What details should thick-walled steel pipes undergo before use
Date:2024-01-12
the choice of thick-walled steel pipe welding method should be based on the material and wall thickness of the thick-walled steel pipe. because different welding methods have different arc heat and arc force, different welding methods have different characteristics. for example: tungsten arc welding is characterized by low current density, stable arc combustion, and good weld shape. it is especially suitable for thin plate welding, but thick plate welding is not an option; plasma arc is characterized by high arc column temperature and high energy density. , the plasma arc has good straightness, its rigidity and flexibility have a wide adjustment range, and it works stably, but it is more complicated to operate; submerged arc welding has the characteristics of deep penetration capability and high wire deposition rate, so the welding speed it can be greatly improved and the welding cost is low, but the working conditions and environment are relatively poor. it can be seen that different welding methods have different capabilities and different operating costs. according to the material and wall thickness of thick-walled steel pipes, a reasonable selection of welding methods is a very important task to ensure welding quality, improve productivity, and reduce costs.
pickling thick-walled steel pipes uses an acid solution to remove oxide scale and rust on the steel surface, which is called pickling. the acids used for pickling include sulfuric acid, hydrochloric acid, phosphoric acid, and mixed acids. the pickling process is to remove the surface oxide scale, then undergo lubrication treatment (carbon steel - phosphorus saponification, stainless steel - butter lime, copper and aluminum tubes - oiled), use the old process - copper plating), and then undergo drawing and deep processing. if thick-walled steel pipes are not pickled, there may be oxides and oil stains on the surface. phosphating liquid nuclear energy cannot be removed them, and the phosphating quality will be reduced. moreover, during the manufacturing process of thick-walled steel pipes, after multiple processes, if you are not careful, scars will be left on the surface of the thick-walled steel pipes, which will reduce the corrosion resistance of the parts and directly affect their service life.
what details should thick-walled steel pipes undergo before use?
1. thick-walled steel pipe cutting: according to the actual required pipeline length, the pipe should be cut with a metal saw or a toothless saw. when using water welding during the cutting process, the raw materials must be protected accordingly. when cutting, fireproof and heat-resistant materials should be used as baffles at both ends of the fracture to catch the sparks and hot iron beans that fall during cutting, and protect the raw materials. original plastic layer.
2. thick-walled steel pipe pipe connection: after the plastic filling is completed, connect and install the pipe and pipe fittings. add rubber pads between the flanges during the connection process, and tighten the bolts to a sealed state.
3. plastic coating treatment for thick-walled steel pipes: after polishing, use oxygen and c2h2 to heat the pipe mouth outside the pipe until the internal plastic layer melts. then skilled workers will evenly apply the prepared plastic powder to the pipe mouth. , it should be noted that the corresponding coating should be applied in place, and the flange plastic coating should be applied above the water stop line. this process should strictly control the heating temperature. if the temperature is too high, bubbles will be generated during the plastic coating process. if the temperature is too low, the plastic powder will not melt completely during the plastic coating process. in the above cases, plastic will be produced after the pipeline is put into use. the phenomenon of layer shedding occurred, and the thick-walled steel pipe part of the pipeline was later corroded and damaged.
4. grinding of the nozzle of thick-walled steel pipes: after cutting, an angle grinder should be used to polish the plastic layer of the nozzle. the purpose is to avoid melting or even burning the plastic layer during flange welding, which will damage the pipe. use an angle grinder to grind the plastic layer of the nozzle.
to improve the corrosion resistance of thick-walled steel pipes and extend the service life of the product, thick-walled steel pipes need to be pickled and passivated to form a protective film on the surface. thick-walled steel pipes have high hardenability, good machinability, and medium cold deformation plasticity and weldability. in addition, the toughness of steel does not decrease much during heat treatment, but it has quite high strength and wear resistance, especially when water quenching. it has high toughness; however, this steel is highly sensitive to white spots, has temper brittleness tendency and overheating sensitivity during heat treatment, has high strength and hardenability, good toughness, small deformation during quenching, and high creep strength at high temperatures. and long-term strength. it is used to manufacture forgings that require higher strength and larger quenched and tempered cross-sections than 35crmo steel, such as large gears for locomotive traction, supercharger transmission gears, rear axles, connecting rods, and spring clips that are subject to heavy loads, and can also be used deep oil well drill pipe joints and fishing tools below 2000m, and can be used in bending machine molds.