Copper pipe, also known as purple copper pipe, is a type of non-ferrous metal pipe with strong corrosion resistance and low oxidation resistance. It is widely used in the installation of modern residential and building water pipes, heating and cooling pipes. Copper pipes need to be well welded during installation to ensure their normal use in the future. So, what is the welding method for copper pipes? What are the welding precautions?

1、 Copper tube welding method

1. Preparation before welding

① Clean the oxide film on the outer surface of the copper pipe joint and the inner surface of the pipe fitting joint. Apply a paste or liquid solder evenly on the cleaned outer surface of the pipe and the inner surface of the pipe fittings. When brazing copper pipes and copper fittings with copper phosphorus solder or low silver copper phosphorus solder, the solder may not be applied.

② Insert the copper pipe into the fitting, insert it to the bottom and rotate it appropriately to maintain a uniform gap. If there is flux applied, the excess flux from the extruded joint should be wiped off with a clean cloth.

2. Perform welding

① When welding, it is necessary to preheat the welded part. Heat the welding area of the copper tube with flame. When the copper tube is heated to a purple red color, remove the flame and lean the solder against the welding joint, allowing the solder to melt and flow into the welded copper part. The temperature after heating can be reflected by the color, with a dark red color of around 600 ° C; Deep red: around 700 ° C; Orange red: around 1000 ° C.

② Apply uniform heating to the joint of the copper tube using a gas flame until it reaches the brazing temperature. During tin brazing, electric heating can also be used to heat the joint to the brazing temperature.

③ Contact the joint heated to high temperature with brazing material to determine the temperature at the joint. If the brazing material does not melt, it indicates that the temperature at the joint has not yet reached the brazing temperature, and further heating of the joint is required; If the brazing material can quickly melt, it indicates that the temperature at the copper pipe joint has reached the brazing temperature. You can continue to heat the joint to maintain the temperature above the brazing temperature, and add brazing material to the gap of the joint. Use the heat at the joint to melt the brazing material into the gap until it is filled. Do not use flames to directly melt the brazing material and apply it to the surface of the gap.

3. Welding cooling

Remove the heat source, stop heating, and let the joint cool and crystallize in a static state to prevent vibration during the cooling and crystallization of the melted brazing material, which may affect the brazing quality. Clean the oxides and welding slag inside the copper tube with dry nitrogen gas, and if necessary, apply clear paint for protection.

4. Repair welding after welding

① During the pressure test of copper pipes, if any leakage is found during welding, repair welding should be carried out. During the repair welding, the nitrogen gas used for the system pressure test should be discharged, and the pressure test should be conducted again after welding.

② Before welding copper pipes, the surface oxide layer should be wiped clean with gauze. After welding, the oxide skin should be removed completely. After quenching in water, the copper tube should be dried without any water droplets. After all welding is completed, the system should be blown clean with nitrogen gas.

2、 Precautions for Copper Tube Welding

1. When welding, it is necessary to wait for the solder to solidify before moving the copper pipe, otherwise the welding part will crack. When welding, it is necessary to wait for the refrigerant to be completely discharged before proceeding, otherwise the refrigerant will produce toxic phosgene when encountering an open flame, which is harmful to human health.

2. Copper pipe welding requires the use of gas flames, and gas cylinders should be placed upright with a distance of more than 5 meters from the open flame to avoid fire accidents. The connection method between the welding torch and the gas cylinder should be correct.

3. When welding copper pipes, construction should be carried out in a well ventilated and well ventilated area. Construction personnel need to wear protective goggles, and there should be fire-fighting equipment at the welding site.

The welding method for copper pipes should not only follow the above instructions, but also wear protective equipment during welding to prevent splashing sparks from scalding the skin. Goggles must be worn because the splashing flames can cause great irritation to the eyes and can easily lead to eye diseases.

Article source: Internet

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