ABSTRACT: This paper mainly introduces the equipment and technology of copper strip longitudinal cladding welding continuous production line, which solves the problems of short cable length, short production cycle, low cost and high production efficiency. The difference between rolling and drawing in Mineral-insulated copper-clad cable is introduced. Keywords: Mineral-insulated copper-clad cable; equipment; material; production process; technical data; rolling and drawing;

1.Overview

Mineral-insulated copper-clad cable cables, also known as mgo insulated cables, are made of inorganic materials. The Mineral-insulated copper-clad cable is made of copper conductor, inorganic insulating material (magnesium oxide powder) and seamless copper pipe or copper strip which is welded by longitudinal cladding. This unique structure makes it fire-resistant, explosion-proof, heat-resistant, non-ageing, non-ignition and non-propagation of fire, as well as non-emission of any harmful gases and smoke under surrounding fire conditions, the utility model is especially suitable for the places or parts with bad environment and high safety requirements, especially for the fire-fighting system lines which are required to ensure safe power supply under fire conditions. Special needs can also be in the metal sheathing extrusion pack a layer of polyethylene or low-smoke halogen-free sheathing. The Mineral-insulated copper-clad cable can be divided into: Distribution Cable, heating cable and heating elements, thermocouple cable and compensation cable, special cable, the most commonly used in practical applications is the distribution cable.

At present, the National Standard of Mineral-insulated copper-clad cable is GB/T13033.1-2007. A new type of mineral insulated special cable has appeared outside the national standard-825 alloy sheathed mineral insulated fire-proof cable. The 825 alloy sheathed mineral insulated fireproof cable is designed to work well in the environment of hydrocarbon explosion flame and high corrosion. The cable consists of one or more conductor core wires, magnesia powder and 825 alloy sheathing. Conductor core wire is generally nickel-clad copper or pure nickel solid core wire. The Outer Sheath of the 825 alloy cable shall not be used as a ground wire. 825 Alloy has good corrosion resistance to acid and Alkali metals in oxidation and reduction environment. High Nickel content makes the alloy have effective stress corrosion cracking resistance. Corrosion resistance in a variety of media such as sulfuric acid, phosphoric acid, nitric acid and organic acids, Alkali metals such as sodium hydroxide, potassium hydroxide and hydrochloric acid solutions. Alloy 825 has been found to have excellent all-round performance in the production of Organic Sulfides, Hydrogen Sulphide and combustible sulphur products at high temperatures, such as in petroleum and petrochemical installations. The 825 alloy sheathed mineral insulated fire-proof cable can not only survive for 30 minutes in the high temperature explosion flame at 1200 °C, but also has strong corrosion resistance to petroleum gas and acid fog. It was tested by Exxon Mobil, placing an 825 alloy cable in an environment very similar to a real hydrocarbon fire. The test procedure states that the cable must be supported in a pit filled with a mixture of gasoline and diesel fuel. When the mixture is ignited, the temperature in the pit rises sharply and Burns vigorously. In the test, the cable specimen not only withstands the high temperature of flame, but also has the destructive turbulent fire. During the whole test period, the average temperature exceeded 1100 °c. due to the characteristics of the test itself, the temperature fluctuated continuously at the level of 1100 °C. The test shows that the cable can continue to work normally in case of fire.

2.Introduction of equipment

2.1 double copper strip wiring device

CONSTRUCTION: the Double Copper Strip setting-out device is a setting-out machine with 2 independent setting-out rods and brake gas brake. Two independent rods can be rotated, each with a diameter of (240-470) mm. The maximum bandwidth is 320 mm and the length of each of the four supporting strips is 600 mm. Up to (all) = 1400 kg, copper tape of 60.5 mm width (up to 700 kg per plate) is commonly used. FUNCTION: to keep a certain tension between the copper strip wire feeder and the copper strip wire accumulator. The beauty of the copper tape stringing machine. When one copper strip is used up, another copper strip is welded with it (Argon is used as shielding gas, UTP silver electrode is filled with Argon arc welding) to ensure continuous production line.

2.2 copper tape wire storage

CONSTRUCTION: Copper Belt Storage Line pulley size is 4 meters high, 2.5 meters wide. On either side are vertical columns, and at the top of the center is a block of pulleys (6 pulleys 360 mm in diameter) . There is also a pulley block in the middle (5 pulleys of 360mm diameter) . The pulley block is not electrically driven but has a hydraulic tension control unit that stops the copper strip in the event that it breaks. (as a protective measure) having a separate pulley fixed in a secure cage that guides the copper into a block such as a pulley block. There is also a signal device to locate the pulleys. FUNCTION: ensure the copper belt and copper belt cleaner have certain tension in the copper belt accumulator. The Copper Strip wire accumulator can store enough copper strip to buy enough time for welding between copper strip and copper strip.

2.3 Copper Belt Washer

CONSTRUCTION: Copper Belt cleaning machine is about 2.5 m long, 1.2 m high and 0.6 m wide. The main components of the housing are made of acid-resistant plastic. It has a system to control the copper content and a system to control the temperature of the cleaning fluid. There are two motors for circulating tap water and cleaning fluids. The inlet and outlet are 100 mm wide. The built-in conveyor belt is 64 mm wide. ROLE: 10%-15% dilute sulfuric acid and 10%-20% hydrogen peroxide on the surface of copper strip pickling, decontamination, oxidation and other chemical reactions. After pickling, the copper strip is washed by water, and finally transferred to the copper strip forming mill through drying at not less than 35 degrees.

2.4 Copper Strip forming mill

CONSTRUCTION: A copper strip forming machine with 13 universal joints, 7 power-guided dies, 2 motors, 7 gearboxes and 7 rollers (all a pair) , the remaining 6 unused are all fixed to the main frame. The first three gearboxes are connected and driven by a motor next to the first gearbox. The last four gearboxes are connected and driven by a motor next to the seventh. The rollers are connected to the transmission that the roller shaft sends out. All of these rolls must be concentric vertical when the copper strip is shaped and rolled. The Motor, gearbox and roll are all the same. Each ring has the same gear-to-tooth ratio of 79:1(transmission and wheels) motor information: General Purpose Motor, 1000 RPM, 3.8 kw DC shunt motor. Armature = 180 volts, 28.5 amperes. Magnetic Field Voltage 210 volts, 1.95 amperes. The motor uses a fan to cool it down. Function: 60.55 mm wide copper strip longitudinal package into 19.8 mm copper pipe, longitudinal package into the gap between the seam is about 0.1 mm to facilitate welding.

2.5 welding system

CONSTRUCTION: The welding box has 3 pairs of water cooling rollers with diameter of 20mm. The silicone oil transmission system consists of a "WatsonMarlow" 504DU pump, a spherical sensor with observation holes, and a silicone oil barrel rack. Vibrating hammer consists of a DC motor and a gearbox in a CAM mechanism. The Motor Control panel consists of a Lincoln welder, a separate high frequency 400 amp power supply, and a torch, cooled by circulating condensate. Seam control panel with Video Camera, touch-type Welding Monitor. ROLE: Copper Strip Longitudinal cladding welding continuous production process is the most important ring is to ensure the quality and stability of welding. The seam of copper strip pipe is tracked and welded automatically by the camera, which ensures the stability and quality of the welding.

2.61 mill

Construction: No. 1 Rolling Mill consists of 7 motors. Its gear-to-tooth ratio is based on the gearbox and motor drive pulley difference. All Roll stands are mounted on the main structure. The roller stands are at right angles to each other. All Roll stands have the same motor, gearbox and rolling area. Each roll stand has a DC motor to drive a belt up to the gearbox. To where it's rolled. Motor Information: "General Motors" 3000 RPM, 2.2 kw DC shunt motor. Armature voltage = 180 V, 13.5 A. Magnetic Field Voltage 210 volts, 0.78 amperes. Motor construction = MD 132160(with tripod). Control System: control all connected to the main line control system. Local control is accomplished by micromanaging the main control desk on the first floor. FUNCTION: The copper wire core, the magnesium oxide and the copper strip are rolled into a semi-product after many times. Cable diameter from No. 1 Roller is 19.07 mm, cable diameter from No. 7 roller is 15.52 mm.

2. No. 71 annealing device, cooling water tank and guide wheel, No. 2 and No. 3 rolling mill construction (No. 1 annealing device) : 125 kw 10,000 hz water-cooled motor, coil box and water cycle, coil diameter 30 mm, glass pad tube outer diameter 26 mm, inner diameter 20 mm, length 1650 mm. Function (No. 1 annealing device) : High Current Induction Heating Cable. Heating principle: 50HZ POWER FREQUENCY CURRENT INTO 10KHZ AC power supply, the use of SCR frequency conversion device, conductive material in the magnetic field is induced, the material itself produces eddy current and hysteresis loss, so that the material itself heating a physical phenomenon. Construction (cooling tank (quenching) and pulley) : 3350 mm x 610 mm x 1600 mm (depth height) cooling tank with guide pulley. Pulley enables vertical movement, 1800mm aluminum pulley, limit switch and LVDT. The flume connects the pipe to the circulation pump and the heat exchanger, controlled by the pump. Role (cooling water tank (quenching) and Pulley) : designed to solve three problems in the production of mineral cables. 1) turn the cable straight from tree to Level 2) cool the cable from No. 1 annealing device 3) provide signal position for the speed control circuit of No. 2 Rolling Mill. Construction (No. 2 mill) : No. 2 Mill consists of 12 motors: All Roll stands are mounted on the main structure. The roller stands are at right angles to each other. All rollers have the same motor, gearbox, and rolling area. The number of teeth per roller varies according to the drive pulley of the gearbox and motor. Motor Information: General Motor 3000 RPM, 2.2 kw DC shunt Ip Motor. Armature voltage 180 volts, 13.5 amperes. Magnetic field voltage = 210 volts, 0.78 amperes. Full Control System: The control unit is connected to the main line control system. Function: Cable diameter from No. 1 Roll is 15.07 mm, cable diameter from No. 12 Roll is 7.88 mm structure: (the principle of No. 3 mill is the same as No. 2 mill) function: cable diameter from No. 1 Roll of No. 3 mill is 9.96 mm, and cable diameter from No. 12 mill is 5.15 mm. 2. No. 82 annealing device, laser Caliper, eddy current Tester Construction (No. 2 annealing device) : There are 250kw, 1000hz water-cooled motor, including six coils with 30mm inner diameter, 4270mm long coil box, water-cooled system, etc. . The outer diameter of the glass liner is 24.5 mm and the inner diameter is 19.5 mm (700 mm long) . Action (No. 2 annealing device) : (with No. 1 annealing furnace, figure province) structure (laser Caliper) : equipped with laser measuring head. The system has alarm box function (laser Caliper) : check whether the outer diameter of the cable is within ± 0.5 mm range. Construction (Eddy Current Tester) : with flaw detection (poorly welded welds) laser head and display instrument panel. Role (Eddy Current Tester) : Detection of bad weld and alarm, equipped with a black punch of the pneumatic device hit a black mark to remind the receiver to separate. (FIG.)2.9 down loop take-up: consists of an upper tray with a v-shaped slot and a lower turntable. The cylinder is 1000 mm in diameter and is controlled by a pneumatic piston known as the Fingers and feedroll. The turntable is 1160mm in diameter and is driven by a chain. FUNCTION: Coil take-up, ensure continuous production to replace the take-up reel.

3 materials 3.1 conductor structure Diagram

The typical structure of the Mineral-insulated copper-clad cable is shown on the right. The conductor, Magnesia and sheath are rolled in combination for many times, and the compactness of the three is very high. If the cable requires anti-corrosion performance, can be in the copper sheath outside another layer of protection. In general, a protective layer is extruded under the guide. In general, the conductor and Sheath are made of copper and the insulating layer is made of magnesium oxide. The conductor size of distribution cable is quite large, ranging from 1mm2 to 400mm2, and the number of wire cores ranges from 1 to 19. Only the conductor section of single-core cable is larger than 25mm2, the conductor cross-section of 7-core, 12-core and 19-core multi-core cables is generally small.

3.2 presentation of materials

The raw materials used in the process of longitudinal cladding welding of copper strip are oxygen-free copper strip with phosphorus, magnesium oxide powder with silicon oil and copper conductor with coil. Oxygen-free copper bands containing phosphorus can weigh up to 700 kg and copper conductors in coils can weigh up to 1 ton. And filling or porcelain column assembly process of a cable can only reach about 200kg, so from the source, continuous production process to ensure the length of the supply of raw materials. Theoretically speaking, in the process of continuous production of copper strip, the quality of raw materials is guaranteed and the electrical stability is high. A 2L1.5 cable can reach about 8 kilometers, due to the constraints of the take-up device, a 2L1.5 cable can be as long as 4 km or so.

3.2.1 conducting materials

Mineral-insulated copper-clad cable uses a solid, nearly circular cross section of annealed, high conductivity, oxygen free copper. The two requirements for conducting materials are the most basic high conductivity for efficient transmission of electrical energy and the extensibility of the material to meet the requirements of the process. Flexible copper with high conductivity can meet the requirements of most distribution cable conductors, oxygen content in oxygen-free copper is very low, the structure of copper is uniform single-phase structure, which is very good for toughness. The rolling ability of oxygen-free copper is superior to that of low oxygen copper rod in all wire diameters.

3.2.2 sheathing materials

The Standard Sheath material is a phosphorus-containing deoxy copper strip (the phosphorus-containing copper strip facilitates welding) . The contents of arsenic, tellurium and sulfur in the copper deoxy-phosphorus strip do not exceed 50 PPM and 15 PPM respectively. In order to ensure the welding stability and welding quality, the two side corners of the phosphor-containing copper oxide strip must be smooth, clean, bright, without burr and oil spot.

3.2.3 insulation

The insulating material of the Mineral-insulated copper-clad cable is inorganic magnesium oxide, which has very stable physical and chemical properties, is non corrosive to copper, has a melting point of up to 2800 °C, high electrical strength, high thermal conductivity, and is non toxic, the purity of the material can be made up to 94% , for special occasions such as nuclear power plants, on the purity of magnesium oxide material requirements are higher. The flow velocity, density and particle size distribution of Mgo are considered in the process of longitudinal cladding welding of copper strip. 1) the velocity is controlled between 160 ~ 210s/100g, 2) the vibrodensity is between 2.13 ~ 2.33 g/cm3,3) the grain size distribution is directly related to the density, the normal grain size distribution is from + 40 ~ 325 mesh, and decreases from high to low.

3.2.3.1 electrical properties of magnesium oxide

The basic purpose of checking the physical and chemical indexes of Magnesia powder is to ensure good electrical properties. The electrical performance index is divided into normal state, hot state and wet state. The normal test is to measure the insulation resistance and voltage resistance of the pipe under normal conditions after it is made. The thermal test is to observe the leakage current, resistance and pressure resistance of the tube under a certain load condition. In fact, the quality of magnesium powder is evaluated by these data. The hygroscopic test is to put the passed or not passed tube into the constant temperature and humidity box (humidity box) in a certain time to observe the hygroscopicity of Mgo. Generally at 42 °C or 50 °C, put 48 or 72 hours to determine the pipe insulation and pressure (on behalf of magnesium oxide insulation and pressure) . 

4. Continuous production technology of Longitudinal cladding welding of Mineral-insulated copper-clad cable copper strip

I'll meet you down at the process flow diagram

Copper Strip Longitudinal cladding welding continuous production line consists of vertical and horizontal parts, the vertical part consists of two inclined cylinders and hoppers with Magnesia powder added on the third floor, pipe forming roll machine, cleaning machine on the second floor, welding machine head, circulating water condensing compressor, pressing wheel and No. 1 Rolling Machine. The horizontal part includes No. 1 annealing induction annealing box on the first floor, two quenching cooling water tanks, three rolling mills, No. 2 annealing induction annealing box, outside diameter detector, Eddy Current Tester and take-up device. First, the 0.95 mm (thickness) * 60.55 mm (width) copper strip on the copper strip wiring device (this is only one kind of specification) is inserted into the copper strip wire storage device. The copper strip is washed by water, pickling and dried at not less than 35 °C by the copper strip cleaning machine, after forming mill forming wheel continuous longitudinal package into a cylindrical shape, in the welding water-cooling roller, copper strip edge of each other aligned close, the gap between the gap is about 0.1 mm, the electrode Rod is used for Argon Arc welding (no filler metal and Argon is used as shielding gas) . Welding grab head and Sheath Center into 110 degrees angle, in order to preheat the copper strip edge. The welding speed of copper strip is 1.0-3.0 M/min, the welding current is about 205-270A, the welding voltage is about 12-13V. We should pay close attention to the surface quality of the copper sheath after welding, the surface of the copper strip is like a dace, there should be no leakage, holes, dripping and other undesirable phenomena. Secondly, the proper stainless steel core setting pipe is selected according to the process requirement, which is put from the bottom of Magnesia powder hopper to the forming mill to the No. 1 mill. At this point, the silicone oil pipe will be inserted into the core tube. The main function of the core tube is to protect

The insulation thickness between the wire core and the copper sheath and between the wire core and the wire core is even, and the wire core is fixed on the lower bracket of the magnesia powder hopper, the upper and lower ports are connected with the powder inlet of the hopper and the fixed core pipe by a "Horn" type rubber sleeve, and the upper and lower ports are tightened and sealed by a stainless steel pipe clamp. In order to ensure that the conducting wire core is not biased in the copper sheath, the lead wire is threaded through the sizing die into the fixed core pipe, and then the lead wire and the conductor wire core are welded together, the sizing die shall be placed in the die sleeve and fixed on the magnesia powder funnel bracket, it is required that the diameter of the sizing die hole should be in a straight line with the nozzle of the wire-core tube (the diameter of the sizing die is about 0.1-0.6 mm smaller than that of the billet of the copper wire core, which mainly plays the role of sizing, straightening and removing the impurities on the surface of the conductor) . The lead wire is then threaded under the seventh roll of the No. 1 mill, at which point magnesium oxide powder is poured from the funnel into the Copper Sheath. In order to ensure that mgo powder is poured smoothly and mgo powder is compacted in the copper sheath, a pair of small hammers strike the copper tube at a certain frequency (frequency is about 20-80 times/minute) between the welding gun and the copper tube sizing wheel. The feeding quantity of mgo powder in the funnel can be controlled by the signal of the powder level sensor in the funnel and inclined cylinder. Both the funnel and inclined cylinder have sensors. After continuous rolling and intermediate induction annealing (twice) , the finished cable diameter can be obtained. Each rolling mill base is equipped with a number of rollers to make the Magnesia powder insulated and compacted, and at the same time to reduce the diameter of the cable, after Rolling, the cable is quenched by intermediate induction annealing (capacity 50-110kW) and a circulating cooling tank with alcohol added. The speed of the whole production line can be set by the master console according to the process parameters, and the power of the annealing furnace can be controlled by hand. In the normal production process, to constantly carry out the intermediate inspection, to check whether the motor speed overload and so on a series of work.

his section mainly introduces the raw materials, auxiliary materials, accessories, process control, quality analysis and other technical requirements.

5. Rolling and drawing 

5.1 rolling mill history

Rolling mill is the equipment to realize metal rolling process. The earliest recorded was the Italian 1480. Vinci, Tuscany designed a sketch of the mill. 1553, a Frenchman, rolled gold and silver plates to make coins. Since then there have been rolling mills in Spain, Belgium and the United Kingdom. A rolling mill designed by 1728 for the production of round bars in the UK, the UK has a tandem small mill at 1766, the first reversible plate mill was put into operation in the UK in the mid 19th century and rolled out marine iron plates. The universal mill was invented in Germany in 1848 and the first continuous mill was built in 1859. The universal section mill was introduced in 1872. The semi-continuous strip mill made in the early 20th century consists of two three-high roughing mills and five four-high finishing mills.

5.2 rolling principle of rolling mill at present, the main equipment of our rolling mill is 14 stand rolling mill from Baylor Company of Germany and 7 stand rolling mill and 12 stand rolling mill from Kanthal company of UK. Principle of Mineral-insulated copper-clad cable: The motion of the two universal joints connected to the DC motor's drive shaft drives the paired rollers connected to the universal joints, in order to achieve rolling purposes. The surface phenomenon of the rolling mill principle is very simple, the large diameter cable or copper conductor through a pair of rotating roll slot, because of the compression of the roll material cross-section reduced, length increase of the pressure processing method. At present, our company is 24.5 mm semi-finished cable directly rolled into the process parameters specified data. At present, the largest roller mill can roll 32 mm cable, 32 mm cable can be rolled directly to 5.15 mm. The Control System of rolling mill is very complex, which is generally divided into three parts: mechanical, hydraulic and electrical control. The precision of rolling mill is related to the level of mechanical manufacturing.

5.3 The mill equipment is constructed. The mill mainly consists of a working stand and a driving device. The work machine base is composed of roll bearing frame, rail base roll adjusting device and so on. Rollers are the parts that cause metal to deform plastically. Work Stand: 1) The roll bearing supports the roll and maintains the fixed position of the roll in the stand. 2) mill rail seat: used for mounting the frame and fixing on the foundation, also called baseboard. It can bear the gravity and tipping moment of the working frame and ensure the accuracy of the installation dimension of the working frame. 3) Roll Adjustment Device: At present, the gap of 14 stand stand mill of German burler company does not need adjustment. According to the pre-set parameters of the main control console, the roll can be replaced automatically, and it only takes about 2 minutes to replace the roll once. The roll gap of the 7-stand and 12-stand rolling mills of Kanthal company in UK needs to be adjusted to change the roll gap. It takes several hours to change the roll gap. Transmission: by the DC motor universal joint gear housing and connecting shaft, etc. . The gear housing distributes the transmission torque to the two rollers. 5.4 DRAWING PRINCIPLE DRAWING PRINCIPLE: A method of drawing a product with the same cross-section shape and size of the die hole by drawing the metal blank through the die hole with the jaws of the drawing machine and drawing it out from the die hole. Unlike the extrusion and rolling processes, the drawing process is achieved by applying a pull force at the front end of the metal to be processed, which is called the drawing force. The ratio of drawing force to the cross-sectional area at the die exit of the metal being drawn is called unit drawing force, that is, drawing stress. In fact, the drawing stress is the Longitudinal stress at the end of the deformation zone. The drawing stress is less than the yield strength of the metal exit die. If the drawing stress is too large than the yield strength of the metal die, it can cause the thin neck of the product, or even break. Therefore, the drawing stress should be less than the metal die after the deformation of the tensile force. 

Source: Global Cable Resources

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