How to improve the quality of gear forgings?

2024-08-14 15:39:21

There are many things to pay attention to when forging Gears, but not every one needs to be strictly monitored. How to improve the quality of gear forgings? The following article mainly discusses it for everyone.

Hardness is an important quality inspection indicator for heat treatment of gear forgings. This is not only because hardness testing is fast, simple, and does not damage the forgings, but also because other mechanical properties can be inferred from the hardness value. Reasonably determining the hardness value after heat treatment will endow the forgings with good usability and play an important role in improving quality and extending durability.

In addition to requiring hardness values, other mechanical performance indicators must also be specified to improve the quality of gear forgings

1. Reasonable combination of strength and toughness. The strength and toughness of steel materials are usually interdependent. For structural forgings, one-time impact toughness is commonly used as a safety criterion, pursuing high toughness indicators without sacrificing strength, resulting in bulky and heavy mechanical products with short service life. On the contrary, for molds and tools, high hardness and strength (torsional strength) are pursued in order to improve wear resistance, while the role of toughness in reducing mold breakage and fracture is ignored, resulting in a short service life. Therefore, investigation and analysis should be conducted on the working conditions and failure modes of forgings, and the strength and toughness indicators that should be selected for forgings should be determined based on a reasonable combination of strength and toughness.

2. Properly handle the relationship between material strength, structural strength, and system strength. Various material strength indicators are measured using standard specimens, which depend on the material's microstructure state (including surface state, residual stress, and stress state). The structural strength of forgings is influenced by size factors and notch effects, while the system strength is related to the interaction with other forgings. There is a significant difference between these three, such as the high fatigue strength of smooth specimens of materials, but the actual fatigue strength of the material may be very low. Therefore, for certain important components, it is more appropriate to determine the mechanical performance indicators based on simulation test results.

3. The strength matching of the composite components should be reasonable. Numerous experiments and practical applications have shown that when the combination components (such as worm gears, chain sprockets, balls and rings, and transmission gears) achieve strength matching, their service life can be extended. For example, the hardness of the ball bearing should be 2HRC higher than that of the ring, and the surface hardness of the driving gear on the rear axle of a car should be 2-5HRC higher than that of the driven gear seat. The same type of steel processed into friction pairs with the same hardness using the same method has relatively poor wear resistance.

4. Surface strengthened forgings should have a reasonable matching of core and surface strength. When surface strengthening parts (such as carburizing quenching, carbonitriding quenching, nitriding, induction quenching, etc.), when the depth of the hardening layer is constant, the core should have appropriate strength to achieve a good match between the core and surface strength, in order to ensure that the forging has a high service life. If the strength of the heart is too low, the transition zone is prone to fatigue sources, leading to a decrease in fatigue performance; If the strength of the heart is too high, the residual compressive stress on the surface is small, and the fatigue life is not long.