Cold brittle of seamless steel tube are: solid solution strengthening elements. High ductility-brittle transition temperature is very strong; there are molybdenum, titanium and vanadium; low content of low and high content of toughness when a brittle transition temperature of the elements of silicon, chromium and copper; reduce toughness-brittle transformation Temperature of nickel, the first increase after the reduction of a brittle transition toughness of manganese. Forming an element of the second phase. The important elements with the second phase to increase the cold-rolled precision steel tube cold brittle is carbon, with the increase of carbon content in the cold rolling precision steel pipe and the increase of pearlite content in cold-rolled precision steel pipe, the average increase of 1% pearlite volume, the average ductility-brittleness transformation temperature increased by 2.2 ℃. Effect of carbon content in ferrite - pearlitic steel on brittleness. The addition of titanium, niobium and vanadium and other micro-alloying elements, the formation of the dispersion of nitride or carbonitride, causing cold-rolled precision steel tube toughness of a brittle transition temperature increase in grain size affect the toughness of a brittle transition temperature, with grain thick, A ductile-brittle transition temperature increases. Refining the grain reduces the cold-brittle tendency of the cold-rolled precision bright steel pipe, which is widely used method.

Straight seam steel pipe caused by the wrong side and its preventive measures:  1, The steel belt sickle bending is caused by the most important factor in the wrong side. In the spiral welded pipe forming, the sickle bending of the steel strip will change the forming angle continuously, resulting in the weld gap change, resulting in the slit, wrong side and even take side. Which can seriously affect the quality of the steel pipe, so the observation of the coil rolling after the sickle bending situation, by controlling the vertical roller to cut the part of the scissors can be cut and the forming angle of the continuous control and correction is in the production process to reduce the steel sickle The wrong side of the effective way.  2, Due to non-trimming strip head and tail of the shape and size of poor precision, butt easily lead to hard-bending caused by the wrong side of the strip.  3, The steel head and tail butt welding seam I high, in the molding process if improper handling, likely to cause a larger wrong side.  4, Poor edge of the strip is another cause of the wrong side of the important reasons.

1, Defective square tube because the processing is not in place, the appearance will be a lot of glitches, and these burrs will be very simple scratches the pipe surface, so the first identification method came out, there are many scratches on the exterior of the Is the quality of the poor. 2, Defective side tube manufacturers in order to reach a large negative public service will increase the amount of product processing when the reduction, and this will result in products of fine and low cross-ribs, so if you find such a situation, then the best side do not buy. 3, So called square tube is because the cross-section of the pipe is square, and poor side of the pipe in this regard is not in place will make the pipe section of the oval-shaped cross-section. 4, Residual side tube is basically not able to reach the standard specifications, so when you buy with a professional ruler about the volume can be briefly resolved.

Why is a large diameter thick-walled tube with two welds? Mainly due to raw material problems and equipment processing problems. Customer requirements of large-diameter steel pipe width of the required width of the steel mills generally do not produce, so the manufacturer must be two plates for welding, and the emergence of this weld situation. Production of large diameter thick-walled tube volume of the main problem is the welding, custom-made taper steel tube, as long as the detection can be detected by the relevant requirements of delivery compared to other products, the broader comparison. Large-diameter thick-walled tube detection method is the main ultrasonic flaw detector, should pay attention to the problem: 1, the volume tube of the same tube section of the longitudinal weld should not be greater than two. 2, volume tube butt weld group corresponding to the inner wall flush when the nominal diameter greater than the tube should be in the back cover welding. In the coil processing process, should prevent the sheet surface damage.

If stainless steel welded pipe in a specific working environment, the need for welding repair, the welding preparation should be carefully checked before, in order to ensure complete removal of defects. Welding of stainless steel tubes shall be carried out in accordance with the welding procedure as assessed in ASME Code Section IX. Welding operators or welding equipment operators performing welding shall comply with the qualification requirements of Volume IX. In addition to A1 or A2 component of the weld metal can be used for P1 material, the weld metal should be equivalent to plate P-No A-No component requirements. When the purchaser agrees, other weld metal that matches the material matrix of the material to be welded may also be used. The weld metal must be evaluated in accordance with ASME Code, Volume IX. If a stainless steel pipe material is required to be subjected to a Charpy impact test, the weld qualification test shall also include welds, heat affected zones and Charpy impact tests of the base metal and shall be reported to the purchaser. If the stainless steel pipe material is to be normalized, quenched and tempered, thermoformed or post-weld heat treated, the steel plate and the welded steel plate for the welding procedure qualification test shall be heat treated as specified by the purchaser. In addition, the repair of the weld should be consistent with the requirements of the construction specifications of the buyer.