A laser friction stir welding method for stainless steel special-shaped parts

Abstract

The application discloses a laser friction stir welding method for stainless steel special-shaped parts, and comprises the following steps: cleaning the butt joint groove and the two sides near the first stainless steel special-shaped part and the second stainless steel special-shaped part of the parts to be welded; clamping and positioning the first stainless steel special-shaped part and the second stainless steel special-shaped part after pretreatment; positioning welding by using a laser; firstly, laser preheating is carried out in front of a stirring head of a friction stir welding device, the preheating temperature of the stainless steel special-shaped part ranges from 400 to 450 DEG C, then, the friction stir welding is carried out at an interval of 5-10 mm, and the laser preheating and the friction stir welding maintain the same speed. The method realizes high-precision, low-deformation space three-dimensional welding by combining laser preheating for reducing the effective melting point of the stainless steel and a six-link friction stir welding numerical control special machine, and the method is applied to the welding of a stainless steel guide rail support seat and a cylinder, and significantly improves the production efficiency and reliability of a reusable launching cylinder system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser welding, in particular to a laser friction stir hybrid welding method for stainless steel special-shaped parts. BACKGROUND

[0002] The popularization and use of recyclable and reusable products are of great significance to resource conservation, environmental protection and sustainable development. At present, the recyclable and reusable of different types of products have penetrated into various industries. For example, the American SpaceX company has made significant progress in rocket recycling and successfully achieved multiple rocket recycling and reuse, which greatly promotes the progress of space technology.

[0003] Major domestic units are carrying out the design and manufacture of recyclable and reusable products. For example, in the field of aerospace, the launch tube system is an important part of missile weapons and equipment. The launch tube system is mainly made of aluminum alloy materials and does not have the function of recyclability and reusability. Moreover, the production cost is high and the production cycle is long. Stainless steel is an ideal material for manufacturing reusable launch tube systems due to its good corrosion resistance, high temperature resistance, heat resistance and strength. However, if stainless steel is used to manufacture the launch tube system, it will still face the problem of three-dimensional space welding of the guide rail support seat and the barrel, which is a typical stainless steel special-shaped part weld. In addition, due to the high melting point and strength of stainless steel, it also needs to meet the requirements of multiple reuse, so the welding quality requirements are higher, resulting in greater welding difficulty, which becomes the main bottleneck problem restricting its large-scale production. If manual drilling into the narrow special-shaped part and manual TIG / MIG welding are still used for production, not only the welding quality cannot be guaranteed, but also smoke, toxic gases and other hazards to workers' physical and mental health and the environment will be produced. In addition, the high melting point of stainless steel also greatly limits the use of conventional friction stir welding, so an efficient, high-quality and green welding method is needed to ensure the welding quality of stainless steel special-shaped parts.

[0004] The patent with the publication number CN116871660A proposes a method for welding a cylinder and a support seat space three-dimensional friction stir welding, which utilizes a back-pulling three-dimensional parallel friction stir welding method to complete the space welding of the key functional components of the aluminum alloy launch cylinder, the saddle-shaped guide rail support seat and the cylinder, and achieves the purpose of completing the welding from the outside of the cylinder, thereby replacing the conventional fusion welding method. However, this method is mainly for welding low-melting-point materials such as aluminum alloy, and its essence still belongs to a conventional friction stir welding category. The melting point of stainless steel is much higher than that of aluminum alloy. If conventional friction stir welding is used, it will have a huge impact on equipment precision, tool wear, clamping force, etc., greatly shorten the service life of the equipment, accelerate the wear of the stirring tool and the clamping system, and significantly reduce the production efficiency. It is not suitable for welding production of large-scale and batch products, and the production cost will also soar. Moreover, due to the slow heat conduction of stainless steel, heat accumulation is easy to occur, and the base material and the weld zone will be deformed due to uneven heat distribution. Meanwhile, the maximum inclination angle of the stirring head in the back-pulling three-dimensional parallel friction stir welding machine mentioned in the patent is 30°, which means that the three-dimensional space welding range is greatly limited, and many special-shaped parts with a weld seam exceeding the inclination angle of 30° cannot be welded. SUMMARY

[0005] To solve the technical problems in the background art, the present application provides a laser friction stir hybrid welding method for stainless steel special-shaped parts, which reduces the effective melting point of stainless steel through laser preheating and realizes high-precision and low-deformation space three-dimensional welding by combining a six-link friction stir welding CNC machine. This method is applied to the welding of stainless steel guide rail support seats and cylinders, significantly improves the production efficiency and reliability of reusable launch cylinder systems, and can be popularized in the fields of aerospace, high-end equipment manufacturing, etc.

[0006] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0007] The present application provides a laser friction stir hybrid welding method for stainless steel special-shaped parts, comprising the following steps:

[0008] S1, pretreatment: cleaning the butt joint groove and the nearby sides of the first and second stainless steel special-shaped parts to be welded;

[0009] S2, clamping: clamping and positioning the first and second stainless steel special-shaped parts after pretreatment;

[0010] S3, laser positioning welding: positioning welding using laser;

[0011] S4, laser friction stir welding: first laser preheating in front of the stir head of the friction stir welding device, the preheating temperature of the stainless steel special-shaped part is 400-450 DEG C, then interval 5-10 mm distance friction stir welding, laser preheating and friction stir welding keep the same speed.

[0012] In the present application, when the preheating temperature of the stainless steel special-shaped part before friction stir welding is selected, the brittle phenomenon of 475 DEG C of stainless steel is considered, especially the brittle temperature range of chromium nickel austenitic stainless steel is generally 450-850 DEG C, when the temperature exceeds the brittle temperature range, the toughness and plasticity of chromium nickel austenitic stainless steel will decrease, and damage such as crack and fracture is easy to occur; At the same time, the temperature range of intergranular corrosion of stainless steel is also 450-850 DEG C, in this temperature range, chromium in stainless steel is easy to combine with carbon to form chromium carbide, which reduces the chromium content near the grain boundary and forms a chromium-poor area, thereby causing intergranular corrosion; The melting point temperature of general stainless steel is usually 1400-1500 DEG C, in order to reduce the melting point, soften the stainless steel material, and also try to reduce the temperature difference between the weld and the nearby area of the base material after welding, and maximize the deformation after welding, the ideal preheating temperature range is finally determined as 400-450 DEG C through test, if the preheating temperature is too high, the stainless steel will produce brittle, intergranular corrosion and other problems, if the preheating temperature is too low, the effect of reducing the melting point, softening the material and reducing the deformation after welding cannot be achieved.

[0013] The present application is finally determined that the interval distance between laser preheating and friction stir welding is 5-10 mm through many tests, in order to ensure good preheating effect. If the interval distance is too small, there will be certain interference between laser preheating and friction stir welding, and because the heat conduction performance of stainless steel is poor, the preheating temperature cannot be expanded to the whole friction stir welding area, so the preheating effect cannot be achieved. If the interval distance is too large, the preheating temperature may have been reduced before friction stir welding, so the preheating effect cannot be achieved.

[0014] Further, in the step S4, before laser preheating, laser preheating test is carried out by using first stainless steel test piece and second stainless steel test piece which have same material and similar structure with the first stainless steel special-shaped part and the second stainless steel special-shaped part, the preheating temperature in the laser preheating test is measured by using infrared thermometer, it is ensured that the measured preheating temperature is in the range of 400-450 DEG C, then the laser power and scanning speed at the measured temperature are recorded, and the heat input of laser welding is calculated according to the following formula:

[0015] Q=ηP / v, wherein η is the thermal efficiency coefficient, the range is 0.8-0.85, when welding stainless steel, the value is generally 0.8, the heat input of laser welding is calculated to be about 5-9 KJ / cm.

[0016] Further, in the step S4, the welding speed of the friction stir welding is 80-100 mm / min, and the laser preheating power is calculated according to the heat input of the laser welding calculated in the laser preheating test, and the formula Q = ηP / v, and the laser preheating power is 1000-1500 W.

[0017] Further, in the step S4, the laser scanning speed is the same as the moving speed of the stirring head, and is 80-100 mm / min.

[0018] Further, the process parameters of the friction stir welding are as follows: the rotating speed of the stirring head is 600-700 r / min, the welding speed is 80-100 mm / min, the penetration depth is 0.1-0.2 mm, and the spindle inclination angle of the friction stir welding device is about 2°.

[0019] Since the high melting point of the stainless steel is reduced after the laser preheating, but is still higher than that of the light metal such as aluminum alloy, the heat required is slightly larger, and therefore the rotating speed of the stirring head is slightly higher than that of the welding of the light metal such as aluminum alloy, and the welding speed is slightly lower, and the rotating speed of the stirring head is greatly reduced compared with the friction stir welding of the stainless steel without preheating.

[0020] Further, the friction stir welding device is a six-link friction stir welding numerical control special machine.

[0021] The laser-six-link friction stir composite welding technology can effectively solve the problem of three-dimensional welding of stainless steel special-shaped parts, including solving the three-dimensional space welding problem of the stainless steel guide rail support seat and the stainless steel cylinder, and successfully meeting the requirements of the reusable launch system of the stainless steel special-shaped parts. The six-link friction stir welding numerical control special machine has a multi-degree-of-freedom hybrid robot configuration, and establishes a hybrid robot structure stiffness model based on the structure matrix method, and a dynamic model of the hybrid robot by using the virtual work principle. The six-link structure is synchronously driven, and the upper and lower ends of each link are connected to the sliding block and the moving platform through the ball joint. On the basis of the classic PID control, the motor control algorithm of the ADRC (active disturbance rejection control) is fused to realize the rotation and inclination of the moving platform, and the maximum inclination angle can reach 90°, so that the inclination angle of the stirring head also reaches 90°, which is much higher than 30°, and therefore the welding of the special-shaped parts in the three-dimensional space is almost not limited. The device has high automation degree and good welding quality consistency, and can not only weld thin plates, but also weld medium-thick plates, which can make up for the problem of insufficient rigidity of the robot friction stir welding of medium-thick plates.

[0022] Further, in the step S3, when the laser positioning welding is performed on the first stainless steel profiled piece and the second stainless steel profiled piece by using the laser, the positioning welding interval is 40-50 mm, and the positioning welding seam length is 10-15 mm.

[0023] The main purpose of the laser positioning welding is to prevent the deformation of the stainless steel profiled piece in the friction stir welding.

[0024] Further, in the step S2, the first stainless steel profiled piece and the second stainless steel profiled piece to be welded are clamped by using the inner support tooling and the outer clamp respectively, and the butt joint gap between the clamped first stainless steel profiled piece and the second stainless steel profiled piece is ≤0.15 mm, and the misalignment between the first stainless steel profiled piece and the second stainless steel profiled piece is ≤0.15 mm.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) In the present application, the laser preheating technology is adopted, and the ideal preheating temperature range (400-450℃) is determined through experiments, so as to avoid the brittleness and intergranular corrosion of the stainless steel, and reduce the material deformation resistance.

[0027] (2) First, laser positioning welding is used to prevent deformation of stainless steel special-shaped parts in friction stir welding, and then the interval between laser preheating and friction stir welding is controlled at 5-10 mm, both of which are synchronized to move and operate (speed 80-100 mm / min) to avoid heat interference and ensure the preheating effect. Laser preheating reduces energy demand, and the welding speed is increased to 80-100 mm / min to adapt to mass production. The tensile strength of the welded joint is more than 95% of the base material, the welding deformation is minimal, the weld surface is well formed, and there are no defects such as no flash and surface peeling.

[0028] (3) Compared with the fusion welding method, the laser-friction stir composite welding has the process characteristics of low stress and small deformation, which can improve the precision of the welded product. At the same time, there is no smoke and spatter in the welding process, the noise is low, it is green and environmentally friendly, the environment is basically not polluted, and the labor environment is good, which basically has no harm to the physical and mental health of workers. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] Embodiment 1

[0031] A laser-friction stir composite welding method for stainless steel special-shaped parts, comprising the following steps:

[0032] S1, laser preheating test:

[0033] A first stainless steel test piece and a second stainless steel test piece similar to the first stainless steel test piece and the second stainless steel test piece are cut out by wire cutting, the first stainless steel test piece and the second stainless steel test piece are clamped, then the laser beam is aligned with the butt joint bevel for preheating, and the infrared thermometer is used to measure the temperature of the preheating area. The infrared thermometer moves closely behind the laser beam, and the moving speed of the two is the same. When the temperature measured by the infrared thermometer is 400℃, the laser power and the laser scanning speed of the preheating laser beam at this temperature are recorded, and the heat input of the laser welding is calculated according to the following formula:

[0034] Q = ηP / v, wherein η is the thermal efficiency coefficient, generally 0.8 when welding stainless steel, and the calculated heat input of the laser welding is about 5 KJ / cm.

[0035] S2, pretreatment:

[0036] The butt joint of the first and second stainless steel special-shaped pieces of the to-be-welded piece and the area of 15-30 mm on both sides are cleaned, and burrs, surface protrusions, oil stains, water rust and the like are removed.

[0037] S3, clamping:

[0038] The first and second stainless steel special-shaped pieces of the to-be-welded piece are clamped by using an inner support tool and an outer clamp respectively, so that the butt joint gap between the first and second stainless steel special-shaped pieces after clamping is ≤0.15 mm, and the misalignment between the first and second stainless steel special-shaped pieces is ≤0.15 mm.

[0039] S4, laser positioning welding:

[0040] The first and second stainless steel special-shaped pieces after clamping are positioned and welded by using a laser beam, the positioning welding interval is 40 mm, and the positioning welding seam length is 10 mm.

[0041] The specific process parameters of the laser positioning welding are as follows: the laser power is 1500 W, the welding speed is 1.0 m / min, the defocusing amount is +4 mm, the protective gas flow is 18 L / min, the purity of the protective gas argon is ≥99.999%, and the laser deflection angle is 8°.

[0042] After the positioning welding is completed, the positioning welding seam is cleaned to remove spatters, dirt and the like on and near the welding seam.

[0043] S5, laser friction stir welding:

[0044] In the laser friction stir composite welding, laser preheating is first performed, and then six-link friction stir welding is performed by using a six-link friction stir welding numerical control special machine, and the laser preheating and the friction stir welding are kept at the same speed. At the starting point, the laser beam is first turned on for laser preheating, and stays for 0.5-1 s. After the predetermined preheating temperature is reached, the laser beam is moved along the path trajectory of the butt joint for preheating. After the laser beam moves along the path trajectory of the butt joint for 5 mm, the six-link friction stir welding numerical control special machine is started, and the welding is started by moving along the path trajectory of the butt joint. In the laser friction stir composite welding, the laser preheating power is 1000 W, the laser scanning speed is the same as the moving speed of the stir head, i.e. 100 mm / min. At the end point, the laser beam is first turned off, and the six-link friction stir welding numerical control special machine is also turned off when it reaches the point.

[0045] The main process parameter range of the friction stir welding is as follows: the rotation speed of the stir head is 700 r / min, the welding speed is 100 mm / min, the penetration depth is 0.2 mm, and the main shaft of the six-link friction stir welding machine is inclined by about 2°.

[0046] Example 2

[0047] A laser friction stir welding method for stainless steel special-shaped parts, comprising the following steps:

[0048] S1, laser preheating test:

[0049] The first stainless steel test piece and the second stainless steel test piece similar to the first stainless steel special-shaped part and the second stainless steel special-shaped part are respectively cut out by wire cutting, the first stainless steel test piece and the second stainless steel test piece are clamped, then the laser beam is aligned with the butt joint groove for preheating, and the infrared temperature measuring instrument is used to measure the temperature of the preheating area, the infrared temperature measuring instrument moves closely behind the laser beam, and the moving speeds of the two are the same, when the temperature measured by the infrared temperature measuring instrument is 450℃, the laser power and the laser scanning speed of the preheating laser beam at each temperature are recorded, and the heat input of the laser welding is calculated according to the following formula:

[0050] Q=ηP / v, wherein η is the thermal efficiency coefficient, generally 0.8 when welding stainless steel, and the heat input of the laser welding is calculated to be in the range of 9KJ / cm.

[0051] S2, pretreatment:

[0052] The butt joint groove and the area of 15-30mm on both sides of the first stainless steel special-shaped part and the second stainless steel special-shaped part to be welded are cleaned to remove burrs, surface protrusions, oil stains and water rust, etc.

[0053] S3, clamping:

[0054] The first stainless steel special-shaped part and the second stainless steel special-shaped part to be welded are clamped by using inner support tooling and outer clamps respectively, to ensure that the butt joint gap between the first stainless steel special-shaped part and the second stainless steel special-shaped part after clamping is ≤0.15mm, and the misalignment between the first stainless steel special-shaped part and the second stainless steel special-shaped part is ≤0.15mm.

[0055] S4, laser positioning welding:

[0056] The first stainless steel special-shaped part and the second stainless steel special-shaped part after clamping are positioned and welded by using laser beam, the positioning welding distance is 50mm, and the positioning welding seam length is 15mm.

[0057] The specific process parameters of the laser positioning welding are as follows: the laser power is 2000W, the welding speed is 1.0m / min, the defocusing amount is +3mm, the protective gas flow is 20L / min, the purity of the protective gas argon is ≥99.999%, and the laser deflection angle is 8°.

[0058] After the positioning welding is completed, the positioning welding seam is cleaned to remove spatters, dirt and the like on and near the welding seam surface.

[0059] S5, laser friction stir welding:

[0060] In the laser friction stir composite welding, laser preheating is first carried out, and then six-link friction stir welding is carried out by using a six-link friction stir welding numerical control special machine. The laser preheating and the friction stir welding maintain the same speed. At the starting point, the laser beam is first turned on for laser preheating, and stays for 0.5-1s. After reaching the predetermined preheating temperature, the laser beam moves along the path trajectory of the butt joint for preheating. After the laser beam moves along the path trajectory of the butt joint for 10mm, the six-link friction stir welding numerical control special machine is started, and also moves along the path trajectory of the butt joint to start welding. In the laser friction stir composite welding, the laser preheating power is 1500W, the laser scanning speed is the same as the moving speed of the stir head, that is, 80mm / min. At the end point, the laser beam is first turned off, and the six-link friction stir welding numerical control special machine is also turned off when it reaches the point.

[0061] The main process parameters of the friction stir welding are as follows: the rotation speed of the stir head is 600r / min, the welding speed is 80mm / min, the penetration depth is 0.1mm, and the main shaft of the six-link friction stir welding machine is inclined by about 2°.

[0062] Example 3

[0063] A laser friction stir composite welding method for stainless steel special-shaped parts, comprising the following steps:

[0064] S1, laser preheating test:

[0065] The first stainless steel test piece and the second stainless steel test piece similar to the first stainless steel special-shaped part and the second stainless steel special-shaped part are respectively cut out by wire cutting. The first stainless steel test piece and the second stainless steel test piece are clamped, and then the laser beam is aligned with the butt joint for preheating. At the same time, the temperature of the preheating area is measured by an infrared temperature measuring instrument. The infrared temperature measuring instrument moves closely behind the laser beam, and the moving speed of the two is the same. When the temperature measured by the infrared temperature measuring instrument is 420℃, the laser power and the laser scanning speed of the preheating laser beam at each temperature are recorded, and the heat input of the laser welding is calculated according to the following formula:

[0066] Q=ηP / v, wherein η is the thermal efficiency coefficient, generally taken as 0.8 when welding stainless steel, and the heat input of the laser welding is calculated as 6.4KJ / cm.

[0067] S2, pretreatment:

[0068] The butt joint and the area of 15-30mm on both sides of the first stainless steel special-shaped part and the second stainless steel special-shaped part to be welded are cleaned to remove burrs, surface protrusions, oil stains and water rust, etc.

[0069] S3, clamping:

[0070] The first stainless steel special-shaped part and the second stainless steel special-shaped part are clamped by using inner support tooling and outer clamps respectively, so as to ensure that the butt joint gap between the clamped first stainless steel special-shaped part and the second stainless steel special-shaped part is ≤0.15 mm, and the misalignment between the first stainless steel special-shaped part and the second stainless steel special-shaped part is ≤0.15 mm.

[0071] S4, laser positioning welding:

[0072] The clamped first stainless steel special-shaped part and the second stainless steel special-shaped part are positioned and welded by using a laser beam, the positioning welding interval is 45 mm, and the positioning welding seam length is 12 mm.

[0073] The specific process parameters of laser positioning welding are: laser power is 1800W, welding speed is 1.2m / min, defocusing amount is +2mm, protective gas flow is 16L / min, purity of protective gas argon is ≥99.999%, and laser deflection angle is 8°.

[0074] After the positioning welding is completed, the positioning welding seam is cleaned to remove spatters, dirt and the like on and near the welding seam surface.

[0075] S5, laser friction stir welding:

[0076] During laser friction stir composite welding, laser preheating is first performed, and then six-link friction stir welding is performed by using a six-link friction stir welding numerical control special machine, and the laser preheating and the friction stir welding maintain the same speed. At the starting point, the laser beam is first turned on for laser preheating, and stays for 0.5-1s. After reaching the predetermined preheating temperature, the laser beam moves along the path trajectory of the butt joint bevel for preheating. After the laser beam moves along the path trajectory of the butt joint bevel for 8mm, the six-link friction stir welding numerical control special machine is started, and also moves along the path trajectory of the butt joint bevel to start welding. In laser friction stir composite welding, the laser preheating power is 1200W, the laser scanning speed is the same as the stirring head moving speed, i.e. 90mm / min. At the end point, the laser beam is first turned off, and the six-link friction stir welding numerical control special machine is also turned off when it reaches the point.

[0077] The main process parameter range of the friction stir welding is: the stirring head rotating speed is 650r / min, the welding speed is 90mm / min, the penetration depth is 0.17mm, and the main shaft of the six-link friction stir welding machine is inclined by about 2°.

[0078] Example 4

[0079] A laser friction stir composite welding method for stainless steel special-shaped parts, comprising the following steps:

[0080] S1, laser preheating test:

[0081] The first stainless steel test piece and the second stainless steel test piece similar to the first stainless steel special-shaped part and the second stainless steel special-shaped part are cut out by wire cutting, the first stainless steel test piece and the second stainless steel test piece are clamped, then the laser beam is aimed at the butt joint groove for preheating, and the infrared temperature measuring instrument is used to measure the temperature of the preheating area, the infrared temperature measuring instrument moves closely behind the laser beam, and the moving speeds of the two are the same, when the temperature measured by the infrared temperature measuring instrument is 430 DEG C, the laser power and the laser scanning speed of the preheating laser beam at each temperature are recorded, and the heat input of the laser welding is calculated according to the following formula:

[0082] Q = ηP / v, wherein η is the thermal efficiency coefficient, generally 0.8 when welding stainless steel, and the heat input of the laser welding is calculated to be 7.2 KJ / cm.

[0083] S2, pretreatment:

[0084] The butt joint groove and the area of 15-30 mm on both sides of the first stainless steel special-shaped part and the second stainless steel special-shaped part to be welded are cleaned, and burrs, surface protrusions, oil stains and water rust are removed.

[0085] S3, clamping:

[0086] The first stainless steel special-shaped part and the second stainless steel special-shaped part to be welded are clamped by using inner support tooling and outer clamp respectively, so that the butt joint gap between the first stainless steel special-shaped part and the second stainless steel special-shaped part after clamping is ≤0.15 mm, and the misalignment between the first stainless steel special-shaped part and the second stainless steel special-shaped part is ≤0.15 mm.

[0087] S4, laser positioning welding:

[0088] The first stainless steel special-shaped part and the second stainless steel special-shaped part after clamping are positioned and welded by using laser beam, the positioning welding distance is 40 mm, and the positioning welding length is 10 mm.

[0089] The specific process parameters of laser positioning welding are as follows: the laser power is 1500 W, the welding speed is 1.0 m / min, the defocusing amount is +2 mm, the protective gas flow is 16 L / min, the purity of the protective gas argon is ≥99.999%, and the laser deflection angle is 8 DEG.

[0090] After positioning welding, the positioning weld is cleaned to remove spatter, dirt and the like on and near the weld surface.

[0091] S5, laser friction stir welding:

[0092] In the laser friction stir welding, laser preheating is first performed, and then six-link friction stir welding is performed by using a six-link friction stir welding numerical control special machine, and the laser preheating and the friction stir welding are kept at the same speed. At the starting point, the laser beam is first turned on for laser preheating, and stays for 0.5-1s, and then moves along the path trajectory of the butt joint bevel to preheat, and after the laser beam moves along the path trajectory of the butt joint bevel by 6mm, the six-link friction stir welding numerical control special machine is started, and also moves along the path trajectory of the butt joint bevel to start welding; in the laser friction stir composite welding, the laser preheating power is 1500W, the laser scanning speed is the same as the moving speed of the stirring head, that is, 100mm / min, and at the end point, the laser beam is first turned off, and when the six-link friction stir welding numerical control special machine welds to the point, it is also turned off.

[0093] The main process parameters of the friction stir welding are as follows: the rotation speed of the stirring head is 630r / min, the welding speed is 100mm / min, the penetration depth is 0.15mm, and the main shaft of the six-link friction stir welding machine is inclined by about 2°.

[0094] Comparative Example 1

[0095] Comparative Example 1 is a comparative test example of Example 3, and the difference between Comparative Example 1 and Example 3 is that:

[0096] In Comparative Example 1, the stainless steel special-shaped parts are not preheated, and the specific steps are as follows:

[0097] S1, pretreatment:

[0098] The butt joint bevels and the regions 15-30mm away from the butt joint bevels of the first stainless steel special-shaped part and the second stainless steel special-shaped part are cleaned, and burrs, surface protrusions, oil stains, and water rust are removed.

[0099] S2, clamping:

[0100] The first stainless steel special-shaped part and the second stainless steel special-shaped part are clamped by using an inner support tool and an outer clamp respectively, so that the butt joint gap between the first stainless steel special-shaped part and the second stainless steel special-shaped part after clamping is ≤0.15mm, and the misalignment between the first stainless steel special-shaped part and the second stainless steel special-shaped part is ≤0.15mm.

[0101] S3, laser positioning welding:

[0102] The first stainless steel special-shaped part and the second stainless steel special-shaped part after clamping are positioned and welded by using a laser beam, the positioning and welding interval is 45mm, and the positioning and welding length is 12mm.

[0103] The specific process parameters of the laser positioning welding are as follows: the laser power is 1800W, the welding speed is 1.2m / min, the defocusing amount is +2mm, the protective gas flow is 16L / min, the purity of the protective gas argon is ≥99.999%, and the laser deflection angle is 8°.

[0104] After the positioning welding is completed, the positioning weld is cleaned to remove spatters, dirt and the like on and near the surface of the weld.

[0105] S4, friction stir welding:

[0106] The friction stir welding is directly performed along the butt joint groove, and the main process parameter range of the friction stir welding is as follows: the rotation speed of the stirring head is 1200r / min, the welding speed is 30mm / min, the penetration depth is 0.1mm, and the main shaft of the six-link friction stir welding machine is inclined by about 2°.

[0107] Comparative Example 2

[0108] Comparative Example 2 is a comparative test example of Example 3, and the difference between Comparative Example 2 and Example 3 is that:

[0109] In Comparative Example 2, the preheating temperature in the laser friction stir composite welding process is controlled at 380℃, and the laser preheating power is 800W. The other steps and parameter settings are the same as those of Example 3.

[0110] Comparative Example 3

[0111] Comparative Example 3 is a comparative test example of Example 3, and the difference between Comparative Example 3 and Example 3 is that:

[0112] In Comparative Example 3, the preheating temperature in the laser friction stir composite welding process is controlled at 470℃, and the laser preheating power is 1600W. The other steps and parameter settings are the same as those of Example 3.

[0113] Experimental performance test:

[0114] The welded joints of the first stainless steel special-shaped part and the second stainless steel special-shaped part in Examples 1-4 and Comparative Examples 1-3 are observed to observe the welding deformation degree, the weld surface forming effect (whether burrs, surface peeling, surface depression and oxidation blackening and the like defects occur at the weld), and three groups of mechanical property tests are respectively performed on the stainless steel special-shaped part welded joints and the base metal at room temperature to obtain the test average value. The test results are shown in Table 1.

[0115] Table 1

[0116]

[0117] From Table 1, in Examples 1-4, the tensile strength of the shaped part welded joint sample reached more than 95% of the tensile strength of the shaped part base metal sample, indicating that the welding quality reached the expected effect, and after laser- friction stir welding, the welding deformation was small, the weld surface was well formed, and there were no defects such as burrs, surface peeling, etc.

[0118] In Comparative Example 1, since the stainless steel shaped part was not preheated, the welding deformation was slightly large, the weld surface appeared blackened by oxidation, the weld surface was concave, and the weld bottom appeared to be not penetrated / not fused.

[0119] In Comparative Example 2, since the preheating temperature was low, a small amount of black spots appeared on the weld surface, and a small amount of not penetrated / not fused appeared on the back of the weld.

[0120] In Comparative Example 3, since the preheating temperature was too high, some traces of cracks appeared in the joint area, and the weld surface was slightly rough.

[0121] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A laser stir friction composite welding method for stainless steel special-shaped parts, characterized in that: The following steps are involved: S1. Pretreatment: Clean the butt joint groove and the areas near the two sides of the first stainless steel special-shaped part and the second stainless steel special-shaped part to be welded; S2, clamping: clamping and positioning the pre-treated first stainless steel special-shaped part and the second stainless steel special-shaped part; S3, Laser tack welding: tack welding using laser; S4, laser friction stir welding: first preheat the laser in front of the stirring head of the friction stir welding device. The preheating temperature range of stainless steel special-shaped parts is 400-450℃. Then, friction stir welding is performed at a distance of 5-10mm. The laser preheating and friction stir welding are kept at the same speed. In step S4, before laser preheating, a laser preheating test is carried out using a first stainless steel test piece and a second stainless steel test piece that are made of the same material and have a similar structure to the first stainless steel special-shaped piece and the second stainless steel special-shaped piece. The preheating temperature in the laser preheating test is measured using an infrared thermometer to ensure that the measured preheating temperature range is between 400 and 450°C. The laser power and scanning speed at the measured temperature are then recorded, and the heat input for laser welding is calculated according to the following formula: Q=ηP / v, where η is the thermal efficiency coefficient, which is 0.8, P is the laser power, and v is the laser scanning speed. The heat input range of laser welding is calculated to be 5-9 kJ / cm; The laser scanning speed is the same as the moving speed of the stirring head in friction stir welding, which is 80-100 mm / min. Based on the heat input of laser welding calculated in the laser preheating test, the laser preheating power range is calculated to be 1000-1500 W. The laser power used in the laser positioning welding process is 1500~2000W.

2. The laser stir friction hybrid welding method for stainless steel special-shaped parts according to claim 1, characterized in that: The process parameter range of friction stir welding is: stirring head rotation speed of 600-700 r / min, welding speed of 80-100 mm / min, and pressing depth of 0.1-0.2 mm.

3. The laser stir friction hybrid welding method for stainless steel special-shaped parts according to claim 2, characterized in that: The friction stir welding device is a six-link type friction stir welding CNC machine.

4. The laser stir friction hybrid welding method for stainless steel special-shaped parts according to claim 1, characterized in that: In step S3, when laser tack welding is performed on the first stainless steel special-shaped part and the second stainless steel special-shaped part using a laser, the tack welding interval is 40 to 50 mm, and the tack weld length is 10 to 15 mm.

5. The laser stir friction hybrid welding method for stainless steel special-shaped parts according to claim 4, characterized in that: The specific process parameters of laser positioning welding are: welding speed of 1.0~1.2m / min, defocus of +2~+5mm, shielding gas flow rate of 15~20L / min, purity of shielding gas argon ≥99.999%, and laser deflection angle of 8°.

6. The laser stir friction hybrid welding method for stainless steel special-shaped parts according to claim 1, characterized in that: In step S2, the first stainless steel special-shaped part and the second stainless steel special-shaped part to be welded are clamped by using an internal support tool and an external clamp respectively. After clamping, the butt gap between the first stainless steel special-shaped part and the second stainless steel special-shaped part is ≤0.15mm, and the misalignment between the first stainless steel special-shaped part and the second stainless steel special-shaped part is ≤0.15mm.

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