Binnenlandse productie van tandwielstaal

With the introduction of advanced foreign models, the localization of various gear steels has brought my country's gear steel to a new level. German Cr{{0}}Mn steel, Japanese Cr-Mo series steel, and American SAE86 steel meet the requirements of medium and small modulus gear steels. Some domestic truck gears use American brand SAE882H steel, such as 8t and 1{{10}}t bridge bevel gears use SAE8822H, the main chemical composition (mass fraction, percent ) of this steel is 0.19-0.25C, 0.70-1.05Mn, 0.15-0.35 Si, 0.35-0.75Ni, 0.35-0.65Cr, 0.30-0.40Mo. The literature believes that controlling the hardenability is the key to solving the problem of gear distortion. To reduce distortion, H steel with Jominy hardenability bandwidth below 4HRC should be used. The precision (contact area) of gears made of H steel after heat treatment is 70 percent to 80 percent higher than that of ordinary steel, and the service life is prolonged. Therefore, industrially developed countries have successively stipulated the hardenability zone of carburized alloy structural steel. Limit the hardenability zone to a very narrow range (4-5HRC) as needed. 1) When ordering in Germany, the hardenability of the steel can be required to be within a given range, or the hardenability of the steel can be narrowed. 17CrNiM06 is very suitable for manufacturing high-modulus and heavy-duty automobile gears. The main chemical composition (mass fraction, percent ) of this steel is 0.15-0.20C, 0.40-0.60Mn, 1.50-1.80Cr, 0.25-0.35Mo, 1.40-1.70Ni. This steel has been produced and used in my country. The literature believes that in the carburizing process of 17CrNiM06 steel gears, while appropriately reducing the carbon potential at the later stage of carburization, the cooling rate after carburization is increased, and air cooling is changed to air cooling to prevent the formation of large carbides, and then high temperature at 630cC Tempering, to precipitate part of alloy carbides, in order to reduce the amount of retained austenite during secondary heating and quenching at 820 degree , and finally obtain a better metallographic structure. 2) The "Styer" heavy-duty truck plant in Austria requires a hardenability bandwidth of 7HRC. 3) Japanese medium- and heavy-duty trucks, such as "Hino" brand KB222 9t trucks and "Nissan" brand CKL20DD 8t trucks, widely use Cr-Mo series steels for transmission gears and rear axle gears, such as SCM420H and SCM822H steels, which are equivalent Domestically produced 20CrMnMoH and 22CrMoH steels in my country.

This type of steel has high hardenability. Within a certain range, the bending fatigue life of the gear increases with the increase of hardenability. The literature pointed out that Changchun FAW started to use 20CrMnTiH steel when producing "Jiefang" brand 9t truck rear axle gears, even if it uses steel with hardenability of group Ⅱ (J9=36-42HRC), the tooth center of the gear wheel after heat treatment The hardness is only 22-24HRC, which does not meet the requirements of the gear technical conditions. When the car is in use, the driving and driven bevel gears of the rear axle will be damaged early. Therefore, Ct-Mo steel with higher hardenability has to be selected. Its main composition refers to Japanese SCM822H gear steel. The main chemical composition (mass fraction, percent ) of this steel is: 0.19-0.25C, 0.55-0.90Mn, 0.15 -0.35Si, 0.85-1.25Cr, 0.35-0.45Mo. After negotiating with the steel mill, a new domestically produced steel grade 22CrMoH was produced, with a hardenability index of J9=36-42HRC, which satisfies the requirements of automobile gears. However, the process performance of this steel is poor, and the gear forging blank can be cut after isothermal annealing treatment. The hardness is 156-207HB, and the metallographic structure is proeutectoid ferrite plus pseudo-eutectoid pearlite. This steel has high hardenability. Normal normalizing is easy to produce granular bainite. The appearance of granular bainite is extremely unfavorable for cutting. It not only greatly reduces the service life of the tool, but also due to the appearance of abnormal structure, it is always accompanied by Due to the inhomogeneity of the metallographic structure, the gear heat treatment distortion will eventually increase. 4) American automakers are trying to reduce production costs while improving the reliability and durability of parts. This requires a high degree of consistency in product geometric dimensions and mechanical properties. To improve the consistency of product performance for heat-treated parts, it is necessary to reduce the degree of dispersion of the hardness of the parts after quenching, which is directly related to the width of the steel's hardenability band. The consistency of the hardness of the gear core will reduce the distortion of the heat treatment, thereby improving the accuracy of the gear, and making the residual compressive stress distribution on the surface of the gear more uniform. American truck transmission gears and rear axle driving bevel gears are made of SAE8620 steel and SAFA820 steel. American SAE8620H, SAE8822H and other grades of steel have also begun to be produced and used in my country (such as Baosteel Group Shanghai Steel No. 5 Plant, etc.), respectively, for medium-duty truck transmission gears and rear axle bevel gears.