However, super duplex steel is sensitive to the third phase precipitation, such as intermetallic compounds, and how to control the process in welding and heat treatment is a difficult problem in the production of this product.
Mature Super Duplex Steel S32750 welded pipe manufacturing process is:
1, the process is specific: raw material inspection-steel plate ultrasonic flaw detection-planer edge-molding-pre-welding--the whole circle-cutting-welding-fixed diameter + heat treatment-pipe end plus-weld ray inspection-pipe end penetration test-hydraulic test-pickling passivation-finished product inspection Mark Packaging Person library.
2, molding in the production of straight seam welded pipe, the production difficulty lies in the effective application of bending moment to the edge of the steel belt, the use of traditional molding technology is difficult to solve, and duplex stainless steel yield strength of about twice times the ordinary austenitic stainless steel, its molding is more difficult. FFX (Flexible molding) as a new molding technology cleverly uses the tension effect when the coil is bent to maximize the bending moment to the edge of the steel strip, and by using the favorable conditions of the roll infinity, the molding degree of the bending edge can be freely adjusted according to the strength and thickness of the steel strip in order to achieve the best welding conditions.
3, welding for this use of plasma arc welding (PAW) and tungsten Argon arc welding (GIAW) composite welding process. First of all, the use of plasma arc welding penetration fusion, so as to achieve single-sided welding, double-sided molding effect, after the use of Tungsten argon arc welding for filling and cover, welding using pure argon protection. In order to reduce the tendency of harmful phase precipitation, the welding process as far as possible to use the lower line energy, the line energy is best not more than 16kj/cm. In addition, the layer asking temperature is very important for the welding of duplex steel, must be controlled under 100 ℃, too high interlayer temperature will increase the tendency of harmful phase precipitation, and ultimately affect product performance.
4, heat treatment after welding heat treatment using induction furnace to the whole pipe solid solution treatment, heat treatment temperature of 1050-1120 ℃, water spray cooling to 40 ℃ below.