Welding precautions of the stainless steel pipe

Welding precautions of the stainless steel pipe shared by Weld Steel Pipe Supplier China.

It started with the rise of bicycle manufacturing. The development of petroleum in the early 19th century, the manufacture of ships, boilers and airplanes during the two world wars, the manufacture of thermal electric boilers after the second world war, the development of chemical industry and the drilling, extraction and transportation of stone, oil and natural gas all strongly promoted the development of steel tube industry in variety, output and quality.

1. Adopt the power source with vertical external characteristics, and adopt the positive polarity (welding wire to negative electrode) for dc.

2. Generally suitable for the welding of thin plates under 6mm, with the characteristics of beautiful welding seam formation and small welding deformation.

3. The shielding gas is argon with a purity of 99.99%. When the welding current is 50~50A, the argon flow is 8~0L/min, and when the current is 50~250A, the argon flow is 2~5L/min.

4. The length of the tungsten electrode protruding from the gas nozzle is 4~5mm, which is better. It is 2~3mm in areas with poor shielding such as fillet welding, and 5~6mm in places with deep grooves.

Galvanized Welded Steel Pipe

5. In order to prevent the appearance of welding holes, rust and oil stains must be cleaned on the welding parts.

6. The arc length of welding is 2~4mm for common steel, and 3mm for stainless steel, but too long is not good for protection.

7. Gas protection shall be implemented on the back of the bottom pass to prevent oxidation of the back of the bottom pass during butt laying.

8. In order to protect the welding pool with argon gas and facilitate welding operation, the Angle between the center line of tungsten pole and the workpiece at the welding place should be maintained at 80~85°, and the included Angle between the filler wire and the surface of the workpiece should be as small as possible, usually around 0°.

9. Windbreak and ventilation. In windy areas, take precautions to block the net, and take proper ventilation measures indoors.

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Classification of welded steel pipes

According to the production method, the welded steel pipes can be divided into two categories: seamless steel pipes and welded steel pipes.

1. Seamless steel pipe can be divided into: hot rolled seamless pipe, cold drawn pipe, precision steel pipe, hot expanding pipe, cold spinning pipe and extrusion pipe, etc. Seamless steel tube with high quality carbon steel or alloy steel, hot rolling, cold rolling (pull).

2. The welded steel pipes are divided into furnace welded pipes, electric welded pipes (resistance welded pipes) and automatic arc welded pipes due to different welding processes. The welded pipes are divided into straight welded pipes and spiral welded pipes due to different welding forms. Welded steel pipe is made of tubular steel plate welded to seam or spiral seam. In terms of manufacturing method, it is divided into welded steel pipe for low-pressure fluid transportation, spiral welded steel pipe, direct welded steel pipe and electric welded pipe. Seamless steel pipe can be used for all kinds of liquid and gas pipelines. Welding pipes can be used for water pipes, gas pipes, heating pipes, etc.

According to the material classification: steel pipe according to the material (that is, steel) can be divided into: carbon pipe and alloy pipe, stainless steel pipe. Carbon pipe can be divided into ordinary carbon steel pipe and high quality carbon structure pipe. Alloy pipe can be divided into: low alloy pipe, alloy structure pipe, high alloy pipe, high strength pipe. Bearing pipe, heat and acid resistant pipe, precision alloy (such as cutting alloy) pipe and high temperature alloy pipe.

According to the type of connection: steel pipe according to the type of pipe end connection can be divided into: light pipe (pipe end without thread) and thread (pipe end with thread). Car silk tube is divided into: ordinary car silk tube and tube end thickening car silk tube. Thickening thread can also be divided into: outside the thickening (with external thread), inside the thickening (with internal thread) and inside and outside the thickening (with internal and external thread) and so on. If the thread type can also be divided into: ordinary cylindrical or conical thread and special thread, etc. In addition, according to customer needs, the car wire tube is generally equipped with pipe connector delivery.

According to the coating characteristics classification: steel tube according to the surface coating characteristics can be divided into: clarinet (not coated) and coated pipe. The coating tube has Galvanized Steel Pipe, aluminum tube, chrome tube, aluminized tube and other alloy layer pipe. Coating tube has outer coating tube, internal coating tube, internal and external coating tube. Commonly used coatings are plastics, epoxy resin, coal tar epoxy resin and various glass - based coatings.

Galvanized Steel Pipe

By use:

1. Use pipes. Such as: water, gas pipe, steam pipe seamless pipe, oil transport pipe, oil and gas trunk pipe. Agricultural irrigation faucet with pipe and sprinkler irrigation pipe.

2. Pipes for thermal equipment. Such as the general boiler with the boiling water pipe, superheated steam pipe, locomotive boiler with the heat pipe, large smoke pipe, small smoke pipe, arch brick pipe and high temperature and high pressure boiler pipe.

3. Pipe for mechanical industry. If aviation structure tube (round tube, elliptic tube, flat elliptic tube), automobile half axle tube, axle tube, automobile tractor structure tube, tractor oil cooler with tube, agricultural machinery with Square & Rectangular Pipe, transformer with tube and bearing with tube.

4. Petroleum geological drilling pipe. Such as: oil drilling pipe, oil drill pipe (kelly and hexagonal drill pipe), drilling straight, oil tubing, oil casing and various pipe joints, geological drilling pipe (core pipe, casing, active drill pipe, drilling straight, press hoop and pin joint, etc.).

5. Pipe for chemical industry. Such as: petroleum cracking pipe, chemical equipment heat exchangers and pipelines for pipe, rust and acid resistance pipe, chemical fertilizer with high pressure pipe and transport chemical medium pipe.

6. Other departments use pipes. Such as: container tube (high pressure gas cylinder tube and general container tube), instrument tube, hand case tube, needle and medical equipment tube. Classification by section shape, etc.

Production process of spiral pipe

Production process of spiral pipe shared by Spiral Pipe supplier China.

(1) raw materials: strip coil, welding wire, flux. Rigorous physical and chemical examination must be carried out before investment.

(2) the end of the strip shall be butt joint by single wire or double wire submerged arc welding. After the steel pipe is rolled, automatic submerged arc welding shall be adopted.

(3) before forming, the strip is smoothed, trimmed and planed, its surface is cleaned and transported, and its edges are bent.

(4) electric contact pressure gauge is adopted to control the pressure of oil cylinder on both sides of the conveyor, ensuring the smooth transportation of the strip.

(5) external control or internal control roll forming.

(6) weld gap control device is adopted to ensure that weld gap meets welding requirements, and pipe diameter, wrong edge quantity and weld gap are strictly controlled.

(7) internal and external welding are performed by single or double wire submerged arc welding with American Lincoln welding machine, so as to obtain stable welding specifications.

(8) all welded welds are inspected by online continuous ultrasonic automatic flaw tester, ensuring 100% non-destructive testing coverage of spiral welds. If there are defects, automatic alarm and spraying mark, production workers according to this at any time to adjust the process parameters, timely elimination of defects.

(9) use an air plasma cutting machine to cut the steel tube into a single root.

(10) after cutting into a single steel pipe, each batch of spiral steel pipe shall carry out a strict first inspection system to check the mechanical properties of welding seams, chemical composition, dissolution status, surface quality of steel pipes and through nondestructive inspection to ensure that the pipe production process is qualified, before it is officially put into production.

(11) where there is continuous acoustic inspection mark on the welding seam, manual ultrasonic and X-ray reexamination shall be conducted. If there is a defect, it shall be repaired and then nondestructive inspection shall be conducted again until it is confirmed that the defect has been eliminated.

(12) the tube where the butt welding seam of strip steel and the t-joint intersecting spiral welding seam are located shall all be examined by X-ray television or film.

(13) each steel pipe is tested by hydrostatic test, and the pressure is radial sealed. The test pressure and time are strictly controlled by the microcomputer testing device of steel pipe water pressure. Automatic printing record of test parameters.

(14) the Oil Pipeline Spiral Steel Pipe end is machined to control the verticality of the end face, groove Angle and blunt edge accurately.

US tariffs have spread across the globe, and the steel market has been “splintered”

US tariffs have spread across the globe, and the steel market has been “splintered”

The reference news network reported on August 1 that the Japanese media said that the global steel market was "divided" by the United States to impose tariffs, and fell into a state of oversupply. In the first half of 2019 (January to June), global crude steel production hit a record high due to the increase in production in China, the largest producer. In the United States, which closed the market, the domestic steel companies once increased production due to the decrease in imported steel from Galvanized Steel Manufacturer, but they have to take countermeasures because of the sluggish domestic demand. If trade frictions lead to a cooling in demand, the balance between supply and demand will be further broken, and the prospects for a global economy will also shine.

According to the "Japan Economics" website reported on July 31, the World Steel Association's statistics released before July 29 showed that global crude Steel Pipe Market output from January to June increased by 4.9% from the same period of the previous year to 9.2506 billion tons, a record high. . China, which accounts for half of global crude steel production, increased by 9.9% to 492.16 million tons, the highest in history.

The report pointed out that Turkish and Russian-made steel, which cannot be exported to the United States due to tariffs, pose a threat to the European market. British steel company, the UK's second-largest steel company, filed for bankruptcy protection, and ArcelorMittal, the world's largest steel company, was forced to cut production.

ASTM A53 Galvanized Steel Pipe

The United States, which sets tariff barriers, is also affected. Due to the addition of tariffs, US steel imports in 2018 decreased by 12% year-on-year. In 2018, the US steel company, the largest steel company in the United States, relaunched two blast furnaces in Illinois that had been discontinued since 2015, making the country's steel industry excited about long-lost production.

According to reports, from January to June 2019, the domestic steel production capacity in the United States increased by 5%, but recently the steel mills have announced a reduction in production. US Steel announced in June that it would suspend two blast furnaces in Michigan and other places. It is estimated that the scale of production reduction will be 200,000 to 225,000 tons per month, equivalent to 3% of the national steel production capacity. AK Steel Holdings, the fourth-largest steel company, will close its Kentucky steel plant during the year.

The report believes that the reason is the slowdown in domestic demand in the United States. The largest demander car industry's new car sales from January to June decreased by 2%, after a lapse of two years. In July 2018, the price of US hot-rolled coils of $1,000/ton fell to around $630. The operating rate of the steel plant in June was 79.5%, which was again lower than the 80% target proposed by the US Department of Commerce at the time of starting the tariff. The White House’s trade protection policy has not worked.

The report pointed out that in addition, Japan has also begun to be affected. In 2018, as various steel companies significantly reduced production due to equipment failures, imported steel increased. Imports of ordinary steel from China increased by 73% from January to May 2019. The inventory of thin steel sheets in Japan has reached the highest level in 10 years.

According to reports, the Organization for Economic Co-operation and Development said that in the three years from 2018, global crude steel production capacity will increase by about 5%, driven by increased production in Asian countries such as China and India. Yamaguchi, a senior analyst at SMBC Nikko Securities, said that "global steel is clearly in a state of oversupply."

According to the report, in the context of oversupply, the market may be fragmented, which may lead to a colder demand. President Hashimoto Eiji of Nippon Steel said that “as long as the trade war continues, this risk will always exist” and show vigilance against the new round of “steel winter”.