The use of heat treatable steels covers the full range of mechanical engineering, especially where dynamic stresses are involved.
Application examples include:
|% Alloy content||Application Examples|
|C22||0.22||Low Stress structural components|
|C35||1035/1038||0.35||Standard Stress structural components|
|C45R||1049||0.45||Standard Stress structural components|
|C55E||0.55||Gear shafts and wheels|
|1% Cr and CrMo Steel|
|28Cr4||0.25||1||Driving wheels and shafts|
|25CrMo4||0.25||1||0.25||Axle arbors, turbine components|
|34Cr4||5132||0.34||1||Axle, axle arms|
|34CrMo4||4135/4137||0.34||1||0.25||High toughness components, incl. crank shafts, axle arbors|
|41Cr4||5140||0.41||1||Axles, control components|
|42CrMo4||4140/4142||0.41||1||0.25||High toughness components for automobiles and aircraft|
|48CrMo4||0.5||1||0.25||Steel for induction hardening up to 250 mm Diameter|
|50CrMo4||4150||0.5||1||0.25||High toughness components for automobiles and aircraft|
|36CrNiMo4||4340/4980||0.36||1||1||0.25||Highly charged components for automobiles and aircraft|
|34CrNiMo6||4337/4340||0.34||1.5||1.5||0.25||Crank shafts, eccentric shafts, gear components|
|30CrNiMo8||0.3||2||2||0.4||Structural components for heavy demands|
|28NiCrMo4||0.28||1||1||0.25||Structural components for very heavy demands|
|33NiCrMoV14-5||0.33||1.3||3.5||0.5||0.2||Generator shafts, high strengt & toughness components|
|36NiCrMo16||0.36||1.8||4||0.7||High strength mechanical engineering components|
|14CrMoV6-9||0.14||1.5||0.9||0.3||High strength welded components|
|30CrMoV9||0.3||2.25||0.25||0.2||High toughness crank shafts, screws, bolts|
|All grades with Mn between 0.5 and 0.9%|
Steel grades are selected to meet property requirements for a given application.
Demand of higher strength and toughness require increasing alloy content for improved hardenability:
Molybdenum’s most important role in these grades is to increase the hardenability and to promote a uniformly hardened microstructure across the full cross section.
This is illustrated with the following series:
|EN Code||SAE/ASTM||% Alloy content|
Adding 1% Cr increases the yield strength by approximately 50%; further addition of 0.25% Mo again raises the strength and extends through-hardening from 100 to 500 mm.
Adding 1% Cr improves the toughness values by 15%; further addition of 0.25% Mo extends excellent toughness to 500 mm cross section.
(The determination of the ruling heat treatment diameter for various geometries is standardized in DIN EN 17201)
Fig. 3 demonstrates the effect of Cr and CrMo additions on the mechanical properties at various carbon contents.
The desired combination of high strength and high notch impact energy is located in the upper right corner of the diagram.
Adding 1% Cr to plain carbon steel moves the property range into the desired direction. A further boost in the direction of high strength combined with adequate toughness is achieved through the addition of 0.25% Mo.