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Welding Process Of 316L Stainless Steel Pipe Jul 10, 2017

  Welding process of 316L stainless steel pipe

  (1) Welding method: Because most of the site is stainless steel pipe and size, according to the welding characteristics of stainless steel, as far as possible to reduce the heat input, so the use of manual arc welding, argon arc welding two methods, D >φ159 mm using argon arc welding bottom, manual arc welding cover surface. d≦φ159 mm full Argon arc welding. 316L stainless steel Welding machine uses the manual arc welding/Argon arc welding Dual-purpose WS7 1400 inverter arc welder.

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  (2) Welding material: austenitic stainless steel is special can be used steel, in order to meet the joint has the same performance, should follow the "equal components" principle to select welding materials, at the same time, in order to enhance the joint resistance to thermal cracking and intergranular corrosion capacity, 316L stainless steel so that a small number of ferrite joints, select Hoocr19ni12mo2 Argon arc welding wire, hand arc welding electrode CHSO22 as filler materials, the composition of the table 1 and table 2.

  (3) Welding parameters. Austenitic stainless steel is a prominent feature of the thermal sensitivity, so the use of small current, rapid welding, multi-layer welding to strictly control the temperature between the layers, so that the temperature between the layers is less than 60 ℃. The specific parameters are shown in table 3.

  (4) Groove form and assembly position welding. 316L stainless steel Groove in the form of V-groove, due to the use of a small welding current, deep penetration, so the blunt edge of the groove is smaller than the carbon steel, about 0-0.5 mm, the slope is larger than the carbon steel, about 65°-700°, the form is shown in Fig L.

  Because of the large thermal expansion coefficient of stainless steel, the welding stress is high, which requires strict positioning welding. For d≦φ89 mm tube using two point positioning, d=φ89-φ219 mm using three point positioning, d≧219 mm using four point positioning, the location of the weld length of $number mm.

  (5) Welding Technical Requirements:

  ① Manual arc welding Welder adopts DC reverse connection, and Argon arc welding adopts direct current connection;

  ② welding wire with stainless steel wire brush off the surface of the oxidized skin, and with acetone cleaning, the electrode should be 200-250 ℃ drying 1h, with the use of;

  ③ Welding before the workpiece on both sides of the slope of the mm range of oil, such as cleaning clean, and with acetone to clean the sides of the groove mm range;

  ④ Argon arc welding, nozzle diameter φ2 mm, tungsten extremely bowl tungsten, specifications φ2.5 mm;

  ⑤ Argon arc welding stainless steel, the back must be filled with argon protection, in order to ensure back forming. Using the method of local argon filling in the pipeline, the flow is 5-14l/min, and the positive Argon flow volume is one 13l/min.

  Bottom welding seam thickness should be as thin as possible, and the root fuse well, when the arc should be a gentle slope, such as the arc shrinkage, the application of polishing machine grinding off. ARC quenching must be applied in the groove, 316L stainless steel and arc pits should be filled to prevent arc pits from cracking.

  Because the stainless steel is austenitic stainless steel, in order to prevent carbide precipitation sensitization and intergranular corrosion, should strictly control the temperature between the layers and the cooling speed after welding, the requirements of the interlayer temperature control under 60 ℃, welding must be immediately water-cooled, and the use of segmented welding. The specific segmentation method is shown in Figure 2. This symmetrical and dispersed welding sequence can increase the cooling speed of the joint and reduce the welding stress.