Are you still worrying defect after steel bar hardening?
Steel bar performance will have defect after hardening, then what should we do? Forever hardening and tempering line can solve your problem.
In order to eliminate the residual stress produced during quenching, improve the plasticity and toughness of the material and obtain good comprehensive mechanical properties after the quenching, we need to do tempering for the steel bar after hardening.
1. The mechanical properties of steel bar after tempering
(1) Strength and strength after tempering at lower temperature for plastic carbon steel will slightly increase, but plasticity basically unchanged. When the tempering temperature is further increasing, the strength will reduce but the plasticity will increase.
(2)The hardness of the steel decreases with the increase of the tempering temperature. Carbon steel with high carbon content has a slight increase in hardness when carbide is precipitated.
(3) Toughness of carbon steel and a chromium-nickel steel in 250-400 ℃ after tempering decreased.In this case, he brittleness is called the first type of temper brittle or tempered martensite brittle. The toughness of chrome nickel steel in the 450- 600 ℃ temperingwill reduce again. The resulting brittleness is known as the second type of temper brittleness or high temperature temper brittleness.
2.The common defects after tempering
(1) Distortion is mainly due to quenching stress redistribution in the process of tempering, so we should use pressure tempering or straightening for the flat shape nad slender parts.
(2) Hardness is not qualified: After tempering using induction heat treating furnace, the parts hardness is too high or too low or uniform, the main reasion is that heating temperature is not uniform.
(3) Reticular crack: If there is surface decarburization for high-speed steel and high-carbon steel, the tempering inner layer is higher than the surface. The surface multi-directional tensile stress caused network cracks. At the same time, due to the surface fast heating speed, the surface will tempered firstly, then casing multi-directional tensile stress.
For high-carbon, high-alloy steel complex knives, molds and high-cold hard roll, due to hardening stress is large, if there is no timely tempering after hardening, it will has the risking of crack.
Important parts need to be tempered after hardening, so it is necessary to understand the performance and defects of the workpiece after tempering. Forever engineers have a wealth of experience, welcome to contact with us if you are facing such problems.
Overseas manager: Tom Wang
Phone: 0086-13303078975(whatsapp, wechat,line)
Specialist of induction heating equipment and system in China; Glad to be your business partner in induction heating field.
Post time: 09-22-2017