A welding method of 15-5PH stainless steel by high frequency pulse argon arc welding

Abstract

A 15-5PH stainless steel high-frequency pulse argon arc welding method is characterized by comprising the following steps: machining the part shape and the welding groove by turning, milling or / and grinding process; first, the part is degaussed, then the welding groove and the area not less than 20mm on both sides of the welding groove are cleaned by using acetone or alcohol to remove oil stains, dust and other impurities; high-frequency pulse argon arc welding is carried out in the solid solution state, the design adopts layered welding, the first layer is bottom welding without wire, the second layer is wire filling welding to cover the surface, the welding material uses the welding wire with similar chemical composition to the base material, and the protective gas uses argon with purity not less than 99.99%; post-weld aging treatment; and welding quality inspection. Compared with the prior art, the application can ensure the performance of the welded joint while improving the weld forming quality, and the weld does not need to be repaired after welding, the weld can meet the welding quality requirements by inspection in the original state of welding, and the first-time qualified rate of the weld can reach 100%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal material welding, in particular to a 15-5PH stainless steel high-frequency pulse argon arc welding method. BACKGROUND

[0002] 15-5PH steel is a kind of martensitic precipitation hardening stainless steel, the tensile strength can reach more than 1200MPa, has high strength, high toughness, good corrosion resistance, excellent machinability and other advantages, is widely used in aerospace, shipbuilding, energy chemical industry, nuclear industry, weapon industry and other fields. Because the working conditions of such parts are harsh, the service environment is bad, so when carrying out welding heat treatment, the quality of the weld is very high. Especially for the load-bearing structure with high fatigue performance, the quality of the weld surface and the inside, the performance of the welded joint, the geometric size of the weld are important factors affecting the fatigue life of the structure, therefore the welding quality inspection must be strictly implemented.

[0003] 15-5PH stainless steel alloy element content is high, low thermal conductivity, high resistivity, using traditional melting welding is easy to produce composition segregation, heat affected zone softening, joint strength lower than the base material and other problems, and the alloy element contains strong hot cracking tendency elements Cu and Ti, there is a certain tendency of hot cracking, so it is very important to control the interlayer temperature, control the welding line energy, limit the depth-width ratio and reduce the tendency of hot cracking for the welding of 15-5PH stainless steel.

[0004] Vacuum electron beam welding, laser welding, pulse argon arc welding has high energy density, heat concentration, small welding heat affected zone, is the best welding method for welding martensitic precipitation hardening stainless steel. However, the above welding methods have their own advantages and disadvantages. Vacuum electron beam welding is difficult to weld large size and complex structure due to the limitation of the size of the vacuum chamber and the welding position, so there is certain limitation. The small hole effect of laser deep penetration welding mode is easy to form pores in the weld, and the welding quality is difficult to control, and the self-fusion welding of laser welding and electron beam welding is easy to appear weld front concave, back excess height and sharp angle at the corner of the base material, which affects the fatigue life of the welded structure. Pulse tungsten argon arc welding has the advantages of stable arc, no spatter, low line energy, etc., which can ensure the welding quality, and the tungsten argon arc welding has the characteristics of high flexibility and strong adaptability, which can be applied to various position welding. However, using the current common low-frequency pulse argon arc welding below 200Hz to weld 15-5PH stainless steel still has the following shortcomings: (1) the tungsten electrode has poor current carrying capacity, and the tungsten electrode will melt and burn when the current is large or the welding time is long, and the particles entering the molten pool will easily cause weld inclusion; (2) using low-frequency pulse argon arc welding to weld 15-5PH stainless steel, due to the poor arc rigidity and small arc force, the weld penetration rate is low, and the weld bead is easy to deviate or the back forming is discontinuous, which affects the weld forming quality. SUMMARY

[0005] The technical problem to be solved by the present invention is to provide a high-frequency pulsed argon arc welding method for 15-5PH stainless steel, which can improve the weld formation quality while ensuring the performance of the welded joint.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a high-frequency pulsed argon arc welding method for 15-5PH stainless steel, characterized by comprising the following steps:

[0007] 1) Parts machining: The shape of the parts and the weld bevels are machined by turning, milling or grinding.

[0008] 2) Pre-welding treatment: First, demagnetize the parts, and then use acetone or alcohol to clean the welding bevel and the area on both sides of it, removing oil, dust and other impurities.

[0009] 3) High-frequency pulsed argon arc welding: 15-5PH stainless steel is welded in the solution-treated state at a temperature of 1035-1052℃, a holding time of 60-90 min, and water cooling; layered welding is adopted, with the first layer being a root pass without wire, and the second layer being a filler pass for the cover pass; welding wire with a chemical composition similar to that of the base metal is used to ensure that the mechanical properties of the weld are close to those of the base metal under the same heat treatment regime; the shielding gas is argon with a purity of not less than 99.99%.

[0010] 4) Post-weld heat treatment: After welding, the welded parts are subjected to aging treatment at a temperature of 550-560℃ for 4 hours and then furnace cooled.

[0011] 5) Welding quality inspection: Conduct quality inspection in accordance with relevant standards and requirements.

[0012] Preferably, the wall thickness of the part in step 1) is 2.5 to 3.8 mm.

[0013] Preferably, the welding bevel in step 1) is a V-shaped butt bevel with a bevel angle of 80°±5° and a blunt edge of 0.5mm.

[0014] As an improvement, the demagnetization process in step 2) involves using a demagnetizer to demagnetize the parts. After demagnetization, a Tesla meter is used to detect the magnetic induction intensity of the parts, and the magnetic induction intensity should be ≤0.2mT.

[0015] Preferably, the tungsten electrode used in step 3) for high-frequency pulsed argon arc welding is a cerium tungsten electrode or a lanthanum tungsten electrode with a diameter of 3.0 to 3.2 mm. The end of the tungsten electrode is ground into a flat truncated cone shape with an included angle of 40° to 60°. The diameter of the truncated cone is 1 / 4 to 1 / 3 of the diameter of the tungsten electrode. This facilitates arc ignition and improves arc stability while ensuring sufficient current carrying capacity of the tungsten electrode.

[0016] Preferably, the horizontal distance between the center of the tungsten electrode tip and the welding wire in step 3) of the high-frequency pulsed argon arc welding is 3.5 to 4.0 mm. Within this distance range, on the one hand, a smaller weld width on the front side can be obtained, and on the other hand, the probability of the welding wire or molten droplets sticking to the tungsten electrode can be reduced, ensuring the stability and continuity of wire feeding.

[0017] Preferably, the welding equipment used for the high-frequency pulsed tungsten inert gas welding in step 3) is an automatic tungsten inert gas welding equipment equipped with an arc voltage tracking system.

[0018] Preferably, the high-frequency pulsed tungsten inert gas welding current in step 3) is DC positive, that is, the workpiece is connected to the positive terminal of the power supply and the tungsten electrode is connected to the negative terminal of the power supply. This can prevent the tungsten electrode from overheating and is conducive to obtaining a narrow and deep weld.

[0019] Preferably, the parameters for the first layer root pass welding in step 3) are: pulse frequency 15-20kHz, peak current 180-200A, base current 100-120A, pulse current amplitude 80-100A, pulse current duty cycle 30-50%, arc voltage 9-10V, welding speed 22-24cm / min, welding torch shielding gas 20-25L / min, drag shield shielding gas 25-30L / min, and back shielding gas 5-10L / min.

[0020] Preferably, the parameters for the second layer filler wire welding in step 3) are: pulse frequency 15-20kHz, peak current 170-190A, base current 90-110A, pulse current amplitude 80-100A, pulse current duty cycle 30-50%, arc voltage 10-11V, welding speed 20-22cm / min, wire feed speed 1000-1200mm / min, welding torch shielding gas 20-25L / min, drag shield shielding gas 25-30L / min, and back shielding gas 5-10L / min.

[0021] Preferably, the interlayer temperature of the high-frequency pulsed argon arc welding in step 3) is strictly controlled below 150°C to prevent grain growth in the heat-affected zone and the generation of reversed austenite.

[0022] Preferably, steps 3) and 4) of the solution treatment and aging treatment are performed under vacuum conditions.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] (1) Regarding the control of welding heat input, prevention of grain growth in the heat-affected zone, and the generation of a large amount of inverted austenite, the present invention adopts the following measures: 1.1) Employing a high-frequency pulsed argon arc welding method, using a smaller base current and a larger peak current, matching a larger pulse current amplitude and a smaller duty cycle; 1.2) Appropriately increasing the welding speed while ensuring penetration, minimizing welding heat input; 1.3) Strictly controlling the interpass temperature below 150℃. These technical measures can effectively reduce the width of the heat-affected zone, prevent softening of the heat-affected zone, and prevent the generation of inverted austenite from adversely affecting the weld strength, plasticity, and toughness.

[0025] (2) Regarding the control of weld formation and dimensional accuracy, the technical advantages of the high-frequency pulsed argon arc welding method of the present invention are as follows: 2.1) It utilizes the high-frequency compression effect of the arc, which improves the energy density and stiffness of the arc, ensures the weld penetration rate, and reduces the weld width; 2.2) It adds a pre-treatment process of demagnetizing the parts before welding, which effectively avoids the arc blow phenomenon caused by residual magnetism generated during the sample processing; 2.3) The design adopts layered welding, in which the first layer of root pass welding does not use filler wire, which can save the energy consumption of the arc heat on the molten welding wire, and solve a series of problems such as uneven back formation, local incomplete penetration, and excessive weld width and reinforcement height that are easy to occur in single-pass welding; 2.4) Strict and stable arc voltage control, using an arc voltage tracking system to monitor the arc voltage in real time during the welding process, automatically controlling the arc height, using a smaller arc voltage, reducing arc energy loss, improving arc energy density, and further ensuring the weld penetration rate and a smaller weld width.

[0026] (3) Regarding the prevention of weld oxidation. The high-frequency pulse argon arc welding method of the present invention adopts a triple protection measure of active protection of the welding torch gas cover + protection of the welding torch tail cover + auxiliary protection of the back of the weld to protect the weld pool with inert gas. Moreover, the solution treatment and aging heat treatment are carried out under vacuum conditions, which can completely solve the problem of weld and base oxidation. The weld is silver or discontinuous light yellow.

[0027] (4) In terms of preventing weld composition segregation and reducing the tendency for hot cracking, the high-frequency pulsed argon arc welding of 15-5PH stainless steel of this invention uses welding materials with a composition similar to that of the base metal and performs welding in a low-strength solution-treated state. After welding, aging treatment is performed to ensure that the mechanical properties of the welded joint are close to those of the base metal under the same heat treatment regime. The weld microstructure is lath martensite and finely dispersed ε-Cu precipitates, and the strength of the welded joint is not less than 90% of the strength of the base metal.

[0028] (5) Regarding the weld formation qualification rate: The high-frequency pulse argon arc welding method of the present invention can achieve single-sided welding and double-sided forming of 15-5PH stainless steel. The weld back reinforcement is uniform, and the transition between the weld toe and the base material is smooth. No manual grinding or machining or other subsequent finishing measures are required. This avoids the influence of human factors on the service performance of components during subsequent processing. The weld can meet the welding quality requirements by inspecting it in its original welding state. The first-pass qualification rate of the weld can reach 100%.

[0029] (6) In terms of welding process adaptability. The high-frequency pulse argon arc welding method of the present invention operates in an open atmospheric environment, is not limited by the size of the vacuum system and working conditions, can form a wide range of component sizes, has low welding energy consumption and cost, and can realize the welding and manufacturing of 15-5PH stainless steel structural parts of different sizes and structures. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the welding bevel;

[0031] Figure 2 This is a schematic diagram of a high-frequency pulsed square wave current waveform;

[0032] Figure 3 This is a rendering of the geometric dimensions of a high-frequency pulsed argon arc weld seam in 15-5PH stainless steel. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] Example 1: Combination Figure 1 , Figure 2 and Figure 3 As shown, the high-frequency pulse argon arc welding method for 15-5PH stainless steel in this embodiment includes the following steps: taking 15-5PH stainless steel with a wall thickness of 2.5mm as an example.

[0035] 1) Part machining: The part's shape and weld bevel are machined using turning, milling, and / or grinding processes. The bevel angle is 75°, and the blunt edge is 0.5mm. Figure 1 As shown;

[0036] 2) Pre-welding treatment: First, demagnetize the parts using a demagnetizer. After demagnetization, use a Tesla meter to test the magnetic induction intensity of the parts. The magnetic induction intensity should meet the requirement of ≤0.2mT. Then, clean the welding bevel and the area on both sides of it with acetone or alcohol to remove oil, dust and other impurities.

[0037] 3) High-frequency pulsed argon arc welding: 15-5PH stainless steel is welded in the solution-treated state at a temperature of 1035–1052℃, a holding time of 60–90 min, and water cooling. Layered welding is used: the first layer is a root pass without wire, and the second layer is a filler pass for the cover pass. Welding process parameters are shown in Table 1. Welding wire with a chemical composition similar to the base metal is used. The shielding gas is argon with a purity of not less than 99.99%. The tungsten electrode is a cerium-tungsten electrode or a lanthanum-tungsten electrode with a diameter of 3.0–3.2 mm. The end of the tungsten electrode is ground into a flat truncated cone shape with an included angle of 40°–60°, and the diameter of the truncated cone is 1 / 4–1 / 3 of the tungsten electrode diameter. The horizontal distance between the center of the tungsten electrode and the welding wire is 3.5–4.0 mm. The interpass temperature is controlled below 150℃.

[0038] Table 1 Welding process parameters

[0039]

[0040] The schematic diagram of the high-frequency pulse square wave current waveform of the present invention is shown below. Figure 2 As shown, where I p For peak current, I b The base current is I, and the peak current I within a single cycle is... p and base current I b The durations are t p and t b Pulse current amplitude I pc =I p -I b The duty cycle of the pulse current is δ = t p / (t p +t b ).

[0041] 4) Post-weld heat treatment: After welding, the welded parts are subjected to aging treatment at a temperature of 550-560℃ for 4 hours and then furnace cooled.

[0042] 5) Welding quality inspection: Conduct quality inspections in accordance with relevant standards and requirements, including visual inspection, non-destructive testing, tensile properties of joints, and weld dimensional characteristics.

[0043] Example 2: Combination Figure 1 , Figure 2 and Figure 3 As shown, the high-frequency pulse argon arc welding method for 15-5PH stainless steel in this embodiment includes the following steps: taking 15-5PH stainless steel with a wall thickness of 3.2mm as an example.

[0044] 1) Part machining: The part's shape and weld bevel are machined using turning, milling, and / or grinding processes. The bevel angle is 80°, and the blunt edge is 0.5mm. Figure 1 As shown;

[0045] 2) Pre-welding treatment: First, demagnetize the parts using a demagnetizer. After demagnetization, use a Tesla meter to test the magnetic induction intensity of the parts. The magnetic induction intensity should meet the requirement of ≤0.2mT. Then, clean the welding bevel and the area on both sides of it with acetone or alcohol to remove oil, dust and other impurities.

[0046] 3) High-frequency pulsed argon arc welding: 15-5PH stainless steel is welded in the solution-treated state at a temperature of 1035–1052℃, a holding time of 60–90 min, and water cooling. Layered welding is used: the first layer is a root pass without wire, and the second layer is a filler pass for the cover pass. Welding process parameters are shown in Table 2. Welding wire with a chemical composition similar to the base metal is used. The shielding gas is argon with a purity of not less than 99.99%. The tungsten electrode is a cerium-tungsten electrode or a lanthanum-tungsten electrode with a diameter of 3.0–3.2 mm. The end of the tungsten electrode is ground into a flat truncated cone shape with an included angle of 40°–60°, and the diameter of the truncated cone is 1 / 4–1 / 3 of the tungsten electrode diameter. The horizontal distance between the center of the tungsten electrode and the welding wire is 3.5–4.0 mm. The interpass temperature is controlled below 150℃.

[0047] Table 2 Welding process parameters

[0048]

[0049] 4) Post-weld heat treatment: After welding, the welded parts are subjected to aging treatment at a temperature of 550-560℃ for 4 hours and then furnace cooled.

[0050] 5) Welding quality inspection: Conduct quality inspection in accordance with relevant standards and requirements.

[0051] Example 3: Combination Figure 1 , Figure 2 and Figure 3 As shown, the high-frequency pulse argon arc welding method for 15-5PH stainless steel in this embodiment includes the following steps: taking 15-5PH stainless steel with a wall thickness of 3.8mm as an example.

[0052] 1) Part machining: The part's shape and weld bevel are machined using turning, milling, and / or grinding processes. The bevel angle is 85°, and the blunt edge is 0.5mm. Figure 1 As shown;

[0053] 2) Pre-welding treatment: First, demagnetize the parts using a demagnetizer. After demagnetization, use a Tesla meter to test the magnetic induction intensity of the parts. The magnetic induction intensity should meet the requirement of ≤0.2mT. Then, clean the welding bevel and the area on both sides of it with acetone or alcohol to remove oil, dust and other impurities.

[0054] 3) High-frequency pulsed argon arc welding: 15-5PH stainless steel is welded in the solution-treated state at a temperature of 1035–1052℃, a holding time of 60–90 min, and water cooling. Layered welding is used: the first layer is a root pass without wire, and the second layer is a filler pass for the cover pass. Welding process parameters are shown in Table 3. Welding wire with a chemical composition similar to the base metal is used. The shielding gas is argon with a purity of not less than 99.99%. The tungsten electrode is a cerium-tungsten electrode or a lanthanum-tungsten electrode with a diameter of 3.0–3.2 mm. The end of the tungsten electrode is ground into a flat truncated cone shape with an included angle of 40°–60°, and the diameter of the truncated cone is 1 / 4–1 / 3 of the tungsten electrode diameter. The horizontal distance between the center of the tungsten electrode and the welding wire is 3.5–4.0 mm. The interpass temperature is controlled below 150℃.

[0055] Table 3 Welding process parameters

[0056]

[0057] 4) Post-weld heat treatment: After welding, the welded parts are subjected to aging treatment at a temperature of 550-560℃ for 4 hours and then furnace cooled.

[0058] 5) Welding quality inspection: Conduct quality inspections in accordance with relevant standards and requirements, including visual inspection, non-destructive testing, tensile properties of joints, and weld dimensional characteristics.

[0059] In the above embodiments, the tensile strength of the 15-5PH stainless steel welded joint can reach more than 90% of that of the base material, and the elongation after fracture is >9%; the weld size is within... Figure 3 Within the range shown.

Claims

1. A method of welding 15-5PH stainless steel by high frequency pulse argon arc welding, characterized by The method comprises the following steps: 1) part processing: using turning, milling or / and grinding process to process the part shape and welding groove; 2) pre-welding treatment: first, demagnetizing the part to make the magnetic induction intensity of the part satisfy ≤0.2mT, then using acetone or alcohol to clean the oil stains, dust and impurities in the welding groove and the area of not less than 20mm on both sides of the welding groove; 3) high-frequency pulse argon arc welding: welding 15-5PH stainless steel in solid solution state, solid solution temperature 1035-1052℃, holding time 60-90min, water cooling; Using layered welding, the first layer is base welding without welding wire, and the second layer is cover welding with welding wire; the welding material is welding wire with similar chemical composition to the base material; The protective gas is argon with purity not less than 99.99%; The first layer base welding parameters are pulse frequency 15-20kHz, peak current 180-200A, base current 100-120A, pulse current amplitude 80-100A, pulse current duty cycle 30-50%, arc voltage 9-10V, welding speed 22-24cm / min, welding gun protection gas 20-25L / min, drag shield protection gas 25-30L / min, back protection gas 5-10L / min; The second layer cover welding parameters are pulse frequency 15-20kHz, peak current 170-190A, base current 90-110A, pulse current amplitude 80-100A, pulse current duty cycle 30-50%, arc voltage 10-11V, welding speed 20-22cm / min, wire feeding speed 1000-1200mm / min, welding gun protection gas 20-25L / min, drag shield protection gas 25-30L / min, back protection gas 5-10L / min; 4) post-welding heat treatment: after welding, aging treatment is performed on the welded part, aging temperature 550-560℃, holding time 4h, furnace cooling; 5) welding quality inspection; The part thickness in step 1) is 2.5-3.8mm; The welding groove in step 1) adopts V-shaped butt groove, groove angle 80°±5°, and blunt edge 0.5mm.

2. The method of welding 15-5PH stainless steel by high frequency pulse argon arc welding according to claim 1, characterized in that The demagnetization treatment in step 2) is using demagnetizer to demagnetize the part, and after demagnetization treatment, the magnetic induction intensity of the part is detected by Tesla meter.

3. The method of welding 15-5PH stainless steel with high frequency pulse argon arc welding of claim 1, wherein The tungsten electrode in step 3) is cerium tungsten electrode or lanthanum tungsten electrode with diameter 3.0-3.2mm, the end of the tungsten electrode is ground into a truncated cone, the end angle is 40°-60°, and the truncated cone diameter is 1 / 4-1 / 3 of the tungsten electrode diameter.

4. The method of welding 15-5PH stainless steel with high frequency pulse argon arc welding of claim 1, wherein The horizontal distance between the center of the end of the tungsten electrode and the welding wire in step 3) is 3.5-4.0mm.

5. The method of welding 15-5PH stainless steel with high frequency pulse argon arc welding of claim 1, wherein The welding equipment in step 3) is automatic tungsten argon arc welding equipment with arc voltage tracking system.

6. The method of welding 15-5PH stainless steel with high frequency pulse argon arc welding of claim 1, wherein The welding current in step 3) is direct current positive connection.

7. The method of welding 15-5PH stainless steel with high frequency pulse argon arc welding of claim 1, wherein The interlayer temperature in step 3) is strictly controlled below 150℃; The solid solution and aging treatment in steps 3) and 4) are both performed under vacuum condition.

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