤ 0.025

≤ 0.035


JIS G4105SCM4400.38-0.430.15-0.350.6-0.85≤ 0.035≤ 0.040.9-1.20.15-0.30
GB 307742CrMo0.38-0.450.17-0.370.5-0.80≤ 0.035≤ 0.0350.9-1.20.15-0.25
BS 970EN190.35-0.450.15-0.350.5-0.80≤ 0.035≤ 0.0350.9-1.50.2-0.40

3.Physical Property

Density g/cm37.85
Melting point °C1416
Poisson's ratio0.27-0.30
Machinability (AISI 1212 as 100% machinability)65%
Thermal expansion co-efficient µm/m°C12.2
Thermal conductivity W/(m.K)46
Modulus of elasticity 10^3 N/mm2210
Electric resistivity Ohm.mm2 /m0.19
Specific heat capacity J/(kg.K)460

Modulus of elasticity 10^3 N/mm2
100 ℃200 ℃300 ℃400 ℃500 ℃

Thermal expansion 10^6 m/(m.K)
100 ℃200 ℃300 ℃400 ℃500 ℃

4. Mechanical Property

Mechanical ConditionRSSTUVW
Ruling Section mm250250150100633020
Tensile Strength Mpa700-850770-930770-930850-1000930-10801000-11501080-1230
Yield Strength Mpa Min480540570655740835925
Elongation %15131513121212
Izod Impact J Min34275454474740
Charpy Impact J Min28225050424235
Hardness Brinell HB201-255233-277233-277248-302269-331293-352311-375

5.High Temperature Strength

For quenched and tempered heavy forgings

Diameter mm
Yield strength MPa
20 ℃100 ℃200 ℃250 ℃300 ℃350℃400℃


Forging temperature should be carried out between 900℃-1200℃,The lower the forging-ending temperature ,the finer the grain size .Hold the temperature till uniform before forge,minimum forging temperature 850°C,so don’t forge below 850℃.AISI 4140 steel  should be cooled as slowly as possible in still air or in sand after forged.


Normalizing is used to refine the structure of forgings that might have cooled non-uniformly after forged,and considered as a conditioning treatment before final heat treatment.Normalizing temperature for AISI 4140 steel should be carried out between 870℃-900℃. hold suitable time for the steel to be thoroughly heated to  complete the ferrite to austenite transformation.Cool in still air.


After Forged,AISI 4140 steel  may be annealed .Annealing temperature should be carried out between 800℃-850℃, hold suitable time for the steel to be thoroughly heated. Cool slowly in the furnace.This treatment will form a structure suitable for machining.The maximum Hardness is 241 HB.


This heat treatment will obtain martensite structure  after quenched.It should be carried out between 840℃-875℃, hold suitable time for the steel to be thoroughly heated, soak for 10-15 minutes per 25 mm section, and quench in oil, water, or polymer as required.Tempering should be followed  immediately after quenched.


Tempering is usually carried out to relieve stresses from the hardening process, but primarily to obtain the required  hardness and mechanical properties. The actual tempering temperature will be chosen to meet the required properties.Heat the AISI 4140 carefully to a suitable temperature ,usually between 550℃-700℃, soak at the temperature for 2 hours per 25mm of ruling section, then cool in air.Tempering between 250℃-375℃ is not avoided as tempering within this range will seriously reduce the impact value,result in temper brittleness .


AISI 4140 steel finds many applications as forgings for the aerospace,oil and gas,automotive, agricultural and defense industries etc.
Typical applications for 4140 steel uses include:forged gears,spindles,fixtures,jigs,collars,Axles,conveyor parts,crow bars,logging parts,shafts,sprockets,studs,pinions,pump shafts, rams, and ring gears etc

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