Seamless heat treatment after welding is a new technology to eliminate residual stress, this technology can improve the metal's resistance to stress corrosion, and heat treatment temperature is higher, the elimination of residual stress, the better, of course, the heat treatment or can effectively improve the corrosion resistance of welded steel pipe. Try to make the weld metal biphasic organization, content to make ferrite controlled more than three percent, five percent, while the need yo selection of quality basic coated electrodes, so that you can limit the welding seam metal three kinds of S, P, C and other content.
Seamless steel pipe corrosion and cracking of austenitic welded joints is relatively serious, no plastic deformation of brittle fracture is its performance, we only reasonable molding and assembly processes, is preventable. When the assembly must be "wary" it, to avoid its "body" to scratch. When the concentration of the electrolyte is saturated or over-saturated state, the smaller volume of metal hydroxide or some kind of salt will be deposited on the surface of the metal layer of insoluble membrane characteristics of this film is very loose, although not It can directly lead to a passivation of metals, but can hinder dissolve the metal, because the electrode surface is covered.
Seamless finish annealing temperature is appropriate. Perforation heating temperature 1180 ~ 1230 , low carbon steel which is the temperature, take 1230-1250, it is appropriate. 35min furnace heating time or time? Furnace time is generally more than 60min. Cause seamless cracks, the test proved that the tube (round) reasons mostly contain more internal cracks, inclusions, gas bags. Perforated temperature, process adjustments can not be ignored, if the temperature is low perforation, adjusted properly, will cause tearing capillary internal organization.
Control of welding deformation of small diameter seamless steel pipe, because of its shape elongated rod class belong, therefore extremely difficult to control the welding deformation. There are major deformation deflection (positive curvature), scoliosis, angular distortion and twisting deformation of welding. For this, the main deformation transverse contraction, the rectangular cross-section dimensions are affected, each side is indented space reserved about 90 percent; after the transverse weld shrinkage riser ends bent inward, so that drum-shaped member is formed ; As the weld large cross section, enter more calories, it would inevitably lead to greater longitudinal shrinkage, so that the deflection member is formed in the longitudinal direction; for the distortion caused by welding deformation caused by the irrational, the correction is very difficult, and sometimes have to cut re-welding or scrap the whole.
The following principles should be welded order to reduce distortion, small-diameter seamless steel pipe butt welding sequence: taken from the middle to both sides of the symmetry STAGED skip welding, welding straight welding deformation generated less than conducive to disperse and release stress , to avoid stress in complex weldment. Straight swing welding, the narrower plastic deformation zone formed by welding start appear only once, but due to the continuous weaving welding, heat input capacity, heated area, large plastic deformation area is caused by compression, thus shrinkage after welding is Great. STAGED jump when welding, each layer very small cross-section, the required heat is small, and each layer is divided into several segments stitch welding, soldering each section are basically re-establishment of a temperature field on a cold steel every time the emergence of a narrow zone of plastic deformation, and thus the average width (ie transverse shrinkage of size) plastic deformation than the corresponding small weld layered straight, longitudinal shrinkage is small, compared to once-through continuous fill swing welding deformation even smaller.
Optimum efficiency control of high frequency welded pipe in welding process
In most cases, optimized welding process, power loss can be reduced 50% and can improve the welding quality, reduce downtime, increase production.
Stress on the trench corrosion of high-frequency straight seam resistance welding pipe
Trench etching is generally believed that acute heat in the welding process, the results of local tissue metal and chemical change caused by quenching.
Technology of straight seam high frequency resistance welded steel pipe
Factors that affect the raw material for the steel pipe welding quality affect the quality of raw materials are mainly steel mechanical properties unstable surface defects and strip geometry deviation big three aspects, therefore, we should focus on these three aspects of control.
