Study on Low Temperature Deformation Annealing of 20G and 12Cr1MoVG SMLS Pipe

12Cr1MoVG is an early successful development, the application of more mature low-alloy pearlite heat steel, low carbon content, process, thermal conductivity, and has a high lasting strength and lasting plasticity. Generally used in the manufacture of steam temperature below 540  in the header, steam pipe, metal wall temperature does not exceed 580  superheater, reheater and part of the casting and forging, is the current high-parameter thermal power plant application of the most common main steam pipe, reheater pipe one of the steel. With the rapid increase in operating parameters and stand-alone capacity and the need for high-temperature boiler piping to large-caliber development, the further research on high-temperature and high-strength boiler tubes is promoted. At present, the domestic production of hot- Diameter specifications up to 720mm, larger diameter smls pipe can only be achieved through the thermal expansion process. High production cost and production equipment expensive hot-rolled smls pipe, the use of a simple production process, stable quality, economical and practical characteristics of the push-type thermal expansion process, in a short period of time to increase the diameter of steel pipe, And low cost, high production efficiency. It is precisely because of this, as the smelting, rolling pipe extension of the main push of the hot-rolled steel pipe to fill the major domestic and foreign steel production of non-standard, special type of large diameter seamless steel pipe blank, to solve the special needs of users.

The push-type hot-rolled steel pipe process is essentially a special heat treatment. The microstructures and mechanical properties of 20G and 12Cr1MoVG smls pipe, the original pipe and the subsequent heat treatment steel tubes were evaluated and compared with GB5310-2008 standard.

The chemical composition of the experimental materials conforms to the requirements of GB5310-2008. The main parameters of the push-type low-temperature deformation annealing specification are: 20G (expansion temperature 80 ~ 730 , expansion ratio of 1.30, expansion tube speed 300mm / min, coil size 750mm, coil frequency 2500Hz and 910  normalizing heat treatment); 12Cr1MoVG Tube temperature 750 ~ 800 , diameter ratio of 1.27, expansion tube speed 170mm / min, coil size 750mm, coil frequency 2500Hz and 990  normalizing +740  tempering).

The results show that the 20G, 12Cr1MoVG seamless hot-rolled steel pipe produced by push-type low-temperature deformation annealing retains the ferrite + pearlite structure of the original pipe, and its grain size, non-metallic inclusions and room temperature mechanical properties are in the form of GB5310-2008 Of the requirements, from the economic costs, energy-saving emission reduction and the current low-carbon economy to promote the reality of the requirements of view, 12Cr1MoVG follow-up heat treatment can be omitted. 20G smls pipe after the low temperature deformation of the ribbon after the organization can be followed by normalizing heat treatment to be eliminated, and follow-up heat treatment tube has a good overall performance, in line with the requirements of GB5310-2008.