U-type Quenching on Valve lock groove surface

With the increasing engine power and emission standards, the design and application of single-cylinder with four-valve and multi-valve are more and more common. Then the valve stem diameter is thinner, and the lock groove is changed from a single to a multi-groove, which is more suitable for use. Due to the smaller diameter of the valve stem and the multi-groove, the bottom diameter of the groove becomes the weakest part, so we need to change the traditional process in order to improve its mechanical properties and matching precision.

For example, about FAW 36D and 29D valve, the valve lock slot has the highest failure Rate after we visit a number of service stations and repair shops. Many domestic factories have different proportions of failure. This failure can damage the cylinder head or even damage the engine block and bring great losses to users. We analyzed and tested the faulty parts & related parts, compared the similar products, and found that the badly worn of old parts, lower of matching precision for new parts. The valve assembly has serious quality defect, the main problem is that the matching clearance is too large.

Our company introduced advanced equipment and adopted a new technology of uniform rotation heating and cooling (U-type quenching) at the beginning of 2012, it meets or exceed the original OEM design drawing.

Surface quenching technology (U-type quenching) is currently only available in a few valve manufacturers in China. The technical characteristic of our products is uniform hardness. Within the diameter 1.5mm, the detection base surface with 0.15mm, the hardness is 50, 50, 48, and 44 HRC, which is the optimum range of the drawing.

During the production process, we control the groove type and size, and the depth & length of quenching, but the matching precision is very important. Therefore, we checked strictly the valve lock pieces to achieve the optimally matching situation, at the same time, we remind the repairman to check the valve spring and the valve seat to avoid accidents.