Welding Quality Control Techniques for Straight Seam Steel Pipes

 　　The quality control of straight seam steel pipes can only be carried out safely in the production operation, and it is also an inevitable factor to ensure the personal safety of the operators. Application areas are mainly in large-span power grid engineering, construction steel structure engineering, electric power and UHV transmission and distribution engineering, mechanical engineering, cross-sea bridges, bridges, (railroad station, airport, stadium steel structure engineering), municipal pipeline network, foundation piling , Water and gas pipelines, road construction and other supporting facilities.

　　1. Check whether the welding wire and flux specifications are correct according to the welding process regulations to prevent improper use of the welding wire and flux, which may cause welding quality accidents.

　　2. Supervise the welding environment. When the welding environment is not good (the temperature is lower than 0℃, the relative humidity is greater than 90%), corresponding measures should be taken before welding.

　　3. Before welding, check the groove dimensions, including gaps, blunt edges, angles, misalignments, etc., whether they meet the process requirements.

　　4. Whether the welding current, welding voltage, welding speed and other process parameters selected for the automatic submerged arc welding process are correct.

　　5. Supervise the welding personnel to make full use of the length of the pilot arc plate at the end of the steel pipe during automatic submerged arc internal and external welding, strengthen the use efficiency of the pilot arc plate during internal and external welding, and help improve the quality of pipe end welding.

　　6. Supervise whether the welding personnel clean up the slag first when repairing welding, whether the joints have been thoroughly treated, and whether there are oil, rust, slag inclusions, water, paint and other dirt at the groove.

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Main Uses of Low Temperature Seamless Steel Tube

 　　The main purpose of the national standard low temperature seamless steel pipe: used in the pharmaceutical industry to produce ethylene, propylene, urea, synthetic ammonia, compound fertilizer and other equipment and processing equipment such as washing, purification, desulfurization, and degreasing. It can also be used to manufacture cryogenic equipment and ultra-low temperature. Refrigerators, pipelines and fittings for transporting ultra-low temperature liquefied gas, such as petroleum gas cryogenic separation equipment, air separation equipment, etc. There are two main types of refrigerated pipe materials, austenite and ferrite. Due to the different crystal structure of austenitic cryogenic pipes, there is no brittle transition temperature in the low temperature section, and there is generally no need to verify its low temperature impact toughness. , But it is stipulated that when the use temperature is not lower than -196℃ (low temperature section), the impact test can be exempted, and when the use temperature is-(ultra-low temperature section), it must be carried out in accordance with the requirements of the design documents. The ferrite tube has an obvious low-temperature brittle transition temperature, and has its suitable low-temperature section. Although the low temperature limits of steel are slightly different in countries around the world, the actual industrial environment (liquid hydrogen) can be as low as -253°C or higher.

　　So far, only steel pipes represented by ferrite-type low-temperature seamless pipes with a service temperature of -196℃ have been successfully commercialized. For safety reasons, countries have formulated special regulations for the production and use of ferrite-type cryogenic pipes. Standards. From the point of view of use, cryogenic pipes mainly include cryogenic pipes and cryogenic heat exchange tubes. Compared with the situation where only a single standard is established for the national and European standards, cryogenic tubes with different uses have different standards. Internationally, low temperature heat exchangers have been developed. The production and acceptance of low-temperature seamless pipes of pipes mostly adopt domestic design, and also adopt reference production of low-temperature pipes. This is not only conducive to adapting to domestic design requirements and realizing domestic substitution, but also conducive to direct export of products to the international market.

　　In fact, with the continuous improvement of the level of localization of large-scale petrochemical equipment, especially the successive export of complete equipment, it is necessary to introduce domestic cryogenic pipes or national standard cryogenic pipes as support, and it is particularly necessary to expand the international cryogenic seamless pipe system. With the continuous improvement of my country's steel equipment and technology, it also has the basis for the localization of low-temperature pipes. The evaluation of over-limit limits and non-standard applicability will not only help to prove the excellent quality of the localization of low-temperature seamless pipes, but also It is possible to explore its limit use temperature and expand the use range.

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How to Know Whether the Seamless Pipe Meets the Standard？

 　　The properties and functions of seamless steel tubes. When seamless steel tubes are made, different materials are used, and seamless steel tubes have different properties. For example, the most common seamless steel tubes in life are used in high-pressure boilers. The pressure and temperature of the high-pressure boiler are high. In this state, the seamless steel tubes are likely to be oxidized and corroded. Material and thermal processing technology have new requirements. Generally speaking, seamless steel tubes are required to have good compactness and corrosion resistance during use.

　　Secondly, for the use and production of seamless steel tubes, there are generally certain requirements for its roughness. Depending on the place you want to use, it is necessary to clarify these conditions to determine which seamless steel tubes to be used for use.

　　If you want to determine the quality of seamless steel tubes, whether they meet the standards you require, how to identify low-quality seamless steel pipes, and purchase high-quality seamless steel tubes, you must pay attention to the following points:

　　1. Whether there are scars on the surface of seamless steel tube.

　　2. Whether the seamless steel pipe is folded.

　　3. Whether the product is prone to burrs.

　　4. Whether there is pitting on the surface of seamless steel tube.

　　5. Whether there are cracks on the surface of the tube.

　　6. Whether the cross section of the tube is regular.

　　7. Whether the composition of the steel is uniform, and whether the end face of the cutting head is smooth and neat.

　　8. Whether the inner diameter of seamless steel tube fluctuates too much.

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What are the common problems in the long distance horizontal directional drilling rig construction

 　　(1) During directional construction: the main problem is that it is difficult to control the direction of the drill pipe instability, and it is difficult to measure the drilling trajectory in real time.

　　(2) During the reaming construction: there are dangers such as "holding poles" and "collapsed holes".

　　(3) When the pipeline is towed back: Excessive drag of the drilling rig causes the pipeline to be easily damaged and deformed, and the foundation of the drilling rig may slip and lose stability when it is towed.

　　(4) Mud ratio problem: Mud is the blood that traverses horizontally and directionally. During long distance construction, there will be clay, silt, hard rock, gravel, silt, sand, etc. in the strata that the drill pipe will pass through. Therefore, the mud is required to have good rheology to ensure a strong ability to carry drill cuttings; it has a low coefficient of friction to ensure good lubrication performance; it has a strong wall protection effect and can form a certain mechanical strength mud on the hole wall. Skin, maintain the stability of the hole wall, and prevent mud leakage.

　　http://www.xysteelpipe.com/info/What-are-the-common-problems-in-the-long-distance-horizontal-directional-drilling-rig-construction-1952-1.htm

Precautions for transportation of large diameter thin wall LSAW steel pipe

 　　Because of the large diameter and thin wall thickness of large-diameter thin-walled LSAW steel pipes, special attention must be paid during transportation. When transporting large-diameter thin-walled straight seam steel pipes, short pipes should be used as support frames in the steel pipes in the form of crosses to prevent deformation. Large-caliber thin-walled straight seam steel pipes generally can only be installed in a carriage 1 to 2 pipes, and wooden bricks should be used at the bottom to pad both sides to avoid rolling and deformation.

　　In addition to preventing rainwater from being exposed to large-diameter thin-walled LSAW steel pipes during transportation, the driver must pay attention to the weather at all times and also pay attention not to touch corrosive chemicals.

　　The characteristics of the use of large-diameter straight seam steel pipes in steel structure engineering:

　　Steel structure straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW pipe) and submerged arc welded straight seam steel pipes according to the production process. Submerged arc welded straight seam steel pipes are divided into UOE, RBE, JCOE steel pipes, etc. according to their different forming methods. Thick-walled straight seam steel pipe, the steel pipe with the ratio of the outer diameter of the steel pipe to the wall thickness of less than 20 is called the thick-walled straight seam steel pipe. Mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industry, boiler pipes, bearing pipes and high-precision structural pipes for automobiles, tractors, etc.

　　The difference between thick-walled straight seam steel pipe and thin-walled straight seam steel pipe is the thickness of the steel pipe wall. It is generally believed that wall thickness/pipe diameter equal to 0.02 is the watershed between thick-walled straight seam steel pipe and thin-walled straight seam steel pipe, and the wall thickness/pipe diameter is less than 0.02 The thin-walled steel pipe is larger than the thick-walled straight seam steel pipe. In terms of application, thin-walled steel pipe is mostly used for pipelines.

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