Quench crack happen in rolled forging is a headache for both suppliers and clients. In this post, we are going to present 7 common tips for quenching crack that may help you prevent the potential risk.
- 1. Proper selection of steel for the process. This largely relies on the designer and product engineer. As a forging supplier, all we need to do is to purchase qualified steel and implement strict incoming inspection as per customized requirement.
- 2.No overheating. Coarse grained steels, usually generated by overheating during the austenitizing portion of the heat treatment cycle, increase hardening depth and are more likely to quench cracking compared with fine grain steels.
- 3.Proper quenching media. If the steel is an oil hardening steel, the use of some overly aggressive quenchants, such as water, brine, or caustic will get the steel harder, resulting in cracking. In YT component, we will double confirm with clients before deciding oil or salt quenching.
- 4.Don’t wait too long between the quenching and the tempering. If parts are not tempered right away, quench cracks can (and will) occur. For example, all the parts supplied to TIMKEN in YT components will be tempered within 4 hours after quenching.
- 5.proper entry of the part/ delivery of the quenchant to the part. This is ignored in most cases. When parts are put together in a basket, the parts along the edges cools faster than those in the center. Part layout can also affect quenching media delivery and effectiveness.
However, even we double check the above points, there is still chance that an instant failure can occur when the stresses are acting in the same direction. How do the stress be created? When material are heat treated to very high strength level, it may contain concentrations of high residual stresses. And it is hard to distinguish from examination, because of brittle failure mode, or lack of decarburization on surface of the fracture.
