First, carbon steel castings heat treatment inspection rules
Considering the complex shape of valve castings, easy to deformation and cracking, the heat treatment of carbon steel castings is usually annealing. Cast steel parts customized
The inspection focuses on monitoring whether the supplier is carried out in accordance with the following heat treatment specifications, and checking the hardness value of the casting. Marine steel castings customized
one Attention points of carbon steel castings during heat treatment
1.1 Whether the furnace temperature rises slowly when it rises to 650℃~800℃
Because in the heating process, especially for carbon steel castings with complex shapes, when the furnace temperature rises to 650 ° C ~800 ° C, it should be slowly heated up, or held at this temperature for a period of time. Because the carbon steel phase change in this temperature range, accompanied by volume change, phase change stress, if the rapid temperature rise, easy to make the casting thin wall part and thick wall part and the temperature difference between the surface layer and the center layer increases, so that the thermal stress of the casting increases, easy to lead to casting cracking.
1.2 Whether the holding time is sufficient
In order to make the temperature inside and outside the casting consistent, and have enough time for the structure to be completely transformed, the holding time of the thick-wall casting is longer than that of the thin-wall casting.
1.3 When carbon steel castings are annealed, they are generally cooled with the furnace.
Second, austenitic stainless steel castings heat treatment inspection rules
Heat treatment of austenitic stainless steel castings usually adopts solid solution treatment and stabilization treatment to make them have the best corrosion resistance.
The inspection focuses on monitoring whether the supplier is carried out according to the following heat treatment specifications.
1. Solid fusion treatment of austenitic stainless steel
The purpose of solid melt treatment is to make the carbide in the steel completely melt and obtain single-phase organization, the method is to heat the casting to 950℃~1175℃, the heating method should be used first low temperature preheating, and then accelerate the heating to the solid melt temperature process, in order to reduce the temperature difference between the surface and the core of the steel casting during the heating process, the solid melt holding time is determined by the thickness of the steel casting wall. Generally, it is calculated according to the wall thickness of 2.5~3min insulation per mm to ensure that all sections of the casting can be heated through. After solid melting and insulation, it is quenched into water, oil or air, and water is commonly used. Air cooling is only applicable to thin-wall castings.
2. Stabilization of Austenitic stainless steel castings
In order to prevent the "sensitization" phenomenon of Austenitic stainless steel castings, alloy elements such as titanium and niobium are added to the steel, and after solid fusion treatment, stabilization treatment is then implemented, that is, the casting is re-heated to 850 ° C ~930 ° C, and the carbon in the steel is fully combined with titanium and niobium to form a stable carbide.
Changshu Hongqiao Cast Steel Co., Ltd. mainly produces various specifications of carbon steel, high, middle and low alloy steel, stainless steel, heat-resistant steel, high manganese steel, high chromium cast iron. For petroleum, chemical industry, metallurgy, mining machinery, coal mining machinery, wind power, nuclear power, Marine and other industries to provide high-quality steel casting, and export abroad. ABS Marine engineering service Marine steel casting custom steel casting custom BOP steel casting production