Definition and classification of hottest steel mat

Definition and classification of steel materials

I. carburized steel

has a high-carbon wear-resistant surface and a low-carbon high-strength toughness center, which can withstand huge impact load, contact stress and wear. In automobile, engineering machinery, machine manufacturing and other industries, gears are widely used. The core structure of carburized parts is about 50% martensite plus other non martensite structures. For important applications (such as aviation carburized gears), the core structure should also be martensite or martensite/bainite structure. The commonly used alloy elements to improve hardenability are chromium, manganese, nickel, molybdenum and boron. From the economic point of view of alloying, Cr Mo steel is more superior. Carburizing steels with important applications and high quality requirements generally contain a certain amount of molybdenum, especially for heavy-duty Lei carburized parts

after the performance of the careful part is determined, the microstructure and performance of the infiltrated layer play a decisive role in the service life. The microstructure of the infiltrated layer is required to be full martensite and alloy carbides with fine, spheroidal and spherical distribution by using energizer. The core of ensuring the microstructure of the infiltrated layer is still hardenability. The infiltrated layer should have high hardness, good microstructure, reasonable residual stress distribution and certain toughness reserve

II. Nitriding steel (nitriding steel)

steel suitable for nitriding (or nitriding) process, called nitriding steel or nitriding steel. Generally speaking, in a narrow sense, it refers to a special kind of steel specially designed, smelted and processed for nitriding parts. Its typical representative is 38CrMoAl

machine parts made of nitrided steel can obtain extremely high surface hardness, good wear resistance, high fatigue strength, low notch sensitivity, certain corrosion resistance and high thermal stability after nitriding treatment. Nitriding treatment is used to treat some wear-resistant parts or precision parts working at higher temperatures, such as crankshaft of internal combustion engine, cylinder sleeve, steam valve and spindle of boring machine. The current efficiency of zinc electrodeposition process can be increased by 2% to 6% The cell voltage can be reduced by 0.050.15v, the current density can be increased to more than 1000a/m2, the grade rate of 0# zinc is high, and the product purchase cost is lower than that of traditional lead based alloy anode plate and spindle sleeve, precision gear and industrial machine tool screw rod

III. The following points should be considered for the alloying of Nitrided Steel:

(1) quenching and tempering treatment should be carried out before nitriding. Nitrided steel should first be quenched and tempered steel, that is, it has sufficient hardenability. Chromium, manganese and molybdenum are effective elements to improve hardenability

(2) in order to keep the strength of the steel unchanged after heating for a long time at nitriding temperature (500 ~ 570 ℃), molybdenum and vanadium are added to the steel. In order to prevent or reduce the brittleness of high temperature tempering, 0.2% - 0.5% Mo was added to steel in the first National Engineering Laboratory approved by Yantai

(3) it is reported that when nitriding, infiltration α The nitrogen atoms of the phase matrix are soluble in α Chromium, molybdenum, tungsten, vanadium, aluminum and other elements in the phase are fully bonded to form alloy nitrides, which are fine particles, and α The phase matrix maintains coherent and dispersed distribution, plays a role of precipitation, improves the hardness of nitriding layer, and can maintain dispersion state and high hardness for a long time at nitriding temperature