For the skilled copper pipe installer, there are a variety of copper pipe connection options available. Not only are there the normal brazed joints, but there are also the excellent performance sleeve joints. We can make joints directly on the pipe and then weld them using hard brazing or bronze welding techniques, or we can use copper and copper alloy brazed sleeves. We can also use a variety of extruded joints. All of these copper pipe connections have been continuously developed and perfected, and they are completely reliable for qualified professional installers. In addition, the combination of copper and casing characteristics allows for long-term, reliable, safe and economical operation of gas, water supply, sewerage, and heating facilities.
Non-processing compression type connection
The use of non-processing compression fittings to implement the mechanical connection of copper pipes, is a relatively simple construction method, simple operation, easy to grasp, the construction personnel only need a little training, you can master the operating skills. It is a common connection method in the current project. When connecting, as long as the end face of the pipe cutout can be kept vertical with the axis of the pipe, and the cutout burr and other clean, pipe assembly is the correct position of the card ring placement, and tighten the nut, you can achieve a tight connection of copper pipe. But this connection, is to rely on the thread on the compression force of the ring to keep the joint tight, so the joint should not be directly buried in the wall, it is advisable to lay the joint in the location can be serviced, so that once the compression force is slack and leakage, by further tightening the nut to maintain the necessary pressure.
Processing compression type connection
The use of processing compression fittings to implement the mechanical connection of copper pipe, is also one of the common construction methods of copper pipe connection, which is different from the construction method of non-processing compression connection, is that the end of the copper pipe must be shaped and processed before construction, that is, the construction of copper pipe, the end of the tube after cutting correction, but also need to use special forming tools, the end of the pipe processing bracket into a cup or cone, and the shape of the cup or cone, the size needs to be Standardized and unified. Because the connection of processing compression copper pipe fittings, is to rely on the cup or conical end of the pipe directly with the copper pipe fittings corresponding to the sealing surface to the tightness of the pipe joint, copper pipe end forming norms or not, directly affect the quality of the joint connection, therefore, engaged in copper pipe processing compression mechanical connection construction personnel, should be the necessary technical training, mastering the processing skills of forming before engaging in construction, in order to ensure that the processing of compression type connection construction quality.
Flange and groove type connection
The connection between the larger diameter copper pipe, copper pipe and valve fittings, as well as copper pipe and equipment, containers, the connection between the general use of flange connection, that is, copper pipe by brazing brass flange, or processing into the form of flanged plus steel flange, the formation of flange type joint, there are bolts and nuts to implement the flange connection. The connection between the larger diameter copper pipe, can also be used groove type connection, that is, the use of special groove forming machinery, the end of the copper pipe tied a depth and width in line with the standard groove connection ring groove, and then use the groove connection fittings, the two copper pipe connected into one. Using this connection, the wall thickness of the copper pipe must comply with the relevant standards. Copper and non-copper groove connection fittings contact surface, should be taken to isolate measures to prevent galvanic corrosion.
The use of plug-in copper fittings to implement the mechanical connection of copper pipes, is currently one of the simple construction methods, simple and convenient operation, the construction personnel only need to be familiar with its operational requirements, a little practice can be mastered. When connected, the end face of the pipe incision should be perpendicular to the axis of the pipe, the burr inside and outside the incision should be cleaned up, and marked with a marker on the outside of the front of the copper pipe to insert the depth, and then force the copper pipe into the pipe fittings to the end to stop the pipe. This bell connection method is to rely on special fittings in the stainless steel clamping ring to fasten the copper pipe in the fittings, the use of fittings and the outer wall of the copper pipe closely with the “O” rubber ring to implement the seal to complete the tight connection of the copper pipe. When using the plug-in connection method, the copper pipe can not be inserted once the exit, such as installation errors need to be changed, you must check the fittings to be sure there is no damage to use again.
Using crimped copper fittings to implement the crimp connection of copper pipes, is one of the newer construction methods, operation is also simple, but need to be equipped with special and complete specifications of crimping machinery. Connection, the pipe notch end face should be perpendicular to the axis of the pipe, the burr inside and outside the notch should be cleaned, and then insert the pipe into the pipe fittings in the end, and gently turn the pipe, so that the pipe and pipe fittings with concentric segments, and then crimping machinery with special copper pipe and pipe fittings crimped into one. This bell connection method, is the use of cold crimping technology to make the copper pipe and pipe fittings into one, the use of rubber seals within the flange of the pipe to implement the seal, complete the tight connection of copper pipe. The use of crimping connection method, pipe laying is very convenient, before crimping, copper pipe and pipe fittings can be freely disassembled, as long as the time of crimping is properly selected, it can make the installation in one step.
The principle and characteristics of brazing
A. Definition of brazing
Brazing is the use of brazing material with a lower melting point than the base material and the base material together with the heating, in the case of the base material does not melt, the brazing material melted wetting and filling into the gap between the two base material connections, forming a brazing seam, in the gap, the brazing material and the base material dissolve and diffuse each other, so as to get a solid bond. Brazing can be divided into two categories according to the melting point of the brazing material used, generally 450°C as the boundary, brazing material melting point <450°C brazing for soft brazing, brazing material melting point >450°C brazing for hard brazing. Soft brazing is simple to operate and easy to master, but its joints.
B. Characteristics of brazing
Firstly, the base material does not melt when brazing, but only the brazing material melts. Secondly, in brazed joints, the brazing material composition and properties are significantly different from the base material, and the melted brazing material needs to fill the gap of the pro-joint by capillary action and improve its load-bearing capacity by the lap area of the joint. The main features of brazing are lower heating temperature, smaller changes in the organization and mechanical properties of the welded parts, flat and smooth joints, little deformation, and the possibility of connecting different materials, high productivity. Therefore, brazing is widely used in the construction of copper pipes. However, the strength of brazed joints is directly affected by the size of the joint assembly gap. Some test data prove that the strength of brazed joints decreases with the increase of the device gap, and the size of the gap also affects the capillary action and brazing area, so the brazed joint assembly should be maintained with a uniform and strict gap to ensure the quality of the brazed joint.
C. The formation process of brazed joints
The formation process of brazed joints is that the base material and brazing material are heated to the brazing temperature, the brazing material melts and flows into the gap of the joint while interacting with the base material to form a new alloy, and then cools and crystallizes in the brazing gap to form a brazed joint. Therefore, the key to a solid joint is that the melted brazing material flows well into the gap to fill the brazing joint and interacts with the base material and cools and crystallizes. In brazing, the gap of the brazing seam is small, and the brazing material needs to flow in the brazing seam under capillary action, which is only formed when the liquid brazing material can wet the surface of the base material, so the wetting of the base material by the liquid brazing material is the key to whether the brazing material can flow into the brazing seam and fill the brazing seam.
Only when the liquid brazing material can dissolve or form a compound with the base material, the brazing material can wet the base material better. Therefore, it is necessary to choose a suitable brazing material so that the liquid brazing material can have sufficient wetting to the base material. The tin brazing material, silver brazing material and copper phosphorus brazing material selected for copper tube brazing have quite good wettability for copper. Secondly, the influence of the oxide on the surface of the base material, the oxide on the surface of the metal prevents the atoms of the brazing material from coming into direct contact with the base material, so that the liquid brazing material is agglomerated into spheres under the action of surface tension, forming a non-wetting phenomenon. Therefore, the oxides on the surface of the base material should be removed during brazing, including those generated during the brazing process, so that the brazing material maintains wettability to the base material. A common method is to choose a suitable brazing flux to effectively remove the oxide.
Type and selection of brazing material and brazing flux
A. The type and selection of brazing material
Brazing material, also known as solder, is a metal or alloy that melts and fills into the brazed joint at a temperature lower than the melting temperature of the base material when brazing. The brazing materials used for brazing copper pipes are as follows.
(1) Tin brazing solder tin brazing solder is mainly composed of tin-lead, tin-antimony, tin-silver and other alloys, which are soft brazing solder with low brazing temperature, good wettability and easy operation, but the joint strength is low and the temperature resistance is poor, mainly used for brazing of small diameter copper water pipes below 2″.
- (a) Tin-lead solder, commonly used is tin-lead solder with 50% of tin-lead each, its melting temperature is 210°C, solidification temperature is 183°C. Because the excessive lead in the solder will affect the water quality in the pipe, it is not suitable for use in domestic water supply pipes, and can be used in drainage pipes.
- (b) Pure tin brazing material, generally the tin brazing solder containing more than 90% tin is called pure tin brazing material. But high-purity tin can not be used as brazing material, because pure tin is white at room temperature, once the temperature drops low enough, it will change to gray, the volume increases by about 25%, which will turn white tin into gray powder, commonly known as “tin epidemic”. Therefore, pure tin solder must be added to 3-5% antimony, or the right amount of lead to prevent tin plague. Its melting temperature is 222°C, solidification temperature is 183°C, is the current tin brazing solder for copper water pipes.
- (c) Tin-silver brazing material, an alloy composed of 96% tin and 4% silver, with a melting temperature of 225°C and a solidification temperature of 221°C. If the silver improves the heat resistance of the brazing material and the strength of the brazing joint, it is a more ideal tin brazing material for brazing copper water pipes.
Don’t market the increase in solidification temperature, in the adjacent joints need to successively braze to bring convenience, can be used in the first welding head in the tin-silver brazing material, after welding head in the use of pure tin brazing material, to avoid after welding head heating temperature on the first welding head to produce adverse effects.
(2) Silver brazing material silver brazing material is mainly composed of silver-copper, silver-copper-tin, silver-copper-zinc and other alloys, is a hard brazing material, with high strength brazing joints, good wettability and other characteristics, but the brazing temperature is high, the operation is difficult, mainly for more than 2 “large diameter copper tubes and brazing joints with high quality requirements and brazing rate requirements.
(3) Copper phosphorus brazing material copper phosphorus brazing material is composed of copper phosphorus binary alloy, is a hard brazing material, because phosphorus can reduce copper oxide, so the use of copper phosphorus brazing material brazing copper without additional brazing flux, brazing process performance, and cheap, so inappropriate to use tin brazing solder brazing copper tube is widely used.
B. Types and selection of brazing flux
Brazing flux is also called brazing solvent, whose main function is to remove the oxide film on the surface of the base material and brazing material, inhibit the re-oxidation of the base material and brazing material in the brazing process, so as to improve the wetting effect of brazing material on the brazed material. Therefore, the brazing flux should have sufficient ability to remove the oxide film on the surface of the base material and brazing material, and the melting point and active temperature of the brazing flux should be lower than the melting point of the brazing material and have sufficient stability in the brazing temperature range. The brazing fluxes used for brazing copper tubes are as follows.
- (1) Tin brazing with brazing flux Tin brazing can use organic brazing fluxes such as rosin. However, its activity is poor, and it is difficult to adapt to the requirements of copper brazing. Therefore, inorganic brazing fluxes consisting of inorganic salts such as zinc chloride are mostly used for tin brazing of copper pipes. Commonly used are solder paste and liquid brazing flux supplied by the market, and can also be configured by themselves.
- (2) Silver brazing with brazing flux copper tube silver brazing, must use the market supply of powdered silver brazing special brazing flux. It can be used directly, or can be made into a paste and then used.
- (3) Copper brazing with brazing flux using copper phosphorus brazing material welding purple copper, generally can be used without brazing flux. However, when brazing copper tubes and brass and other copper alloys, copper brazing flux is also required, and the main component of copper brazing flux is borax, which can be used in bottles of copper soldering powder supplied by the market, and can also be configured by itself, and should be modulated into a paste when used.
The types and applications of copper brazing connection
A. Tin brazing connection of copper pipes tin brazing connection of copper pipes is soft brazing, although the brazing temperature is low and the operation is simple, but the strength of the joint is low and the temperature resistance is poor, so it is mainly used in pipes with medium of water below 2″, such as hot and cold water supply and drainage pipes and air-conditioning water pipes, etc.
- (1) Ordinary welding type brazing requires the operator to add solder from the outside of the pipe and dissolve it into the gap, and form a brazed joint after cooling and crystallization. The quality of the brazed joint needs to be determined by the operating skills.
- (2) Built-in tin ring type built-in tin ring type pipe is in the production, the casing of the pipe at the inside of the pressed a ring-shaped groove, and cast in the groove with the inner wall of the pipe flush with the tin brazing solder, brazing, no need to add solder, only the implementation of heating at the joint, heating can be conventional flame heating method, can also use the electric heating method, that is, the use of special electric heating clamp held at the joint, and then energized Heating, so that the tin brazing material ring in the groove of the tube dissolves and fills the gap at the joint, and then brazes the joint after cooling and crystallization. The quality of brazed joints is easy and the operating skills required are low, but the cost is high.
B. Phosphor bronze brazing connection of copper tube
Phosphor bronze brazing connection of copper pipe is hard brazing, the joint strength is higher, temperature resistance is better, suitable for brazing connection of small and large diameter copper pipes of various media, but its brazing temperature is higher, and the requirement of operation skills is higher. Because when brazing, the temperature of the joint directly affects the phosphorus copper brazing material on the wettability of the copper tube, as well as the brazing material in the brazing seam mobility, especially in the brazing of large-diameter copper tubes, to make phosphorus copper brazing material can be better dissolved into the brazing seam, must control the heating temperature of the joint, and can maintain a good joint in the circumferential and length direction temperature uniformity, if there is a local temperature of overheating or too low, will affect the joint in the brazing material If the local temperature is too hot or too low, it will affect the flow of brazing material in the joint, thus affecting the quality of the brazed joint.
C. Silver brazing connection of copper tubes
Although the brazing temperature is high and the operation is difficult, the silver brazing material has better wettability and fluidity compared with the phosphor bronze brazing connection under the same brazing conditions, which makes it easier to melt into and fill the brazing seam, thus making it easier to get the quality of the brazed joint. This makes it easier to guarantee the quality of brazed joints.
There are many methods of processing copper tubes, but they can be divided into two categories: hot processing and cold processing. Such as extrusion manufacturing billet, oblique rolling perforation and other methods are heated to much higher than the recrystallization temperature of copper billet for deformation processing, so as to get the billet. The billet is then made into a tube at room temperature by cold rolling and cold drawing methods. This traditional process has been used for many years and is still in use today.
The production process is to melt and cast electrolytic copper into solid ingots, and then heated to more than 850°C in the heating furnace, one by one into the extrusion machine extrusion into billets, and then through cold rolling or multiple linear stretching to disc stretching required billets. Extrusion is divided into two kinds of high extrusion ratio and low extrusion ratio, both of which have refined grain organization and good surface quality. High extrusion ratio extrusion billet specifications are small, thin wall thickness, can be directly in the continuous direct machine or disc stretching machine for processing; low extrusion ratio extrusion can be used for large ingot extrusion large specifications billet, and then extended processing with cold rolling mill. For the same size and specifications of the ingot, high extrusion ratio requires a larger extrusion tonnage, and extrusion of the tube wall thickness tolerance is large.
At present in China is very popular is the continuous casting and rolling supply method, this is a new supply method in the 1990s, its production process is the horizontal continuous casting of hollow tube billet cut off the milling surface directly into the three-roller planetary rolling mill to roll out smaller diameter thin-walled copper pipe. As the three-roller mill can make the rolled copper tube without rotation, so it is easy to reel online into a tray. It is characterized by a short production process, eliminating the reheating and extrusion process, whether in saving energy, reducing equipment investment, reducing costs in all methods have the advantage.
Source: China Copper Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)