Views:1 Author:Site Editor Publish Time: 2015-07-15 Origin:Site
The refrigeration system in refrigeration and air conditioning generally uses non-ferrous metal materials such as copper and aluminum. During the manufacturing, installation and maintenance process, the welding of the pipeline is a key link. It not only affects the appearance but also affects whether the system can work normally. The problem must be highly valued. The air conditioning copper pipe refers to the connecting copper pipe connecting the indoor unit of the air conditioner to the outdoor unit. The air-conditioning copper tube has the characteristics of hard texture, non-corrosion, high temperature resistance and high pressure resistance, so it is very popular among people. Air-conditioning copper pipes can be divided into two types: ordinary air-conditioning copper pipes and degreased air-conditioning copper pipes. Of course, according to the use of air-conditioning copper pipes, it can be divided into R22 air-conditioning copper pipe, R410A central air-conditioning copper pipe, capillary copper pipe, and special-shaped copper pipe. When the air conditioner is installed, the new refrigerant air conditioner uses the special R410A air conditioning copper tube to connect the air conditioner to the outside machine and the inner machine. The welding of the air conditioner connecting tube R410A copper tube is directly a factor affecting the cooling effect. The correct operation procedure is very good. important. The copper tube and the copper tube are generally welded by silver, and the silver electrode has a silver content of 25%, 15% or 5%; and a copper-phosphorus series electrode can also be used. They all have good fluidity and do not require flux. The choice of solder copper tube is an important raw material for refrigeration equipment, mainly used to make heat exchangers and connecting pipes and fittings. Refrigeration and air conditioning pipe fittings are mostly made of copper (purple) pipes. Commonly used solder types are copper-phosphorus solder, silver-copper solder, copper-zinc solder, and the like. In the welding, according to the characteristics of the pipe material, the solder is selected correctly and skillfully operated to ensure the quality of the welding.
1. Brazing of copper and copper for similar materials may be carried out using phosphor bronze solder or phosphor bronze solder with low silver content, such as 2% or 5% silver-based solder. This solder is cheaper and has a good solution, using caulking and wetting processes, and does not require flux.
2. Welding of different types of materials
(1) Copper and steel or copper and aluminum may be soldered with silver-copper solder and appropriate flux. After welding, the residual flux near the solder joint must be cleaned with hot water or steam to prevent corrosion. When using flux, it is best to dilute it into a paste with alcohol and apply it to the surface of the solder joint. When welding, the alcohol evaporates quickly to form a smooth film that is not easily lost, and at the same time avoids the danger of water immersing in the refrigeration system.
(2) Copper and iron may be soldered with phosphor bronze or brass strip solder, but a corresponding flux such as borax, boric acid or boric acid may be used. The welding operation is different for welding different materials. The size of the welding torch and the temperature of the flame are different when the pipe diameter is different. The size of the flame can be controlled and adjusted by two needle valves during welding. The flame is adjusted according to oxygen. The volume ratio of acetylene gas can be divided into three types: carbonized flame, neutral flame and oxidized flame.
1, the type and characteristics of the flame
(1) Carbonized flame is characterized by a volume ratio of oxygen to acetylene gas of less than 1, slightly oxygen deficient, easy to bring carbon particles into the metal and affect the flow of solder, black smoke, the temperature is about 2700, can be used for drying the pipeline Bake and so on.
(2) Neutral flame is characterized in that the size of the flame core depends on the composition, consumption and flow rate of the combustion gas. The diameter of the nozzle hole of the torch determines the diameter of the flame core, and the flow rate of the mixture determines the core of the flame. The length, the flame of the neutral flame is divided into 3 layers, the flame core is sharply tapered, the color is white and bright, the inner flame is blue-white, and the outer flame gradually changes from lavender to orange and blue from the inside to the outside, and the temperature is about 3000. ~3500 °C, the ratio of the volume of oxygen to acetylene gas is 1:1.2. The tube welding of refrigeration and air conditioning uses a neutral flame.
(3) The oxidizing flame is characterized in that the flame core is conical, the length is obviously shortened, the contour is not clear, the color is dim, the outer flame is shortened, the flame is blue, and the flame is accompanied by a sound, and the sound is determined by the sound. Oxygen pressure, the temperature of the oxidizing flame is higher than that of the neutral flame, and is suitable for the welding of brass fittings. The nature of the flame is chosen according to the type of metal being welded and its nature, and should be carefully selected for scientific use.
2. Adjusting the flame Before starting the ignition, first open the valves of the oxygen cylinder and the acetylene cylinder according to the operation rules, so that the low-pressure oxygen meter is indicated at 0.2~0.5Mpa, and the acetylene gas in the eye is indicated at 0.05Mpa. Then slightly open the oxygen valve of the torch. Then slightly open the acetylene gas valve on the welding torch, colleague, quickly ignite from the back of the welding tip. Do not ignite on the front side of the tip to avoid burning fire. It can be adjusted after ignition. The adjustment of the two valves is to adjust the ratio of oxygen and acetylene gas immersed in the welding torch mixture to obtain different flames.
3, the welding step should be strictly in accordance with the steps of the welding, otherwise, it will affect the quality of the welding.
(1) Preparation and piping
1. Check that the amount in the oxygen and acetylene bottles is sufficient.
2. Check the drawing requirements to ensure that all components are complete and functional.
3. Ensure that the optical path of the pipeline is horizontal and vertical, pay attention to the directivity of each valve.
4. Depending on the dimensions and pipe diameter required by the drawing, use a tape measure to measure the length and use the line number pen several times.
5. After the thick copper pipe is to be fixed, remove it with a cutter, and make sure that the cutting edge is flush and not deformed.
6. Use a hoe to flatten the edges of the cut and wipe it clean with a rag.
7. The surface of the pipe to be welded is cleaned or flared. The flared bell mouth should be smooth, round, burr-free and crack-free. The thickness of the bell mouth should be evenly polished. Use sandpaper to clean the copper pipe joint to be welded. Finally, wipe it with a dry cloth. Otherwise, it will affect the solder flow and the quality of the weld.
8. Except for the welding of copper and copper, all the pipe fittings are cleaned with gauze or stainless steel wire brush before welding to expose the bright metal surface. (The inner surface should be cleaned, the metal shavings and sand should be removed)
9. Insert the copper tubes to be welded on each other (note the size) and align them with the center.
1. When welding, the nitrogen gas should be passed through the welded pipe to prevent oxidation.
2. Acetylene gas should pass through the non-oxidation welding generator to prevent oxidation of the outer surface of the welded object.
1. When welding, the weldment must be preheated. The flame is baked at the hot copper tube. When the copper tube is heated to purple, the flame is removed and the solder is placed at the weld to melt the solder and flow into the welded copper. The temperature after heating can be reflected by the color. The temperature is high and low, dark red: about 600 degrees Celsius; deep red: about 700 degrees Celsius; orange: about 1000 degrees Celsius.
2. When welding, the gas welding flame shall not directly heat the electrode.
3. For parts that are easily deformed under high temperature conditions, damaged parts should be protected accordingly. For example, angle valves, evaporators, condensers, etc. should be welded with wet gauze and then welded. For solenoid valves, expansion valves, liquid mirrors, and four-way valves, they must be disassembled and then welded. Take the above measures.
4. When welding, when the copper tube is annealed after welding, the annealing temperature is not lower than 300 degrees Celsius.
5. After the welding is completed, cool and clean the oxide and slag in the tube with dry nitrogen.
(4) repair welding
1. In the process of pressure test, it is found that the weld has leakage repair. When repairing the weld, the nitrogen pressure tested by the system should be released, and the pressure should be re-tested after welding.
2. Clean the surface of the oxide layer on the front waist and clean it with gauze. After repair welding, the scale should be removed. After quenching in water, the copper tube should be dried and no water droplets should exist.
3. After all soldering, purge the system with nitrogen. Summary of welding steps
1. Prepare welding gas, equipment and materials;
2, wear protective equipment;
3. Check the status of welding equipment and tools;
4. Open the bottle valve, adjust the outlet pressure of the oxygen pressure reducer to 0.15~0.2MPa, and adjust the outlet pressure of the acetylene pressure reducer to 0.01~0.02MPa;
5. Open the acetylene regulating valve - ignition - adjust the acetylene regulating valve to make the flame length moderate;
6, open the oxygen regulating valve - slowly withering the flame into a neutral flame;
7. Adjust the flame in the order of neutral flame (small) → add acetylene → feather-like flame becomes large → add oxygen → adjust to neutral flame (large);
8. According to the neutral flame (large) → reduce oxygen → appear plume flame → reduce acetylene → wither as a neutral flame (small) in the order of flame;
9. Make the tip of the flame core 2~4mm away from the weldment, perpendicular to the pipe, and uniformly heat the entire length of the weld to the magenta;
10. Applying a flux, when the flux becomes a transparent liquid and uniformly wets the weld, the solder coated with the flux is heated until the solder is sufficiently melted and satisfactorily filled with the weld;
11. Remove the flame and keep the weldments not misaligned before the solder is completely solidified;
12, close the acetylene valve, and then turn off the oxygen valve to extinguish;
13. Adjust the pressure reducer and close the bottle valve;
14, finishing tools, equipment, sweeping the scene.