Types and application tempered

Depending on the performance requirements of workpiece, its tempering temperature tempering can be divided into the following categories:

(A) low-temperature tempering (150-250 degrees)

The resulting low-temperature tempering is tempered martensite. The goal is to maintain a hardened steel under high hardness and wear resistance of the premise, to reduce their stress and brittle hardening, so as not to crack or premature failure when used. It is mainly used for cutting and cutting all kinds of high-carbon, measuring tools, Die, Rolling and carburizing parts, tempering hardness is generally HRC58-64.

(Ii) tempering (350-500 degrees)

Tempers income is tempered troostite. The aim is to obtain a high yield strength, high toughness and elastic limit. Therefore, it is mainly used for a variety of springs and hot die processing, tempering hardness is generally HRC35-50.

(C) high-temperature tempering (500-650 degrees)

The resulting high temperature tempering is tempered sorbite. Customary combination of quenching and tempering heat treatment called quenching, which aims to get the strength, hardness and ductility, toughness good mechanical properties. It is widely used in automobiles, tractors, machine tools and other important structural parts, such as rods, bolts, gears and shafts. After tempering hardness is generally HB200-330. Chemical reaction atmosphere and metal

One. Chemical reaction atmosphere and steel

1. Oxidation
2Fe + O2 → 2FeO
Fe + H2O → FeO + H2
FeC + CO2 → Fe + 2CO

2. Restore
FeO + H2 → Fe + H2O FeO + CO → Fe + O2

3. carburizing
2CO → [C] + CO2
Fe + [C] → FeC
CH4 → [C] + 2H2

4. nitriding
2NH3 → 2 [N] + 3H2
Fe + [N] → FeN

II. The role of various atmosphere on metals

Nitrogen: In ≥1000 degrees will react with Cr, CO, Al.Ti
Hydrogen: can copper, nickel, iron, tungsten reduction. When the hydrogen in the water content of 0.2-0.3 percent, will make steel decarbonization
Water: When ≥800 degrees, iron, steel oxidation and decarbonization, which does not react with copper
Carbon monoxide: its reducing and hydrogen similar carburizing steel can

III. The impact of various types of atmosphere on the resistive element
Nickel-chromium wire, iron chrome aluminum: sulfur atmosphere harmful to the resistance wire