Plasma and submerged-arc welding back-gouging-free combined welding structure for thick plate

Abstract

The utility model provides a thick plate plasma and submerged arc welding back-gouging-free combined welding structure which is characterized in that a groove is formed in the edge of a base material, one side of the groove is a reverse groove surface, the other side of the groove is a front groove surface, and a truncated edge is arranged between the reverse groove surface and the front groove surface; the edges of the two base materials are in butt joint, the distance between the truncated edges is not larger than 1 mm, and the truncated edges are fixed through reverse argon arc or welding rod positioned welding before front groove welding. According to the method, the corresponding groove form is optimized, namely, the back gouging step in traditional submerged arc thick welding operation is omitted, smoke pollution and personnel injury are reduced, the risks of crack and corrosion reduction caused by the back gouging operation to the root of a welding joint are eliminated, and the advantage of free forming of the back face of plasma welding single-face and double-face welding is exerted; meanwhile, the occupancy rate of a single welding seam of the plasma welding machine and the submerged arc welding machine is reduced, cross operation is achieved, the equipment utilization rate of the two welding modes is increased, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of welding, in particular to a thick plate plasma and submerged arc welding root cleaning-free combined welding structure. Background Art

[0002] Plasma welding is a high-energy-density arc formed by strongly compressing the free arc through external restraint. It is now mostly used for welding thin plates with a thickness of 4 to 14 mm. Similar to TIG welding, it can be used as a backing weld to achieve the effect of free forming on the back of a single-sided weld, eliminating the need for root cleaning operations. However, due to its limited penetration ability, it has not been popularized in thick plate welding.

[0003] Although traditional double-sided submerged arc welding can be applied to thick plate welding, it requires back cleaning. Incomplete carbon planing can lead to cracks and reduced corrosion resistance after welding. The fume pollution generated during the cleaning process, as well as health risks and wasted work time, have become disadvantages in the application of submerged arc welding. In order to achieve an efficient, stable welding method for thick plate welding without post-weld cleaning, a solution is now sought. Summary of the Invention

[0004] In order to solve the above problems, the present invention discloses a thick plate plasma and submerged arc welding root cleaning-free combined welding structure, wherein the edge of the base material is grooved, one side is a reverse groove surface, and the other side is a front groove surface, and a blunt edge is formed between the reverse groove surface and the front groove surface;

[0005] The two base metal edges are butted together, with the blunt edges no larger than 1mm apart. These blunt edges are secured by reverse argon arc or rod tack welding before the front groove weld. The blunt edges and the front groove are welded together using a P+T (P stands for plasma welding, and T stands for Tungsten Inert Gas Welding) welding head.

[0006] Preferably, a horizontal step transition is made between the reverse bevel surface and the blunt edge.

[0007] Preferably, an R-shaped root radius transition is performed between the reverse groove surface and the blunt edge.

[0008] Preferably, the edges of the two parent materials are butted together, and the groove angle formed by the two opposite groove surfaces is 20 to 30 degrees.

[0009] Preferably, the edges of the two parent materials are butted together, and the groove angle formed by the two front groove surfaces is 60-70°.

[0010] The beneficial effects of the present invention are as follows: the present invention adopts a combined welding structure of plasma welding + submerged arc welding, and optimizes the corresponding groove form, that is, the root cleaning step in the traditional submerged arc thick welding operation is eliminated, smoke pollution and personal injury are reduced, and the risk of cracking and corrosion reduction at the root of the welding joint caused by the root cleaning operation is eliminated, and the advantage of free forming of the back side of single-sided and double-sided welding of plasma welding is brought into play; at the same time, the occupancy rate of single welds of plasma welding machines and submerged arc welding machines is liberated, cross-operation is realized, the equipment utilization rate of the two welding methods is improved, and production efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of the base material groove of the present invention;

[0012] Figure 2 This is a schematic diagram of the first type of docking of the parent materials of the present invention;

[0013] Figure 3 This is a schematic diagram of the second type of docking of parent materials of the present invention;

[0014] Figure 4 It is a schematic diagram of base material welding of the present invention.

[0015] List of reference numerals:

[0016] 1. Reverse bevel surface; 2. Blunt edge; 3. Front bevel surface; 4. Horizontal step; 5. R-arc root radius. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inward" and "outward" refer to directions toward or away from the geometric center of a particular component, respectively.

[0018] like Figures 1 to 4 As shown, this embodiment is carried out on the distillation tower R20013, the inner cylinder S30408, the longitudinal butt joint thickness is 30mm, and the welding operation includes the following steps:

[0019] Step 1: Before assembling the longitudinal joints, grooves are opened along the width of the plate. The outer grooves need to have horizontal platform steps. Here, the outer groove is the back groove surface 1, and the groove angle is reduced to 20-30 degrees, as well as the inner groove, and the inner groove is the front groove surface 3, with a groove angle of 60-70 degrees. There are 2 blunt edge transitions between the back groove surface 1 and the front groove surface 3, and the depth of the inner groove is 5mm, while the total depth of the blunt edge 2 and the front groove surface 3 is 10mm, and the allowance is the depth of the outer groove;

[0020] Furthermore, a horizontal step 4 is used to transition between the blunt edge 2 and the reverse bevel surface 1, and the length of the horizontal step 4 is 3 mm, or an R-shaped arc root radius 5 is used to transition between the blunt edge 2 and the reverse bevel surface 1, and the radius of the arc transition is 6 mm.

[0021] Step 2: After rolling the cylinder and before welding, remove impurities such as water, rust, and oil from the groove surface of the weld joint and the surrounding 20mm range of the parent material and polish it to a metallic luster. Use an angle grinder, wire brush, or other tools to thoroughly clean the gap between the blunt edges.

[0022] Step 3: The gap and misalignment of the control group are both ≤1mm, meeting the assembly requirements of free forming on the back side of the plasma welding primer.

[0023] Step 4: Before welding, set a back-gas protection hood on the outside of the butt joint. The edge of the hood should protrude a part to fit the outer groove to ensure the effectiveness of the outer back-gas protection during the inner bottom welding.

[0024] Step 5: Place the cylinder of the equipment to be welded on the roller frame, and move the cross-arm plasma P+T welding head into the inside to perform internal base welding and filling and covering welding (plasma welding base welding, motorized argon arc welding filling and covering), and weld a total of 10mm thick. The outer back protection cover moves synchronously to prevent back oxidation and ensure the back of the root is formed and welded through.

[0025] Step 5: After the inner side welding is completed, remove the external back protection device and inspect the back side of the weld for quality by visual inspection and 100% PT. 100% PT requires a level I qualification. No overall backside root cleaning is performed. After 100% PT, simple repair welding is performed on some backside defects to confirm that they are qualified. Then prepare for external submerged arc filling welding.

[0026] Step 6: Use a submerged arc welding trolley on the outside of the cylinder to perform 20mm thick filling and cover welding on the outside in a multi-layer and multi-pass welding manner.

[0027] Summary: In step 1, a new type of combined welding groove is used. Its inner groove depth and blunt edge retain the current structure of plasma-welded thin plates. The horizontal step 4 and R-arc root radius 5 transform the thick plate into the current thin plate welding structure. That is, the total thickness of the blunt edge 2 and the front groove surface 3 is small to adapt to the welding parameters of conventional plasma-welded thin plates. At the same time, the structure ensures that the molten iron on the back of the base weld can fully expand under the action of surface tension, forming a smooth and effective weld back profile, eliminating the need for overall back root cleaning. This eliminates the risk of cracking and reduced corrosion resistance caused by carburization after carbon planing of the back of materials such as stainless steel. At the same time, avoiding root cleaning also avoids smoke pollution and harm to workers during carbon planing, improving working conditions and protecting workers' health. After adopting the horizontal step 4 and R-arc root radius 5, the outer groove angle can be appropriately reduced. Under the premise of not affecting the submerged arc welding operation, the amount of back filler of the weld can be reduced, reducing material and labor consumption, and reducing the degree of post-weld deformation.

[0028] Steps 2 through 6 utilize a combination of internal plasma arc welding and external submerged arc welding. This method frees plasma arc welding from its previous limitation to thin plate welding, broadening its application and increasing equipment utilization. Plasma welding pre-primes the interior, eliminating the subsequent root cleaning required before external welding, thus minimizing environmental pollution and harm to operators.

[0029] Simultaneously, plasma welding and submerged arc welding can be cross-operated. After plasma welding completes the rooting of a certain circumferential seam, submerged arc welding can immediately follow up with the filler weld. Simultaneously, while plasma welding is completing the rooting of one seam, submerged arc welding can be performing the filler weld of another seam. This breaks the previous practice of only being able to complete the entire weld seam, regardless of whether plasma arc welding or submerged arc welding is used. This significantly reduces the equipment occupancy time for plasma welding and submerged arc welding of a single seam, enabling cross-operation and improving the equipment utilization efficiency of plasma welding and submerged arc welding machines.

[0030] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above-mentioned embodiment, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A thick plate plasma and submerged arc welding root cleaning-free combined welding structure, characterized in that: The edge of the parent material is beveled, one side is a reverse bevel surface (1), the other side is a forward bevel surface (3), and a blunt edge (2) is formed between the reverse bevel surface (1) and the forward bevel surface (3); The edges of the two parent materials are butted, and the spacing between the blunt edges (2) is no more than 1 mm. The blunt edges (2) are fixed by plasma welding, and the front groove surfaces (3) are fixed by argon arc and the back of the welding rod.

2. The thick plate plasma and submerged arc welding root cleaning-free combined welding structure according to claim 1, characterized in that: A horizontal step (4) is provided between the reverse bevel surface (1) and the blunt edge (2).

3. The thick plate plasma and submerged arc welding root cleaning-free combined welding structure according to claim 1, characterized in that: An R-shaped root radius (5) transition is made between the reverse groove surface (1) and the blunt edge (2).

4. The thick plate plasma and submerged arc welding root cleaning-free combined welding structure according to claim 1, characterized in that: The edges of the two base materials are butted together, and the groove angle formed by the two opposite groove surfaces (1) is 20 to 30 degrees.

5. The thick plate plasma and submerged arc welding root cleaning-free combined welding structure according to claim 1, characterized in that: The edges of the two parent materials are butted together, and the groove angle formed by the two front groove surfaces (3) is 60 to 70 degrees.

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