Tin-lead brazing method for stainless steel and structural steel

Abstract

The invention provides a tin-lead brazing method for stainless steel and structural steel, which comprises the following steps of: before brazing the stainless steel and the structural steel, pre-plating tin-nickel alloy on a welding part of a stainless steel and structural steel part, and then welding by using an alcohol rosin brazing flux as a soldering flux and using tin-lead brazing filler metal. The tin-lead brazing weldability of stainless steel and structural steel can be effectively improved, the quality and stability of a welded joint are improved, the corrosion resistance of welded parts and components is improved, the welding production efficiency can be improved by 1-2 times, and meanwhile the corrosion risk of residual brazing flux after welding on a part welding line area and a part base body is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of stainless steel and structural steel welding, and in particular relates to a tin-lead brazing method for stainless steel and structural steel. Background Art

[0002] Aviation oxygen supply products use a large number of stainless steel and structural steel brazing structures. The traditional process of stainless steel and structural steel brazing is to use mechanical methods (such as sandpaper polishing, etc.) to remove the oxide film at the welding site before brazing, use organic solvents such as alcohol or acetone to remove oil stains at the welding site, use inorganic acid brazing flux (ZnCl2+NH4Cl aqueous solution) as flux, and use tin-lead solder for welding.

[0003] The problems are:

[0004] 1. The oxide film on the surface of stainless steel is relatively dense, and most of the stainless steel parts of aviation oxygen supply products are small-diameter thin-walled pipes. It is difficult to completely remove the stainless steel oxide film on the end face of the pipe and the inner and outer surfaces, which affects the smooth progress of the subsequent welding process;

[0005] 2. The welding quality is unstable, and cold welding is likely to occur where the local oxide film is not completely removed;

[0006] 3. Inorganic acid flux is not easy to clean thoroughly (especially if there are cold welds), and the risk of corrosion to the weld and the part substrate is high (rust near the weld of parts has occurred many times in the field). Summary of the invention

[0007] The purpose of the present invention is to provide a method for tin-lead brazing of stainless steel and structural steel to solve the problems of welding difficulty, unstable welding quality, poor corrosion resistance of parts after welding, and unqualified environmental tests when tin-lead brazing of stainless steel thin-walled pipes and structural steel parts is performed.

[0008] The present invention provides a method for tin-lead brazing of stainless steel and structural steel, the method comprising:

[0009] Pre-plating tin-nickel alloy on stainless steel parts and structural steel parts to form a 3-6μm thick pre-plated tin-nickel alloy layer on the parts to be welded;

[0010] Use tin-lead solder to weld stainless steel parts and structural steel parts pre-plated with tin-nickel alloy.

[0011] Optionally, the tin-lead solder uses S-Sn60PbSbA; during soldering, the heating temperature of the solder is 183-220°C.

[0012] Optionally, the pre-plating of the tin-nickel alloy is performed using an electrochemical deposition process.

[0013] Optionally, organic solvents are used to remove oil stains and oxide layers from the parts to be welded before and after welding stainless steel parts and structural steel parts.

[0014] Optionally, alcohol rosin flux is used as the soldering flux.

[0015] Optionally, stainless steel parts and structural steel parts can be pre-plated with tin-nickel alloy and then welded within 24 hours to avoid contaminants on the pre-plated surface.

[0016] Optionally, stainless steel parts and structural steel parts can be cleaned with alcohol or acetone within 1 hour after welding to remove residual flux in the weld area.

[0017] Optionally, a tin layer is pre-plated on the surface of the part using an electrochemical deposition process, and the process parameters are:

[0018] The composition and concentration of the bath solution: nickel chloride, 250g / L~300g / L, stannous chloride, 40g / L~50g / L, sodium fluoride, 30g / L~35g / L, ammonium fluoride 60g / L~70g / L; current density: 0.5~3A / dm2; bath temperature: 55~70℃;

[0019] Nickel chloride has the molecular formula NiCl2·6H2O.

[0020] The advantages of the present invention are: the brazing method of stainless steel and structural steel described in the present invention has the following significant advantages: 1. Effectively improve the brazing weldability of stainless steel and structural steel parts, making the welding operation process simpler and smoother; 2. Significantly improve the corrosion resistance of welded parts; 3. Improve the welding quality level and stability; 4. The welding production efficiency can be increased by 1 to 2 times. DETAILED DESCRIPTION

[0021] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with the embodiments. The following text is only used to describe one or several specific implementations of the present invention, and does not strictly limit the protection scope of the specific claims of the present invention.

[0022] The present invention provides a method for brazing stainless steel and structural steel, the brazing method comprising:

[0023] Pre-plating tin-nickel alloy on stainless steel parts and structural steel parts to form a 3-6μm thick pre-plated tin-nickel alloy layer on the parts to be welded;

[0024] Use tin-lead solder to weld stainless steel parts and structural steel parts pre-plated with tin-nickel alloy.

[0025] Optionally, the tin-lead solder uses S-Sn60PbSbA; during soldering, the heating temperature of the solder is 183-220°C.

[0026] Optionally, the pre-plating of the tin-nickel alloy is performed using an electrochemical deposition process.

[0027] Optionally, organic solvents are used to remove oil stains and oxide layers from the parts to be welded before and after welding stainless steel parts and structural steel parts.

[0028] Optionally, alcohol rosin flux is used as the soldering flux.

[0029] Optionally, stainless steel parts and structural steel parts can be pre-plated with tin-nickel alloy and then welded within 24 hours to avoid contaminants on the pre-plated surface.

[0030] Optionally, stainless steel parts and structural steel parts can be cleaned with alcohol or acetone within 1 hour after welding to remove residual flux in the weld area.

[0031] Optionally, a tin layer is pre-plated on the surface of the part using an electrochemical deposition process, and the process parameters are:

[0032] The composition and concentration of the bath solution: nickel chloride, 250g / L~300g / L, stannous chloride, 40g / L~50g / L, sodium fluoride, 30g / L~35g / L, ammonium fluoride 60g / L~70g / L; current density: 0.5~3A / dm2; bath temperature: 55~70℃;

[0033] Nickel chloride has the molecular formula NiCl2·6H2O.

[0034] The present invention pre-plates tin-nickel alloy on the surface of the welding part of stainless steel and structural steel parts before welding, and the weldability can be effectively improved. Alcohol rosin brazing flux is used as the flux, and since rosin is easily soluble in organic solvents, it is easy to clean after welding, and the corrosion risk of the weld area and the part substrate is greatly reduced.

[0035] This embodiment provides a brazing method for stainless steel and structural steel, the brazing method comprising: pre-plating the stainless steel parts and structural steel parts with tin-nickel alloy to form a 3-6 μm thick pre-plating layer at the parts to be welded; and welding the pre-plated stainless steel parts and structural steel parts with tin-lead solder. Alcohol rosin brazing agent is used as flux.

[0036] In this embodiment, the surface of the stainless steel and structural steel parts to be welded is pre-plated with tin-nickel alloy before welding, which greatly improves the weldability. Alcohol rosin brazing flux is used as the flux, and since rosin is easily soluble in organic solvents, it is easy to clean after welding, and the corrosion risk to the weld area and the part substrate is greatly reduced.

[0037] In this embodiment, the thickness of the tin-nickel alloy layer is 3-6 μm. If the tin-plated layer is too thin, the plating layer will be unstable during welding, affecting the welding quality; if the tin-plated layer is too thick, it may affect the assembly size of the parts.

[0038] In this embodiment, the tin-lead solder is S-Sn60PbSbA; during welding, the heating temperature of the solder is 185-200°C. During the pre-plating treatment, the electrochemical deposition process is used to pre-plated tin-nickel alloy on the surface of the parts. After the stainless steel parts and structural steel parts are pre-plated, welding is performed within 24 hours to avoid the formation of pollutants on the surface of the pre-plated layer. Pollutants include oxide film and oil stains. If the interval is too long, too much oxide film and oil stains will form on the surface of the pre-tinned layer, affecting the welding effect.

[0039] In this embodiment, a tin layer is pre-plated on the surface of the part by an electrochemical deposition process, and the process parameters are: composition and concentration of the bath: nickel chloride (NiCl2·6H2O), 250g / L~300g / L, stannous chloride (SnCl2), 40g / L~50g / L, sodium fluoride (NaF), 30g / L~35g / L, ammonium fluoride (NH4F) 60g / L~70g / L; current density: 0.5~3A / dm2; bath temperature: 55~70°C.

[0040] Within 1 hour after welding stainless steel parts and structural steel parts, use alcohol or acetone to clean and remove residual flux in the weld area to reduce the corrosion of the flux to the parts.

[0041] Taking the welding of a stainless steel thin-walled pipe and structural steel parts as an example, the main process of brazing is as follows:

[0042] (1) Pre-plating a 3-6 μm tin-nickel alloy layer on the surface of the welding part of stainless steel and structural steel parts by electrochemical deposition;

[0043] (2) Use alcohol to clean and remove oil stains from the welding parts;

[0044] (3) Apply alcohol rosin solution flux to the welding part of the parts;

[0045] (4) Heat the brazing material to 183-220°C and melt it and add it to the welding joint;

[0046] (5) After the weld has cooled, use alcohol or acetone to clean and remove the residual flux in the weld area of ​​the part within 1 hour;

[0047] (6) Inspect welding quality and parts surface cleaning quality;

[0048] (7) Complete the warehousing procedures for qualified parts.

[0049] The above 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 principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for soldering stainless steel and structural steel with tin-lead, characterized in that: The brazing method comprises: Pre-plating tin-nickel alloy on stainless steel parts and structural steel parts to form a 3-6μm thick pre-plated tin-nickel alloy layer on the parts to be welded; Use tin-lead solder to weld stainless steel parts and structural steel parts pre-plated with tin-nickel alloy.

2. The brazing method according to claim 1, characterized in that: The tin-lead solder is S-Sn60PbSbA; during soldering, the heating temperature of the solder is 183-220°C.

3. The brazing method according to claim 1, characterized in that: The pre-plated tin-nickel alloy is deposited using an electrochemical deposition process.

4. The brazing method according to claim 1, characterized in that: Before and after welding stainless steel parts and structural steel parts, organic solvents are used to remove oil stains and oxide layers on the welded parts.

5. The brazing method according to claim 1, characterized in that: Alcohol rosin flux is used as flux.

6. The brazing method according to claim 1, characterized in that: After pre-plating tin-nickel alloy on stainless steel parts and structural steel parts, welding should be carried out within 24 hours to avoid the formation of contaminants on the surface of the pre-plating layer.

7. The brazing method according to claim 6, characterized in that: Within 1 hour after welding stainless steel parts and structural steel parts, use alcohol or acetone to clean and remove residual flux in the weld area.

8. The brazing method according to claim 3, characterized in that: The electrochemical deposition process is used to pre-plated tin on the surface of the parts. The process parameters are: The composition and concentration of the bath solution: nickel chloride, 250g / L~300g / L, stannous chloride, 40g / L~50g / L, sodium fluoride, 30g / L~35g / L, ammonium fluoride 60g / L~70g / L; current density: 0.5~3A / dm2; bath temperature: 55~70℃; Nickel chloride has the molecular formula NiCl2·6H2O.