Production and manufacturing method of austenitic stainless steel capillary tube with outer diameter range of 3.0 mm-5. 0mm

Abstract

The invention provides a production and manufacturing method of an austenitic stainless steel capillary tube with the outer diameter range of 3.0 mm-5. 0mm, and belongs to the technical field of stainless steel capillary tube preparation. The austenitic stainless steel capillary tube is obtained by sequentially carrying out butt joint, forming, welding and heat treatment drawing on steel strips. According to welding, backing welding is conducted through ultra-narrow gap fiber laser, then capping operation is conducted through heat conduction semiconductor welding, the welded tube is obtained, the forming quality of austenitic stainless steel longitudinal welding seams can be effectively guaranteed, various welding defects are avoided, the mechanical performance of the prepared stainless steel capillary tube meets the ASTM A632 standard requirement, and the production cost is lowered. And the hardness meets the ASTM A269 standard requirement.

Description

Technical Field

[0001] This invention relates to the field of stainless steel capillary preparation technology, and in particular to a method for producing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm. Background Technology

[0002] Most existing welding processes employ single-layer argon arc welding, which uses argon gas to protect the metal welding material. A high current melts the welding material into a liquid state on the substrate, forming a molten pool that achieves a metallurgical bond between the weld metal and the welding material. This technique is primarily used for large-diameter pipes. Compared to composite welding, single-layer welding involves a higher heat input, a higher risk of welding deformation, and an increased probability of welding defects. Weld quality issues (such as misalignment, undercut, and incomplete penetration) are more likely to occur, and welding defects are more prone to occur at start-up and shutdown points. Production efficiency is also lower compared to composite welding. Furthermore, there is limited development of small-diameter capillary tubes, which cannot meet the specific pipe diameter requirements of certain industries or applications. Summary of the Invention

[0003] In view of this, the present invention provides a method for manufacturing austenitic stainless steel capillary tubes with an outer diameter of 3.0 mm-5.0 mm, comprising the following steps:

[0004] (1) Steel strip butt welding: Take the steel strips to be welded and butt them longitudinally to form a weld. Align the stainless steel welding wire with the weld and use argon arc welding to weld, so that the thickness tolerance of the weld does not exceed 0.06mm.

[0005] (2) Steel strip cleaning and forming: The steel strip is inspected, uncoiled and straightened, then ultrasonically cleaned, and then formed into the shape of a control tube by a roller pressing device and a tube forming device;

[0006] (3) Welding tube making: First, ultra-narrow gap fiber laser is used for root welding, and then heat conduction semiconductor welding is used for cover operation to obtain welded tube;

[0007] (4) Heat treatment drawing: The welded tube is heat treated and drawn by bright annealing to obtain austenitic stainless steel capillary tubes with an outer diameter of 3.0mm-5.0mm.

[0008] Preferably, the steel strip in step (1) has a specification of 23-24mm × 0.7mm.

[0009] Preferably, in step (1), the welding process is set with the following parameters: nozzle flow rate of the welding machine is 6-8 L / min, back shielding gas flow rate is 4-5 L / min, welding current is 45-50 A, welding speed is 20-25 m / min, electrode spacing is 1.5-2 mm, and electrode angle is 20-21°; the back shielding gas is Ar gas.

[0010] Preferably, the ultrasonic cleaning power in step (2) is 180-200W; the extrusion pressure of the roller pressing device is 100-110Mpa.

[0011] Preferably, the specific steps of welding and pipe making in step (3) are as follows:

[0012] Welding is controlled at 22-28℃. First, the laser welding machine's beam axis angle is fixed at 90°, with a tilt angle less than 16°. The distance from the lower edge of the lens to the welding surface is controlled at 195mm for ultra-narrow gap fiber laser welding. Then, the external shielding gas flow rate is set to 3-8L / min, the internal shielding gas flow rate to 3-6L / min, the fiber power to 700-800W, the semiconductor power to 800-900W, and the welding speed to 2.0-2.2m / min. Both the external and internal shielding gases are argon. Through this series of standardized operations, the forming quality of the longitudinal weld seam of austenitic stainless steel can be effectively guaranteed, avoiding various welding defects.

[0013] Preferably, the welded pipe in step (3) has a specification of φ8mm×0.7m; the maximum depth and width of the defect size of the welded pipe are less than 0.100 mm.

[0014] Preferably, the bright annealing temperature in step (4) is 1000-1070℃, the running speed is 3.5-4.0m / min, the holding time is 4-4.5min, the cooling rate is 4-4.5m / min, and the temperature after cooling is room temperature.

[0015] Preferably, the bright annealing in step (4) is carried out in a protective gas atmosphere, wherein the protective gas is a mixture of argon and ammonia decomposition protective gas.

[0016] Preferably, the pulling process in step (4) has a traction speed of 3.0 m / min, a traction force of 450 N, a pulling force of 550 N, and a time of 6.0 min.

[0017] Preferably, the austenitic stainless steel capillary tube in step (4) has a size of φ3.0-5.0mm×0.78mm.

[0018] Preferably, the maximum depth and width of the austenitic stainless steel capillary defect size in step (4) are less than 0.100 mm.

[0019] The different steps of this invention have the following effects:

[0020] (1) Steel strip butt joint:

[0021] Steel strip butt welding is a crucial initial step in the entire production process. First, austenitic stainless steel strips that meet specific chemical composition and physical property requirements are carefully selected to ensure excellent toughness and machinability.

[0022] (2) Molding:

[0023] The key to the forming process lies in controlling the degree and uniformity of the steel strip deformation to ensure that the wall thickness of the tube blank is uniform and the roundness meets the requirements. Uniform wall thickness and good roundness play a decisive role in the stability and welding quality of subsequent welding processes, and also help to improve the dimensional accuracy and appearance quality of the final capillary.

[0024] (3) Welding:

[0025] ① The quality of the root pass welding directly affects the strength and sealing of the entire weld. Ultra-narrow gap fiber laser welding technology can ensure that there are no defects at the root of the weld, providing a reliable guarantee for subsequent processes.

[0026] ② During the welding process of heat-conducting semiconductor caps, a smooth and flat weld formation can be achieved, effectively avoiding surface defects such as undercut and weld beads that may occur with traditional welding methods. Simultaneously, precise temperature control can optimize the welding thermal cycle, further improving the microstructure of the weld metal and enhancing its mechanical properties and corrosion resistance.

[0027] (4) Heat treatment drawing:

[0028] During the heating process, the pipe is heated evenly to reach an appropriate temperature, thereby eliminating residual stress generated during welding, improving the microstructure of the weld and heat-affected zone, and enhancing the toughness and plasticity of the material.

[0029] Drawing is the process of applying tensile force to a tube using a drawing die, thereby reducing its diameter and appropriately changing its wall thickness to achieve the required dimensional accuracy and surface quality.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention provides a method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0mm-5.0mm, belonging to the technical field of stainless steel capillary preparation. The invention sequentially butt-joints, forms, welds, heat-treats, and draws steel strips to obtain austenitic stainless steel capillary tubes. The welding process first employs an ultra-narrow gap fiber laser for the root pass, followed by heat-conducting semiconductor welding for the cap pass, resulting in a welded tube. This effectively ensures the forming quality of the longitudinal weld seam of the austenitic stainless steel, avoids various welding defects, and the mechanical properties of the prepared stainless steel capillary tubes meet the requirements of ASTM A632 standard, while the hardness meets the requirements of ASTM A269 standard. Attached Figure Description

[0032] Figure 1 This is a detailed structural diagram of the capillary prepared in Example 1;

[0033] Figure 2 A 20X macroscopic image of the capillary weld prepared in Example 1;

[0034] Figure 3 A 20X macroscopic image of the capillary parent material prepared in Example 1;

[0035] Figure 4 The macroscopic structure of the weld bead in the capillary of Comparative Example 1;

[0036] Figure 5 The image shows a macroscopic view of the weld seam of the capillary tube in Comparative Example 2.

[0037] Figure 6 This is a macroscopic image of the surface of a capillary in Comparative Example 2. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments.

[0039] Example 1

[0040] A method for manufacturing austenitic stainless steel capillary tubes with an outer diameter of 3.0mm-5.0mm, comprising the following steps:

[0041] (1) Steel strip butt joint: Take a steel strip with a specification of 23.7×0.7mm and butt it longitudinally to form a weld. Align the stainless steel welding wire of grade ER316L with the weld and set the argon arc welding parameters as follows: nozzle flow rate 8L / min (Ar), back shielding gas flow rate 5L / min (Ar), welding current 50A, welding speed 20m / min, electrode spacing 2mm, and electrode angle 21° to perform welding, so that the thickness tolerance of the weld does not exceed 0.06mm;

[0042] (2) Steel strip cleaning and forming: The steel strip is inspected and the surface of the steel strip should not have defects such as burrs, pits, delamination, cracks, etc. If there are defects such as burrs and pits that can be repaired, they can be ground. After grinding, the surface of the steel strip should be flat. Then, the strip is uncoiled and straightened, and ultrasonic cleaning is performed with a working current of 2A. Then, it is formed into the shape of a control tube by a roller pressing device with a pressure of 100 MPa and a tube forming device.

[0043] (3) Welding tube making: Welding is carried out at 22-28℃. First, the beam axis angle of the laser welding machine is fixed at 90° and the tilt angle is less than 16°. The distance from the lower edge of the lens to the welding surface is controlled at 195mm for ultra-narrow gap fiber laser welding. Then, the external shielding gas flow rate is set to 5L / min, the internal shielding gas flow rate is 5L / min, the fiber power is 700W, the semiconductor power is 800W, and the welding speed is 2.0m / min for heat conduction semiconductor welding. Finally, the longitudinal weld is ground to obtain a welded tube with a specification of φ8mm×0.7m. The maximum depth and width of the defect size of the welded tube are less than 0.100mm.

[0044] (4) Heat treatment drawing: The welded tubes were heat-treated and drawn using a bright annealing method to obtain austenitic stainless steel capillary tubes with a diameter of 4.16mm × 0.78mm; the process was carried out under a protective gas of argon and ammonia decomposition (argon was used in the capillary tube cavity, and ammonia was used in the furnace cavity). The bright annealing temperature was 1070℃, the running speed was 4.0m / min, the holding time was 4.5min, the cooling method was rapid cooling, and the cooling rate was 4.5m / min. The final temperature is room temperature. The annealing and drawing processes are carried out simultaneously. The drawing process is 8-6.35-solution-4.16-solution (the tube passes through the drawing die, and the outer diameter is drawn from 8mm to 6.35mm. After solution treatment, it is drawn again to 4.16mm). The tube passes through the annealing furnace twice (the first and second times are both 4.5min). The traction speed of the drawing process is 3.0m / min, the traction force is 450N, the drawing force is 550N, and the time is 6.0min.

[0045] The maximum depth and width of the defects in the austenitic stainless steel capillary tubes are less than 0.100 mm.

[0046] The mechanical properties of the austenitic stainless steel capillary tube prepared in Example 1 were tested according to the requirements of ASTM A632 standard. The experiment was repeated three times, and the results are shown in Table 1.

[0047] Table 1

[0048] Tensile strength RM (MPa) Yield strength RP0.2 (MPa) Elongation (%) 609 308 61.5 607 305 61.0 610 312 62 Standard value: ≥586 MPa Standard value: ≥276 MPa Standard value: ≥35%

[0049] The specific structural diagram of the capillary prepared in Example 1 is shown below. Figure 1 The hardness of the austenitic stainless steel capillary tubes prepared in Example 1 was tested according to the requirements of ASTM A269 standard (≤200HV), and the results are shown in Table 2:

[0050] Table 2

[0051] Specification Weld (HV) Heat-affected zone (HV) Base material (HV) Base material 90° (HV) Base material 180° (HV) 4.16×0.78 148.9 147.6 146.8 145.9 145.5

[0052] Dissolve 100g of analytical grade copper sulfate (CuSO4·5H2O) conforming to GB / T665 in 700mL of distilled or deionized water, then add 100mL of superior grade sulfuric acid conforming to GB / T625. Dilute with distilled or deionized water to 1000mL to prepare a 16% sulfuric acid-copper sulfate solution. The experiment was conducted according to the XDKC / QD-ZJ-15 intergranular corrosion operating procedure. Macroscopic analysis was performed using a stereomicroscope at 20x. The results are as follows: Figure 1-2 .like Figure 1 This is a 20X macroscopic image of the capillary weld prepared in Example 1. Figure 2 A 20X macroscopic image of the capillary matrix material prepared in Example 1. From... Figure 1 and Figure 2 It can be seen that no cracks caused by intergranular corrosion were found on the surface and cross-section of the sample (cracks originating from the corners of the curved parts of the sample, as well as slip lines, wrinkles, and surface roughness without cracks, cannot be considered as cracks caused by intergranular corrosion). The inspection is qualified.

[0053] Comparative Example 1

[0054] A method for manufacturing austenitic stainless steel capillary tubes with an outer diameter of 3.0mm-5.0mm, the steps are the same as in Example 1, except that heat conduction semiconductor welding is not performed in Comparative Example 1.

[0055] The mechanical properties of the capillary in Comparative Example 1 are shown in Table 3 (the experimental method is the same as in Example 1).

[0056] Table 3

[0057] Tensile strength RM (MPa) Yield strength RP 0.2 (MPa) Elongation (%) 863 614 38 865 621 37 868 636 35 Standard value: ≥800 MPa Standard value: ≥500Mpa Standard value: ≥15%

[0058] Comparative Example 1: Macroscopic structure of a capillary (macroscopic analysis using a laboratory microscope) Figure 4 .from Figure 4 It can be seen that due to the special diameter of the pipeline, the welding difficulty is increased, and cracks appear at the weld location.

[0059] Comparative Example 2

[0060] A method for manufacturing austenitic stainless steel capillary tubes with an outer diameter of 3.0mm-5.0mm, the steps are the same as in Example 1, the difference being that Comparative Example 2 does not perform argon arc welding for single-layer welding.

[0061] Macroscopic structure of capillary welds, such as Figure 5 .from Figure 5 It can be seen that the weld is not fully penetrated and there is no weld reinforcement.

[0062] Intergranular corrosion experiments were conducted on the capillary of Comparative Example 2 (same as Example 1). The macroscopic structure of the tube surface is as follows: Figure 6 .from Figure 6 It can be seen that during the welding process, the heat-affected zone may become sensitized due to improper heating, leading to an increased tendency for intergranular corrosion. Cracks caused by intergranular corrosion were found on the inner and outer surfaces of the sample, resulting in failure to pass inspection.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm, characterized in that, Includes the following steps: (1) Steel strip butt welding: Take the steel strips to be welded and butt them longitudinally to form a weld. Align the stainless steel welding wire with the weld and use argon arc welding to weld, so that the thickness tolerance of the weld does not exceed 0.06mm. (2) Steel strip cleaning and forming: The steel strip is inspected, uncoiled and straightened, then ultrasonically cleaned, and then formed into the shape of a control tube by a roller pressing device and a tube forming device; (3) Welding tube making: First, ultra-narrow gap fiber laser is used for root welding, and then heat conduction semiconductor welding is used for cover operation to obtain welded tube; (4) Heat treatment drawing: The welded tube is heat treated and drawn by bright annealing to obtain austenitic stainless steel capillary tubes with an outer diameter of 3.0mm-5.0mm.

2. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The steel strip in step (1) has a specification of 23-24mm × 0.7mm.

3. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, In step (1), the welding process is set with the nozzle flow rate of the welding machine as 6-8 L / min, the back shielding gas flow rate as 4-5 L / min, the welding current as 45-50 A, the welding speed as 20-25 m / min, the electrode spacing as 1.5-2 mm, and the electrode angle as 20-21°; the back shielding gas is Ar gas.

4. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The ultrasonic cleaning power in step (2) is 180-200W; the extrusion pressure of the roller pressing device is 100-110Mpa.

5. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The specific steps for welding and pipe making in step (3) are as follows: Welding is controlled at 22-28℃. First, the beam axis angle of the laser welding machine is fixed at 90°, the tilt angle is less than 16°, and the distance from the lower edge of the lens to the welding surface is controlled at 195mm for ultra-narrow gap fiber laser welding. Then, the external shielding gas flow rate is set to 3-8L / min, the internal shielding gas flow rate to 3-6L / min, the fiber power to 700-800W, the semiconductor power to 800-900W, and the welding speed to 2.0-2.2m / min for heat conduction semiconductor welding. Finally, the longitudinal weld is ground. Both the external and internal shielding gases are argon.

6. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The specifications of the welded pipe in step (3) are φ8mm×0.7m; the maximum depth and width of the defect size of the welded pipe are less than 0.100 mm.

7. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The bright annealing temperature in step (4) is 1000-1070℃, the running speed is 3.5-4.0m / min, the holding time is 4-4.5min, the cooling rate is 4-4.5m / min, and the temperature after cooling is room temperature.

8. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The bright annealing in step (4) is carried out in a protective gas atmosphere, which is a mixture of argon and ammonia decomposition protective gas.

9. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The specific parameters for the pulling process in step (4) are: traction speed of 3.0 m / min, traction force of 450 N, pulling force of 550 N, and time of 6.0 min.

10. The method for manufacturing austenitic stainless steel capillary tubes with an outer diameter range of 3.0 mm to 5.0 mm according to claim 1, characterized in that, The austenitic stainless steel capillary tube in step (4) has a size of φ3.0-5.0mm×0.78mm; the maximum depth and width of the defect size of the austenitic stainless steel capillary tube are less than 0.100mm.

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