A method for solving the problem of excessive gap in butt weld groove of crack arrest steel

Abstract

The present invention relates to a method for solving the problem of excessive gap in crack arrest steel butt welds. The method comprises cleaning the butt weld groove, installing a ceramic liner, preheating the butt weld before welding, and butt welding. Before butt welding, surfacing welding is performed on one side of the welding groove. After the surfacing welding is completed, preheating is performed again before welding, and then butt welding is performed. The technical solution of the present invention solves the problem of excessive gap in crack arrest steel butt weld grooves by installing a steel liner for surfacing welding, controls the gap in the butt weld grooves within the range required by the butt welding process regulations, solves the cost and construction difficulties brought about by traditional welding methods, avoids the problem of opening the knife to replace the plate and reassembling, improves the original groove retention rate, and reduces production costs.

Description

Technical Field

[0001] The invention relates to the field of welding in the shipbuilding industry, and in particular to a welding method for solving the problem of excessive gap in butt weld grooves of crack arrest steel. Background Art

[0002] Crack arrest steel is a kind of steel that can prevent brittle cracks. It is defined as Kca≥6000N / Or steel with crack arrest properties measured by other methods based on the crack arrest temperature (CAT). As a new material, its processing, welding, repair, grinding and other process requirements are more stringent than those of conventional high-strength hull structural steel.

[0003] In actual production, due to precision control limitations, the gap between the crack arrest steel butt weld groove often exceeds the 4-8mm required by the welding procedure specification. Currently, the main method to deal with this problem is to replace the plate and reassemble it. This method is difficult to implement, has high production costs, and significantly affects the product production cycle.

[0004] Existing technologies, such as the invention patent with application number 201711058091.4, disclose a welding method for high-strength crack-arrest steel, including a pre-weld cleaning process, a positioning welding process, a preheating process, and a main weld welding process. However, this welding method is not suitable for welding crack-arrest steel with a groove gap of 8-25mm. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for solving the problem of excessive groove gap of crack arrest steel butt welds, which is applied to groove welding with a groove width of 8-25 mm. On the one hand, it solves the problem of excessive groove gap of crack arrest steel butt welds, and on the other hand, it satisfies the requirements of weld metal tensile strength ≥510N / mm² and impact energy ≥39J at -20℃. The technical objectives of the present invention are achieved through the following technical solutions:

[0006] A method for solving the problem of excessive gap in butt weld grooves of crack arrest steel, comprising cleaning the butt weld groove, installing a ceramic liner, preheating the butt weld before welding, and butt welding; before butt welding, surfacing welding is performed on one side of the welding groove, and after surfacing welding is completed, preheating is performed again before butt welding is performed.

[0007] Furthermore, the cladding to butt welding specifically includes the following steps:

[0008] S1. Install arc striking plate and arc extinguishing plate at both ends of the weld respectively;

[0009] S2. Install a steel liner on the back of the welding groove and clean the groove;

[0010] S3. Preheat the welding area;

[0011] S4. Perform surfacing welding on one side of the groove, then remove the steel liner and install a ceramic liner on the back of the weld groove;

[0012] S5. Preheat the welding area again, and then perform butt welding. Perform butt welding in the order of base welding, filling welding, and cover welding.

[0013] Furthermore, during surfacing welding, the angle between the welding gun and the weld is 60-70°, the welding wire diameter is 1.2mm or 1.4mm, the welding current of surfacing welding is 180-260A, and the arc voltage is 24-36V; the welding current of base welding is 180-220A, and the arc voltage is 23-34V; the welding current of filling welding is 180-250A, and the arc voltage is 24-35V; the welding current of cap welding is 185-245A, and the arc voltage is 26-33V.

[0014] Furthermore, during surfacing welding and butt welding, the welding slag is removed after each weld, and each layer and each weld is welded in a stepped shape at the arc starting plate, staggered by 30-50mm to avoid excessive stress concentration between the welds. The arc starting length is not less than 30mm, the arc extinguishing length is not less than 50mm, and the thickness of each layer of weld is controlled at 4-5mm, the width of a single weld is not more than 12mm, and the interlayer temperature is controlled at 120-250℃.

[0015] Furthermore, during surfacing welding, the groove form is V-shaped, the blunt edge length is 0-2mm, the groove angle is 45-50°, and the groove gap is 8-25mm; the butt welding groove form is V-shaped, the blunt edge length is 0-2mm, the groove angle is 45-50°, and the butt welding groove gap is 4-8mm.

[0016] Furthermore, the preheating temperature before surfacing welding and preheating before butt welding is 120-150°C.

[0017] Furthermore, after the steel liner is removed, the surfacing weld is ground to ensure that the surface of the surfacing weld inside the groove is flat and smooth.

[0018] Furthermore, semi-automatic flux-cored CO2 gas shielded welding is used for cladding and butt welding. The purity of CO2 gas during welding is greater than 99.9%, and the gas flow rate is 15-25L / min.

[0019] Furthermore, after the butt welding is completed, samples of the weld joint are taken for mechanical property testing, including the tensile strength and impact energy of the weld joint metal.

[0020] The beneficial effect of the present invention is that the technical solution of the present invention solves the problem of out-of-tolerance of the butt weld groove of the crack arrest steel by installing a steel pad for surfacing welding, controls the butt weld groove gap within the requirements of the butt welding process regulations, solves the cost and construction difficulties brought by traditional welding methods, avoids the problem of opening the knife to change the plate and reassembly, improves the original groove retention rate, and reduces production costs; at the same time, through the welding method of the present invention, it can be achieved that the tensile strength and impact energy of the weld metal meet the quality requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a surfacing construction flow chart of the present invention.

[0022] In the figure, 1. Groove gap; 2. Overlay welding; 3. Steel liner; 4. Ceramic liner; 5. Butt weld groove gap. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with specific embodiments:

[0024] A method for solving the problem of excessive gap in crack arrest steel butt weld grooves is provided. The method includes cleaning the weld groove, installing a ceramic backing, preheating the butt weld, welding the butt weld, and inspecting the weld quality. In this embodiment, 85mm thick crack arrest steel EH47 CAS is selected, and the horizontal welding position is selected. The excessive gap groove is V-shaped, with a blunt edge of 0-2mm, a groove angle of 45-50°, and a groove gap of 25mm. The welding method of the present invention is described as an example. Specifically, the following steps are included:

[0025] S1. Install arc-starting plates and arc-extinguishing plates with the same thickness as the weldment at both ends of the weld. The material of the arc-starting plates and arc-extinguishing plates are EH36, with a size of 150×150mm. The thickness of the weldment is controlled within ±2mm, and the groove form is the same as the weldment groove form.

[0026] S2. Install the steel liner 3. Install the steel liner 3 on the back of the welding groove. The liner thickness is 10 mm and the material is AH32. The steel liner 3 fits tightly against the back of the groove. After the installation of the steel liner 3 is completed, clean the groove end face and the surrounding impurities. Use a grinding wheel machine to grind the groove end face and the area within 20 mm to remove rust and scale.

[0027] S3. Preheating before surfacing welding: Use electric heating to preheat the area within 100mm on both sides of the joint. Use a thermometer to measure the preheating temperature, and control the preheating temperature at 120-150℃.

[0028] S4, cladding 2 welding, cladding 2 welding groove form is V-shaped, blunt edge length is 0-2mm, groove angle is 45-50 degrees, groove gap 1 is 8-25mm, such as Figure 1 As shown, the cladding area is welded by multi-layer and multi-pass semi-automatic flux-cored CO2 gas shielded welding. When welding, the angle between the welding gun and the weld is 60-70 degrees, the welding wire diameter is 1.4 mm, and the welding wire AWS quality grade is A5.29. E81T1-K2C; welding current is 220~250A, arc voltage is 31~35V; purity of CO2 gas for welding: 99.9%, gas flow rate: 20-21L / min; after each weld, the welding slag is thoroughly removed and the welding quality is carefully checked. The arc starting positions of each weld in each layer on the arc starting plate are different, and the arc starting positions of each layer on the arc starting plate are also different, staggered by 30~50mm, the arc starting length is not less than 30mm, the arc extinguishing length is not less than 50mm, and the thickness of each layer of weld is controlled at 4~5mm, and the width of a single weld is not more than 12mm; interlayer temperature range: 120~250℃, and the interlayer temperature of the surfacing welding in this embodiment is controlled at 130-221℃.

[0029] After the cladding is completed, the steel liner is removed. The steel liner is removed by carbon arc gouging and grinding with a grinder. Damage to the cladding weld is avoided during the removal process. After the steel liner is removed, the internal area of the cladding weld groove is polished smooth with a grinder. The polished butt weld groove is V-shaped, with a blunt edge of 0-2mm, a groove angle of 45-50°, and a butt weld groove gap of 4-8mm. The butt weld groove is then cleaned, removing impurities from the end face of the butt weld groove and its surroundings. The end face of the butt weld groove and the area within 20mm are polished with a grinder to remove rust and scale.

[0030] Install the ceramic liner 4 on the back of the butt weld groove. During installation, peel off the heat shrink plastic paper, align the center of the liner with the center of the groove, and gently tap the liner with a small wooden hammer to ensure that the ceramic liner 4 fits tightly against the back of the butt weld groove, and that the joints between the ceramic liners 4 push against each other without gaps.

[0031] S5. Preheat again before butt welding. Use electric heating to preheat the area within 100mm on both sides of the butt joint. The preheating temperature is controlled at 120-150℃. Use a temperature measuring instrument to measure the preheating temperature. The distance between the temperature measuring point and the center of the joint is 75mm.

[0032] Butt welding is carried out by semi-automatic flux-cored wire CO2 gas shielded welding multi-layer multi-pass welding Figure 1For surfacing area welding, the included angle between the welding gun and the weld is 60-70°, the welding wire diameter is 1.4mm, and the AWS quality grade of the welding wire is: A5.29E81T1-K2C; the base weld: the welding current is 210-220A, and the arc voltage is 31-32V; the filling weld: the welding current is 230-250A, and the arc voltage is 31-34V; the cap weld: the welding current is 210-240A, and the arc voltage is 29-32V. The purity of CO2 gas used for welding is 99.9%, and the gas flow rate is 20-21 L / min. After each weld, the welding slag is thoroughly removed and the welding quality is carefully checked. The welds of each layer are welded in a stepped shape at the arc striking plate, staggered by 30 to 50 mm. The arc striking length is not less than 30 mm, and the arc extinguishing length is not less than 50 mm. The thickness of each layer of weld is controlled at 4 to 5 mm, and the width of a single weld is not more than 12 mm. The interlayer temperature range is 120-250°C. In this embodiment, the interlayer temperature of butt welding is controlled at 130 to 200°C.

[0033] Finally, the weld joints are subjected to ultrasonic testing and magnetic particle testing, and the weld joint samples are subjected to mechanical property testing, including the tensile strength and impact energy of the weld joint metal. The tensile strength and impact energy of the weld joint metal should meet the requirements of metal tensile strength ≥510N / mm² and impact energy ≥39J at -20℃ respectively.

[0034] When performing surfacing and butt welding, the thickness of each layer of weld should be controlled at 4-5mm. In the flat and overhead welding positions, the width of a single weld shall not exceed 16mm. In the horizontal welding position, the width of a single weld shall not exceed 12mm. In the vertical welding position, the width of a single weld shall not exceed 25mm.

[0035] This embodiment is only a further explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for solving the problem of excessive gap in butt weld groove of crack arrest steel, characterized in that: The method includes cleaning the butt welding groove, installing a ceramic liner, preheating the butt welding, and butt welding. Before butt welding, surfacing is performed on one side of the welding groove, and after surfacing is completed, preheating is performed again before butt welding is performed. The cladding to butt welding process specifically includes the following steps: S1. Install arc striking plate and arc extinguishing plate at both ends of the weld respectively; S2. Install a steel liner on the back of the welding groove and clean the groove; S3. Preheat the welding area; S4. Perform surfacing welding on one side of the groove, then remove the steel liner and install a ceramic liner on the back of the weld groove; S5. Preheat the welding area again, and then perform butt welding. Perform butt welding in the order of base welding, filling welding, and cover welding.

2. A method for solving the problem of excessive groove gap in butt welding of crack arrest steel according to claim 1, characterized in that: During surfacing welding, the angle between the welding gun and the weld is 60-70°, the welding wire diameter is 1.2mm or 1.4mm, the welding current of surfacing welding is 180-260A, and the arc voltage is 24-36V; the welding current of base welding is 180-220A, and the arc voltage is 23-34V; the welding current of fill welding is 180-250A, and the arc voltage is 24-35V; the welding current of cap welding is 185-245A, and the arc voltage is 26-33V.

3. A method for solving the problem of excessive groove gap in butt welding of crack arrest steel according to claim 1, characterized in that: During surfacing welding and butt welding, the welding slag shall be removed after each weld. Each layer and each weld shall be welded in a stepped shape at the arc starting plate, staggered by 30-50mm. The arc starting length shall not be less than 30mm, the arc extinguishing length shall not be less than 50mm, the thickness of each layer of weld shall be controlled at 4-5mm, the width of a single weld shall not be greater than 12mm, and the interlayer temperature shall be controlled at 120-250℃.

4. A method for solving the problem of excessive groove gap in butt welding of crack arrest steel according to claim 1, characterized in that: The groove form of cladding welding is V-shaped, the blunt edge length is 0-2mm, the groove angle is 45-50°, and the groove gap is 8-25mm; the groove form of butt welding is V-shaped, the blunt edge length is 0-2mm, the groove angle is 45-50°, and the butt welding groove gap is 4-8mm.

5. The method for solving the problem of excessive groove gap in butt welding of crack arrest steel according to claim 1, characterized in that: The preheating temperature before cladding welding and butt welding is 120-150℃.

6. A method for solving the problem of excessive groove gap in butt welding of crack arrest steel according to claim 1, characterized in that: After the steel liner is removed, the surfacing weld is ground to ensure that the surface of the surfacing weld inside the groove is flat and smooth.

7. A method for solving the problem of excessive groove gap in butt welding of crack arrest steel according to any one of claims 1 to 6, characterized in that: The cladding and butt welding adopt semi-automatic flux-cored wire CO2 gas shielded welding. The purity of CO2 gas during welding is greater than 99.9%, and the gas flow rate is 15-25L / min.

8. The method for solving the problem of excessive groove gap in butt welding of crack arrest steel according to claim 1, characterized in that: After butt welding is completed, samples of the weld joint are taken for mechanical property testing, including the tensile strength and impact energy of the weld joint metal.

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