• Surface crack of seamless steel tube continuous casting slab

    Seamless steel pipe in the casting process, pulled out from the mold of the slab, the solidification interface of the crystal strength is very small, when the slab subjected to external forces (thermal stress, drum force, roller pressure, straightening force) exceeds, At the critical value, a crack occurs in the solid-liquid surface and propagates along the columnar crystal until the solidified shell can resist the external force. Surface cracks in several cases: the crack across the thickness of the slab direction, the center of the equiaxed zone crack is a curved fine grain along the grain boundaries, the arc-side cracks are generally crack straight line crack, the outer arc side of the crack is generally crack along the crystal. The crack along the grain boundary is a stress crack, and the rip crack is a crack that crosses the grain destructively and is the result of the external force. Improvements are as follows: 1, Improve the precision of the arc casting machine to avoid solidification at the initial solid-liquid interface is too large stress to prevent cracks along grain boundaries. 2, Using appropriate speed up the casting speed and within a certain range to increase the amount of cooling water, increase the water flow rate, lower water temperature and other methods to achieve forced cooling. 3, Strictly control the composition of steel, especially carbon content control. 4, Increase the electromagnetic stirring continuous casting, molten steel superheat control at 40 ℃ below.
  • Weld tube oxidation occurs

    There are three major causes of oxidation of the welded pipe: 1, The production process reasons: This is one of the reasons lead to oxidation of steel products, from the production process and product characteristics, the product surface to form a thin oxide film is to avoid the oxidation of the underlying process, but also steel products different from other steel products, one of the main features, but by welded pipe production process inadequate or inadvertently led to the performance of the oxide film is not complete, not continuous, the oxygen in the air will be directly with the product of some elements of the redox reaction, resulting in the performance of the product appear oxidation phenomenon. 2, The product ingredients ratio reasons: Some manufacturers in order to reduce production costs, thereby reducing some such as chromium, nickel and other important elements of the proportion of content, while increasing other elements such as carbon content, this is not strictly in accordance with the product model, product features. For example, if the content of chromium in 304 stainless steel pipe is insufficient, it will not only affect the corrosion resistance and formability of welded pipe, but also be used in chemical industry, equipment and production industry. There are potential product quality and safety risks; the same time, also affect the appearance of the product and anti-oxidation properties. 3, Man-made reasons: This is also one of the most commonly encountered products of some consumers in the use of stainless steel oxidation products, some consumers in the use and maintenance of improper operation, in particular, some of the welded pipe for the food and chemical equipment industry pipe products. There is a high probability of anthropogenic oxidation. For artificially produced weld pipe oxidation, it is necessary to have correct knowledge of product usage and to regularly and reasonably maintain and maintain it, so as to reduce oxidation caused by improper use by man.
  • Pre-weld quality of straight seam steel pipe

    Pre-welding quality includes joint quality and weld quality. (1) Forming seam no wrong edge or wrong edge less than the specified value, the general provisions of the wrong edge ≤ 8% of the thickness, the maximum does not exceed 1.5mm. (2) To ensure that the weld penetration and the appropriate amount of melting, it is necessary to ensure that welding does not crack, does not burn through the phenomenon, but also to control the weld height, welding seam remaining height does not affect. (3) Continuous bead, forming a good, in order to facilitate the guarantee of the quality of the final welding. (4) The weld does not exist welding deviation, porosity, cracks, slag, burn through and the back of the weld and other defects, the weld center deviation ≤ 1 mm. (5) No electric arc burns, splashing small, does not affect the pipe bevel and surface quality. (6) Weld and base metal match, weld metal physical and chemical properties to meet quality requirements.
  • Common way to form the submerged arc welded pipe

    Due to their excellent performance, submerged arc welded pipe will occupy a large proportion of transmission fluid pipes in the future. Long-distance oil and gas pipelines and submerged arc welded pipe will gradually replace spiral submerged arc welded pipes. The common way of submerged arc welded pipe formation is analyzed, the advantages and disadvantages of various forming methods are analyzed, and suggestions and opinions on how to choose submerged arc welded pipe in actual engineering design are put forward. Material due to the chemical composition of the raw material, although it is normal during the welding process, the weld appears cracked and tube cracks sometimes appear in the size and sound accompanying the embrittlement of the weld. Then the welding color is more blue, the temperature is normal. Sometimes we can see the deviation from the weld center, is the edge of the parent material adhesion, the formation of irregular grooves, resulting in the chemical composition of this phenomenon is raw material embrittlement. Double-sided submerged arc welded straight seam steel pipe was invented in 1940, a new method of welding and hand welding in front of it, the same place is that it is with flux, but not the skin electrode, special flux metallurgical slag. This coating system consists of a funnel through the pipe to the front of the soldering flux. The second difference is that the electrode is not used, the use of wire, because the wire can be continuous; electrode, we burn an electrode must have a welding head, must stop running, change the electrode, and then welded.
  • Hot expansion process requirement of straight seam steel pipe

    As the expansion process to increase the raw material defects, the special requirements of steel pipe expansion must meet the following requirements: 1, Tube material eddy current testing after the supply. 2, The outer surface without hair lines, folding and other defects. No delamination and other defects exist on the inner surface. 3, No glitches on the pipe end, the verticality of the required cut tangential ≤ 1mm. 4, Pipe diameter tolerance control ≤ ± 0.8% 5, pipe wall thickness tolerance control ≤ ± 10% 6, Steel spiral ≤ 0.3mm, no visible helical Road 7, The expansion of the hot end of the pipe end of the pipe expansion, hot bar end of the pipe length must be guaranteed.
< 1 ... 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 ... 67 >
close