Improving the surface wear resistance, corrosion resistance, fatigue resistance and strength, is to extend component life, the rational allocation of performance, to ensure the stability of critical systems. Therefore, the surface heat treatment technology, has been of great concern, has developed rapidly, to improve the performance of various types of components are playing an increasingly important role.
According to statistics, more than 80% of mechanical products scrap parts caused by the failure is due to the surface, but the real strength of the material as a whole due to insufficient generation fracture or deformation of a small proportion of component failure (in fact, many parts of rupture, its crack The first is also generated from the surface).
Penetration depth is generally 0.1 ~ 1.5mm, a moderate depth, mainly for surface hardening. Surface organizations (martensite + carbide + retained austenite), the surface stress state of high compressive residual stresses. After quenching, the surface hardness of up to 58 ~ 65HRC, core hardness is generally about 30HRC, has good abrasion resistance, good contact fatigue strength, flexural fatigue strength, the ability of anti-adhesion and high impact toughness bite. Heat deformation tend to be larger, but not easy to crack. This process is suitable for low-carbon steel, alloy steel, such as 15,20,12CeNi3,20Cr2Ni4,20Cr, 15CrMo, 20CrMo, 20CrMnTi and other iron-based powder metallurgy and materials, mainly used for surface require abrasion resistance, fatigue, and good toughness heart heavy load parts. The process used by the lower cost of steel or moderate, high investment in equipment.
The process of diffusion layer is shallow, generally 0.1 ~ 1.0mm, mostly used for surface hardening. Surface organizations (carbonitride + nitrogen martensite + residual austenite), the surface is high compressive residual stress state. After quenching, the surface hardness of 60 ~ 65HRC, high abrasion resistance, good contact fatigue strength and good bending fatigue strength and good resistance to bite ability and good toughness. Tendency to heat deformation and cracking tendency with carburizing processes. This process is suitable for low-carbon steel, and iron-based powder metallurgy materials, such as carbon steel 40Cr, 35CrMo, 42CrMo and other low-carbon steel, carbon steel and iron-based powder metallurgy Materials with carburizing. The main requirements for surface abrasion resistance, fatigue resistance, toughness and heart in good part load.
The process of the diffusion layer is thin, generally 0.1 ~ 0.4mm, is mainly used for surface hardening. Surface organizations (nitrogen + carbon compounds containing nitrogen solid solution), the surface is high compressive residual stress state. After nitriding, surface hardness is generally 800 ~ 1200HV (63 ~ 71HRC), high wear resistance, but also has good contact fatigue strength, good bending fatigue strength, good resistance to bite ability and good toughness. Nitriding deformation and cracking tendency tendency small. Parts after nitriding, generally no longer be processed. Under special circumstances, only a small amount of grinding process. This process is suitable material for carbon alloy steel and ductile iron nitriding, such as 38CrMoAl, 3Cr13,35CrMo, 42CrMo, 20CrMnTiT, QT600-3 so on. The main requirement for high surface abrasion important parts.
Compound layer diffusion layer is generally 0.005 ~ 0.020mm, mainly used for surface hardening. Surface hardened layer organization (carbonitride layer + inner surface nitrogen diffusion layer), the surface of the high compressive residual stress state. After Nitrocarburizing, surface hardness is generally 500 ~ 800HV (50 ~ 63HRC), high wear resistance, contact fatigue strength and flexural fatigue strength is better, the best anti-bite ability. Nitrocarburizing processing deformation and cracking tendency tendency small. Nitrocarburizing treatment, usually the last step, and then the process is not allowed.
Depending on the choice of frequencies, the hardened layer in the range of 0.8 ~ 50mm, is mainly used for surface hardening. Surface martensite, the surface for the high compressive residual stress state. Surface hardness of up to 55 ~ 65HRC, high wear resistance, good contact fatigue strength, good flexural fatigue strength and good resistance to bite ability. Less deformation and cracking tendency. After induction hardening, usually go through grinding.
Flame hardening of the surface-hardened layer is generally 1 ~ 12mm, mainly used for surface hardening. Surface organizations quenched martensite, the surface for the high compressive stress state. Surface hardness of up to 55 ~ 63HRC, surface abrasion resistance is high, with good contact fatigue strength, good flexural fatigue strength and good resistance to bite ability. Small deformation hardening and cracking tendency. After the flame quenching, generally go through grinding. This process is suitable material for carbon steel. The main requirements for surface wear parts.
Optimum efficiency control of high frequency welded pipe in welding process
In most cases, optimized welding process, power loss can be reduced 50% and can improve the welding quality, reduce downtime, increase production.
Stress on the trench corrosion of high-frequency straight seam resistance welding pipe
Trench etching is generally believed that acute heat in the welding process, the results of local tissue metal and chemical change caused by quenching.
Technology of straight seam high frequency resistance welded steel pipe
Factors that affect the raw material for the steel pipe welding quality affect the quality of raw materials are mainly steel mechanical properties unstable surface defects and strip geometry deviation big three aspects, therefore, we should focus on these three aspects of control.
