The method of dealing with the overheating temperature of sprocket forgings

After forging, in order to prevent surface cracking, high carbon steel and high alloy steel forgings need to be stacked after forging, cooled in furnace, buried in sand or baked in front of furnace, and then heat treated in time. Forging greatly improves the forging density and service life of the sprocket. The most important of these is heat treatment. In terms of experience, the sprocket is made of 42CrMo forging material, normalized, quenched and tempered HB240-280, and then surface quenched to HRC45-50. Heat-treated sprockets are much more wear-resistant and steel is much more practical. If the working environment is harsh and the frequency of use is high, South Korea’s overall spray quenching technology can be used, and the quenching depth can reach 15-20mm. On the premise that the overall internal structure of the sprocket is uniform, the wear depth will also be provided. At present, the domestic quenching depth can only reach 3-8mm. If the depth is increased to 15-200mm, the service life of the sprocket forging will also increase by 2-3 times.

Austenitic stainless steels need to be in water immediately after forging. The aim is to maintain its existing particle size as quickly as possible, not to grow. At the same time, I don't want to precipitate more internal tissue or particles and then do a solution treatment. Sprocket forgings are usually driven by chains and racks, with large shaft spacing, constant transmission ratio, strong vibration absorption capacity, certain adaptability to harsh environments, and small force for reliable work on the shaft. It is suitable for low-speed, heavy-load and high-temperature conditions. It has a wide range of transmission power and speed, compact structure, large transmission ratio, high efficiency, and long service life. It can be used in environments where the center of the two shafts is far away. Sprocket forgings are usually driven by a chain and rack, with the gears meshing with each other. Compared with gears, sprocket forgings are available in single row, double row and multi row.

All other conventional medium-low carbon steel and medium-low alloy steel forgings must be air-cooled after forging. Its purpose is to make it cool evenly, have a uniform structure, and have uniform performance, prevent grain growth and mixed crystals, and facilitate writing marks. The surface temperature of ferrous metal forgings before heat treatment should not be less than 50°C to prevent white spots.

Carbon steel forgings need to process blanks before forging, so overheating during the heating process means that the metal blanks used in carbon steel forgings are heated at too high a temperature, stay in the specified forging and heat treatment temperature range for too long, or the thermal effect is too high to cause grains thick. After the carbon steel forging is overheated, the Widmanstatten structure will appear. After the martensitic steel is overheated, the intragranular texture often appears, and the overheated structure is often judged by the keratinization of carbides. After the titanium alloy is overheated, there are obvious β-phase grain boundaries and straight and slender Widmanstatten structure. After the alloy steel is overheated, the fracture will appear stone fracture or strip fracture. Overheated structure, due to coarse grains, will reduce mechanical properties, especially impact toughness.