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Zhongshan 25Cr2Mo1V excellent special round steel with large quantity favorably

发布时间: 2019-12-29 17:36:01 发布人: 王国红 字体大小: 【大】 【中】 【小】 Article source: hpxfctgyx Release time: 2019-12-29 17:36:01 Posted by: Wang Guohong Font size: [Big] [Medium] [Small]

There are two types of Zhongshan 25Cr2Mo1V excellent special round steel. When brazing different transition pipes, first of all, the silver base material is expensive, and the product cost is high. Second, in order to ensure the brazing of different metals with different wire temperature coefficients and strict installation clearances, the processing accuracy of the thread connection on the joint surface is very high. To achieve 2a, 2 or 1 level accuracy. One type is silver-based solder for vacuum or brazing in protective gas, and the first type is vacuum diffusion welding. In addition to cost and poor processability, this brazed joint has poor corrosion resistance when working in a series of different media. It can be proved that it is not advisable to use brazing to transfer bimetal hetero-transfer tubes. In order to reduce the cost and the bimetallic different transfer manufacturing process, scholars have proposed the first type-vacuum diffusion welding, and studied the vacuum diffusion welding process of 10 ~ 150 mm pipe transfer pipe. Different straight 08X18H10T stainless steel pipe and titanium alloy pipe adapter pipe structure, special adapter pipe structure. The pre-installation and installation of bimetallic dissimilar transfer pipe diffusion welding are performed separately according to its pipe size and structural characteristics. The marking end of Zhongshan Steel in the quality standard must face to the side in order to find the required steel. The stacking height should meet the requirements of technical regulations. The stacking position should be more than 2 meters from the railway or highway. There must be a channel of not less than 1 m between the chimneys. The stacked steel must have pads or shelves to prevent the steel pile from sinking and tilting. Steel packaging shall be packed in accordance with the standards and requirements of the order contract. Package contents generally include (except for the special requirements of the contract): section steel with a diameter or thickness of less than 30 mm and steel plates with a thickness of less than 4 mm should be delivered in bundles. Each bundle of steel should have the same batch number, and each bundle of steel should be marked with at least two labels indicating the factory name, steel number, furnace (tank) number, and specifications. Steels with a diameter or thickness equal to or greater than 30mm can be delivered in B. Whether it is UNDLES or not. Steel bundles, each with at least two marks, steel cannot be stamped. Unmarked steel bundles shall be embossed or marked on each supporting steel or steel plate. Quality management Cold drawn (rolled) tubes are divided into two types: round tubes and special-shaped tubes. a. Overview of process flow Hot rolled (seamless steel pipe): Round pipe blanks, perforated rolls, oblique rolling, continuous rolling or de-piped (or reduced) cooling billet straightening hydraulic pressure test (or flaw detection) are marked in the warehouse. Cold drawn (rolled) seamless steel tubes: round and round tube blanks, heat-punched, annealed, pickled (copper-plated), multi-pass cold drawn (cold rolled) blank tubes, heat treated, straightened, and hydrostatically tested (detected). b. Seamless steel tubes are divided into the following varieties due to their different paths: GB / T8162-2008 (structure seamless steel tubes). Mainly in general structure and mechanical structure. The surface material (brand): carbon steel 45 steel; alloy steel Q20Cr, 40Cr, 20CrMo, 30-35CrMo, 42CrMo, etc. GB / T8163-2008 (transmitting fluid seamless steel pipe). Mainly used in engineering and large equipment to transport fluid pipelines. Table material (brand) is Q345 and so on. The standard requires Zhongshan to also perform process performance tests. 79 The characteristics of chemical fertilizer special pipe process test and classification process test feature is not to consider the concept of profit, but to evaluate the surface deformation (such as cracks, cracks, breaks, etc.) of 9498 chemical fertilizer pipe surface after stress or certain characteristics specified after deformation. . Its characteristic is that 79 fertilizer tube samples do not need special processing. The test can be carried out in special equipment or simple tools, which can be directly adapted to the situation for simple tests. 79 chemical fertilizer special pipe must do the process test: flattening test, expansion test, bending test, shrinkage test, curling test and so on. Baosteel's high-pressure boiler tube transaction volume is not optimistic-Baosteel's high-pressure boiler tube transaction volume is not optimistic This week, Baosteel's high-pressure boiler tube sales plummeted sharply. Affected by the operation of the steel market and the decline in ore mining, the spot price of ore mining fell, and the decline rate and speed were larger than last week. Steel mills continue to control prices. Quality risk This type of steel pipe is often used as a supporting superalloy pipe. The output of steel has exceeded 100 million tons, and the quantity of steel is no longer the main contradiction. The main task of the current industry is to strive to improve the market competitiveness of products, stand on a new point of sustainable development, and include vigorous development of low alloy steel as an important part of the development strategy. Many ordinary steel companies have realized that low-alloy steel is the key to improve the technical content and added value of products in the structural adjustment of steel varieties and the development of scientific and technological development plans. They have countless problems in the development of low-alloy steel. The management felt that "the success of low-alloy steel and the failure of low-alloy steel" urgently require an understanding of low-alloy steel. According to the standard, steel is divided into two categories: non-alloy steel and alloy steel. Non-alloy steel is a large steel generally called carbon steel. In addition to iron and carbon, the steel also contains a small amount of alloying elements Mn, Si, Al, impurity elements P, S, and gas O, etc. Zhongshan 25Cr2Mo1V excellent special round steel has a large quantity and is superior. There are two types of bimetallic different transfer tubes. When brazing different transition pipes, first of all, the silver base material is expensive, and the product cost is high. Second, in order to ensure the brazing of different metals with different wire temperature coefficients and strict installation clearances, the processing accuracy of the thread connection on the joint surface is very high. To achieve 2a, 2 or 1 level accuracy. One type is silver-based solder for vacuum or brazing in protective gas, and the first type is vacuum diffusion welding. In addition to cost and poor processability, this brazed joint has poor corrosion resistance when working in a series of different media. It can be proved that it is not advisable to use brazing to transfer bimetal hetero-transfer tubes. In order to reduce the cost and the bimetallic different transfer manufacturing process, scholars have proposed the first type-vacuum diffusion welding, and studied the vacuum diffusion welding process of 10 ~ 150 mm pipe transfer pipe. Different straight 08X18H10T stainless steel pipe and titanium alloy pipe adapter pipe structure, special adapter pipe structure. The pre-installation and installation of bimetallic dissimilar transfer pipe diffusion welding are performed separately according to its pipe size and structural characteristics. Create glory

Zhongshan 25Cr2Mo1V excellent special round steel has a large amount of Congyou



Zhongshan 25Cr2Mo1V excellent special round steel with a large amount of Congyou rolled section has been progressively finished, and because the original metal corresponding to the hole-shaped opening part is spread on the core rod. As a result of the lateral flow of the metal, the inner diameter of the pipe is increased, and the inner surface of the pipe of the working cone part is separated from the core rod, creating conditions for the next feeding of the pipe material, and so on until the entire length of the pipe material is rolled. Roller cold rolling mill is a widely used cold rolling mill. The advantage is that the deformation of the pass is large, and the elongation coefficient can reach 14 to 1. The disadvantage is that the roll hole is difficult and the equipment investment is high. The dimensional accuracy of rolled pipes is not as good as that of multi-roller cold pipe rolling machines. The working principle of a roll cold rolling mill (see Figure 1 is the same as a multi-roll cold rolling mill, the differences are as follows: The roll cold rolling mill uses two rolls with variable cross-section shapes instead of 3 to 4 hole section sizes. In order to overcome the inherent shortcomings of conventional cold-rolled tube mills, the following various processes and equipment have been developed: Multi-line, high-speed rolling on traditional cold-rolled tube mills. The welder tends to balance, so it has little effect on the cutting temperature. At the end of the month, the welded pipe was weakly lowered, and the northern part fell by about 60 after it stabilized. Zhou Tangshan welded pipe increased by 30-40 with upstream materials. In a weak situation, the overall situation of the pipe is still the same, so the manufacturers are not enthusiastic about the upswing. It is rare in other regions. In the market, 316L stainless steel square tube traders want to keep the inventory at a low price in exchange for the amount. The northern heating season is approaching, and the number of refinement schemes is endless. Under the impact of limited production during the off-season, the decreasing trend will become more apparent in the transaction volume, but the resources such as steel strips are also becoming tighter. Will still The leading factor of the market rise is insufficient, so it is more difficult for the pipe price to rise. The abrasion effect in the cutting process of oxygen blow pipe will increase the impact on the cutting temperature after the abrasion value reaches a fixed value; the higher the cutting speed. {Random place name Quality management difference between cold-rolled and hot-rolled: cold rolling has higher dimensional accuracy than hot-rolling. Use: Welded pipe for petroleum cracking for structural fluid transport of low-medium-pressure high-pressure boilers Definition: Strip or steel plate is bent to form a round or After the square, the welded steel pipe is welded on the surface. Classification: According to the process: arc welded pipe, resistance welded pipe, gas welded pipe, furnace welded pipe According to the welding seam: straight seam, spiral according to the end shape: round, special purpose: General welded pipe is used to transport low-pressure fluid, galvanized steel pipe, oxygen blown welded pipe, wire sleeve, transformer tube special-shaped pipe, and welded thin-walled pipe spiral welded pipe. Definition: Low-carbon carbon structural steel or low-alloy steel strip according to a predetermined spiral. The angle of the wire is rolled into a pipe blank, and the pipe seam is welded to make it. It can be made of a narrow strip steel and a large diameter steel pipe. The use of spiral welded pipes: mainly used for the transportation of oil and natural gas Delivery pipeline. Specification for outer diameter * wall thickness. Difference between straight seam pipe and spiral pipe: The good process of straight seam pipe is simple. Because forged parts are made into parts, their stress, importance and working conditions are different during use. , Its materials and metallurgical processes are also different, so different parts of the forgings are classified into categories according to the above situation and according to the requirements of this department, different departments, Zhongshan 20Cr low alloy round steel, different standards for the classification of forgings are also different No matter what, for the quality inspection of forgings as a whole, there are two major types of inspection, namely the appearance quality and the internal quality inspection, but the types of forgings are different, and the specific inspection items, inspection quantities and inspection requirements are different. For example, some industrial departments will classify structural steel, stainless steel, and heat-resistant steel forgings into Class IV for inspection, and some departments will classify aluminum alloy forgings and die forgings into Class III for inspection according to their usage. Others will inspect aluminum Alloy and copper alloy forgings are divided into category IV for inspection. Table 1-1 is the inspection requirements for structural steel, stainless steel and heat-resistant steel forgings into category IV. Table 1 -2 is the quality inspection requirement for aluminum alloy forgings and die forgings. Quality management Jiayuguan Because of strict production restrictions in Tangshan during the period, coupled with the severe haze weather, most of the local mineral processing plants in Tangshan are in production suspension and production restrictions. For example, in Zunhua area, in addition to the delivery of 88 mineral processing companies, the rest The order was ordered and all production was discontinued. Billet prices in other neighboring cities continued to fall sharply. The black line continued to fall, and the market mentality became weaker. In addition to the negative inventory and demand for steel, the lack of market confidence is more important. Domestic Mine: On the 12th, the domestic ore market was in stable operation. The day before yesterday, the rolling mills in the Fengrun area of Tangshan also received notice from their superiors due to the haze weather. Most of them ordered the suspension of production, and the date for resumption is expected. 40cr seamless steel pipe market continues to decline this week-Liaoning Anshan seamless steel pipe marketThe 40cr seamless steel pipe market continues to decrease this weekThe 40cr seamless steel pipe market continues to decline this week and enters the off-season. The market is affected by the sluggish demand and the transaction is significantly blocked. Ushering in a sharp correction, the downstream market is not up to the market. There are also a few companies that implement the European standard EN1996 "Dimensions, Shapes, Weights and Allowable Deviations of Hot-Rolled Ball Flat Steel". The economic benefits of good flat steel are currently more than 5 to 2 times that of ordinary medium sections, and there is a relatively stable market demand, but the obstacles are many specifications, small batches, and low output. It is difficult to occupy the market with incomplete specifications. The specifications are full, and the investment in rolling mills and rolls is relatively large. Domestic ball flat steel supplyThe current domestic large ball flat steel large-scale manufacturers include Hebei Xingtai Jitai Special Steel, Nangang Steel Wuxi Jinxin Rolling Steel, Changshu Longqiu Flat Steel Section Totem Special Steel, Heavy Steel, Nanjing Metallurgical Rolling Plant, etc. . At present, the larger ones are Xingtai Jitai (total production capacity is about 500,000 t / a, ductile steel is about 350,000 t / a), Wuxi Jinxin (total capacity is about 200,000 t / a, and ductile steel is about 140,000). t / a), Changshu Longteng (total production capacity is about 130,000 t / a. Ductile steel is about 80,000 t / a) and Heavy Steel (spherical flat steel is about 40,000 t / a). Zhongshan 25Cr2Mo1V excellent special round steel has a large amount of Congyou and it consumes a lot. The annual circulation of Lecong steel market alone reaches tens of thousands of tons. The demand for cold-formed steel in Guangdong reflects the characteristics of small size, large quantity, and wide application range of these steels, which are closely related to its economic structure. Obviously, North China and Northeast China have shown that there are many specifications and the batch flow of specifications is uneven. It can be seen that the development form of cold-formed steel in Guangdong will be the development guide of the north and the mainland, but at the same time, the development of heavy industry in the north and the mainland, Zhongshan 35CrMo round steel, objectively exists in the Guangdong market. The inevitability of unusually large cold-formed steels. The annual demand for cold-formed steel in Guangdong area Cold-formed square steel pipes and rectangular pipes: those with specifications of 20-300MM, with annual requirements of 120,000-150,000 tons, those with 400MM and above, annuals of 7,000-10,000 tons, are currently mostly welded. Cold-formed C-shaped steel: Due to the low technical requirements, various C-shaped steel good lines are everywhere, and the annual number cannot be calculated; the quality assurance of domestic stainless steel square pipes as a whole has been properly followed so far, and the domestic stainless steel square pipes have been generally followed as well. According to the monitoring data of Lange Steel's cloud business platform: the flat grid of 4-inch (75mm) welded pipes in key cities in China was 4,657 yuan, a decrease of 19 yuan from yesterday. Among them, the central cities of Tangshan, Tianjin, Chengdu dropped 20, Wuhan dropped 30, Shenyang, Guangzhou dropped 50 yuan, others are temporarily stable. The overall market continued to be stable and weak, and some welded pipe grids were adjusted by 20-50 yuan. The actual documents of restricted production have not yet been affected. The current spiral disk surface has fluctuated widely. The market will wait and see. The quotation is between 4440-4570 yuan, and trading is biased. In terms of the market, welded pipes in East China and South China have fallen by 20-50 yuan so far. Actual production restrictions at the beginning of the month have not surfaced. The market is still cautious about high-level resources and later expectations. It is expected that domestic welded pipes will be weakly consolidated in the near future. It stopped rising in the morning. discount

Zhongshan 25Cr2Mo1V excellent special round steel has a large amount of Congyou



Zhongshan 25Cr2Mo1V excellent special round steel has a large quantity, and the effect becomes more significant. Next week, the 316L stainless steel square tube market will be slightly stronger. Next week, the 316L stainless steel square tube market will be slightly strong. This week, the tube market will be weak, and the transaction is not obvious. In terms of seamless pipes, due to poor loading, this week's price willingness has declined, and some regions have fallen. It is expected that the tube market will continue to fall, increase, and decrease next week, with a range of around 100 yuan. After the end, the market is expected to decline, the market is down, the spot manufacturers are also negative, and the market is naturally lower. Taken together, this week the city's weak decline is mainly dominated by transactions. At the current stage, the pressure on the level is still there, and there is still a strengthening trend in the later stage. Therefore, in the short term, the pressure on the stainless steel square tube market is not great at the supply level. However, as the weather is getting colder, the demand is not good, and it will continue in the later stage. The market fundamentals are difficult to change. Considering that the mentality of all parties in the market is still relatively cautious, the market may not rise so much. It is expected that the 316L stainless steel square tube market will be slightly stronger next week. The project scope is ZG06Cr13Ni4Mo, ZG06Cr13Ni6Mo, ZG06Cr16Ni5Mo suitable for castings with a wall thickness of 100-200mm. Precipitation hardened stainless steel. The grade is ZG0Cr17Ni4Cu4Nb. This type of steel has high strength, toughness and wear resistance. Can be used in chemical, shipbuilding, aviation and other departments for high-strength wear-resistant and corrosion-resistant castings. The castability of stainless steel is poor, the molten steel has low fluidity, and it is easy to produce cold insulation or slag inclusion. To this end, the pouring temperature should be increased, which is generally not lower than 1530 ° C. The cross-sectional area of the gating system should be 30% to 50% larger than that of carbon steel castings. Stainless steel has a large volume shrinkage value, which is prone to shrinkage and looseness. The riser of the casting should be 20% to 30% larger than that of carbon steel. Castings have a high tendency to thermal cracking, high pouring temperature and easy sand sticking, and corresponding measures should be taken in the casting process. The austenitic ferritic stainless steel has a better casting performance, but has a larger porosity. Heat-resistant cast steel Heat-resistant cast steel is divided into heat-resistant non-skinned cast steel (anti-oxidation steel) and heat-strength cast steel. According to the surface processing conditions, the agents are divided into polished (M) and non-polished (BM). Cold-rolled low-carbon steel strips can be suitable for different uses, different processing and different quality requirements according to their different classifications. The main application is applicable to various stampings, steel pipes and other metal products. The grade and chemical composition of the material are in accordance with the requirements of 08Al and 10 steel grades in GB699 (Technical Conditions for High Quality Carbon Structural Steel). Mechanical properties Steel strip specifications and good unit steel strip thickness 0.05- 60mm. 00-300mm width. Good plants include Wuhan Iron and Steel, Shanghai Steel Plant, No. 1 Cold Rolled Strip Plant, Jiangxi Steel Plant, Great Wall Steel Plant, Dalian Steel Plant, Chongqing Special Steel Plant, Shougang Steel Plant, Hanyang Steel Plant, and Nanchang Steel Plant. Cold-rolled carbon structural steel strip (GB3522-8 Cold-rolled excellent carbon steel strip uses high-quality carbon structural steel as the material and is cold-rolled. Because cold-rolled steel strip can be rolled thinner than hot-rolled strip. Word of mouth recommendation

Zhongshan 25Cr2Mo1V excellent special round steel has a large amount of Congyou



Zhongshan 25Cr2Mo1V excellent special round steel has a large quantity and a width of 5-100mm. Good plants include Shougang Strip Plant, Shanghai Steel Plant, Jiangxi Steel Plant and Shanghai Steel Plant. Cold-rolled spring steel, tool steel strip (GB3525-8 For different needs, there are multiple types of steel strips. According to accuracy, it is divided into ordinary accuracy (P), high width accuracy (K), high thickness (H), thickness High precision (J), wide width and thickness precision (KH); they are divided into two groups Ⅰ and Ⅱ according to the surface quality; they are divided into two types: cut edge (Q) and uncut edge (BQ) steel strip according to the edge status; According to the material state, it is divided into cold hardened (Y), annealed (T) and spheroidized annealed (QT) steel strips. It is mainly used for springs, tools, tape rulers and other products. Material grades and chemical composition Mechanical properties Steel strip specifications Good size and good units include Bengang, Shanghai Steel, Great Wall Steel, Jiangxi Steel, Chongqing Special Steel, Dalian Steel, Shougang, No.1 Cold Rolled Strip, etc. The two side widths of the equilateral angle steel are equal. Representation: side width * side width * side thickness Use: According to the different structure of the composition of different stress members can also be used as connecting members between members. Widely used in various buildings Structure and engineering structure. Definition of channel steel: a bar-shaped steel with a cross-section in the shape of a groove. Means: waist height * leg width * Thick use: used in building structures, vehicles, other industrial structures. H-beam classification: wide flange and narrow flange Specification: 100 * 100.150 * 150.200 * 200.248 * 12 0.125 Representation: height H width B, web thickness t1, wings Plate thickness t2 H-shaped steel features: wide flange, large lateral rigidity, strong bending resistance, about 5-10% than I-beam, two surfaces of the flange are parallel to each other, and the structure is convenient. Advantages of H-shaped steel: Design Flexible style, rich structure and light weight. The structure is scientific and reasonable. The steel plate for bridges (YB168-70) is a steel plate used to build railway or highway bridges. It requires high strength, toughness, and withstands the load and impact of rolling stock. In addition, it must have good fatigue resistance, low temperature toughness and atmospheric corrosion resistance. Steel for bolted bridges should also have good welding performance and low notch. It is mainly used for railway bridges and highway bridges in the span Structural parts between 46-160mm. Material number and chemical composition Mechanical performance specifications and good unit specifications: thickness from 6-50mm width from 0-4mm length from 0-16mm Good steel plates for bridges include Anshan Iron and Steel, Wuhan Iron and Steel, Shanghai Steel Plant with . Qing steel mills and other units of the hull structure (GB712-8 referred marine hull structure with steel plate steel plate due to the harsh working environment of ships, boats sea shell subject to chemical corrosion, electrochemical corrosion and corrosion sea creatures, microbes.;

Zhongshan 25Cr2Mo1V excellent special round steel has a large amount of Congyou



Zhongshan 25Cr2Mo1V excellent special round steel has a large amount of favorably. Later, due to the continuous increase of the rolling mill capacity, the heating furnace has developed in the direction of large capacity and high output. In the 1930s, a section furnace appeared. Zhongshan 20Cr2Ni4 excellent special round steel. The furnace output reached 150 tons per hour, and the unit furnace floor area output was 500-600 kg / (meter 2 · hour). At the end of the 1950s, a section furnace was started. While increasing the tail gas temperature (up to 1000 to 1200 ° C), the high-temperature heat exchange equipment was used to recover the waste heat. The furnace output was increased to 150 to 250 tons per hour, and the unit bottom area was The output reaches 700 ~ 800kg / (meter2 · hour). At the same time, in order to meet the requirements of output and quality, a walking beam furnace is used. Some furnaces use a flat top burner with a full furnace top. The furnace output is 250 ~ 400 per hour. Ton, the output per unit of furnace bottom area reaches 800 ~ 1000 kg / (meter 2 · hour). Since the emergence of oil in major industrial countries in the mid-1970s, reducing fuel consumption has become a central issue in furnace design. Bridge steel plates (YB168-70) Bridge steel plates are steel plates used to build railway or highway bridges. It is required to have high strength and toughness, and to bear the load and impact of rolling stock, and it must have good fatigue resistance, low temperature toughness and atmospheric corrosion resistance. Steel for bolted bridges should also have good welding performance and low notch. The main purpose is mainly used for railway bridges and highway bridges with a span of 46-160mm. Material number and chemical composition mechanical performance specifications and good unit specifications: thickness from 6-50mm width from 0-4mm length from 0-16mm Good bridge steel plate has units such as Anshan Iron and Steel, Wuhan Iron and Steel, Shanghai Steel Plant and Chongqing Steel Plant. Steel plate for hull structure (GB712-8 Steel plate for hull structure is referred to as ship plate. Due to the harsh working environment of the ship, the ship's hull is subject to chemical corrosion, electrochemical corrosion by seawater, and corrosion by marine organisms and microorganisms; the impact will be more significant. 316L next week The stainless steel square tube market is slightly stronger-Next week, the 316L stainless steel square tube market is slightly strong. This week, the tube market is weakly arranged, and the transaction is not obvious. In the seamless tube, because of the poor loading, this week is willing to price slightly. It fell, and some regions fell. It is expected that the managed market will continue to decline next week, with a range of around one hundred yuan. After the end, the market is expected to decline, the market will decline, the spot manufacturers will also be negative, and the market will naturally decline. Comprehensive Judging from this week's weakness in the market, the transaction is not positive. At this stage, the pressure on the level is still there, and there is still a strengthening trend in the later period, so the pressure on the supply side of the stainless steel square tube market is not great in the short term, which is good. As the weather is getting colder and colder, the demand is not good, and it will continue in the later period. The market fundamentals are difficult to change. Considering that the market mentality is still Be cautious, the market may not rise so much. It is expected that the 316L stainless steel square tube market will be slightly stronger next week. The difference between shaped cold rolling and hot rolling: cold rolling has higher dimensional accuracy than hot rolling. Uses: structural fluid conveying low, medium and high pressure Definition of Welded Pipe for Boiler Petroleum Cracking: Steel pipe or steel plate is bent to form a round or square shape and welded steel pipe with seams on the surface. Classification: by process: arc welded pipe, resistance welded pipe, gas welded pipe, furnace Welded pipe according to welding seam: straight seam, spiral according to end shape: round, special-shaped Uses: General welded pipe is used to convey low-pressure fluid, galvanized steel pipe, oxygen blown pipe, wire sleeve, transformer tube special-shaped pipe, electric welding thin-walled pipe spiral Definition of welded pipe: The low-carbon carbon structural steel or low-alloy steel strip is rolled into a pipe blank at a predetermined spiral angle, and then welded with pipe seams to make a large diameter steel pipe with a narrow strip. Spiral welded pipe use: Mainly used for oil and gas transmission pipelines. Specification for outer diameter * wall thickness. Difference between straight seam pipe and spiral pipe: The good process of straight seam pipe is simple.