1. Coating method and brushing process should be based on the physical properties of the selected coating, construction conditions and the shape of the steel structure to be painted and should be consistent with the coating specifications or product specifications. 2. Painting should be carried out before the appearance of steel surface inspection to ensure that the steel surface cleanliness and surface roughness to meet the design requirements. 3. The interval between surface pretreatment and coating should be shortened as much as possible. In general, the coating should be finished within 4 hours under the environment of the working site; the sunny day of the workshop operation or low humidity should not exceed 12 hour. 4 When the temperature of the painted steel structure surface is lower than 3 ℃ above the dew point or the relative humidity of air is more than 85%, the construction work should be stopped unless otherwise specified in the design. 5. To be welded in the construction site of the steel structure, the weld on both sides of the first brush should not affect the performance of the shop primer welding, welding heat affected area should be carried out after the secondary surface cleaning, according to design requirements to re-coating. 6. Coating should be carefully maintained after the coating, should be avoided before curing rain, exposure and trampling, lifting the handling process should take appropriate measures to minimize the damage to the coating. 7. Coating interval between the layers should be consistent with the product specification or specification requirements, such as more than the longest interval of time, the application of coarse abrasive cloth and then brushing the next brushing coating to ensure coating Between the binding force.

Welded pipe manufacturers in the production of high-frequency welded pipe in the process, will face the tube surface was scratched the situation, the main reason for this is due to the guide roller and squeeze roller caused. The following specific analysis. 1. Scraping caused by the guide roll generally occurs on both sides of the high-frequency welded pipe, the characteristics of the wound is relatively large, continuous strong. Reasons include: (1) The height of the guide sleeve position is not correct, such as the guide roller bearing damage, the guide roller can not be a good control of high-frequency welded pipe, so that friction with the guide sleeve caused by scratches. (2) When the guide roll deviation from the high-frequency welded pipe production line rolling center line is too large, the guide sleeve and guide roller relative difference is too large, resulting in both sides of high-frequency welded pipe scratches. 2. Scratches caused by high-frequency welding squeeze rollers occur mainly at the bottom of high-frequency welded pipe. Reasons include: (1) The hole does not match, resulting in high-frequency welded pipe surface scratches, the hole does not match the factors are: squeeze roller bearing damage, squeeze roller axial movement, squeeze roll hole size is not the same, the two extrusion Roller height position is different from the extrusion roller bending and assembly instability. (2) Squeeze roller height does not match. The lower edge of the squeeze roll hole pattern should be consistent with the height of the rolling line, and the height of the guide roll is determined by the wall thickness of the high frequency welded pipe. If the guide roller is too low, the edge of the extrusion roller hole rounded corner of the high-frequency welded pipe will cause the bottom of the scratches. (3) Squeeze pressure on the roller is insufficient. Especially the two-roll structure of the squeeze roller device, when the pressure on the lack of high-frequency welded pipe tension in the role, the roller will appear on the elevation angle, the R edge of the hole prominent, resulting in high-frequency welded pipe Scratch the lower part. When the squeeze roller hole R-round grinding sharp, it will increase the scratches.

Fracture of longitudinal welded pipe: It was found through the study found that when the temperature is lower than a particular temperature value, the data will be changed to brittle state, the impact absorption work decreased significantly, a phenomenon known as cold and brittle, high-strength metal materials The data organization is far from uniform isotropic tissue will have cracks, there will be inclusions, pores and other defects, these defects can be seen as micro-cracks in the material. Therefore, the design should also be based on the operating temperature of the component to select the appropriate data of the cold and brittle transition temperature. In general, it is assumed that the data is uniform and continuous isotropic. According to this method, the design is considered to be safe, and accidental breakage may occur. Due to defects such as cracks in hot-rolled tube or high-precision cold drawn tube is made cylinder, seamless steel tube cold drawn. The use of the process of fracture, almost no plastic deformation occurs, are generally brittle fracture. Brittle fracture is caused by a variety of reasons such as: grain boundary precipitates, regardless of its strength than the matrix strength of strong or weak, are the reasons for the occurrence of cracks; grain boundary inclusions segregation is the cause of fracture; In addition, Even in the far less than the yield limit of the alternating load, it will cause the occurrence of fatigue fracture phenomenon.

First, the rational selection. On the mold should be selected for precision messy material deformation of a good micro-deformation of steel, carbide segregation serious die steel should be a reasonable casting and quenching and tempering treatment, the larger and can not be casting mold steel can be solid solution double fine heat treatment. Reasonable choice of heating temperature, control the heating rate, the mold can be used for precision messy slow heating, preheating and other methods of equilibrium heating to reduce the mold heat treatment deformation. Second, the correct operation of the heat treatment process and a reasonable tempering heat treatment process is to reduce the deformation of a useful tool for precision messy method. Precise messy mold deformation reasons are often messy, but we only need to master the deformation rules, analysis of the causes of their attack, the choice of abnormal methods to avoid the deformation of the mold can be reduced, but also can be controlled. Third, the precision messy mold carry out pre-heat treatment to eliminate the mechanical processing of the rest of the stress occurred. On the precision messy mold, in the conditions permitting, try to use vacuum hardening and quenching after cryogenic treatment. In ensuring the hardness of the mold under the premise, try to use pre-cooling, grading cooling quenching or quenching process. Fourth, the mold planning description should be reasonable thickness should not be too poor, the shape should be symmetrical, deformation on the larger mold to master the deformation rules, set aside allowance for large, sophisticated messy mold can be used in combination planning. For some precision messy mold can use pre-heat treatment, aging heat treatment, quenched and tempered nitriding heat treatment to control the accuracy of the mold. In the repair mold sand holes, pores, wear and other defects, the choice of cold welding and other heat affected small repair equipment to avoid the repair process deformation of the attack.

Quality inspection methods and equipment of seamless steel pipe 1, Chemical composition analysis Instrumental analysis and chemical analysis can be used. For chemical analysis of the sample sub-smelting samples, ingot drill cuttings samples, pipe samples. Smelting samples are generally used instrumental analysis method, the pipe finished sample using chemical analysis and analysis together. Commonly used chemical analysis instruments are: infrared carbon and sulfur analyzer, direct reading spectrometer, X-ray fluorescence spectrometer.   2, Size and shape detection Check the contents include: wall thickness, diameter, length, bending, ellipticity, port slope and the obtuse angle and cross-sectional shape of special-shaped steel pipe. 3, Surface quality testing Naked eye inspection and nondestructive inspection. There are many non-destructive testing methods such as: ultrasonic testing, eddy current testing, magnetic detection, magnetic flux leakage testing, electromagnetic and ultrasonic flaw detection flaw detection. Each method has its own advantages and disadvantages: suitable for the detection of steel pipe surface or near the surface: eddy current testing, magnetic detection, magnetic flux leakage detection, penetration testing. Penetration testing is limited to inspection of the surface defects of the steel pipe. Magnetic particle inspection, magnetic flux leakage testing, eddy current testing is limited to ferromagnetic material inspection. Eddy current testing is more sensitive to point defects, other crack detection sensitivity. Ultrasonic detection of steel pipe surface detection reaction is relatively rapid, the internal qualitative analysis of steel there are still some difficulties, and ultrasonic inspection is also affected by the shape and grain size of steel pipe restrictions. 4, Chemical properties testing (Tensile test, toughness test, hardness test), hydraulic test and corrosion test (intergranular corrosion test, anti-hydrogen cracking test-HIC, anti-sulfide stress cracking test-SSCC) at room temperature or a certain temperature. 5, Steel pipe process performance test Including flattening experiments, ring pull tests, flaring and crimping experiments, bending experiments. 6, Metallographic analysis Including low magnification and high magnification. 7, Oil-specific pipe thread parameter detection Including coupling pattern detection, pipe thread detection and tightening of the pipe body and coupling after the detection.