20G seamless steel cryogenic deformation and annealing studi
20G seamless steel cryogenic deformation and annealing studies 12Cr1MoVG
20G and 12Cr1MoVG boilers with high-quality carbon steel, alloy steel representatives, in practice, has been widely used and developed. 12Cr1MoVG is the early development of successful application of the more mature and strong low-alloy steel pearlite heat, low carbon content, technology, thermal conductivity, and has a high creep rupture strength and ductility. Generally used in the manufacture of steam at temperatures below 540 ℃ collection box, steam pipes, metal wall temperature does not exceed 580 ℃ superheater, reheater and some casting and forging, high-parameter power plant is currently the most common main steam pipes, tubes of steel reheat. With the needs of the operating parameters and unit capacity of the power plant units as well as a sharp increase in temperature boiler to large diameter pipeline development, and promote the further study of high-temperature high-strength boiler tubes, and produce domestic hot-rolled (pull) the largest seamless steel pipe outside path specifications of 720mm, larger diameter seamless steel pipe thermal expansion path only through other processes to achieve. Relatively high production costs and production equipment is expensive in terms of hot-rolled seamless steel tubes used with the production process is simple, stable quality, economical and practical features of standard thermal expansion push technology, you can make pipe diameter increases in a short period of time, and low-cost, high production efficiency. Precisely because of this, as smelting, pushing standard hot-rolled steel pipe mainline expansion extends well to fill the domestic major steel production of non-standard and special types of large diameter seamless steel pipe blank lack solve the special needs of users .
Standard push a special thermomechanical treatment process is the essence of thermal expansion pipe. Through low-temperature deformation and annealing 12Cr1MoVG 20G seamless steel pipe and through the original heat-treated steel subsequent comparative analysis study microstructure, mechanical properties at room temperature, etc., and with reference to GB5310-2008 standards were evaluated.
Experiment with the chemical composition of the material to meet the requirements of GB5310-2008. Push standard cryogenic deformation annealing specification main parameters are: 20G (Flaring temperature 80 ~ 730 ℃, expanded diameter ratio 1.30, flaring speed 300mm / min, coil size 750mm, coil frequency 2500Hz and 910 ℃ normalizing heat treatment); 12Cr1MoVG (expansion tube temperature 750 ~ 800 ℃, expanded diameter ratio 1.27, flaring speed 170mm / min, coil size 750mm, coil frequency 2500Hz and 990 ℃ normalizing + 740 ℃ tempering).
The results showed that the use of low-temperature deformation annealing standard push production 20G, 12Cr1MoVG seamless thermal expansion pipe retained ferrite + pearlite structure of the original pipe, its grain size, non-metallic inclusions and room temperature mechanical properties are reached GB5310-2008 the request, from an economic cost, energy saving and low-carbon economy today advocated the practical requirements of view, 12Cr1MoVG subsequent heat treatment may be omitted. 20G seamless band structure produced after the original tube cryogenic deformation annealing, can be eliminated by subsequent normalizing heat treatment, and subsequent heat treatment tube has good overall performance, meet the requirements of GB5310-2008.