Production of 12Cr1MoVG seamless steel pipe
 
Production and welding process of 12Cr1MoVG seamless steel pipe
 

(1) 12Cr1MoVG seamless steel pipe forging and rolling
The initial forging temperature of 12Cr1MoVG seamless steel pipe is 1180~1145℃, the final forging temperature is greater than 850℃, and it is cold after forging.
 
 
(2) Hot and cold processing of 12Cr1MoVG seamless steel pipe
The small diameter 12Cr1MoVG steel pipe can be cold-bent without heat treatment after bending. Large-diameter thin-wall 12Cr1MoVG pipe can be cold-bent, and high-temperature tempering heat treatment is required after bending. Large-diameter thick-walled pipes are hot-bent. The heating temperature of the hot-bent pipe is 980℃, and the final bending temperature is >800℃. After bending, normalizing and tempering heat treatments are also required.
 
 
(3) 12Cr1MoVG seamless steel tube heat treatment
The finished 12Cr1MoVG steel pipe should be subjected to normalizing + tempering heat treatment. The heat treatment specification is more sensitive to the performance of the steel.
Recommended normalizing temperature is 980~1020℃. The holding time is 1 minute per millimeter of wall thickness, but not less than 20 minutes;
The tempering temperature is 720~760℃, and the holding time is more than 2 hours. When the wall thickness is greater than 30mm to 40mm, forced cooling should be performed; when the wall thickness is greater than 40mm, it should be tempered.
The quenching temperature is 950~990℃, the tempering temperature is 720~760℃, and the holding time is more than 2 hours. When the final rolling temperature of the steel pipe is 980~1020℃ normalizing temperature, hot rolling can be used instead of normalizing.
The normal structure of the finished 12Cr1MoVG steel pipe after heat treatment is ferrite + pearlite + bainite. If the tempering heating temperature is too high after normalizing, there will be a phase transition point product that is not allowed to exist-yellow block martensite, tempering Low temperature tends to cause embrittlement.
 
 
(4) 12Cr1MoVG seamless steel pipe welding process:
Welding materials: manual welding, gas shielded tungsten electrode and melting electrode automatic welding or submerged arc automatic welding, etc. For small-diameter 12Cr1MoVG thin-walled steel pipes, argon arc welding can be used for bottoming, manual welding or automatic welding of the cover surface. For boiler headers, large-thick wall 12Cr1MoVG steel pipes can be welded with argon arc welding for submerged arc automatic welding. The welding seam of the pipe seat can be welded by using the method of inner hole argon arc welding and manual welding of the cover surface. Manual arc welding uses E5515-B2-V (R317) electrode, and automatic welding uses H08CrMoV welding wire. Although the steel has good weldability, it has the tendency of cold cracking and brittleness. It should be preheated at 200~250℃ before welding (small diameter thin-walled steel can not be preheated before welding), and should be 700~740 after welding. ℃ stress relief heat treatment.