AISI 4140 | 709 | SCM440 | EN19 High Tensile Steel

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AISI 4140 | 709 | SCM440 | EN19 High Tensile Steel  Alloy Steel


AISI 4140 Suppliers - ASSAB 709, SCM440, EN19, 1.7225 High Tensile Steel (42CrMo4) 


ASSAB 709 is equivalent to 

Country USA German British Japan China Australia
Standard ASTM A29 DIN 17200 BS 970 JIS G4105 GB/T 3077 AS 1444
Grades 4140 1.7225/ 42crmo4 42CrMo4 SCM440 42CrMo 4140

 

Mechanical Properties Requirements of EN19 Steel in Condition “T” – to AS 1444-1996

Section mm 0.2% Proof Stress MPa Tensile Strength MPa
Elongation on 5.65√So

%

Impact Izod Charpy

J          J

Hardness HB
*up to 63 680 n 850 – 1000 14 –           – 248 – 302
*up to 100 665 min 850 – 1000 15 54min 50min 248 – 302

** Applies only to bars bright drawn after hardening and tempering

 

MECHANICAL PROPERTIES of SCM440 Steel – Hardened and tempered in section size listed

Section mm Yield Strength MPa Tensile Strength MPa
Elongation

%

Impact Izod J Hardness HB
50 770 930 17 90 275
100 710 920 15 70 270
200 570 850 14 60 250

** Typical Mechanical Properties for guidance only

 

Heat Treatment for 42CrMo4 / SCM440 Steel Shaft 

Annealing


Heat to 800 oC – 850 oC, hold until temperature is uniform throughout the section and cool in furnace.

Flame or Induction Hardening

Alloy Steel 7225, hardened and tempered bar can be further surface hardened by either the flame or induction hardening methods resulting in a case hardness in excess of Rc 50.

Parts should be heated as quickly as possible to the austenitic temperature range (840 C – 870 C) and “required case depth followed by an immediate oil or water quench, depending upon hardness required, workpiece” size/shape and quenching arrangements.

“Following quenching to hand warm, most components should be tempered between 150 C – 200 C to remove” quenching stresses in the case. This will have little effect on case hardness and will reduce the risk of grinding cracks.

Hardening


Machinery Steel 4140QT , Heat to 840 oC – 875 oC, hold until temperature is uniform throughout the section, soak for 10 – 15 minutes per 25 mm section, and quench in oil, water, or polymer as required.

*Temper immediately while still hand warm.

 

Nitriding


EN19 steel with hardened and tempered bar can also be successfully nitrided, giving a surface hardness of up to Rc 60. Nitriding is carried out at 490 oC – 530 oC, followed by slow cooling (no quench) reducing the problem of distortion. Parts can therefore be machined to near final size, leaving a grinding allowance only. The tensile strength of the core is usually not affected since the nitriding temperature range is generally below the original tempering temperature employed.

Normalizing

Heat to 870 oC – 900 oC, hold until temperature is uniform throughout the section, soak for 10 – 15 minutes and cool in still air.

Stress Relieving

Heat to 680 oC – 700 oC, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm section, and cool in still air.

 

Tempering

Re-heat to 550 oC – 700 oC as required, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm of section, and cool in still air.

*** Notes on Heat Treatment

Heating temperatures, rate of heating and soaking times will vary due to factors such as work piece size/shape also furnace type employed, quenching medium and work piece transfer facilities etc.. Please consult your heat treater for best results.

Machining


42CrMo4 (4140QT) in the hardened and tempered as supplied condition has good to very good machinability and operations such as sawing, turning, drilling, broaching, hobbing, milling and tapping can be carried out satisfactoraly using machine manufacturers recommendations for suitable tool type – feeds and speeds.

Welding


Welding of AISI4140 in the hardened and tempered condition (as normally supplied), is not recommended and should be avoided if at all possible, as the mechanical properties will be altered within the weld heat affected zone. It is preferred that welding be carried out on 4140 while in the annealed condition, and that the work piece, immediately on cooling to hand warm, is then stress relieved at 595 oC – 620 oC prior to hardening and tempering.

If welding in the hardened and tempered condition is really necessary, then the work piece, immediately on cooling to hand warm, should be if possible stress relieved at 15 oC below the original tempering temperature (if known).




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