Welding technology of SA213-T91 and 12Cr1MoV dissimilar steel thin-wall small diameter pipe
Zhanjiang Power Plant (524099), Guangdong Province (524099) Xu Chunyi Unit 1 of Zhanjiang Power Plant with a capacity of 300MW. In November 1996, the high-temperature reheater had a tube explosion. During the process of replacing the blown and thinned tubes, 4mm) dissimilar steel butt welded joints .
1 Weldability analysis Light-weight heat-resistant steel, the chemical composition is shown in Table 1. The former has a large tendency to harden and poor welding performance. Welds and heat-affected zones are prone to produce high-hardness martensite and bainite structures, which increase the brittleness of the joints and increase the residual stress, resulting in cold cracks. The latter contains more carbon and alloy elements, and the weld seam and heat affected zone are prone to hardened structure. When the rigidity of the weldment and the joint stress are large, cold cracks are easy to occur, and reheat cracks are easy to occur during the post-weld heat treatment process. When the two heat-resistant steels are butt welded, the welding is more difficult.
2 Welding process qualification test 2.1 Test preparation 1 A set of welding tools such as welding machine and argon arc welding torch, American MX2 infrared thermometer, WDJK's H08Cr2MoMnWVTiB welding wire, its chemical composition and mechanical properties are between two base materials, purity Two bottles of 99.98% argon etc.
Using manual tungsten argon arc welding, the power polarity is DC positive connection. The pipe joint is in the form of a butt joint, and its bevel angle, blunt edge and clearance are appropriate.
The visible arc is visible during welding, the droplets are in place accurately, to ensure penetration, and the back of the weld is evenly formed. In order to be the same as the on-site conditions, the horizontal welding is used in the test position, the argon protection flow rate is 79L / min, the inner wall argon filling flow rate is 56L / min. Before welding, the groove of the test piece, the welding wire is degreased and rusted, and the oxide film is removed.
2.2 Heat treatment with technological parameters for 30min. Temperature rise * C According to Table 2 Welding process parameters Welding wire diameter Welding current arc voltage Welding speed level 2.3 Welding seam evaluation After welding, the appearance inspection is qualified, two pieces are taken for fracture test, and the results are all qualified.
According to SD143 * 85 "Technical Specifications for Construction and Acceptance of Electric Power Construction (Radiation Inspection of Butt Welding of Steel Pressure Pipelines)" standard, X-ray inspection of other weldments is conducted, and the results are all Class I, which meets the requirements of the standard.
Follow the requirements of "Technical Evaluation Regulations" to carry out tensile, bending and other mechanical performance tests. The results of the tensile test are shown in Table 3. There are two pieces for face bending and back bending, the diameter of the bending shaft is 8, and the bending angle is 50. The test result has no cracks.
The evaluation results show that the use of H08Cr2MdMnWVTiB welding wire and manual tungsten argon arc welding to complete the base material is to make the welding method of 12Cr1MoV and SA213-T91 dissimilar steels of 60mmX4mm is correct, and it is not possible to control the 5ChhaAcadcJoalElectronicPublishing Table 3 tensile test results. The base metal welding seam is welded by the 12Cr1MoV side 3 on-site welding. During the repair process of the high-temperature reheater tube explosion of No. 1 furnace, the on-site welding is difficult due to the complicated location of the tube row. In order to facilitate the operation of the argon arc welding torch and ensure the penetration of the root of the weld, the groove gap is properly added 0.51. 3.1 Prepare the groove surface for color inspection before welding, no cracks, and remove the oil stains in the groove and the sides within 50mm, Sundries, rust, etc.
Flow 80 ~ 90A, welding speed 30 3.2 When welding on site, care should be taken to keep the molten pool in a good protection state of argon gas, to ensure that the penetration of the root of the weld and the joints should not have arc pits, the tube is protected by argon filling to prevent Oxidation. Welding is carried out in strict accordance with the established welding process, and the post-weld heat treatment temperature is controlled at 750 * C * 10 holding time. After welding, no defects are found by X-ray inspection, and the quality meets the relevant requirements of the Ministry of Standards. And after a long period of operation, the situation is good.
4 Conclusions Welding wire welding 12Ci.1MoV and SA213 * T91 dissimilar steel thin-walled small-diameter pipe, after welding, 750-temperature 30min heat treatment, the welding process is reasonable and feasible.
13): Xu Chunyi, born in 1968, is an engineer, mainly engaged in welding management.
Flame spraying repair of the surface of the plunger of the hydraulic press Daqing Petrochemical Company Acrylic Fiber Factory (163714) Shang Yunpeng hydraulic plunger The plunger of the hydraulic press is often damaged due to some unexpected reasons during use, resulting in oil leakage in the pulled part. The system is not working properly, so the plunger surface must be repaired as soon as possible.
1 Selection of repair method 1.1 Analysis of the cause of strain on the plunger of the hydraulic press Abrasion Due to the reciprocating motion of the plunger for a long time, the plunger surface wears out, making the contact between the plunger and the sealing ring uneven, if there are small external particles On the plunger, it is brought into the sealing ring with the movement of the plunger, causing the plunger surface to be scratched.
Corrosive chemical equipment is often in contact with strong corrosive media such as acids, alkalis, salts, etc .; chemical production processes are often carried out under enhanced conditions such as high temperatures, high pressures, and high flow rates. These conditions have strengthened the corrosion effect, and the metal surface is damaged by local defects such as ulcers, deep depressions, spots, etc. caused by the corrosion of the medium, resulting in the pulling of the cylindrical surface.
There are high hardness points in the hydraulic oil, which are brought into the friction pair during work to cause strain.
1.2 The method for repairing the surface of the plunger of the hydraulic press is 510mm in width. The length of the strain varies greatly, a few centimeters short, and more than 1m long. Accordingly, the use of oxyacetylene flame spraying method is more economical and reasonable.
The deformation of the metal of the plunger and the change of the metallographic structure are particularly beneficial for repairing long workpieces such as plungers.
The coating structure is porous, can store oil, and has good lubrication performance.
The cost is low, the cycle is short, the wear resistance is good, and the equipment is not complicated, not limited by the site, and easy to operate.
2. Oxyacetylene flame spraying process of the surface of the hydraulic press plunger pulls the surface. Clean the surface of the pull area with gasoline or acetone to improve the bonding strength of the coating and the substrate. The plunger of the cylinder to be repaired generally has a relatively large diameter and is often hollow, see.
The shape of the scratches is trimmed with an angle grinder to shape the scratches. The purpose is to add the bonding area of ​​the coating and the substrate and achieve mutual fitting. When grinding, the grinding wheel must be held firmly, and must not touch the area other than the strain. After polishing, pre-heat the pulled area to about 150 * C with flame, then the plunge depth of the i plunger is generally 1mmMid and the amount is UtogI, and then polish it again with an angle grinder. // wwkuet
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