At the beginning of this century, the German automobile industry used high Ni alloy steel to produce high load truck gears. In 1928, the Cr Ni series steel ecn45 containing 4.5% Ni was adopted as the standard steel. The truck gear for the famous sports car silver arrow was made of ecn45 steel. During World War II, in order to save Ni, Cr Mn series truck gear steel was developed. After decades of continuous improvement and improvement, Cr Mn series truck gear steel has become the main variety of medium and small modulus truck gear steel. This kind of steel has cheap alloying elements and good performance. From the perspective of economy and resources, this kind of steel is still excellent, but its quality is not too stable, the combination of strength and toughness is slightly poor, and the grain coarsening tendency is slightly large.
The famous ZF company added trace B to Cr Mn series truck gear steel to form a unique ZF series truck gear steel, which is also widely used by automobile manufacturers. For heavy-duty truck gears with large modulus, Cr Ni series steel 18ernis containing 2% Ni replaces ecn45 steel. So far, the gear hardenability of Mercedes Benz and other automobile companies is still the best. With the promotion of the worldwide energy-saving wave and the continuous adoption of new processes, the material potential is gradually explored. The Cr Ni Mo steel 17CrNiMo6 (ZF steel) containing 1.6% Ni is gradually replacing 18crnis for large modulus and heavy load truck gears due to its good process properties.
In the United States, sae25 series steel containing 5% Ni was used to produce truck gears in the early stage. Before World War II, sae46 series containing 2% Ni and sae48 series containing 3.5% Ni were widely used. For the same reason, after the war, the United States developed sae4o series yoke steel and Cr Ni Mo series sae86 series truck gear steel containing 0.55% Ni. At present, sae86 (typically 8620) and SAE40 (typically 4023) series steels are used for small module truck gears, while sae46 and sae48 series steels of Ni Mo series are still used for large module heavy-duty truck gears.
In Japan, chromium steel and chromium phase steel are mainly used. For example, chromium steel scr415, scr415 and chromium aluminum steel SCM415, scm418, SCM420, scm421 and scm822 are widely used in Japanese automobile industry. Chrome steel is mostly used for gearbox gears of small cars. SCM415, scm418, scm42o and scm421 with low key content in chromium key steel are mostly used for transmission gears of medium and light trucks. Scm822 with high aluminum content and nickel chromium phase steels, such as sncm415 and sncm420, are mainly used for heavy truck gearbox gears requiring high hardenability and high core toughness.
In the UK, traditional nickel steel is still used, and Ni Mo en35 steel and Ni Cr Mo EN352 steel are used for light and medium-sized vehicles. Heavy duty vehicles use en355 steel with high Ni Cr Mo content.
In Germany, ZF series steel has gradually replaced 16mncrs and 20mncrs steel of Mn CR series for light and medium-sized truck gears, while 14nicr10, 14nicr4 and 14nicr18 steel are mainly used for heavy vehicles.
Due to different resource conditions and different development histories of metallurgical industry and automobile industry in various countries, the selection and processing technology of truck gear materials also have their own characteristics. The common feature of truck gear materials in industrial developed countries is multi variety and serialization, and there are different materials for truck gears with different modules. In terms of material composition, the development trend of medium and small modulus truck gears is from Ni containing steel to non Ni containing steel, while large modulus heavy truck gears are replaced by high Cr and Ni alloy steel with less Cr, Ni and Mo alloy steel.