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Lijiang Hydraulic Parts Factory (Chuzhou 646006, China) Li Hua In recent years, with the continuous development of the liquid newspaper industry, hydraulic cylinders, which are one of the hydraulic components, are also developing in the direction of large bore diameter, large thickness and helium pressure, which is for hydraulic pressure. The welding technology of the cylinder block and the quality of the Dong also put forward more stringent requirements. In the past, in the CO: welding, defects such as root penetration, cracks in the first layer of the weld, pores and slag inclusions often occur, causing serious leakage of the hydraulic cylinder and the cylinder head falling off.
In view of the above situation, we solved some problems in the welding by analyzing the reasons and formulating measures, improving the production efficiency, reducing the production cost, and making the 0 welding better applied to the production of hydraulic cylinders.
The hydraulic cylinder is welded by the cylinder head, the cylinder tube and the pipe joint seat. The structure is as follows: the cylinder head and the cylinder tube are made of 45 steel, the medium carbon steel is carbon-bearing, and the welding feature is the weld metal after welding. Carbon-containing hydraulic cylinder structure 1. Cylinder head 2, cylinder block 3. The pipe joint capacity is also relatively high, and the weld heat affected zone is prone to low plastic hardened structure. The result is not only easy to generate hot crack, but also easy to produce cold crack. . The greater the thickness of the workpiece, the greater the rigidity, the more serious this phenomenon. D For this feature, we first select the U-shaped groove on the weld bevel to reduce the proportion of the metal weld metal of the base metal, thus reducing the welding. The carbon content of the metal is prevented from generating hot cracks. Secondly, preheating before welding is the most effective means to eliminate cracks in the weld metal and base metal. Because preheating reduces the cooling rate of the weld metal and the base metal of the heat affected zone, which is beneficial to the escape of hydrogen in the weld metal and avoid cracks; at the same time, it can reduce the shrinkage of the weld; etc. Finally, after welding Fire treatment can reduce the final strength of the heat-affected zone, eliminate the post-weld stress, prevent cracks during welding and after welding, ensure the stability of the weldment structural size, eliminate harmful cold work hardening, and obtain special mechanical properties or metallurgy. Organization to improve the mechanical properties of welded joints.
If the root is not penetrated, the welding current is too small, the grid voltage is too long, and the angle of the torch is incorrect. For these reasons, we have taken the following measures: 1 Select a special nozzle to ensure that the wire is within the specified range. 2 Select a large current to compensate for fluctuations in the grid. 3 The position of the welding torch is correctly placed and the angle of the welding wire is strictly controlled.
When the welding current is too large and the arc voltage is too low, although the root penetration problem can be solved, the T penetration is large, and cracks are easily formed in the center line of the weld, and the base metal is melted to the weld. The increase in the proportion of the middle, coupled with the welding speed is too fast, will make the weld pool become longer, the grains grow almost linearly toward the axis of the weld, and the form of the weld in the weld will segregate the weak surface; The width of the weld is reduced, the shape factor of the weld is reduced, and the cooling speed of the first weld is too fast. These will cause the crack D at the center line of the weld to pass the test, correctly select the groove form, and take the weld. Pre-heating, the first layer uses a small gauge slow welding speed to make the weldment slowly cool the welding method, which can solve and avoid the crack in the first layer of the weld.
Pore ​​practice proves that the pores are mainly caused by insufficient purity of the shielding gas, the workpiece is not clean, and the wire is stretched too long. Therefore, as long as the purity of the gas is zero, the gas is purified 12 times before use, and the X parts are cleaned without oil and other impurities. The dry elongation of the wire is guaranteed within the specified range, and the pores can be overcome.
The slag inclusion slag is mainly caused by the uncleanness of the workpiece or the welding wire, which is caused by a series of metallurgical reactions during the welding process. In order to ensure the welding quality, the workpiece or welding wire oil, rust and other debris should be completely removed before welding; the welding slag of each layer of the weld be cleaned during the welding process, and the D-division 1.2mm copper-plated welding wire will not be generated. (Gas purity guarantee is greater than 99.5%, welding according to the following process parameters, you can get satisfactory results.
Place the cleaned and assembled hydraulic cylinder on the welding hydraulic tire, adjust the position of the welding torch, and ensure that the wire extension length is within 15mm, and the advance amount is 1015mm (see).
Preheat to 200250t: and then weld. Welding current 180纛X resistance x Henan Pingdingshan high-voltage switch factory process (467000) Zhang Guihua welding shell is SF6 fully enclosed combined electrical appliances (hereinafter referred to as the processing process see.
The main components of GIS). In the GIS high-voltage equipment, the electrical conductors are uniformly assembled in the casing through the insulating support, and the casings are reliably connected by the sealing flange. The casing is filled with 0.40.6MPa SF6 gas, and the annual air leakage rate is <1%. It belongs to metal low jade pressure vessel. Due to the positional dimension of the pipe barrel welding and the quality difference of the flange thickness and the quality of the weld leakage, the casing has a high processing repair rate, which seriously affects the production progress. After the process analysis, production verification, changing the original shell plus XT. Art method, the processing quality of the shell and the welding quality are obviously improved. The selection of casing deformation analysis and processing method is described as follows: D 10mm, flange diameter 4001200mm. The casing material is generally 5A02 (LF2) rust-proof aluminum, Q235A carbon structural steel.
The schematic diagram of the original shell processing flow can be seen from the components of the shell. The cylinder is a thin-walled tubular shape. It is a schematic diagram of the typical shell parts of the GIS product. The shell parts are difficult to process and easy to deform. The outer dimensions of the body are composed of the cylinder body, the pipe body welding, the flange and the like. The original housing must be 600mmX 200A, arc voltage 3034V, welding speed 0.20, 4m/min. Force tempering treatment. Tempering temperature 600X: about, the holding time is determined according to the welding current of each layer 240250A, the thickness of the arc voltage workpiece, the thicker and thicker the workpiece, the longer the time, then with 34-36V, the welding speed is 0.2 0.4m/min, more than many times Layer welding, pay attention to ensure that the dry elongation of each weld wire is 15mm. The coal seams overlap each other, and the overlapping welds are not less than 1/3 of the width of the weld bead. After welding one weld, the weld slag must be removed and the latter layer should be used. The tempering effect of the latter weld on the previous layer and the previous weld and the hammer elimination to eliminate the y stress, refine the grain, reduce the tendency of cold and crack, improve the mechanical properties of the weld, and enhance the cylinder block of the hydraulic cylinder. Strength (see welding sequence). The welding sequence is cooled by the furnace.
After the hydraulic cylinder block is welded according to the above requirements, the weld seam is ultrasonically flawed to reach the manual ultrasonic flaw detection method of GB11345-89 steel weld joint and the grade A of the flaw detection result grade n. The tensile strength test is larger than the base metal, and the hydraulic cylinder can be satisfied. Cylinder use requirements.
Welding process welding is completely feasible.
Compared with manual arc welding, C2 welding material consumption is 42.6% of manual arc welding, energy consumption is 36.7% of manual arc welding, and 0 welding cost is only 59% of manual arc welding. Each weld is welded. There must be no defects, and the defects should be removed after repair welding. Then (4) 0 welding is applied to the production of hydraulic cylinders to ensure the welding quality continues to weld the next weld. The interlayer temperature should not be lower than 150T. To improve production efficiency. Ultrasonic flaw detection of post-weld welds to reduce costs and reduce labor intensity. (20000716) Walnut Worker (Heat Processing >
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