A welding method for stainless steel composite plate equipment cylinder

Abstract

This invention relates to a welding method for the cylindrical body of a stainless steel composite plate equipment, comprising: 1) cutting a V-shaped bevel into the cylindrical body; 2) tack welding the pre-existing weld gaps using a double-gun TIG welding method; 3) longitudinal welding employing a three-layer welding process: the first layer is completed in one pass using a double-gun TIG welding method; the middle layer is completed in one pass using manual arc welding; and the third layer is completed in one pass using manual arc welding; 4) transverse welding employing a three-layer welding process: the first layer is completed in one pass using a double-gun TIG welding method; the middle layer is completed in one pass using manual arc welding; and the third layer is completed using multiple passes of manual arc welding for a final weld finish. This invention not only improves welding efficiency but also produces excellent weld quality, easily meeting the relevant requirements of drawings and specifications.

Description

Technical Field

[0001] This invention relates to the field of stainless steel composite plate metal welding technology, and in particular to a welding method for equipment cylinder made of stainless steel composite plate (304+Q235+304). Background Technology

[0002] With the increasing demand for petrochemical products, their output is also increasing year by year, making the production, transportation, reaction, and storage of liquefied petrochemical products particularly prominent issues. Traditional anti-corrosion technologies for single-layer carbon steel equipment cylinders are no longer sufficient in terms of corrosion resistance, reliability, and economic efficiency, requiring methods such as adding corrosion inhibitors, using plastic inner coatings, and employing non-metallic pipes. To address the corrosion problem of petrochemical products on equipment cylinders, stainless steel composite plates are widely used in corrosive environments such as petroleum and chemical industries due to their excellent corrosion resistance and processing performance. However, the cost of using pure stainless steel plates is high, especially when used for equipment cylinders. The welding process for traditional single-material steel plates is relatively simple, and the welding quality is easy to control. However, welding composite steel plates involves dissimilar steels, making the welding process more complex and the welding quality harder to control.

[0003] The existing welding process suffers from significant differences in chemical composition and physicochemical properties between the base layer and the cladding layer. During welding, this can easily lead to dilution and segregation of the cladding layer weld, or other welding defects, making it difficult to obtain high-quality welded joints. The existing welding process, such as... Figure 4 As shown, the all-argon welding process consists of six layers: 1) bottom sealing weld of the inner wall of the cylinder, 2) cladding weld, 3) transition layer weld, 4) base layer weld, 5) transition layer weld, and 6) surface cover weld. A 10mm thick composite plate weld seam requires all six layers of all-argon welding, making the process extremely complicated. Summary of the Invention

[0004] The purpose of this invention is to provide a welding method for the cylinder of a stainless steel composite plate equipment, which can not only improve welding efficiency, but also produce excellent weld quality and easily meet the relevant requirements of drawings and specifications.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for welding a stainless steel composite plate equipment cylinder includes the following steps:

[0007] 1) The middle base layer of the composite board is a carbon steel layer, and the two side cladding layers are stainless steel layers; the rolled composite board equipment cylinder is plasma cut to form a V-shaped bevel angle, with a blunt edge reserved. The height of the blunt edge is the thickness of the cladding layer. The bevel is polished with an angle grinder, and the composite board of the equipment cylinder is joined together.

[0008] 2) When assembling composite plates, leave a gap for spot welding. Spot welding is done by argon arc welding with two guns. After the equipment cylinder is formed, add several arc plates to the inner wall of the weld to prevent welding deformation. Grind all the surface of the spot weld meat to remove the surface oxide layer, and grind the left and right ends of the weld point into bevels to facilitate good connection with the spot weld meat during the full welding process.

[0009] 3) Longitudinal welding: The weld seam adopts a three-layer welding method. The first layer is the root layer, which is a dissimilar steel welding of stainless steel and carbon steel. Stainless steel argon arc welding wire is used, and the welding is completed in one go using a double argon arc welding gun. The middle layer is a carbon steel base layer welded with carbon steel welding rods and the filling is completed in one go using manual arc welding. The third layer is the surface layer, which is a dissimilar steel welding of carbon steel and stainless steel. Stainless steel welding rods are used, and the filling is completed in one go using manual arc welding. This completes the longitudinal weld seam welding of the equipment cylinder.

[0010] 4) Horizontal welding: The weld seam adopts a three-layer welding method. The first layer is the root layer, which is a dissimilar steel welding of stainless steel and carbon steel. Stainless steel argon arc welding wire is used, and the welding is completed in one go using a double argon arc welding gun. The middle layer is a carbon steel base layer welding, which is a weld filler weld completed in one go using carbon steel welding rods and manual arc welding. The third layer is the surface layer, which is a dissimilar steel welding of carbon steel and stainless steel. Stainless steel welding rods are used, and multiple welding passes are made for the surface layer using manual arc welding.

[0011] The thickness of the steel plate cladding is 1-2mm, and the thickness of the intermediate base layer is 8-12mm.

[0012] The V-groove has a single-sided angle of 30° and a weld gap of 3-4 mm.

[0013] The composite board is made of 304+Q235+304.

[0014] In the longitudinal welding of step 3) above, the root pass welding uses ER309 argon arc welding wire with a diameter of 2mm. The main welding gun is used on the outside of the cylinder, and the auxiliary welding gun is used on the inside of the cylinder. The current of the main welding gun is set to 50-70A, and the current of the auxiliary welding gun is 10A lower than that of the main welding gun. The intermediate pass welding uses J422 carbon steel welding rod with a diameter of 4mm and a welding current of 105-120A. The surface pass welding uses A302 stainless steel welding rod with a diameter of 4mm and a welding current of 100-110A.

[0015] In the horizontal weld of step 4) above, the root pass welding uses ER309 argon arc welding wire with a diameter of 2mm. The main welding gun is used on the outside of the double-gun welding cylinder, and the auxiliary welding gun is used on the inside of the cylinder. The current of the main welding gun is set to 80-100A, and the current of the auxiliary welding gun is 10A lower than that of the main welding gun. The intermediate layer welding uses J422 carbon steel welding rod with a diameter of 4mm and a welding current of 110-130A. The surface layer welding uses A302 stainless steel welding rod with a diameter of 4mm and a welding current of 120-130A.

[0016] Before welding, dry the welding rod at 230-250℃ and keep it at that temperature for 1 hour.

[0017] Before welding, use acetone or alcohol to remove oil and other contaminants from within a 20cm radius on both sides of the bevel. For argon arc welding, the argon gas purity must be above 98%.

[0018] Compared with existing technologies, the beneficial effects of this invention are:

[0019] 1. This invention employs a three-layer welding method for the composite steel plate: the bottom layer is welded using argon arc welding, while the base layer and surface layer are welded using manual electric arc welding. It features stable process performance, excellent comprehensive mechanical properties, and good corrosion resistance.

[0020] 2. The present invention is less likely to cause segregation due to dilution of the cladding weld or other welding defects, and can obtain high-quality welded joints. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the stainless steel composite plate of the present invention;

[0022] Figure 2 This is a schematic diagram of the longitudinal weld seam assembly welding process of the stainless steel composite plate of the present invention;

[0023] Figure 3 This is a schematic diagram of the welding process of the transverse weld seam assembly of the stainless steel composite plate equipment cylinder and the equipment cylinder of the present invention.

[0024] Figure 4 This is a schematic diagram of the original welding process for stainless steel composite plates (304+Q235+304).

[0025] In the diagram: 1-base layer, 2-intermediate layer, 3-top layer, 4-first weld, 5-second weld, 6-third weld, 7-base layer, 8-multilayer layer, 9-weld gap, 10-inner wall weld, 11-multilayer weld, 12-process layer weld, 13-base layer weld. Detailed Implementation

[0026] The present invention will now be described in detail, but the scope of the present invention is not limited to the embodiments described below.

[0027] Example:

[0028] In this embodiment, the assembly, welding, and installation of the gas cooler in the new converter project of Shandong Laiwu Steel Group are taken as an example. The gas cooler has a diameter of 5.02m and a height of 21m, and is assembled and welded in 7 layers on site. The gas cooler cylinder material is a double-sided stainless steel (304+Q235+304) composite plate with a thickness of 10mm. The cladding layer of 304 stainless steel is 1mm thick, and the base layer of Q235 carbon steel is 8mm thick. Figure 1 As shown.

[0029] The converter body is installed according to the following steps:

[0030] 1) See Figure 1 The core layer 7 of the composite panel is a carbon steel layer (Q235, δ=8mm), and the two side cladding layers 8 are stainless steel layers (304, δ=1mm); see Figure 2 , Figure 3 The rolled composite plate equipment cylinder is plasma cut to form a V-shaped bevel angle. The angle of a single side of the V-shaped bevel is 30°, so the combined angle of the V-shaped bevel is 60°. A 1mm blunt edge is reserved, and the bevel is polished with an angle grinder. The composite plates of the equipment cylinder are then joined together.

[0031] Dry the A302 stainless steel welding rod (φ4mm) at 230℃ and keep it at that temperature for 1 hour; dry the J422 carbon steel welding rod (φ4.0mm) at 230℃ and keep it at that temperature for 1 hour.

[0032] Remove oil and other contaminants from within a 20cm radius on both sides of the bevel using acetone or alcohol. Prepare ER309 (φ2.0mm) argon arc welding wire with an argon purity of at least 98%.

[0033] 2) When assembling composite plates, leave a gap for spot welding. The gap should be 3-4mm. Spot welding should be done using argon arc welding with two guns. After the equipment cylinder is formed, add 4 arc plates (evenly distributed along the length of the weld) to the inner wall of each weld to prevent welding deformation. The arc plates should be set perpendicular to the weld and the two ends of the arc plates should be welded to the inner wall of the cylinder. Grind all the surface of the spot weld meat to remove the surface oxide layer, and grind the left and right ends of the weld point into an angle to facilitate good connection with the spot weld meat during the full welding process.

[0034] 3) Longitudinal welding: see Figure 2The weld seam adopts a three-layer welding method. The first layer is the root layer 1 (weld seam of the inner wall of the equipment cylinder), which is a dissimilar steel welding of stainless steel (304) and carbon steel (Q235). Stainless steel argon arc welding wire is used, and the welding is completed in one go using argon arc welding double guns. The middle layer 2 is the carbon steel base layer (Q235) welding, which is completed in one go using carbon steel welding rods and manual arc welding. The third layer is the surface layer 3, which is a dissimilar steel welding of carbon steel (Q235) and stainless steel (304). Stainless steel welding rods are used, and the welding is completed in one go using manual arc welding. This completes the longitudinal weld seam welding of the equipment cylinder.

[0035] In the longitudinal welding, the root layer 1 welding uses ER309 argon arc welding wire (φ2.0mm), and the argon flow rate can be adjusted according to the outdoor environment. The main welding gun current is set to 50-70A, and the auxiliary welding gun current is 10A lower than the main welding current. The intermediate layer 2 welding uses J422 carbon steel welding rod (φ4.0mm), and the welding current is 105-120A. The surface layer 3 welding uses A302 stainless steel welding rod (φ4.0mm), and the welding current is 100-110A.

[0036] 4) Horizontal welding: see Figure 3 The weld is a three-layer weld. The first layer is the root layer 1 (weld on the inner wall of the equipment cylinder), which is a weld between stainless steel (304) and carbon steel (Q235) dissimilar steels. Stainless steel argon arc welding wire is used, and the weld is completed in one go using argon arc welding with two guns. The middle layer 2 is a weld between carbon steel (Q235) and carbon steel (304) dissimilar steels. Stainless steel welding wire is used, and the weld is completed in one go using manual arc welding. The third layer is the surface layer 3, which is a weld between carbon steel (Q235) and stainless steel (304) dissimilar steels. Stainless steel welding wire is used, and the weld is completed in three passes using manual arc welding.

[0037] In the horizontal weld, the root pass 1 is welded using ER309 argon arc welding wire (φ2.0mm), and the argon flow rate can be adjusted according to the outdoor environment. The main welding torch current is set to 80-100A, and the auxiliary welding torch current is 10A lower than the main welding current. The intermediate layer 2 is welded using J422 carbon steel welding rod (φ4.0mm), and the welding current is 110-130A. The surface layer 3 is welded using A302 stainless steel welding rod (φ4.0mm), with a welding rod diameter of 4mm and a welding current of 120-130A.

[0038] When implementing the improved welding process of argon arc welding and manual electric arc welding for double-sided stainless steel composite plates according to the present invention, the following points should be noted:

[0039] 1) Carbon steel welding materials must not be used for welding on the cladding base material.

[0040] 2) After the filler layer is welded, the slag must be removed before the cover layer is welded to avoid affecting the welding quality.

[0041] 3) Control the intergranular corrosion of stainless steel welding materials. The interlayer temperature should not exceed 100℃ (when welding the next layer after completing one layer, the temperature of the weld should not exceed 100℃).

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method of welding a stainless steel clad equipment cylinder, characterized by, Includes the following steps: 1) The middle base layer of the composite board is a carbon steel layer, and the two side cladding layers are stainless steel layers; cut a V-shaped bevel into the rolled composite board equipment cylinder, leaving a blunt edge. The height of the blunt edge is the thickness of the cladding layer. Then, join the composite boards of the equipment cylinder together. 2) When assembling composite plates, spot welding is performed between the reserved weld seams. The spot welding is done using argon arc welding with two guns. After the equipment cylinder is formed, an arc plate is added to the inner wall of the weld seam. The arc plate is set perpendicular to the weld seam, and the two ends of the arc plate are welded to the inner wall. 3) Longitudinal welding: The weld seam adopts a three-layer welding method. The first layer is the root layer, which is a dissimilar steel welding of stainless steel and carbon steel. Stainless steel argon arc welding wire is used, and the welding is completed in one go using a double argon arc welding gun. The middle layer is a carbon steel base layer welded with carbon steel welding rods and the filling is completed in one go using manual arc welding. The third layer is the surface layer, which is a dissimilar steel welding of carbon steel and stainless steel. Stainless steel welding rods are used, and the filling is completed in one go using manual arc welding. This completes the longitudinal weld seam welding of the equipment cylinder. 4) Horizontal welding: The weld seam adopts a three-layer welding method. The first layer is the root layer, which is a dissimilar steel welding of stainless steel and carbon steel. Stainless steel argon arc welding wire is used, and the welding is completed in one go using a double argon arc welding gun. The middle layer is a carbon steel base layer welding, which is a carbon steel welding rod, and the weld seam is filled in one go using manual arc welding. The third layer is the surface layer, which is a dissimilar steel welding of carbon steel and stainless steel. Stainless steel welding rod is used, and the welding is performed in multiple passes using manual arc welding. In the longitudinal welding of step 3) above, ER309 argon arc welding wire with a diameter of 2mm is used for the root pass welding. The main welding gun is outside the double-gun welding cylinder, and the auxiliary welding gun is inside the cylinder. The current of the main welding gun is set to 50-70A, and the current of the auxiliary welding gun is 10A lower than that of the main welding gun. For the intermediate layer welding, J422 carbon steel welding rods with a diameter of 4mm and a welding current of 105-120A are used; for the surface layer welding, A302 stainless steel welding rods with a diameter of 4mm and a welding current of 100-110A are used. In the horizontal weld of step 4) above, the root pass welding uses ER309 argon arc welding wire with a diameter of 2mm. The main welding gun is used on the outside of the double-gun welding cylinder, and the auxiliary welding gun is used on the inside of the cylinder. The current of the main welding gun is set to 80-100A, and the current of the auxiliary welding gun is 10A lower than that of the main welding gun. The intermediate layer welding uses J422 carbon steel welding rod with a diameter of 4mm and a welding current of 110-130A. The surface layer welding uses A302 stainless steel welding rod with a diameter of 4mm and a welding current of 120-130A.

2. The method of claim 1, wherein the method further comprises: The thickness of the steel plate cladding is 1-2mm, and the thickness of the intermediate base layer is 8-12mm.

3. A method for welding the cylinder of a stainless steel composite plate equipment according to claim 1 or 2, characterized in that, The V-groove has a single-sided angle of 30° and a weld gap of 3-4 mm.

4. The method for welding the cylinder of a stainless steel composite plate equipment according to claim 1, characterized in that, The composite board is made of 304+Q235+304.

5. The method for welding the cylinder of a stainless steel composite plate equipment according to claim 1, characterized in that, Before welding, dry the welding rod at 230-250℃ and keep it at that temperature for 1 hour.

6. The method for welding the cylinder of a stainless steel composite plate equipment according to claim 1, characterized in that, Before welding, use acetone or alcohol to remove oil and other contaminants within a 20cm radius on both sides of the bevel.

Images