There are a lot of matters to pay attention to gear forging
, but not every item should be strictly paid attention to, how to improve the quality of gear forging? The following article is mainly to tell you.
Hardness is a very important quality test index of gear forgings heat treatment, not only because the hardness test is fast, simple and does not damage the forgings, but also from the hardness value can infer other mechanical properties, reasonable determination of hardness after heat treatment will give the forgings with good performance, to improve the quality, prolong the durability has an important role.
In addition to the hardness value, other mechanical properties must be specified:
1. Reasonable coordination of strength and toughness. Usually the strength and toughness of iron and steel materials are mutual ebb and flow. For structural forgings, a common impact toughness as a criterion of safety, the pursuit of high toughness index, without sacrificing strength, resulting in heavy and bulky mechanical products, not long life. On the contrary, for the mold, in order to improve wear resistance and pursue high hardness and high strength (torsional strength), but ignore the toughness to reduce the role of the mold blade collapse and fracture, the service life is not long. Therefore, the working conditions and failure forms of forgings should be investigated and analyzed, according to the strength and toughness reasonable coordination to determine the strength and toughness of the forgings should be selected.
2. Correctly handle the relationship between material strength, structural strength and system strength. Various material strength indicators are measured using standard samples, which depend on the microstructure of the material (including surface state, residual stress and stress state). The structural strength of forgings is affected by size factors and notch effect, while the system strength is related to the interaction of other forgings. There are great differences between these three, such as the material of smooth test rod fatigue strength is high, but the physical fatigue strength may be very low. Therefore, it is more appropriate to determine the mechanical properties of some important parts according to the simulation test results.
3, the strength of the assembly should be reasonable. A large number of tests and actual use show that when the assembly (such as worm gear and worm, chain sprocket, ball and ring and transmission gear) reach the strength match, the service life can be extended. For example, the hardness of the ball should be 2HRC higher than that of the ring, and the surface hardness of the driving gear of the rear axle of an automobile should be 2 to 5HRC higher than that of the driven gear seat. The same steel treated by the same method into the same hardness friction pair, wear resistance is relatively poor.
4, surface strengthening forgings, heart and surface strength should be reasonable match. Surface strengthening parts (such as carburizing quenching, carburizing quenching, nitriding, induction quenching, etc.), when the hardening layer depth is certain, the heart should have the appropriate strength, so that the heart and surface strength to achieve a good matching state, in order to ensure that the forging has a high service life. If the core strength is too low, the transition zone is easy to produce fatigue source, resulting in the decline of fatigue performance; If the core strength is too high, the surface residual compressive stress is small, and the fatigue life is not long.
this is open die forging produced by tongxin precision forging company