Tempered steel, generally refers to the carbon content in 0.3-0.6% of medium carbon steel.

1 introduction

The so-called tempered steel, generally refers to the carbon content in 0.3-0.6% of medium carbon steel.Generally, the parts made of this kind of steel are required to have good comprehensive mechanical properties, that is, to maintain a high strength and have good plasticity and toughness, people often use tempering treatment to achieve this purpose, so people used to call this kind of steel tempering steel.Tempered steel is widely used in the structural parts of all kinds of machines.

Quenched martensite in the temperature range of 500~650℃.After tempering, the strength, plasticity and toughness of the steel have a good match.The composition of tempered steel is carbon 0.25% ~ 0.5% carbon steel or low alloy steel and medium alloy steel.Tempered steel is widely used in the structural parts of all kinds of machines.The most widely used quenched steels are chromium quenched steels (such as 40Cr, 40CrSi), chrome-manganese quenched steels (such as 40CrMn), chrome-nickel quenched steels, (such as 40CrNiMo, 37CrNi3A), boron-containing quenched steels, etc.

2 performance characteristics

In addition to the general metallurgical low and high power structure requirements.the main mechanical properties of steel,and the cold brittle transition temperature.fracture toughness and fatigue resistance, which are closely related to the reliability.Under specific conditions, it is also required to have wear resistance, corrosion resistance and certain heat resistance.Due to the use of high temperature tempering,the stress in the steel can be completely eliminated, the hydrogen embrittlement failure tendency of steel is small, the notch sensitivity is low, the brittle failure resistance is large.

Most tempered steel are of medium carbon alloy construction with yield strength (0.2) of 49-1200 mpa.It is a low carbon alloy structural steel with a yield strength (0.2) of 490-800mpa and high plasticity and toughness.A few precipitated hardened tempered steels with yield strength (0.2) up to more than 1400Mpa belong to high strength and ultra high strength steel.

to be continued.

Ms Sharon Wan

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