Higher susceptibility to welding thermal cracking, prone to arc pit cracking and liquefaction cracking; prone to intergranular corrosion; prone to splitting brittle σ phase. Preheating and rapid cooling are not required to reduce the residence time in the sensitization temperature zone and high temperature to avoid intergranular corrosion and σ-phase and the occurrence of coarse cast organization. Strictly control the temperature between channels, preferably at room temperature, and certainly not beyond 100℃. It is necessary to polish the carburized layer after the carbon arc gas planer is cleared, and it is necessary for PT to acknowledge that there is no shortcoming, together with the polishing requirement to choose ceramic low sulfur grinding wheel or resin grinding wheel.


In addition to making the flange pipe expansion joint have outstanding anti-oxidation function and high temperature strength, it can press down the precipitation of brittle σ phase during the long time aging process at high temperature, which is seen to have outstanding arrangement stability. In the flange pipe expansion joint specification, Brinell hardness is the most widely used, and the indentation diameter is often used to indicate the hardness of the material, which is both intuitive and convenient. But about the harder or thinner flange pipe expansion joint material of flange pipe expansion joint pipe is not used. The flange pipe expansion joint flange pipe expansion joint experiment is the same as the Brinell hardness test, are indentation test method.
The difference is that it is measuring the depth of the indentation. The flange pipe expansion joint experiment is a very widely used method, in which HRC is second only to Brinell hardness HB in the flange pipe expansion joint tube specification. flange pipe expansion joint can be applied to determine the metal material from very soft to very hard, it makes up for the Brinell method is not, more concise than the Brinell method, can be read out directly from the hardness machine dial hardness value. However, because of its small indentation, the hardness value is not as correct as the Brinell method.