Solder for stainless steel welding and welding method thereof

Abstract

The invention discloses a welding flux for stainless steel welding and a welding method thereof.The welding flux takes 304 stainless steel as a welding base material and comprises, by mass, 75% of scaling powder and 25% of alloy powder; the soldering flux comprises 42%-47% of a solvent, 45%-50% of an active mixture, 5% of rosin, 2%-2.5% of a thixotropic agent and 0.5%-0.8% of an emulsifier. The alloy powder comprises 0.5%-0.7% of Ni, 0.2%-0.5% of Bi, 3%-4% of Cu and the balance Sn, and the solvent is obtained by compounding diethylene glycerol, glycol dihexyl ether and ethylene glycol butyl ether according to the proportion of 5: 7: 8. The active mixture is obtained by compounding hydroxyalkylamine, adipic acid and triethanolamine according to the proportion of 2: 1: 1, the spreading area of the welding solder on the 304 stainless steel surface is about 161.28 mm < 2 > through optimization of the welding solder formula, the tensile strength and the shear strength of a brazed joint are about 25.42 MPa and 35.89 MPa respectively, and the good welding effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel welding, in particular to a solder for stainless steel welding and a welding method thereof. Background Art

[0002] In the application field of stainless steel materials, 304 stainless steel is increasingly used in pipeline systems due to its good corrosion resistance, heat resistance and mechanical properties. However, in the welding process of 304 stainless steel, especially fusion welding and medium and high temperature brazing, some difficult problems are often encountered, which seriously affect the welding quality and the overall performance of the pipeline system.

[0003] The shortcomings of the existing technology are mainly reflected in the following aspects: First, the corrosion resistance of the weld area decreases during welding. Since 304 stainless steel is prone to intergranular sensitization at high temperatures, the organizational structure of the weld area changes, thereby reducing the corrosion resistance; second, it has poor adaptability to environments containing C1 ions and is prone to corrosion leakage; third, the welding method is complicated, the operation is difficult, and the welding efficiency is low. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a solder for stainless steel welding and a welding method thereof, which solves the problem of poor stainless steel welding performance in the prior art.

[0005] To achieve the above objectives, in a first aspect, the present application provides a welding filler metal for stainless steel, taking 304 stainless steel as a welding substrate, and the welding filler metal comprises, by mass fraction: Flux 75%, alloy powder 25%; The soldering flux comprises: 42% to 47% solvent, 45% to 50% active mixture, 5% rosin, 2% to 2.5% thixotropic agent, and 0.5% to 0.8% emulsifier; The alloy powder comprises: 0.5% to 0.7% Ni, 0.2% to 0.5% Bi, 3% to 4% Cu, and the balance is Sn. The particle size of the alloy powder is 200 to 300 meshes.

[0006] Preferably, the solvent is prepared by mixing diethylene propylene glycol, dihexyl glycol ether and ethylene glycol butyl ether in a ratio of 5:7:8.

[0007] Preferably, the active mixture is prepared by mixing hydroxyalkylamine, adipic acid and triethanolamine in a ratio of 2:1:1.

[0008] Explanation: Hydroxyalkylamine, adipic acid and triethanolamine, as key components of flux, each play an important role in the stainless steel welding process. They cooperate with each other to promote the welding reaction and improve the quality and reliability of the welded joint. Among them, hydroxyalkylamine, as an organic stannous salt, mainly provides active tin ions during the welding process. Active tin ions can more easily react with oxides on the metal surface, thereby effectively removing the oxide layer, exposing a clean metal surface, and creating good conditions for welding. By providing active tin ions, hydroxyalkylamine can accelerate the chemical reaction during the welding process, making the combination between the solder and the substrate tighter, thereby improving the strength and sealing of the welded joint. As an organic acid, adipic acid mainly plays a role in adjusting the pH value in the flux. Adipic acid can also react with oxides on the metal surface to remove the oxide layer, while enhancing the fluidity of the solder, making it easier for the solder to spread on the metal surface and form a good solder joint. As an organic amine, triethanolamine plays a major role in the flux to enhance the stability and fluidity of the soldering liquid. Triethanolamine can reduce the surface tension of the flux, making it easier to penetrate into the tiny gaps of the soldering joints. At the same time, it enhances the fluidity of the solder, making it easier for the solder to spread and diffuse on the metal surface, thereby improving the quality and reliability of the soldering joints.

[0009] Preferably, the thixotropic agent is ethyl cellulose, hydrogenated castor oil, or hardened castor oil; and the emulsifier is emulsifier 6500.

[0010] Preferably, the spreading area of ​​the welding solder on the surface of 304 stainless steel is 161.28 mm 2 The tensile strength and shear strength of the brazed joint are 27.33MPa and 37.33MPa respectively.

[0011] Preferably, the method for preparing the welding solder comprises the following steps: Step 1: Prepare flux: S01, preparing a solvent by compounding diethylene glycol, dihexyl glycol ether and ethylene glycol butyl ether in a ratio of 5:7:8; SO2, hydroxyalkylamine, adipic acid and triethanolamine are compounded in a ratio of 2:1:1 to obtain an active mixture; S03, placing a solvent with a mass fraction of 42% to 47% and 5% rosin in a stirred reactor equipped with a heating device, heating to 140° C., and fully dissolving the rosin under ultrasonic stirring until the rosin is completely dissolved in the solvent; S04, add 45% to 50% of active mixture, 2% to 2.5% of thixotropic agent, and 0.5% to 0.8% of emulsifier in sequence, stir until the fluid with uniform composition is stable, place in a sealed container and let stand to obtain flux; Step 2, preparing alloy powder: 0.5% to 0.7% Ni, 0.2% to 0.5% Bi, 3% to 4% Cu, and Sn are mixed and sieved to obtain alloy powder; Step 3, welding solder, weigh 25% alloy powder and 75% flux and put them into a mixer, stir them under nitrogen protection at room temperature to make welding solder.

[0012] To achieve the above object, in a second aspect, the present application provides a welding method for stainless steel welding solder, comprising the following steps: S001. Clean and polish the stainless steel welding area of ​​the two pieces of 304 stainless steel to be welded; S002. Apply the stainless steel welding solder evenly to the stainless steel welding area; S003. Use a heat source to heat the stainless steel welding area to 300°C and overlap the position to be welded; S004. After welding, clean the stainless steel.

[0013] Preferably, before starting welding and after completing welding, the welding area is cleaned with a stainless steel pickling paste to remove stains and residual stainless steel welding solder. The stainless steel pickling paste is used to remove stainless steel rust, oxide scale, and weld spot dirt generated by welding.

[0014] Preferably, the stainless steel pickling paste is used in step S1 as follows: Apply the stainless steel pickling paste to the stainless steel welding area with a thickness of 1 to 2 mm and a treatment temperature of 80°C. Keep it for 10 minutes and then wipe it dry, and immediately perform step S2; The method of using the stainless steel pickling paste in step S4 is as follows: Apply the stainless steel pickling paste to the welding spot and oxide scale with a thickness of 1 to 2 mm, and to the welding seam with a thickness of 2 to 4 mm; the treatment temperature is between 80 and 120°C, keep it for 15 minutes, then rinse with clean water and wipe dry.

[0015] Preferably, the stainless steel pickling paste comprises: 60% to 63% corrosive agent, 20% to 24% oxidant, 5% to 7% filler, 4% to 5% thickener, 4% to 5% corrosion inhibitor and 1% to 2% viscosity regulator; The corrosive agent is a mixture of 5% hydrofluoric acid and 15% dilute hydrochloric acid in a ratio of 1:1; The oxidant is potassium permanganate; The filler is a mixture of magnesium fluoride and magnesium sulfate; The thickener is magnesium stearate; the balance is water; The corrosion inhibitor is a mixture of molybdate, silicate and benzotriazole in a ratio of 5:2:1.

[0016] Explanation: In the stainless steel pickling paste, the corrosive agent is used to remove oxides and dirt on the surface of the stainless steel; the oxidant is used to promote chemical reactions and improve the pickling effect; the filler is used to adjust the density and fluidity of the pickling paste; the thickener is used to increase the viscosity of the pickling paste to prevent it from being lost during use; the corrosion inhibitor is used to slow down the corrosion of the stainless steel substrate during the pickling process and protect its surface from damage; the viscosity regulator is used to adjust the overall viscosity of the pickling paste to make it more convenient to use.

[0017] The present invention provides a solder for stainless steel welding and a welding method thereof, which has the following beneficial effects: The solder for stainless steel welding and the welding method thereof, the solder flux is composed of a solvent, an active mixture, rosin, a thixotropic agent and an emulsifier, the solvent is compounded by diethylene glycol, dihexyl glycol ether and ethylene glycol butyl ether, the boiling points of these solvents are different, and an effective active temperature range is formed in the compounded mixture, when the temperature reaches this range, the solvent begins to volatilize, taking away oxides and impurities on the metal surface, and at the same time, the hydroxyalkylamine, adipic acid and triethanolamine in the active mixture begin to chemically react with the metal surface, further removing oxides and promoting welding; by optimizing the solder formula, the spreading area of ​​the solder on the surface of 304 stainless steel is 161.28 mm 2 The tensile strength and shear strength of the brazed joint are about 25.42MPa and 35.89MPa respectively, which has a good welding effect.

[0018] The solder for stainless steel welding and the welding method thereof are mainly composed of Sn-Cu alloy, with a melting point range of 280-320°C, meeting the requirement that the welding temperature is lower than 450°C, reducing welding deformation and stress cracking in the brazing process of 304 stainless steel, avoiding the sensitization temperature range of stainless steel, and reducing the risk of intergranular corrosion; through the deoxidation and oxide film removal effects of the stainless steel pickling paste, the wetting and spreading properties of the solder are greatly improved; when applied to 304 stainless steel, the joint surface is clean, without voids and inclusions, and has a good welding effect. DETAILED DESCRIPTION

[0019] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0020] Preparation Example 1: preparing a soldering flux material A1: the soldering flux comprises: 42% solvent, 50% active mixture, 5% rosin, 2.5% thixotropic agent, and 0.5% emulsifier, including the following steps: S01, preparing a solvent by compounding diethylene glycol, dihexyl glycol ether and ethylene glycol butyl ether in a ratio of 5:7:8; SO2, hydroxyalkylamine, adipic acid and triethanolamine are compounded in a ratio of 2:1:1 to obtain an active mixture; S03, placing a solvent and 5% rosin in a stirred reactor equipped with a heating device, heating to 140° C., and fully dissolving the rosin under ultrasonic stirring until the rosin is completely dissolved in the solvent; S04, adding the active mixture, thixotropic agent, and emulsifier in sequence, stirring until the fluid with uniform and stable composition is formed, placing the fluid in a sealed container and letting it stand to obtain a soldering flux; It needs to be further explained in the preparation example of the present invention that the thixotropic agent is ethyl cellulose, hydrogenated castor oil, and hardened castor oil; and the emulsifier is emulsifier 6500.

[0021] Preparation Example 2: Preparation of a flux material A2: The difference from Preparation Example 1 is that the soldering flux comprises: 45% solvent, 47.5% active mixture, 5% rosin, 2% thixotropic agent, and 0.5% emulsifier.

[0022] Preparation Example 3: Preparation of a flux material A3: The difference from Preparation Example 1 is that the soldering flux comprises: 47% solvent, 45.2% active mixture, 5% rosin, 2% thixotropic agent, and 0.8% emulsifier.

[0023] Preparation Example 4, preparing a welding solder for stainless steel, comprising the following steps: Step 1, selecting the flux material A1, A2 or A3 obtained in the above-mentioned preparation example 1; Step 2: Preparation of alloy powder: 0.5% Ni, 0.2% Bi, 4% Cu, and Sn were mixed and sieved to obtain alloy powder B1; 0.7% Ni, 0.4% Bi, 3% Cu, and Sn were mixed and sieved to obtain alloy powder B2; 0.5% Ni, 0.5% Bi, 3.5% Cu, and Sn were mixed and sieved to obtain alloy powder B3; Step 3, welding solder, weigh 25% of alloy powder B1, B2, B3 and 75% of flux material A1, A2 or A3 respectively, put them into a mixer, and stir them under nitrogen protection environment at room temperature to make welding solder; Get welding solders A1B1, A1B2, A1B3, A2B1, A2B2, A2B3, A3B1, A3B2, A3B3.

[0024] Example S1, the following welding is performed using welding materials A1B1, A1B2, A1B3, A2B1, A2B2, A2B3, A3B1, A3B2, and A3B3, respectively, which are recorded as Examples 1-9; A welding method for stainless steel welding solder comprises the following steps: S001. Clean and polish the stainless steel welding area of ​​the two pieces of 304 stainless steel to be welded; S002. Apply the stainless steel welding solder evenly to the stainless steel welding area; S003. Use a heat source to heat the stainless steel welding area to 300°C and overlap the position to be welded; S004. After welding, clean the stainless steel.

[0025] Comparative Example 1: The above-mentioned stainless steel brazing operation is performed using a common ZnCl2-NH4Cl brazing flux on the market, wherein the ZnCl2-NH4Cl brazing flux is composed of 1.8g zinc chloride + 0.6g ammonium chloride + 7.6g water; In comparative example 2, the above-mentioned stainless steel brazing operation was performed using a common H3PO4-C2H5OH brazing flux on the market, wherein the H3PO4-C2H5OH brazing flux was composed of 20 ml 50% orthophosphoric acid + 30 ml ethanol.

[0026] Test Example S1, the welding results of the embodiment and the comparative example were tested to test the spreading area and welding strength of the welding solder on the surface of 304 stainless steel, and the results in Table 1 were obtained. The tensile strength test method of the brazed joint is as follows: referring to the test method specified in GB / T11363 "Brazed Joint Strength Test Method", Examples 1-9 and Comparative Examples 1 and 2 are tested; during the test, the brazed joint is installed on a tensile testing machine, and a tensile force is applied at a certain speed until the joint breaks, and the tensile strength of the joint is calculated by measuring the maximum tensile force before breaking and the brazing area of ​​the joint; The shear strength test method of the brazed joint is: use a shear tester to apply shear force to the brazed joint at a certain speed, measure the maximum shear force at the time of destruction, and output the shear strength of the brazed joint; Table 1 Stainless steel welding performance test results

[0027] Summary: Through the optimization of welding solder formula, the average spreading area of ​​welding solder on the surface of 304 stainless steel is 161.28 mm 2 The average values ​​of tensile strength and shear strength of the brazed joint are about 27.33MPa and 37.33MPa, respectively, which has a good welding effect; it is better than Comparative Example 1 and Comparative Example 2, and has a good brazing effect.

[0028] In summary, the solder for stainless steel welding and the welding method thereof provided by the present invention have the following technical advantages compared with the prior art: the solder does not contain halogen elements, will not corrode the stainless steel substrate, does not contain lead elements, and meets the industry's lead-free requirements; the active temperature range of the flux matches the alloy powder, and the solder has good wetting and spreading properties; the addition of active mixtures promotes stainless steel bonding and improves interface bonding strength.

[0029] Example S2, when welding with welding solders A1B1, A1B2, A1B3, is different from Example S1 in that before starting welding and after completing welding, the welding area is cleaned by stainless steel pickling paste A to obtain Examples 10, 11, and 12, and the welding area is cleaned by stainless steel pickling paste B to obtain Examples 13, 14, and 15.

[0030] Furthermore, the stainless steel pickling paste in step S1 is used as follows: Apply the stainless steel pickling paste to the stainless steel welding area with a thickness of 1 to 2 mm and a treatment temperature of 80°C. Keep it for 10 minutes and then wipe it dry, and immediately perform step S2; The method of using the stainless steel pickling paste in step S4 is as follows: Apply the stainless steel pickling paste to the welding spot and oxide scale with a thickness of 1 to 2 mm, and to the welding seam with a thickness of 2 to 4 mm; the treatment temperature is between 80 and 120°C, keep it for 15 minutes, then rinse with clean water and wipe dry.

[0031] Further, the stainless steel pickling paste A comprises: 60% corrosive agent, 24% oxidant, 5% filler, 5% thickener, 5% corrosion inhibitor and 1% viscosity regulator; The stainless steel pickling paste B comprises: 63% corrosive agent, 20% oxidant, 7% filler, 4% thickener, 4% corrosion inhibitor and 2% viscosity regulator; The corrosive agent is a mixture of 5% hydrofluoric acid and 15% dilute hydrochloric acid in a ratio of 1:1; The oxidant is potassium permanganate; The filler is a mixture of magnesium fluoride and magnesium sulfate; The thickener is magnesium stearate; the balance is water; The corrosion inhibitor is a mixture of molybdate, silicate and benzotriazole in a ratio of 5:2:1.

[0032] Test Example S1, the welding results of the embodiment and the comparative example were tested to test the spreading area and welding strength of the welding solder on the surface of 304 stainless steel, and Table 2 was obtained; Table 2 Test results of stainless steel welding performance based on stainless steel pickling paste

[0033] Summary: The present invention provides that the welding area is cleaned by using a stainless steel pickling paste before starting welding and after completing welding, which helps to improve the welding effect.

[0034] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A solder for stainless steel welding, using 304 stainless steel as the welding base material, characterized in that: By mass fraction, the welding solder comprises: Flux 75%, alloy powder 25%; The soldering flux comprises: 42% to 47% solvent, 45% to 50% active mixture, 5% rosin, 2% to 2.5% thixotropic agent, and 0.5% to 0.8% emulsifier; The alloy powder comprises: 0.5% to 0.7% Ni, 0.2% to 0.5% Bi, 3% to 4% Cu, and the balance is Sn. The particle size of the alloy powder is 200 to 300 meshes.

2. The solder for stainless steel welding according to claim 1, characterized in that: The solvent is prepared by mixing diethylene propylene glycol, dihexyl glycol ether and ethylene glycol butyl ether in a ratio of 5:7:

8.

3. The solder for stainless steel welding according to claim 1, characterized in that: The active mixture is prepared by mixing hydroxyalkylamine, adipic acid and triethanolamine in a ratio of 2:1:

1.

4. The solder for stainless steel welding according to claim 1, characterized in that: The thixotropic agent is ethyl cellulose, hydrogenated castor oil, and hardened castor oil; the emulsifier is emulsifier 6500.

5. The solder for stainless steel welding according to claim 1, characterized in that: The spreading area of ​​the welding solder on the surface of 304 stainless steel is 161.28 mm 2 The tensile strength and shear strength of the brazed joint are 27.33MPa and 37.33MPa respectively.

6. The solder for stainless steel welding according to claim 1, characterized in that: The preparation method of the welding solder comprises the following steps: Step 1: Prepare flux: S01, preparing a solvent by compounding diethylene glycol, dihexyl glycol ether and ethylene glycol butyl ether in a ratio of 5:7:8; SO2, hydroxyalkylamine, adipic acid and triethanolamine are compounded in a ratio of 2:1:1 to obtain an active mixture; S03, placing a solvent with a mass fraction of 42% to 47% and 5% rosin in a stirred reactor equipped with a heating device, heating to 140° C., and fully dissolving the rosin under ultrasonic stirring until the rosin is completely dissolved in the solvent; S04, add 45% to 50% of active mixture, 2% to 2.5% of thixotropic agent, and 0.5% to 0.8% of emulsifier in sequence, stir until the fluid with uniform composition is stable, place in a sealed container and let stand to obtain flux; Step 2, preparing alloy powder: 0.5% to 0.7% Ni, 0.2% to 0.5% Bi, 3% to 4% Cu, and Sn are mixed and sieved to obtain alloy powder; Step 3, welding solder, weigh 25% alloy powder and 75% flux and put them into a mixer, stir them under nitrogen protection at room temperature to make welding solder.

7. A welding method for stainless steel welding solder, using the welding solder according to any one of claims 1 to 6, characterized in that: The following steps are involved: S001. Clean and polish the stainless steel welding area of ​​the two pieces of 304 stainless steel to be welded; S002. Apply the stainless steel welding solder evenly to the stainless steel welding area; S003. Use a heat source to heat the stainless steel welding area to 300°C and overlap the position to be welded; S004. After welding, clean the stainless steel.

8. A welding method for stainless steel welding solder according to claim 7, characterized in that: Before welding and after welding, clean the welding area with stainless steel pickling paste.

9. A welding method for stainless steel welding solder according to claim 8, characterized in that: The method of using the stainless steel pickling paste in step S1 is: Apply the stainless steel pickling paste to the stainless steel welding area with a thickness of 1 to 2 mm and a treatment temperature of 80°C. Keep it for 10 minutes and then wipe it dry, and immediately perform step S2; The method of using the stainless steel pickling paste in step S4 is as follows: Apply the stainless steel pickling paste to the welding spot and oxide scale with a thickness of 1 to 2 mm, and to the welding seam with a thickness of 2 to 4 mm; the treatment temperature is between 80 and 120°C, keep it for 15 minutes, then rinse with clean water and wipe dry.

10. A welding method for stainless steel welding solder according to claim 9, characterized in that: The stainless steel pickling paste comprises, by mass fraction, 60% to 63% of a corrosive agent, 20% to 24% of an oxidant, 5% to 7% of a filler, 4% to 5% of a thickener, 4% to 5% of a corrosion inhibitor, and 1% to 2% of a viscosity regulator; The corrosive agent is a mixture of 5% hydrofluoric acid and 15% dilute hydrochloric acid in a ratio of 1:1; The oxidant is potassium permanganate; The filler is a mixture of magnesium fluoride and magnesium sulfate; The thickener is magnesium stearate; the balance is water; The corrosion inhibitor is a mixture of molybdate, silicate and benzotriazole in a ratio of 5:2:1.

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