How to adjust the weld gap is an important step in stainless steel welded pipe production, such as the gap is too large, resulting in a decrease of proximity effect, eddy heat is insufficient, the joint between the weld crystal bad and incomplete fusion or cracking; Gap is too small to cause proximity effect increases, the welding heat is too big, cause the burning of the weld; Or weld after extrusion, rolling the deep pit formation, affect the surface quality of the weld.
The torch in stainless steel welding control processing has a wealth of experience, the following will introduce for everybody four effective way to control the weld gap.
1, the welding temperature control
Welding temperature is mainly affected by high frequency eddy current thermal power, as long as change the capacitance and inductance of loop or voltage and current can change the size of the excitation frequency, so as to achieve the aim of controlling the welding temperature. For low carbon steel, welding temperature control in 1250 ~ 1460 ℃, the wall thickness 3 ~ 5 mm penetration can meet the requirements. In addition, the welding temperature can be accomplished by adjusting the welding speed.
2, the control of extrusion
Two edges of tube billet heating to welding temperature, under the extrusion of squeezing roller, forming a common metal grain interpenetrate, crystallization, eventually forming solid weld. If the extrusion pressure is too small, the amount of common crystal small, weld metal strength drops, stress produces after cracking; If the extrusion pressure is too large, will make molten metal being squeezed out of the seam, not only reduce the weld strength, and can produce a large number of inside and outside burr, even cause the welding seam defects such as.
3, high frequency induction coil position control
High frequency induction coil should be close to squeeze roll as far as possible. Located away from the squeezing roller, induction coil, if effective heating time is longer, heat affected area is broad, weld strength; On the other hand, the lack of weld edge heating, bad after extrusion molding. Impedor is a magnet for or a compound tube, the impedance of cross-sectional area should not be less than steel pipe diameter usually 70% of the cross-sectional area, its role is to make the induction coil, steel pipe weld edge and magnet form a electromagnetic induction loop, proximity effect, eddy heat concentrated near the steel pipe weld edge, the tube billet is heated to the welding temperature. Impedance for a drag in the tube billet steel wire, the center should be relatively fixed position in the center of the close to squeeze roll. Powered on, due to the steel pipe billet rapid movement, impedance device by pipe wall friction loss is bigger, often need to change.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)