Technological strength

Pipe manufacturing process

Editor:河北鹏鑫管道装备集团有限公司 │ Release Time:2019-01-03 

1. Raw materials


 1.1 The choice of materials is in line with the relevant standards of the pipe producing country and the raw material standards required by the owner.


 1.2 After entering the factory, the inspectors first verify the original material certificate issued by the manufacturer and the material inspection report of the imported manufacturer. Check whether the identification on the material is complete and consistent with the quality certificate.


 1.3 The newly purchased materials shall be re-examined, and the chemical composition, length, wall thickness, outer diameter (inner diameter) and surface quality of the materials shall be strictly tested according to ASME and DIN17175 standards. The batch number and pipe number of the materials shall be Make a record. Materials that do not meet the requirements are not allowed to be stored and processed. The inner and outer surfaces of the steel pipe are not allowed to have cracks, folds, rolling, crusting, separation and hairline. These defects should be completely removed. The removal depth should not exceed the negative deviation of the nominal wall thickness. The actual wall thickness of the cleaning place should not be less than the wall. The minimum allowed by the thickness. On the inner and outer surfaces of the steel pipe, the size of the defects allowed to exist shall not exceed the relevant provisions in the corresponding standard, otherwise it shall be rejected. The scale of the inner and outer surfaces of the steel pipe should be removed and treated with anti-corrosion treatment. The anti-corrosion treatment should not affect the visual inspection of the naked eye and can be removed.


In order to ensure compliance with the specifications specified by the materials, the materials required by the customer shall also be tested as follows:


1. Mechanical properties Mechanical properties are in accordance with DIN17175 and ASME requirements. For the alloy steel pipe to do the transverse mechanical properties test (including the lateral impact test), the impact test is the Charpy V test, the number of inspections is the same as the tensile test.


2, process performance


2.1 The steel pipe is 100% ultrasonic non-destructive testing according to SEP1915, and provides the standard sample of ultrasonic flaw detection. The standard sample defect depth is 5% of the wall thickness, and the maximum is not more than 1.5mm.


2.2 Steel pipe for flattening test 3 Actual grain size The actual grain size of the finished alloy steel pipe shall not be coarser than Grade 4, and the grade difference of the same furnace number shall not exceed Grade 2, and the grain size test shall be in accordance with ASTM I 12-95. The number of times is 10 times per heat treatment batch per furnace number.


2, cutting and cutting


2.1 Before the cutting of high-temperature and high-pressure alloy pipe fittings used in power plants, the first calculation of the materials should be carried out. According to the calculation results of pipe strength, and considering the thinning and deformation of the pipe fittings in the production process, the key parts of the pipe fittings ( For example, the outer arc of the elbow, the thickness of the three-way shoulder, etc., and the influence, select the material with sufficient margin, and consider whether the stress enhancement coefficient after the pipe fitting is in accordance with the pipe design stress coefficient and the flow area of the pipe and other factors. . The hot press tee should calculate the radial material compensation and the compensation of the shoulder material during the pressing process.


2.2 For high-alloy pipe materials, the gantry-type band saw cutting machine adopts the method of cold cutting to cut the material. For other materials, it is generally avoided to cut with flame, and the band saw is used to prevent the material from being hardened during the cutting process or improperly operated. Cause defects such as cracks.


2.3 According to the design requirements, the outer diameter, wall thickness, material, pipe number, furnace batch number and pipe material flow number of the raw materials should be marked and transplanted when cutting and cutting. The logo is marked by low-stress stencil and paint spraying. The operation contents are recorded on the production process flow card.


2.4 After the first piece is cut, the operator shall perform the self-inspection and report to the special inspection personnel of the testing center for special inspection. After the inspection is passed, the other parts shall be cut off, and each piece shall be tested and recorded.


3 hot pressing (push) made


3.1 The hot press forming process of high pressure pipe fittings (especially tee) is an important process, and the heating of the billet can be heated by a fuel heating furnace. Before the billet is heated, first use a hammer, a grinding wheel, etc. to clean the chip surface, oil, rust, and low-melting metals such as copper and aluminum. Check that the marking of the blank meets the design requirements.


3.2 Clean up the debris in the furnace, check whether the heating circuit, oil circuit, trolley and temperature measurement system are normal, and whether the oil is sufficient.


3.3 The billet is placed in a heating furnace for heating, and the workpiece is isolated from the furnace table by using refractory bricks. The heating rate is strictly controlled according to different materials at 150 ° C / hour, and the heating is more than 1 hour when the material is heated above 30-3 ° C. . During the heating and holding process, it is monitored by digital or infrared thermometer and adjusted at any time.


3.4 When the billet is heated to the specified temperature, it is baked and pressed, and the press is completed with a 2500 ton press and a tube mold. When pressing, the temperature of the workpiece is controlled by an infrared thermometer to be not less than 850 ° C. When the temperature is too low, the workpiece is returned to the furnace for reheating and heat preservation before pressing.


3.5 The thermoforming of the product fully considers the law of the metal flow of the thermoplastic deformation during the forming process of the finished product. The forming die attempts to have a small deformation resistance to the hot working of the workpiece, and the pressed tire mold is in an intact state, and according to the requirements of the ISO9000 quality assurance system. Regular verification of the tire mold is performed to control the amount of thermoplastic deformation of the material such that the actual wall thickness at any point on the tube is greater than the minimum wall thickness of the connected straight tube.


3.6 For large-diameter elbows, the medium-frequency heating is used for push-type, and the push-making equipment uses a large elbow pusher. The pushing process adjusts the heating temperature of the workpiece by adjusting the power of the intermediate frequency power supply. Generally, the control is performed at 950-1020 °C, and the pushing speed is controlled at 60-100 mm/min.


4 heat treatment


4.1 For 10CrMo910, 12Cr1MoV and other finished products, our company strictly carries out heat treatment according to the heat treatment system stipulated in DIN17175 and ASME standards. Generally, the heat treatment of small pipe fittings can be performed by electric resistance furnace, and the heat treatment of large diameter pipe fittings or elbow can be carried out in the oil heat treatment furnace.


4.2 The furnace of the heat treatment furnace is clean and free of oil, ash, rust and other metals different from the treatment materials.


4.3 The heat treatment is strictly carried out according to the heat treatment curve required by the “heat treatment process card”. The temperature rise and fall of the alloy steel pipe is controlled to be less than 200 ° C / hour.


4.4 The automatic recorder records the temperature rise and fall at any time and automatically adjusts the temperature and holding time of the furnace according to the predetermined parameters. During the heating process of the pipe fittings, the flame is blocked by the fire wall to prevent the flame from being directly sprayed onto the surface of the pipe fitting, so that the pipe fitting does not have overheating or overheating during the heat treatment process.


4.5 After the heat treatment, the alloy pipe fittings shall be metallographically inspected one by one. The actual grain size of the alloy is not coarser than grade 4, and the grade difference of the same furnace number pipe does not exceed 2 grades.


4.6 Perform hardness testing on the heat-treated pipe fittings to ensure that the hardness of any part of the pipe fittings does not exceed the standard requirements.


4.7 After the heat treatment of the pipe fittings, the scale of the inner and outer surfaces is removed by sand blasting until the metallic luster of the material is visible. Scratches, pits and other defects on the surface of the material shall be smoothed by tools such as grinding wheels. The thickness of the polished pipe parts shall not be less than the minimum wall thickness required by the design.


4.8 Fill in the heat treatment record according to the pipe number and mark, and rewrite the incomplete mark on the surface of the pipe and the flow card. 5 groove processing


5.1 The groove processing of high-pressure pipe fittings is carried out by mechanical cutting. Our company has more than 20 machining equipments such as lathes and power heads. It can be based on the welding technical regulations of DL869 thermal power plant and GD87 "Steam power pipe parts and components typical of thermal power plants. Design Manual, DL/T695-1999 "Power Station Steel Butt Welded Pipe Fittings" and the double V-shaped or U-shaped groove and inner groove and outer groove used by the tenderer to process various thick-walled pipe fittings, the company can completely follow The tenderer's groove map and technical requirements are processed to ensure that the pipe fittings are easy to handle and weld during the welding process.


5.2 After the pipe groove is completed, the inspection personnel shall inspect and accept the outer dimensions of the pipe fittings according to the requirements of the drawings, and rework the products with unqualified geometric dimensions until the products meet the design dimensions.


6 welding


6.1 For the welding of pipe fittings such as “welding tee” and “welding elbow” to be welded, the welding work is carried out by professional welders with many years of welding experience, and the appropriate welding procedure qualification is carried out according to the requirements, and the mechanical properties of the weld are tested. The welding process is guided by the process specification. The welding process is assessed by a qualified welding procedure. The process qualification meets the requirements of the ASME Boiler and Pressure Vessel Codes ninth volume welding and brazing process qualification, and the welder is also qualified as a welder. The welder's welding project during the welding process is inconsistent with the items that pass the test and cannot be welded. During the welding process, the quality assurance engineer stipulates the monitoring and measurement of the stopping point and witness point of the welding process to ensure that the key process of welding does not have any defects and problems. Welding of alloy materials strictly controls welding parameters such as interlayer temperature, preheating temperature, and number of welded layers, and careful layer cleaning is performed. Tempering is performed immediately after welding to ensure that the performance of the welded joint meets the specifications.


6.2 The welding process shall be carried out strictly in accordance with the “welding process instruction card” formulated by the company. The welding process shall be such as to avoid defects such as incomplete penetration, porosity, pinching, cracks and undercuts.


6.3 Post-weld heat treatment of pipe fittings may be carried out in an electric resistance furnace or an oil-fired furnace, or may be carried out in a far-infrared heating furnace to ensure that the welded joint has similar mechanical properties and other technical indexes as the base metal.


6.4 Welds of welded pipe fittings shall be tested by 100% ray or ultrasonic. According to JB4730-2005 standard, the ultrasonic wave shall reach Class I, and the radiation shall reach Grade II.


7 test


7.1 For high-pressure pipe fittings, all kinds of tests are carried out according to the requirements of DL869, DL5031 and other standards before leaving the factory. According to ASME B31.1, all tests are completed by professional inspectors with corresponding qualifications approved by the State Bureau of Technical Supervision.


7.2 High-pressure three-way, elbow, outer surface of the head and the head for magnetic powder (MT) detection, ultrasonic bending and flaw detection of the outer arc side of the elbow, the shoulder of the three-way shoulder and the diameter of the head, and the weld at the weld of the welded pipe Flaw detection or ultrasonic flaw detection. The forged tee or elbow is ultrasonically inspected before machining.


7.3 Magnetic particle inspection shall be carried out within 100 mm of the groove of all pipe fittings, and the flaw detection shall ensure that there are no defects such as cracks caused during the cutting process at the groove.


7.4 Surface quality. The inner and outer surfaces of the pipe are not allowed to have cracks, shrinkage holes, ash, sand, folding, leakage welding, heavy skin and other defects. The surface should be smooth, no sharp scratches are allowed, the depth of the depression is not more than 1.5mm, and the maximum size of the depression It should not be greater than 5% of the circumference of the pipe and not more than 40 mm. There shall be no cracks, pores, craters and splashes on the surface of the weld and no undercuts. The inner corner of the tee shall be smoothly transitioned. All fittings were 100% surface visual inspection. The cracks, sharp corners, pits and other defects on the surface of the pipe are ground by a grinder, and magnetic particle inspection is performed on the grinding place until the defect is eliminated. The thickness of the polished pipe is not less than the minimum thickness of the design.


7.5 The following tests shall be carried out for the fittings of special requirements of customers:


7.5.1 Hydraulic test All pipe fittings can be tested with the system for hydraulic pressure (the hydraulic test pressure is 1.5 times the design pressure and the time is not less than 10 minutes). In the case of complete quality documentation, the factory fittings may not be hydrostatically tested.


7.5.2 Actual grain size The actual grain size of the finished pipe fittings shall not be coarser than Grade 4, and the grade difference of the same furnace pipe fittings shall not exceed Grade 2. The grain size inspection shall be in accordance with YB/T5148-93 (or ASTM E112-95). The method is carried out, and the number of inspections is once per furnace number + once per heat treatment batch.


7.5.3 Microstructure: The manufacturer shall carry out the microstructure inspection and provide the photomicrograph according to the relevant provisions of GB/T13298-91 (or the corresponding international standard). The number of inspections is the number per furnace + size (diameter × wall) Thick) + heat treatment batch 1 time. 8, packaging, identification


    The outer surface of the pipeline should be coated with anti-rust primer. The exterior is painted according to different tubes. The paint is uniform, no bubbles, no wrinkles and peeling. The groove is treated with special anti-rust agent. Small forged pipe fittings or important pipe fittings are packed in wooden boxes, and large pipe fittings are generally bare. All pipe fittings are protected by a plastic (plastic) ring to protect the pipe from damage. Ensure that the final product is shipped without any cracks, scratches, scratches, heavy skin, sand, interlayers, slag inclusions. In the obvious part of the pipe fittings, mark the pipe fittings such as pressure, temperature, material, and caliber. The stamp is a low stress stamp.


9, shipping


The delivery of pipe fittings should be based on the actual situation to select qualified transportation methods. Generally, domestic pipe fittings adopt the method of steam transportation. In the process of automobile transportation, the flexible packaging tape with high strength is required to firmly bind the pipe fittings and the car body. When the vehicle is running, it cannot be bumped and rubbed with other pipe fittings, and measures against rain and moisture are prepared. When the pipe fittings are delivered, the delivery condition of the alloy steel pipe parts is: normalizing + tempering; the delivery status of carbon steel is: normalizing.


10. Technical documents available


Products are reviewed for quality records and reports, as well as technical documentation, prior to delivery, and may be reviewed by the owner prior to delivery. The documents submitted with the goods are: Design parameters of the quality assurance book processing parts, test report of the design drawing pipe fittings (including A raw material re-inspection report; B-ray inspection report; C heat treatment report; D ultrasonic flaw detection report; E magnetic particle inspection report; F coloring Penetration inspection report; G geometry inspection report; H various types of reports negotiated with the user) Material and weight of the pipe fittings Other necessary documents.


The pipeline factory configuration performs the following work:


Pipe design


1. Design the direction of the pipeline and the location of the pipe ring weld, the relative distance from the platform, the hole, the straight pipe section of the pipe, the relative position of the hole of the elevator block, the socket, etc., the weld of the factory and the weld of the site.


2.2. Design the piping and piping, valves, equipment, flow measuring devices and other groove forms, the welding C value at the groove or the corresponding inner diameter value, the minimum design wall thickness at the groove and the weld coefficient.


3. Design the opening and size of the cross section of the weld metal filling, the requirements for the forming of the inner wall of the girth weld and the welding height of the outer wall. For example, the design of the structure and related data of the socket for the exhaust point of the thermal measuring point is designed. The design of the socket is calculated by the area compensation method. For the full penetration fillet of the tube seat according to the ASMEB31.1 power pipeline method Design. 4. For the branch pipe that opens the hole, such as the safety valve socket, the calculation method of the thermal pipe socket cannot be simply adopted. In the design, the calculation method of the thick-walled tee is used to calculate the groove height of each section of the branch pipe, and it is also required to follow ASMEB31.1. Power Pipe Design The height of the fillet of all cross-section fillet welds of each section.


5. It can assist the design institute to draw the installation drawings and piping drawings of the pipeline after the slope calculation of the pipeline, and mark the hydrophobic slope of the pipeline and the calculation angle of the fitting in the piping installation diagram. For this reason, the piping engineer of the factory should understand the actual habits and installation conditions of the construction company to carry out the slope cutting calculation, calculate the angle of the pipe fittings and the elevation of each node after the slope cutting, and consider the pipe system after cold tightening. The effect of the tube on the size of the tube.


6. The factory understands the design requirements of the design institute's thermal, chemical and other professional manufacturers and performance commissioning units for various measuring points, and the requirements of these specifications are reflected in the piping design.


7. According to the requirements of the pipeline installation drawings of the design institute, design and select the attachments and hangers, the clamps of the pipe, the supports, the stoppers and other accessories.