Causes of carburization in the process of making long strips of cemented carbide

1. Features: The surface of tungsten carbide strip products is black and shiny, and the cross-section has small graphite spots or nest-shaped spots. In severe cases, the product feels lubricated and has black marks when touched by hand.
2. Reason: The total carbon content in the cemented carbide strip is too high, or the carbon content of the filler is too high, or the concentration of hydrocarbons in the gas phase of the low temperature zone is too high, or the C in the graphite boat diffuses to In the sintered body, or when the molding agent is removed, the heating rate is too fast and the time is short, and the molding agent is cracked to generate free graphite and cause alloy carburization.
3. Sources of free carbon:
⑴ Cracking of forming agent in dewaxing (degumming) process
⑵ Diffusion of carbon in the graphite boat
⑶ Control of the sintering atmosphere in the vacuum furnace
4. Judgment: Carburization of long tungsten carbide products will generally affect the performance. It should be judged according to the requirements of each brand and application. Unqualified products should be returned to the production unit for processing.