Production Technology Improving Process of ERW Steel Pipe

Straight seam welded pipe (ERW straight seam welded steel pipe) is formed on the hot rolled plate of the forming machine, the skin effect and proximity effect of the high frequency current, melting of the pipe edge heating to the extrusion roller pressure welding to achieve production. The application of high-frequency resistance welding method in pipeline production in the 1950s has witnessed more and more mature production technology and continuous improvement of product quality in the past decade or so.

First of all, in the quality of raw materials, the production of ERW steel pipe has been significantly improved, the composition of the steel design of low carbon, low P, S, micro-alloying; smelting process smelting, ladle refining, vacuum degassing, continuous casting and other new technologies In addition to the ERW controlled rolling and cold rolling process, the technology has enabled the appearance size of the hot rolled steel strips of large and medium caliber ERW steel tubes to be greatly improved in appearance quality, physical properties and chemical properties. The steel pipelines produced by Baoshan Iron and Steel Company, the highest level of hot rolled strip steel in my country, have met the American Petroleum Institute API 5L standard and are at the international advanced level.

Followed by the middle and large diameter ERW molding welding and heat treatment process of the production process to achieve the computer automatic control, high frequency and computer automatic compensation system welding process heat input energy is effectively controlled to prevent welding heat input welding cold caused by low welding heat input and Excessive combustion caused by high energy. The heat treatment temperature control allows the heat treatment process to achieve the best results according to the process requirements, effectively ensuring the quality of the steel pipe welding and heat-affected zone.

In addition, the progress of ERW tube straight seam welded pipe inspection technology has achieved full online or offline ultrasonic or eddy current weld risk damage, and the hydraulic pressure test may be under the supervision of a computer, stress testing and regulatory requirements. The promotion and implementation of the standard and specification APIQ1 ISO9000 series ensure the quality assurance in the whole process of production, inspection, sales and service of medium and large caliber ERW straight seam steel pipes.

In recent years, various countries have been actively adopting ERW straight seam welded pipe and spiral welded pipe seamless pipe in place, in industrialized countries, ERW straight seam pipe diameter Ф610mm less, ERW steel pipe has reached about 70% of the proportion. Our production capacity of ERW Longitudinal also occasion enhanced.


Order--Alloy Seamless Pipes to Incheon Korea

Standard: A335 p5
Specification: 457mm*15mm  168.3mm*7.11mm  60.3mm*3.91mm
Surface: Bare
Ends: Bevel
Quantity: 0.834T
Production Time: 15~20 days
Destination: Incheon port
Sales Expert: Olivia Rong


Treatment Technology of Stainless Steel Seamless Pipes

Stainless steel seamless pipes treatment technology refers to the processing of achieving uniform silver, and has a metallic luster. This is generally referred to the production of large stainless steel seamless pipes. Because large stainless steel seamless pipe is manufactured through stamping, folding and welding process, the surface of workpiece has oil, rust, macular, which is neither beautiful, and easy to rust, reducing its stainless steel quality and value.

To make stainless steel seamless pipes achieve the standard, the surface must be finished. After forming matte treatment, that can achieve beautiful appearance, but also improve its anti-corrosion and anti-discoloration performance. After the above method, the corrosion resistance of stainless steel seamless pipes can be increased by 2 to 3 times.

Stainless steel seamless pipes does not rust due to the existence of chromium, nickel components, and then through the matt treatment, not only can eliminate the matrix impurities and iron-rich layer, but also can make chromium on the surface, forming a complete purification film, play a better anti-corrosion effect. According to the complexity of stainless steel seamless pipes and user requirements, we can choose different processing technology, such as mechanical polishing, chemical polishing, electro chemical polishing and other methods to achieve specular gloss.


The Basic Method of Rust Removal for Boiler Tube

Mechanical properties of seamless steel should be taken into consideration when testing its hardness which related to the quality and performance after deformation, stamping, cutting and other processing. Thus, all seamless steel pipes need mechanical property test, the test has two types: tensile test and hardness test.

Tensile test is use a seamless steel pipe sample, and then pull the sample on the machine till it’s broken, therefore can
test its tensile strength, yield strength, and elongation. The tensile test is the most common method to test the mechanical property of metal material. As long as the mechanical property is required, all metal material need to have tensile test. Particularly for those metal materials have complicated shapes that are not easy to be tested, the tensile test is the only way to test its mechanical property.

Hardness test is use a indenter and pressed it into the surface of sample pipes slowly, then measure the depth or dimension of the indentation so that can get the hardness. The hardness test is the simplest and the most convenient method to test the mechanical property of certain material. The hardness test is non-destructive, and has similar values in terms of the relationship between hardness and tensile strength. The hardness of material can be converted into tensile strength values which have great practical significance.

Since the tensile test is not easy to undertake, and it’s convenient to converted hardness to strength, therefore, more and more manufactures choose to test hardness of material rather than its strength. As the development of manufacturing technique and testing technology, materials such as seamless steel pipes and stainless steel pipes which cannot test hardness directly in the past, now can test directly. Thus, the hardness test will gradually replace the tensile test.


API 5L PSL1 and PSL2 Differences for API 5L Line Pipe

API 5L line pipe of all grades have PSL1 and PSL2 two product specifications, they are different on chemical composition, manufacturing processes, mechanical strength, heat treatment, test records, traceability etc.
Line pipes in API 5L PSL2 is higher than PSL1

PSL is the short name of product standard level. The product standard level of line pipe have PSL1 and PSL2, also we could say the quality standard divided in PSL1 and PSL2. PSL2 is higher than PSL1, not only the inspection standard is different, also the chemical property, mechanical strength standards are different. So when place the order for the API 5L line pipe, there should be stated clearly for the size, grades these general specification, also have to clarify the production standard leve, PSL1 or PSL2.
PSL2 is more strictly than PSL1 on the chemical properties, tensile strength, non-destructive test, and impact test.

Different impact test methods for PSL1 and PSL2
API 5L PSL1 steel line pipe not required to do the impact test.
For API 5L PSL2 steel line pipe, except Grade X80, all the other grades of API 5L line pipe required the impact test at temperature of 0℃. The average value of Akv: longitudinal direction≥41J, tranverse direction≥27J.
For API 5L Grade X80 PSL2 line pipe, at 0℃ for all the size, impact test the Akv average value: longitudinal direction≥101J, tranverse direction≥68J.

Different hydraulic test for API 5L line pipe in PSL1 and PSL2
For API 5L PSL2 line pipe shall perform the hydraulic test for each single pipe, and in the API standard specification not permit to have Non-destructive test replace the hydraulic test, this also is a big difference between Chinese standard and API 5L standard. For PSL1 not required Non-destructive test, for PSL2 shall do the Non-destructive test for each single pipe.

Different chemical composition for API 5L line pipe in PSL1 and PSL2
Chemical composition and mechanical strength is also different between API 5L PSL1 line pipe and API 5L PSL2 line pipe. For the detailed specification as below. API 5L PSL2 have restrictions with the carbon equivalent content, where for the carbon mass fraction greater than 0.12%, and equal or less than 0.12%. Different CEQ shall be applied. For line pipe in PSL2 tensile strength have maximum limits. More info please review API 5L Specification part 9.2 and 9.3.


Wall Thickness Deviation of Seamless Steel Pipe

​The most common defects for seamless steel pipe is uneven wall thickness. For example carbon steel pipe, thickness deviation from the capillary puncher at least 7.5%, reducing the elongation rolling to 4.5% increase to 7% after expanding, then after tension reducing to 4.5%.

Seamless steel pipe wall thickness deviation performance reasons:

Since puncher in the head with a perforated plunger between the first support frame centering rollers cantilever structure is formed, so that the head during piercing irregular beating, so the head will be uneven force within the tube, causing the wall thickness deviation.

Manufacturing precision equipment and structures
Since the stability of the perforator roll and the guide plate is poor, so that the device generates a large jump in the perforation, the impact of the tube thickness of the device manufacturer; old structure and centering rollers on the roller and is generally due to the lower roller is not an institution drive, so the centering rollers, its center at the time of the actual installation and adjustment, the theory is not easy to pinpoint the center generated when the plunger hold three centering rollers, so that will result in the perforated top radial centering rollers hold the rod being produced uneven stress, poor stability, causing the wall to produce deviations.

Tube heating process
Heating tube is very important, if uneven heating the heating tube, and will produce yin surface discontinuity such that the perforator is offset occurs plug during piercing, resulting in the low temperature side capillary wall thickness of the thin wall high temperature .

Cutting the tube
Quality tube cutting rates will also have a significant impact on the pipe wall thickness deviation, because the use of shears cutting knife edge quality is not high, sings like a horse section generated more serious moments of piercing machine head bite Slide into the produce section, as well as causing eccentric produce thickness deviation.


High Quality Requirement of Seamless Steel Pipes

Seamless steel tube, the very important role in the national economy, is a kind of economic cross-section steel. It is widely applied in many departments such as petroleum, chemical industry, boiler,
power stations, ships, machinery manufacturing, automobile, aviation, aerospace, energy, geology, architecture and military industry and so on.
2. Classification of Seamless Steel Pipe
(1)According to the cross-section shape: circular cross-section pipe, special-shaped cross-section pipe.
(2)According to the material: carbon steel pipe, alloy steel pipe, stainless steel pipe, composite pipe.
(3)According to the connection ways: threaded pipe, welded pipe.
(4)According to the mode of production: hot rolling (squeeze, top, expand), cold rolling (pull out).
(5)According to utility: boiler tube, OCTG pipe, pipeline, structural pipe, chemical fertilizer pipe.

3. The quality requirements of seamless steel pipe
(1) The steel chemical composition: the chemical composition of steel is one of the most main factors that affect the performance of seamless steel tube, and it is also the main basis that formulates process parameters about rolled tube and heat treatment process of steel tube.
A. Alloy elements: put them according to the purpose
B. Residual elements: put them and properly control when steeling
C. The harmful elements: strictly control (As, Sn, Sb, Bi, Pb), gas (N, H, O)