Flame brazing standard four-step welding method

Abstract

The invention discloses a flame brazing standard four-step welding method which specifically comprises the following steps: 1) heating a base material to a brazing temperature of 735-840 DEG C, and selecting a proper welding angle according to the difference between the structural form of a welding spot and the wall thickness of the base material; (2) adding brazing filler metal; 3) heat preservation and drainage; and (4) the welding seam is filled with the returned brazing filler metal, specifically, the remaining 30%-40% of the brazing filler metal is added into the welding seam again, and it is guaranteed that welding spots are full. The method has the advantages that the step design is reasonable, the quality and reliability of welding points are improved, meanwhile, the training period of welders is effectively shortened, the product quality is guaranteed, the training cost is reduced, meanwhile, through implementation of a standard four-step welding method, due to the fact that brazing filler metal is separately added twice, the welding beading defect is greatly reduced, and the welding quality is improved. The phenomenon that the brazing filler metal is wasted by weld beading is avoided, and cost is effectively saved.

Description

Technical Field

[0001] The invention relates to a flame brazing standard four-step welding method. Background Art

[0002] With the rapid development of the air-conditioning manufacturing industry and the increasingly fierce market competition, flame brazing technology and welding quality are becoming more and more important. However, most of the manual flame brazing of some domestic enterprises still uses the traditional two-step welding method, which not only requires high personal skill level and welding experience of welders, but also makes it difficult to guarantee the quality and dimensional accuracy after welding. Therefore, the application of high-level and technically mature standard four-step welding method of flame brazing technology, the realization of standardized welding in the brazing process, the formulation of reasonable brazing process and brazing rhythm, is undoubtedly a major breakthrough in the field of brazing to improve product quality, shorten welder training cycle, and establish corporate image. At present, in the domestic air-conditioning and refrigeration manufacturing industry, the training cycle of welders for flame brazing is generally more than 1 year.

[0003] Principle and characteristics of flame brazing: Flame brazing is mainly a method of heating brazing by flame formed by the combustion of natural gas and oxygen. Flame brazing is a simple and practical brazing method. It is very versatile, easy to operate, requires simple and light equipment, and has a wide source of gas. This method is mainly used for brazing carbon steel, low alloy steel, stainless steel, copper and its alloys, carbide tools, etc. with copper-based brazing filler metals and silver-based brazing filler metals, and is particularly suitable for components with different cross-sectional qualities. It can also be used for brazing small and thin-walled weldments such as aluminum and its alloys, which can ensure a higher brazing quality; it can braze products with irregular shapes; the brazing joints are flat and smooth, and the appearance is beautiful; the bad state of the brazing process can be observed at any time, and timely control can be made to avoid producing too many defective products; the quantitative control of the brazing ring brazing filler metal ensures the uniformity and stability of the brazing filler metal filling; the size of the brazing firepower and the brazing time can be freely set. However, flux needs to be added during brazing, and the brazing ring may be partially oxidized; there are also certain limitations on the regulation of the flame temperature.

[0004] Analysis of the pros and cons of the traditional flame brazing two-step welding method: During flame brazing, in order to ensure uniform heating, the flame should first be moved back and forth to heat the entire part to be welded to the brazing temperature, so that the brazing agent and brazing material melt and fill the entire weld gap. In order to compensate for the heat loss of the joint parts of the good thermal conductor and reduce the stress cracking caused by thermal shock, in addition to correct heating, the joint must also reach the brazing temperature range evenly so that the brazing material can flow freely and fill the gap. Traditional manual flame brazing is generally divided into two steps, namely the first step of heating the base material to the brazing temperature (the brazing temperature of the commonly used copper tube for air conditioning is between 735℃-840℃. Figure 1 is the judgment standard for heating the base material to the brazing temperature); the second step is to add brazing material from the back of the base material, from the beginning of the melting of the brazing material to the end of filling the weld (Figure 2 is the position and angle of adding brazing material).

[0005] The advantages of the traditional manual flame brazing two-step welding method are fast welding speed and high efficiency, but the disadvantages are also as follows:

[0006] Too fast welding speed leads to insufficient mutual diffusion between the base material and the solder: the liquid solder diffuses with the base material while filling the gap with capillary. This diffusion can be attributed to two types: one is the diffusion of liquid solder into the base material; the other is the dissolution of solid base material into liquid solder. In the brazing process, the factors that affect the dissolution of the base material into the liquid solder can be roughly divided into material factors and process factors. Material factors refer to factors that affect the dissolution process related to the physical properties of the base material and the solder. The process factors mainly include the influence of temperature, the influence of heating and holding time, and the influence of the amount of solder. Due to the interaction between the solder and the base material, the composition and organization of the brazing seam are quite different from the original composition and organization of the solder and are often uneven. The brazed joint organization has three zones: 1) The part of the base material close to the interface is called the diffusion zone; 2) There is a bright band between the diffusion zone and the center of the brazing seam called the interface zone; 3) The central organization mainly composed of the solder is called the central zone of the weld.

[0007] The formation of a brazed joint is that under certain conditions, the liquid solder flows into the gap between the solid base materials by itself and is held in the gap by capillary force. After cooling, the solder solidifies. Therefore, in the process of forming a brazed joint, it is inevitable to involve the wetting and spreading of the solder on the base material, the flow of the solder, and the capillary filling. In order for the liquid solder to fill the capillary gap of the brazing joint, the prerequisite is that the liquid solder must be able to wet the base material well (referring to the process of replacing the solid-gas interface with the solid-liquid interface, thereby reducing the free energy of the system).

[0008] The ability of the solder to wet the parent material is only a basic prerequisite for completing the brazing connection. To obtain a high-quality brazing joint, it is necessary to ensure that the liquid solder can automatically flow into the weld gap to complete the connection between the two components. The force of the liquid solder to automatically fill the gap comes from the capillary action. In the actual flame brazing operation process, the weld gap is often uneven due to the influence of the pipeline assembly gap, inclination angle, etc., and the capillary force due to different weld gaps is often uneven. The traditional flame brazing two-step welding method does not have enough insulation time, which will lead to insufficient dissolution of the weld solder. Summary of the invention

[0009] The object of the present invention is to provide a standard four-step flame brazing method to solve the problems raised in the above background technology.

[0010] In order to solve the above technical problems, the technical solution provided by the present invention is: a standard four-step flame brazing method, which specifically includes the following steps:

[0011] 1) Heat the base material to a brazing temperature of 735°C-840°C, and select a suitable welding angle based on the structure of the solder joint and the wall thickness of the base material;

[0012] 2) Add solder: add 60%-70% of the solder used, and verify the weight and length of the solder used for the solder point according to the solder point diameter and welding gap; add solder length of 60%-70% of the standard length, and immediately remove the remaining solder from the base material. At this time, the solder has filled the weld;

[0013] 3) Insulation and drainage: The welding flame uses the avoidance method or retreat method to insulate the solder joint, so that the temperature of the solder joint is always maintained between the brazing temperature of 735℃-840℃. During the insulation and drainage process, the naked eye can clearly see the melted solder in the weld penetrate into the weld, and the solder above the weld gradually decreases until it completely penetrates into the weld;

[0014] 4) Fill the weld with solder: Add the remaining 30%-40% solder to the weld again to ensure that the weld is full.

[0015] Preferably, the avoidance method in step 3) is to ensure the stability of the welding temperature, avoid insufficient welding temperature or excessive welding temperature, which may lead to over-burning of the welding, and use the flame avoidance method to control the welding temperature.

[0016] Preferably, the flame is removed from the base metal immediately as the solder penetrates the base metal, and the solder is swung left and right to avoid the flame before overheating to maintain the soldering temperature of the base metal.

[0017] Preferably, in the step 3), the retreat method is to determine the position, and when the solder penetrates the base material and begins to penetrate, that is, when the solder begins to flow, move the flame away from or close to avoid the flame to maintain the welding temperature of the base material.

[0018] Preferably, in step 3), the flame is appropriately selected according to the overlap length to guide the solder downward to completely penetrate the interior of the rectified weld.

[0019] The advantages of the present invention are: reasonable step design, which not only improves the quality and reliability of the welding points, but also effectively shortens the training period of welders, ensures product quality and reduces training costs. At the same time, through the implementation of the standard four-step welding method, because the solder is added twice separately, the generation of weld nodules is greatly reduced, the waste of solder caused by weld nodules is eliminated, and costs are effectively saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a standard chart for judging whether the base material has been heated to the brazing temperature.

[0021] Figure 2 This is a diagram of the position and angle of adding solder.

[0022] Figure 3 It is the weld structure diagram of copper and solder.

[0023] Figure 4 This is the weld structure diagram of brass and solder. DETAILED DESCRIPTION

[0024] For the purpose of the following detailed description, it should be understood that the present invention may adopt various alternative changes and step sequences, unless expressly specified to the contrary. In addition, except in any operating examples, or otherwise indicated, all numbers representing the amount of ingredients used in the specification and claims should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and the attached claims are approximate values ​​that vary according to the desired performance to be obtained by the present invention. At least it is not intended to limit the application of the doctrine of equivalents to the scope of the claims, and each numerical parameter should at least be interpreted according to the number of reported significant figures and by applying ordinary rounding techniques.

[0025] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0026] In addition, it should be understood that any numerical range described herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the stated minimum value of 1 and the stated maximum value of 10, i.e., having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0027] Example 1

[0028] A standard four-step flame brazing method comprises the following steps:

[0029] 1) Heat the base material to a brazing temperature of 735°C-840°C, and select a suitable welding angle based on the structure of the solder joint and the wall thickness of the base material;

[0030] 2) Add solder: add 60%-70% of the solder used, and verify the weight and length of the solder used for the solder point according to the solder point diameter and welding gap; add solder length of 60%-70% of the standard length, and immediately remove the remaining solder from the base material. At this time, the solder has filled the weld;

[0031] 3) Insulation and drainage: The welding flame uses the avoidance method or retreat method to insulate the solder joint, so that the temperature of the solder joint is always maintained between the brazing temperature of 735℃-840℃. During the insulation and drainage process, the naked eye can clearly see the melted solder in the weld penetrate into the weld, and the solder above the weld gradually decreases until it completely penetrates into the weld;

[0032] 4) Fill the weld with solder: Add the remaining 30%-40% solder to the weld again to ensure that the weld is full.

[0033] As a preferred implementation of this embodiment, the avoidance method in step 3) is to ensure the stability of the welding temperature, avoid insufficient welding temperature or excessive welding temperature, which may lead to over-burning of the welding, and use the flame avoidance method to control the welding temperature.

[0034] As a preferred implementation mode of this embodiment, when the solder penetrates the base material, the flame is immediately removed from the base material, and the solder is swung left and right to avoid the flame before excessive heating to maintain the welding temperature of the base material.

[0035] As a preferred implementation of this embodiment, in step 3), the flame is appropriately selected according to the overlap length to guide the solder downward to completely penetrate the interior of the rectified weld.

[0036] Example 2

[0037] A standard four-step flame brazing method comprises the following steps:

[0038] 1) Heat the base material to a brazing temperature of 735°C-840°C, and select a suitable welding angle based on the structure of the solder joint and the wall thickness of the base material;

[0039] 2) Add solder: add 60%-70% of the solder used, and verify the weight and length of the solder used for the solder point according to the solder point diameter and welding gap; add solder length of 60%-70% of the standard length, and immediately remove the remaining solder from the base material. At this time, the solder has filled the weld;

[0040] 3) Insulation and drainage: The welding flame uses the avoidance method or retreat method to insulate the solder joint, so that the temperature of the solder joint is always maintained between the brazing temperature of 735℃-840℃. During the insulation and drainage process, the naked eye can clearly see the melted solder in the weld penetrate into the weld, and the solder above the weld gradually decreases until it completely penetrates into the weld;

[0041] 4) Fill the weld with solder: Add the remaining 30%-40% solder to the weld again to ensure that the weld is full.

[0042] As a preferred implementation of this embodiment, the retreat method in step 3) is to determine the position, and when the solder penetrates the base material and begins to penetrate, that is, when the solder begins to flow, move the flame away or closer to avoid the flame to maintain the welding temperature of the base material.

[0043] As a preferred implementation of this embodiment, in step 3), the flame is appropriately selected according to the overlap length to guide the solder downward to completely penetrate the interior of the rectified weld.

[0044] The technical implementation improvement cases of the flame brazing four-step welding method of the present invention are as follows

[0045] Through continuous in-depth research and exploration of flame brazing technology, while inheriting the welding experience and technology of the air-conditioning company, based on its own welding experience and market and process leakage analysis experience, it organized development, process, quality, production and other related personnel to go deep into the production site to find work pain points and leakage hazards, and created and organized a number of quality hazard improvements.

[0046] The "flame welding and then brazing sealing" technology for the process pipe mouth copper tube for air conditioning fluorine injection was created: During the production process of the air conditioning outdoor unit, vacuuming, fluorine injection and other process operations are required, so the development center will reserve a separate For the pipe mouth of the pipe with a large diameter, the brazing filler metal is used to weld and seal the pipe mouth after the fluorine injection is completed. The original welding and sealing industry generally adopts the process of brazing filling and welding, with a single brazing filler metal quota of 1.8 grams, a welding cycle of 8 seconds, and a leakage rate of about 35PPM; based on its own welding experience, it pioneered the copper tube melting and brazing filler resealing technology, that is, first melt the copper tube at the pipe mouth and fill the pipe mouth, and then use the brazing filler metal for secondary sealing. After the change, the single brazing filler metal quota was reduced to 0.2 grams, the leakage rate was reduced to less than 5PPM, and the welding cycle was reduced to 6 seconds. This method has been promoted to three factories for synchronous switching, saving brazing filler metal. The three factories can save more than 600,000 yuan in brazing filler metal costs each year (the three factories are calculated based on 10 million sets of air conditioners each year: 10 million sets * 1.6 grams / set / 1000*70 yuan / kg = 1.12 million yuan).

[0047] The first condenser outlet single pipe reducer welding to eliminate stress leakage: the original condenser outlet pipe of the air conditioning company all adopted The copper tube with a diameter that is shrunk twice is designed. After being inserted into the condenser and welded, it undergoes helium inspection, evacuation, fluorine injection and other processes. The bending of the pipe causes stress to be transmitted to the condenser tube mouth and wrinkles. The friction between the end plate and the wrinkled part of the copper tube during operation causes leakage at the tube mouth. Leakage at this point accounts for more than 45% of the total leakage. Through research and design, the method of using thin-diameter copper tubes and thick-diameter copper tubes to be welded together using flame brazing can effectively prevent stress transfer (a. The thin-diameter copper tube will deform itself after being stressed, reducing stress transfer. b. The diameter-changing part is spliced ​​by flame brazing. The copper tube becomes soft due to heat during brazing, further increasing the deformation margin of itself under stress, and preventing stress from being transferred to the condenser tube mouth.). After the improvement, leakage at this point is eliminated, and the procurement cost is saved because the copper tube becomes thinner.

[0048] The first fluorine-injected process pipe tee reinforced welding point to prevent leakage: The fluorine-injected process pipe of the air-conditioning outdoor unit is generally designed to be welded in parallel with the throttle valve on the same tee. During the production process, the process of evacuation, fluorine injection, sealing and other processes repeatedly bend the process pipe, causing the bottom welding point to crack and leak, accounting for more than 40% of the process leakage. After research, a reinforced welding point is added above the welding point between the process pipe and the throttle valve tee. The bending stress of the process is all concentrated on the reinforced welding point, which fully protects the tee welding point and prevents crack leakage at this point.

[0049] The first manual flame brazing technology for the ends of stainless steel beam tubes and copper tubes: The cost reduction project of the air conditioning development center requires the copper beam tubes to be switched to stainless steel products. During the on-site batch verification process, the copper tubes used for welding at the ends of the pipelines were found to be soft. During the helium inspection of the two devices, the quick connectors could not be stuck due to the soft copper tubes, which posed a safety hazard of the connectors flying off. This once caused the entire cost reduction project to face abortion. Based on its own four-step welding method experience, it was the first to research that manual flame brazing instead of furnace brazing can improve the degree of softening of the copper tube, ensure that the hardness of the copper tube after welding meets the requirements for the use of the two-device quick connector, promote the implementation of the manufacturer switch, and ensure the smooth implementation of the cost reduction project. This alone can save the company more than 5 million yuan in procurement costs each year.

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A standard four-step flame brazing method, characterized in that: The specific steps include: 1) Heat the base material to a brazing temperature of 735°C-840°C, and select a suitable welding angle based on the structure of the solder joint and the wall thickness of the base material; 2) Add solder: Add 60%-70% of the solder required, and verify the weight and length of the solder used for the solder point according to the solder point diameter and welding gap; add solder length of 60%-70% of the standard length, and immediately remove the remaining solder from the base material. The solder has filled the weld; 3) Insulation and drainage: The welding flame uses the avoidance method or retreat method to insulate the solder joint, so that the temperature of the solder joint is always maintained at The brazing temperature is between 735℃ and 840℃. During the heat preservation and drainage process, the molten brazing filler metal in the weld can be clearly seen to penetrate into the weld. The solder above the weld gradually decreases until it completely penetrates the weld; 4) Fill the weld with solder: Add the remaining 30%-40% solder to the weld again to ensure that the weld is full.

2. A flame brazing standard four-step welding method according to claim 1, characterized in that: The avoidance method in step 3) is to ensure the stability of the welding temperature, avoid insufficient welding temperature or excessive welding temperature, which may lead to over-burning of the welding, and use the flame avoidance method to control the welding temperature.

3. A flame brazing standard four-step welding method according to claim 2, characterized in that: As the solder penetrates the base metal, immediately remove the flame from the base metal, and swing left and right to avoid the flame before overheating to maintain the base metal's welding temperature.

4. A flame brazing standard four-step welding method according to claim 1, characterized in that: In the step 3), the retreat method is to move the flame away or closer to avoid the flame after the position is determined and the solder penetrates the base material and begins to penetrate, that is, when the solder begins to flow, to maintain the welding temperature of the base material.

5. A flame brazing standard four-step welding method according to any one of claims 1 to 4, characterized in that: In the step 3), the flame is appropriately selected according to the overlap length to guide the solder downward to completely penetrate the interior of the rectified weld.

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