Large diameter straight seam steel pipe welding, including pre-welding, welding and welding outside the three processes. The so-called pre-welding is in the steel forming, the use of continuous high-speed gas shielded welding method of forming steel pipe welding. After the pre-welding, respectively, within the steel pipe, multi-wire submerged arc welding. In the case of high-speed gas-shielded pre-welding, there are currently two methods. One is the use of single-wire dual-power high-current high-speed gas protection pre-welding, such as the United States, Germany that is used in this way; the other is double-wire high-speed gas protection pre-welding, Japan is the use of this method. At present, more applications are monofilament high-speed gas protection pre-welding method, in a reasonable welding process conditions, can achieve not less than 7m / min high speed, and straight bead forming beautiful. Large diameter straight seam steel pipe is a product of the construction industry, steel structure is also one of the building industry, so the steel structure and straight seam steel pipe produced between the inseparable association. Now in the straight seam steel pipe plant in the steel structure accounted for most of the production, so straight seam steel pipe manufacturers for the production of steel pipe with the process and process requirements are very strict, good steel pipe to grasp the straight seam steel pipe Market dynamics, and now a large profit margins of straight seam steel pipe is gone forever, so only a large amount is king, in the increasingly serious competition in how to receive more orders bigger only grasp the quality of products at the same time And constantly grasp the market dynamics and laws to grasp the lifeline of the market. Large diameter straight seam welded steel pipe as the first process of pre-welding, that is to ensure quality. Pre-welding quality, not only its own quality problems, but also affect the follow-up, the quality of welding. Its quality requirements, targeted mainly as follows: 1, The weld should be continuous, and the appearance of forming to avoid uneven, in order to facilitate the final quality assurance of welding; 2, To ensure the appropriate penetration depth and the amount of welding, it is necessary to ensure that welding does not crack after welding, but also within the welding does not produce burning through the phenomenon; 3, To have a higher welding speed, in order to improve production efficiency.

Spiral steel pipe in the factory should be done before the mechanical performance test and flattening test and flaring test, and to meet the standards requirements. Spiral steel pipe quality testing methods are as follows: 1, From the surface to determine, that is, the appearance of inspection. The appearance inspection of welded joints is a simple and widely used inspection method. It is an important content of finished product inspection. It is mainly to find the defects of the weld surface and the deviation of the dimension. Generally through the naked eye, with the help of standard templates, gauges and magnifying glass and other tools for testing. If the weld surface defects, there will be defects within the weld may be. 2, The physical method of test: the physical test method is to use some physical phenomena to measure or test method. Materials or parts of the internal defects of the inspection, are generally used nondestructive testing methods. Nondestructive testing with ultrasonic testing, ray detection, penetration testing, magnetic testing and so on. 3, The pressure vessel strength test: pressure vessels, in addition to sealing test, but also for strength testing. Commonly there are two kinds of water pressure test and air pressure test. They are able to verify the tightness of the welds of vessels and piping operating under pressure. The pressure test is more sensitive and faster than the water pressure test. At the same time, the products after the test do not have drainage treatment, which is especially suitable for products with difficulty in drainage. But the risk of test than the water pressure test. When carrying out the test, the corresponding safety technical measures must be observed to prevent accidents during the test. 4, The density of the test: storage of liquid or gas welding containers, the welding seam is not dense defects, such as penetrating cracks, pores, slag, not penetration and loose tissue, can be used to find the density test. Denseness test methods are: kerosene test, water test, water test and so on. 5, Hydrostatic test: Each pipe should do hydrostatic test without leakage phenomenon, the test pressure is calculated by the test P = 2ST / D where the S-hydrostatic test test stress Mpa, hydrostatic test test stress by Corresponding to the standard steel yield minimum (235Mpa) 60% of the selected. D ≥ 508 Test pressure holding time of not less than 10 seconds 4, non-destructive testing of steel pipe welding seam, the steel head of the first seam and the circumferential seam should be Perform X-ray or ultrasonic inspection. Spiral welds in the direction of flammable ordinary fluids shall be subjected to 100% SX-ray or ultrasonic inspection and shall be subjected to X-ray or X-ray for helical welds of steel pipes for the transport of general fluids such as water, sewage, air and heating steam. Ultrasonic examination (20%).

Bending process can be divided into many kinds, there are bending, bending and other means to push, these methods can be divided into two kinds of cold bending and bending bending state. For different bends of the processing technology used is different, different characteristics of the elbow is not the same. The main reason that causing the quality of elbow decline and the attention method: 1, Pure bending, the tube under the action of the external force M in the outer layer of the lateral arm wall tensile stress and thinning, the inner stress, the role of thickening, resultant N1 and N2 to the tube cross-section changes. Therefore, GBJ235-82, for a variety of pressure levels under the conditions of the RX value and the amount of thinning outside are clearly defined, the purpose is to control the RX and SX To ensure quality. 2, The previous article has been mentioned, the elbow when the lateral tension of the material, the medial position of the neutral axis of pressure and bending method is different from the top bend (compression bending) work in the neutral axis from the outer wall of about 1/3, in the bending (bending) work, the neutral axis from the outer wall 2/3. Therefore, the thin-walled pipe is bent, and it is advantageous to use a bending method. 3, The accuracy of curved tire is also one of the factors affecting the quality of elbow. We bend fetal production, in addition to size requirements to control in a certain tolerance range, but also requires users to use in accordance with bending pipe diameter to select the corresponding bending tire. 4, The pipe itself, the bending performance and surface corrosion, may also affect the quality of elbow. On-site construction, the operator should also be aware of the material being processed pipe, processing performance and surface corrosion to make production judgments.

Seamless steel pipe identification methods are: 1, With the eyes, welded pipe diameter will have a very obvious weld, the color and other parts of the steel pipe is different. 2, The chemical composition of the material for analysis, the pipe material will be relatively poor, impurity and harmful elements content will be higher. 3, For mechanical performance analysis or process performance analysis, for flaring test, the welded pipe easy to crack. 4, For eddy current testing, eddy current injury control of welded steel pipe may be more alarm.

Carbon steel is one of the most popular grades of steel that are used globally. The material is considered very useful for industrial pipe fabrications. Carbon steel easily works in an array of fabrication methods, including hardening, machining, welding etc. Various components are hardened with the help of carbon steel so that they last for a longer period of time. This steel helps machining in a convenient way as there are no chips or cracks on the machines during the machining process. Also, they are used to create durable joints during the welding of machines or equipments. Depending upon the application, the metal workers vary the amount of carbon so that the product does the job exactly how it is intended to do. Carbon steel pipes have a wide range of uses . They are used almost everywhere be it buildings, infrastructure, irrigation, automobiles, machines or various appliances. They are basically used for low pressure conveyance of various fluids and gases. ·         Transporting Fluids Carbon steel pipes are considered the best in the business for transporting of various fluids like water, sewage, oils and other compatible fluids. This is because these carbon steel pipes are highly resistant to shocks and vibrations. The pressure of water which is fluctuating in the carbon steel pipe and the shock pressure of water hammer do not have an impact on these pipes. These pipes are also used to carry petroleum in large amounts by petroleum industry. ·         Transporting fluid under ways on roads with heavy traffic We all know the traffic conditions these days. We witness a lot of traffic and people stuck on roads for hours with their vehicles. These heavy traffic conditions put extreme pressure on roadway foundations. In such scenarios, carbon steel pipes become the primary choice when there is a need to transporting fluids through pipelines under roadways. ·         Withstand heat treatment in closed heating and condensation systems Carbon steel pipes are known for their use wide use in industrial processes that involve industrial heating, condensation, steam etc. These steel pipes are ideal for these processes because they are great in handling high heat, extreme cold and even transporting gases such as steam. They are present in the heating systems in the form of a thin-wall with comparatively lower level of carbon content with a layer of zinc. There are many suppliers that are providing seamless carbon steel pipe and fittings service which can be availed easily. This pipes offer better durability and strength. They are useful for construction work and in heat-transfer systems. This pipes are easier to form and can be bend as per requirement so you can use them at various angles and is different shapes.