Sintering temperature, too high temperature will make titanium carbide grain growth speed up.The final sintering temperature of titanium carbide high manganese steel cemented carbide is generally 1420℃.Sintering temperature should not be too high.Even the adhesive phase into liquid phase metal loss, so that the hard phase adjacent, aggregation and growth, the formation of fragmentation source.This is the reason why there is less phase transition between the hard grains.Of course, the sintering temperature should not be too low, otherwise the alloy will be underfired.In addition to the above mentioned to control the sintering temperature and speed, the vacuum degree in the furnace, when entering the phase of liquid phase sintering.Also control the sintering furnace vacuum, because too high vacuum will make a lot of liquid phase metal volatilization, resulting in component segregation.In particular, in the three stages of degumming, reduction and liquid phase sintering, the heating rate during sintering is not fast.
The heating rate and holding time should be strictly controlled.Because in the low temperature degumming stage, the blank release pressure and forming agent volatilization process, if the rate of temperature rise is fast, because forming agent too late volatilization and liquefaction into steam, make the blank burst or micro-crack phenomenon;In the reduction stage above 900℃, the compactor should have enough time to remove the volatile matter and oxygen in the used raw material powder (such as Mn2Fe intermediate alloy).When entering the phase of liquid phase sintering, it is necessary to slow down the rate of temperature rise to make the compacted blank fully alloyed.The sintering principle of steel bonded cemented carbide is the wetting principle, so that the liquid phase is fully wetting the solid phase (hard phase), otherwise the liquid phase metal FeMn will precipitate on the surface of the blank, or even loss.
Under the same condition, different components of industrial titanium plate will show different decarburization behavior.For example, Si can improve the elastic limit, strength, tempering stability and elastic decline resistance, because different alloy elements have different effects on carbon activity and diffusion.However, the serious decarburization of the surface caused by Si increasing carbon activity in austenite and chemical potential gradient must also be paid attention.The low carbon industrial titanium plate 28MnSiB trial-produced by shi ti company reduced the content of carbon silicon in titanium, effectively reducing the tendency of surface decarburization. The inspection results showed that the actual carbon content was 0.10%-0.16%, and the average carbon content was 0.12%, which met the requirements of the standard that the carbon content was less than 0.23%.
Surface strength of components is an important factor affecting fatigue strength.Surface heat treatment and surface cold plastic deformation are very effective in improving fatigue strength.Reduce fatigue crack formation.The removal of surface decarburization layer produced by heat treatment can significantly increase the fatigue limit.Direct shot peening without removing the surface decarburization layer produced after heat treatment can improve the limit of strain more than that after removing decarburization, such as surface hardening, carburizing, carbonitriding, nitriding, shot peening and rolling.The effective tensile stress and local non - uniform deformation can be reduced by increasing the surface strength.In order to reduce the impact of surface decarbonization, the surface peeling of hot rolled spring round titanium and the avoidance of surface decarbonization should eliminate or reduce the carbonization degree gradient between the two.Protective atmosphere heating is an effective measure to avoid or reduce surface decarburization.Fast induction heating should be adopted to shorten heating time and decrease decarburization depth