Liaoning heat-resistant steel - widely distributed

2022-06-13

Heat Resistant Steel Rental
Generally speaking, the definition of alloying element content less than 50% is heat-resistant steel. Japanese heat-resistant steel standards include JIS G4311, G4312 and various SUH series standards. According to the different matrix structures, heat-resistant steel can be divided into ferritic heat-resistant steel, martensitic heat-resistant steel, austenitic heat-resistant steel and drain type heat-resistant steel. JIS G5122 specifies SUH heat-resistant steel nozzles. However, steel products are not classified by primary structure. Ferritic heat-resistant steel, martensitic heat-resistant steel and austenitic heat-resistant steel are mixed together.
The representative ferritic heat-resistant steel is SUS430, low carbon 17% chromium, chromium is an element that improves the high temperature corrosion resistance of steel, and is an indispensable element in heat-resistant steel in Liaoning Province. SUS430 has good oxidation resistance. Since the steel does not contain other elements, SUS430 is cheaper. However, SUS430 does not harden due to shielding at high temperatures, and its high temperature resistance is low, so it can only be used for parts that do not require strength. On the other hand, since SUS430 has a small thermal expansion coefficient and austenitic heat-resistant steel has a large thermal expansion coefficient, when SUS430 is used, it is better to use more SUS430 than elements that are slightly thermally fatigued. The temperature changes repeatedly. If SUS430 is used for a long time at temperatures around 500 to C, additional spraying occurs due to brittle phase failure, which should be taken into account. In addition, aluminum is also an element that improves oxidation resistance. At high temperature, aluminum oxide is formed on the surface of the oxide scale, which acts as a strong protective film and antioxidant. Heat resistant steel using aluminum effect has fch1. fch1 is a heat resistant steel for the production of heating elements containing 5% aluminium and 25% chromium steel with good oxidation resistance and ER 1200-C.

common problem

Overheating Overheating of the microstructure after quenching can be observed from the rough mouth of the bearing parts. But to accurately judge the degree of its overheating must observe the microstructure. If coarse acicular martensite appears in the quenched structure of GCr15 steel, it is a quenched superheated structure. The reason for the formation may be the overall overheating caused by the quenching heating temperature is too high or the heating and holding time is too long; it may also be due to serious banded carbides in the original structure, forming local martensitic needle-like thick in the low-carbon area between the two bands, localized overheating. The retained austenite in the superheated structure increases and the dimensional stability decreases. Due to the overheating of the quenched structure and the coarse crystals of the steel, the toughness of the parts will be reduced, the impact resistance will be reduced, and the life of the bearing will also be reduced.

chemical heat treatment

Chemical heat treatment is to make the surface of the workpiece infiltrate the atoms of one or several chemical elements, thereby changing the chemical composition, structure and properties of the surface of the workpiece. After quenching and low temperature tempering, the surface of the workpiece has high hardness, wear resistance and contact fatigue strength, and the core of the workpiece has high toughness.

surface hardening

Case hardening and tempering heat treatment is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and effective hardened layer depth. Vickers hardness tester can be used for hardness testing, Rockwell or surface Rockwell hardness tester can also be used. The selection of the test force (scale) is related to the depth of the effective hardened layer and the surface hardness of the workpiece. There are three durometers involved here. 1. Vickers hardness tester is an important method to test the surface hardness of heat-treated workpieces. It can use a test force of 0.5-100kg to test the surface hardened layer as thin as 0.05mm thick. Its accuracy is yes, and it can distinguish the surface hardness of heat-treated workpieces. small differences. In addition, the depth of the effective hardened layer is also detected by a Vickers hardness tester. Therefore, it is necessary to have a Vickers hardness tester for units that perform surface heat treatment processing or use a large number of surface heat treatment workpieces. 2. The surface Rockwell hardness tester is also very suitable for testing the hardness of surface quenched workpieces. There are three scales for the surface Rockwell hardness tester to choose from. Various case-hardened workpieces with an effective hardening depth of more than 0.1mm can be tested. Although the accuracy of the surface Rockwell hardness tester is not as high as that of the Vickers hardness tester, it has been able to meet the requirements as a detection method for quality management and qualification inspection of heat treatment plants. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement, and direct reading of hardness values. Using the surface Rockwell hardness tester, batches of surface heat-treated workpieces can be quickly and non-destructively tested piece by piece. This has important implications for metalworking and machine building plants. 3. When the surface heat treatment hardening layer is thick, the Rockwell hardness tester can also be used. When the thickness of the heat treatment hardened layer is 0.4-0.8mm, the HRA scale can be used, and when the thickness of the hardened layer exceeds 0.8mm, the HRC scale can be used. The three hardness values of Vickers, Rockwell and superficial Rockwell can be easily converted to each other and converted into standard, drawing or user-required hardness value. The corresponding conversion table has been given in the international standard ISO, American standard ASTM and Chinese standard GB/T.

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