LSAW welded pipe is a steel pipe with a straight weld parallel to the longitudinal direction of the steel pipe, also called straight seam steel pipe, made by bending a steel plate or strip and then welding the connection points. LSAW welded pipe production process is simple, uniform wall thickness, high production efficiency, low cost, and its specifications are flexible to adjust to meet the requirements of different pipe diameters, thus developing rapidly, often used in a variety of industrial production and urban pipeline construction.
First, straight seam welded pipe processing methods
1. Forging steel: the impact of the hammer using reciprocating motion or press to change the billet into the required shape and size of the pressure processing method.
2.Extrusion: the metal is put into the closed extrusion Jane, pressure is applied at one end, and the metal is extruded from the specified die hole to obtain the same shape and size of the finished product processing method. It is mainly used in the production of non-ferrous steel.
3.Rolling: a pressure processing method to make the steel metal billet pass through the gap of a pair of rotating rolls (various shapes), due to the compression of the rolls, so that the material cross-section is reduced and the length is increased.
4.Drawn steel: is the rolled metal billet (profiles, tubes, products, etc.) through the die hole drawn into sections to reduce the length, mainly for cold processing.
Second, the straight seam welded pipe production process distinction
According to the production process of LSAW steel pipe, can be divided into high-frequency LSAW steel pipe and submerged arc welding LSAW steel pipe:
1.Submerged arc welding
First of all, the entire steel plate should be ultrasonic inspection, and then through the milling machine on the two edges of the plate surface double-sided milling, the use of pre-bending machine equipment on the edge of the plate pre-bending, so that the edge of the plate has a curvature in line with the requirements of the curvature. After this, the plate is pre-bent using a JCO forming machine to press one half of the plate into a J-shape, and after stamping, the other half is pressed into a C-shape, finally forming an open O-shape.
The formed LSAW steel pipe is continuously welded by gas-shielded welding (MAG), longitudinal multi-wire submerged arc welding (up to four wires) is used to weld the inner side of the LSAW steel pipe, and longitudinal multi-wire submerged arc welding is used to weld the outer side of the submerged arc welded steel pipe.
2.High frequency welding
High-frequency welding is based on alternating current charge, electromagnetic induction principle in the conductor of eddy current heat flow effect and masking effect, the edge of the weld steel heated to a molten state, and then use the roller extrusion process to achieve the intergranular combination of butt weld, so as to achieve the purpose of welding. High frequency welding belongs to induction welding. It can also be called pressure-based welding, does not require welding filler material, welding without spatter, welding heat-affected area is narrow, beautifully formed after welding, good welding mechanical properties.
Third, straight seam welded pipe quality inspection
LSAW pipe from raw materials to welding and then to the finished product will undergo a systematic testing to ensure the quality of each link, steel pipe welding will be carried out in turn after the first ultrasonic flaw detection (mainly on both sides of the weld and the parent material of the flaw detection), the first X-ray flaw detection (in order to ensure the sensitivity of the flaw detection), the diameter of the expansion and the hydrostatic test (hydrostatic test opportunities for automatic record-keeping). Processing qualified straight seam steel pipe, will be the second ultrasonic flaw detection, the second X-ray flaw detection, magnetic particle inspection of the end of the pipe and other inspection processes to complete the entire process.
1. Ray flaw detection: ray flaw detection is the use of rays can penetrate the material and in the material has the property of attenuation to find defects in a flaw detection method, ray inspection is mainly used to test the welded pipe weld internal cracks, unwelded, porosity, slag and other defects.
2.Ultrasonic flaw detection: in the metal and other uniform media propagation, due to the interface in different media will produce reflections, so it can be used for internal defects inspection. Ultrasonic can test any weldment material, any part of the defects, and can be more sensitive to find the location of the defects, but the nature of the defects, shape and size is more difficult to determine. So straight seam welded pipe ultrasonic flaw detection is often used in conjunction with ray inspection.
Fourth, the use of straight seam welded pipe
LSAW pipe in the daily, has a very wide range of applications, such as: water supply projects, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction and other fields. Although most of the LSAW pipes we rarely see in life, but in industry and people's lives, LSAW pipes have an important role:
1.Conveying water, gas, air, oil and heating steam and other low-pressure fluid purposes;
2.Applicable to a variety of structures in construction, machinery, transport, aviation, oil extraction and other industries;
3.Low alloy high-strength structural pipe for large venues, bridges, TV towers, high-rise buildings, industrial plants and other infrastructure construction.
Under the rapid development of urbanisation, LSA steel pipe occupies a very important position, such as in natural gas, bridges, marine output, piling and steel structure and other pipeline projects have outstanding contribution, especially in the steel structure, in the construction site, construction site and so on, play a different role.
Like Zhejiang Perception Valley, Guangzhou Convention and Exhibition Centre, Guangdong Nanhai Comprehensive Pavilion, Changchun Convention and Exhibition Centre, Tianjin Convention and Exhibition Centre, Xi'an Convention and Exhibition Centre and other building construction projects, all adopt LSA steel pipe as the use of steel structure materials, especially as the largest exhibition in the north of the Tianjin Convention and Exhibition Centre, LSA steel pipe with green, environmentally friendly, efficient advantages, laying a new type of green wisdom and innovation of the Tianjin Exhibition Centre, a new type of convention and exhibition total complex.
Huayang Steel Pipe, as the supplier of the above comprehensive convention and exhibition centres, continuously carries out technological innovation, develops high-quality LSAW steel pipe product lines, adopts domestic and foreign technologically mature production equipment, and is equipped with advanced welding equipment and inspection and testing equipment, establishes quality management system, adapts to the market demand, responds to the reduction of carbon emissions and environmental protection, and provides LSAW steel pipe to our customers with high-quality service and excellent products.
