Tool heat treatment process operating skills

The majority of the heat treatment process cycle operation is a collective operation. Therefore, heat treatment processing technology boundaries are not clear, such as a number of parts quenching may be completed by the two shifts, quenching and tempering often consists of two service completion, coupled with the uneven quality of workers, small enough to improve management practices, production The process often appears quality problems. Problems, analyze problems, to find out why, is not only time-consuming, laborious, and sometimes can not find the real reason.
1 carburized gear low hardness
Record 800 (capsule) the infusion Unicase gas carburizing furnace nitride carburized gear claim after carburizing surface hardness 58 ~ 63HRC, when the sampling parts of the surface hardness of 52 to 56HRC. Carburizing, quenching; quenching heating or cooling problem, and sometimes difficult to conclude. Emergency batch of gear production tasks, the author has been detected gear to take three tied with wire, re-heated in a salt bath furnace, quenching in an oil bath, about 30 ~ 40 minutes after the last detected quenching hardness 63 ~ 65HRC . Hardening group of gear pump Jian hardness, all qualified. This way to cut the Gordian knot, although not necessarily able to identify the real cause of the problem, but to solve the urgent needs of the production.
2 bar quenching cracks
There are a number of 14mm x 240mm 40Cr the pensions materials by quenching and tempering is buried, after about a week (when used) was discovered almost all the crack, the crack shape the longitudinal single crack, the majority of crack through both ends of the bar surface. Judge quenching cracks crack the duty operator has failed to honor it. Check the job log, can only be found in the the batch bar for the second class quenching, three shifts tempering, parts and materials, quenching temperature and the cooling medium and process parameters are not recorded. I take a bar with 45 steel joints with heated in a salt bath furnace, and then quenching in salt water, after cooling about 20 ~ 30 minutes, the bar cracking, and the shape of the crack and the crack shape. In the face of the facts, the operator admitted mistakenly batch bar as 45 steel quenched.
Box-type resistance furnace annealing uneven hardness
The process route: annealing → band saw cutting → the roughing → quenched → fine cars → grinding → nitride. Band saw cutting, often find a bar on the uneven hardness, the local high hardness, low efficiency of the cutting blade wear quickly. After analysis, the front bar length due to the installed furnace or bar. The box-type resistance furnace mouth neither heating resistance wire, heat loss, so for the average box-type resistance furnace, furnace installed parts from the furnace inside the mouth 200 to 300mm, in order to ensure uniform heating temperature of the furnace parts.
 4 cast iron quenching should be controlled micro-alloying elements
Thermal conductivity of cast iron. Poor, ships oil cold quenching. The matrix of the cast iron and steel, is also composed of pearlite and ferrite. Cast iron with high carbon content, the increase in carbon content can increase hardenability, but after all, do not increase. Therefore, to improve hardenability of cast iron: they rely on micro-alloying elements in cast iron control good content of alloying elements, in order to ensure the quality of heat treatment and quenching.