How to get seamless steel pipes?

What are seamless steel pipes?

Seamless steel pipes are long, hollow tubes that are used for a variety of purposes. Raw steel is first cast into a more workable starting form. It is then made into a pipe by stretching the steel out into a seamless steel pipe.

Production Process of Seamless Steel Pipe

According to manufacuring process of seamless pipe,seamless pipe can be divided into hot rolled seamless tube and cold drawn seamless tube.

Cold drawn seamless steel tubes process:

round tube → heating → perforation → Heading → annealing → pickling → oiled (copper) → multi-pass cold drawn (cold rolled) → blank tube → heat treatment → straightening →hydrostatic testing (testing) → mark → storage.

The general cold strip mills, volume should go through continuous annealing (CAPL unit) to eliminate cold hardening and rolling stress, or batch annealing reach the mechanical properties of the corresponding standard specifies. Cold rolled steel surface quality, appearance, dimensional accuracy better than hot-rolled plate, and right-rolled thin product thickness is about 0.18mm, so the majority of users favor.

Hot rolled seamless steel pipe deformed process

Hot-rolled seamless steel pipe production base deformation process can be summarized as three stages: perforation, extension and finishing.

The main purpose of the perforation process is to become a solid round billet piercing hollow shell. Capillary in the specifications, accuracy and surface quality can not meet the requirements of the finished product, further improvements are needed to deform the metal through. The main purpose of the stretching machine is further reduced sectional view (main compression wall) for a larger axial extension, so that the capillary improved dimensional accuracy, surface quality and organizational performance.

Characteristics of seamless steel pipe

Seamless steel pipe for the use of engineering and construction is very widely, it is a hollow steel strip no seams, it is mainly used to transport liquids pipelines, different look and general steel,one of those heavy type steel, it has a strong resistance to corrosion, resistant to general corrosion.

Will not rust, this performance makes seamless steel tubes extend the life, the most important is that it is very clean and no toxins.

Compared with other seamless steel pipe having strong mechanical resistance, impact regardless of how high a temperature is not interested in the use of seamless steel pipe, it is mounted and the other pipe is the same, can replace other piped water and other liquids. 

Characteristics of seamless steel pipe are as follows:

• high precision can do small batch production.
• smaller diameter.
• weldability strong, high compression capability.
• steel pipe superior performance, relatively dense metal.
• Steel Cross area is more complex.
• high precision cold drawn products, good surface quality.

Annealing Process of Seamless Steel Pipe

Annealing process of seamless steel pipe has the following:
① Complete annealing. Used to refine the medium and low carbon steel by casting, forging and welding after the emergence of poor mechanical properties of coarse thermal tissue. The workpiece is heated to the total transformation of ferrite into austenite temperature above 30 ~ 50 ℃, holding for a period of time, and then slowly cooling with the furnace, the austenite in the cooling process changes again, you can make the steel tissue thinning.
②Spherical annealing. Used to reduce the tool steel and bearing steel after forging high hardness. The workpiece is heated to the beginning of the formation of austenite steel temperature above 20 ~ 40 ℃, slowly cooling after the insulation, in the process of pearlite in the lamellar cementite into a spherical shape, thereby reducing the hardness.
③ Isothermal annealing. To reduce the high nickel, chromium content of the alloy steel structure of high hardness, for cutting. Generally first to a faster cooling to the most unstable temperature of austenite, holding the appropriate time, austenite into a twist or sorbite, hardness can be reduced.
④ Recrystallization annealing. To eliminate the metal wire, thin plate in the cold drawing, cold rolling process of hardening (hardness, plastic decline). Heating temperature is generally the beginning of the formation of steel austenite temperature below 50 ~ 150 ℃, the only way to eliminate the hardening effect of the hardening of the metal.
⑤ Graphite annealing. Used to make a large amount of cementite cast iron into a good plastic malleable cast iron. The process is to heat the casting to about 950 ℃, the insulation after a certain period of time appropriate cooling, so that the formation of cementite decomposition floc graphite.
⑥ Diffusion annealing. To make the chemical composition of the alloy casting homogenization, improve its performance. Method is not in the premise of melting, the casting heated to the highest possible temperature, and a long time insulation, until the alloy in the distribution of various elements tend to evenly after the slow cooling.
⑦ To stress annealing. Used to eliminate the steel castings and welding parts of the internal stress. For the steel products after heating began to form austenite temperature below 100 ~ 200 ℃, after insulation in the air cooling, you can eliminate the internal stress.

API SPEC 5L/ 5CT

Applications of Seamless Steel Pipe

1. Structural seamless steel pipe (GB / T8162-2008) seamless steel pipe for general structure and mechanical structure.

2 fluid seamless steel pipe (GB / T8163-2008) is generally seamless steel pipe used for conveying water, oil, gas and other fluids.

3. The low-pressure boiler seamless steel pipe (GB / T3087-2008) is used in the manufacture of various structural low and medium pressure boiler superheater

Steam pipes, boiling water pipes and superheated steam locomotive boiler tubes, opium pipe, small pipe and brick arch effective high-quality carbon structural steel hot-rolled and cold drawn (rolled) seamless steel pipe.

4. quality carbon steel high-pressure boiler seamless pipe (GB5310-2008) and above is used to manufacture high pressure water tube boiler heating surface with steel, alloy steel and heat-resistant stainless steel seamless.

5. Fertilizer equipment with high pressure seamless steel pipe (GB6479-2000) is applied to the working temperature of -40 ~ 400 ℃, working pressure of high-quality carbon structural steel and alloy steel 10 ~ 30Ma of chemical equipment and pipe seamless steel tubes.

6. Petroleum cracking seamless pipe (GB9948-2006) is applied to the oil refinery furnace tubes, heat exchangers and pipe seamless steel pipe.

7. Geological Drilling Pipe (YB235-70) is available for the geological department of the steel core drilling, use can be divided into the drill pipe, drill collars, core pipe, casing and precipitation tubes.

8 diamond core drilling seamless pipe (GB / T3423-82) is a drill, core rods for diamond core drilling seamless steel pipe casing.

9 oil drilling pipe (YB528-65) is used for oil drilling at both ends of thickening or external upset seamless steel tubes. Steel sub-threading and not two, Threading Pipe Fittings links, no threading methods and tools useful butt joint connection.

10. Ship carbon steel seamless pipe (GB5312-2009) is to create Class I pressure vessels piping, Ⅱ grade pressure piping, boiler and Superheater carbon steel seamless pipe. Carbon steel seamless pipe wall temperature does not exceed 450 ℃, alloy steel seamless pipe wall temperature exceeds 450 ℃.

11. The automobile axle casing seamless steel pipe (GB3088-82) manufacturing automobile axle casing and the drive axle axle shaft tubes of high-quality carbon structural steel and alloy structural steel hot-rolled seamless steel tubes.

12. The diesel engine with high-pressure tubing (GB3093-2002) is to create high-pressure diesel injection systems of cold drawn seamless tubes.

13 hydraulic and pneumatic cylinder with precision internal diameter seamless steel pipe (GB8713-88) is the manufacture of hydraulic and pneumatic cylinder with a cold drawn or cold rolled precision seamless steel tubes with precision diameter size.

14. drawn or cold rolled precision seamless steel pipe (GB3639-2000) is used for high dimensional accuracy mechanical structure, hydraulic equipment and good surface finish cold drawn or cold rolled precision seamless steel tubes.

15. Structure with stainless steel seamless pipe (GB / T14975-2002) is widely used in hot-rolled chemical, petroleum, textile, medical, food, machinery and other industrial corrosion-resistant pipes and structural parts and components made of stainless steel (extrusion, expansion) and cold drawn (rolled) seamless steel pipe.

16. Fluid transport stainless steel seamless pipe (GB / T14976-2002) is a hot-rolled for the transmission fluid made of stainless steel (extrusion, expansion) and cold drawn (rolled) seamless steel pipe.

17. Shaped seamless steel pipe is in addition to other general term seamless pipe cross-sectional shape. Press the pipe cross-section can be divided into different shapes and sizes and so shaped seamless steel pipe wall thickness (code D), ranging shaped seamless steel pipe wall thickness (code-named BD), variable diameter shaped seamless steel pipe (code-named BJ). Shaped seamless steel tubes are widely used in various structural parts, tools and machinery parts. And the tube compared Pipes generally have a greater moment of inertia and section modulus, flexural torsional greater capacity, can greatly reduce the structural weight, saving steel.

ERW Steel Pipe Vs Seamless Steel Pipe

1. Comparison of wall thickness tolerance between erw steel pipe and seamless steel pipe
ERW steel pipe: hot-rolled coil is used as raw material, the thickness limit of modern hot-joining can be controlled within 0.05mm, and the seamless steel pipe is produced by round steel perforation, the wall thickness deviation is large, and the subsequent hot rolling can partially eliminate the wall. Thickness unevenness, but the current advanced unit can only be controlled within ±5~10%t, corresponding to the thickness of 8.94mm steel pipe.
Seamless steel pipe: The limit of wall thickness control accuracy is 0.9mm.
2. ERW steel pipe and seamless steel pipe compared with outer diameter tolerance
ERW steel pipe: adopts cold-bending forming, and the sizing is completed by 0.6% reduction. The process temperature is basically constant at room temperature, so the outer diameter control is accurate and the fluctuation range is small, which is good for eliminating black leather buckle;
Seamless steel pipe: It adopts hot-rolling forming process, and its sizing is completed at 8000C. The raw material composition, cooling conditions and cooling state of the steel pipe have a great influence on the outer diameter, so the outer diameter control is difficult to be accurate and fluctuates. The range is large.
3. Comparative tensile test of erw steel pipe and seamless steel pipe
The tensile performance indexes of seamless steel tubes and erw steel tubes are in line with API standards, but the strength of seamless steel tubes is generally at the upper limit and the plasticity is at the lower limit. In comparison, the strength index of erw steel tubes is in an excellent state, and the plasticity index is higher than the standard 33.3%. The reason is that the performance of the raw material of the erw steel pipe-hot rolled coil is guaranteed by means of microalloying smelting, refining outside the furnace and controlled cooling and rolling; the seamless steel pipe mainly relies on the means of increasing the carbon content, and it is difficult to ensure the strength and plasticity. Reasonable match.
4. ERW steel pipe and seamless steel pipe compared ovality
ERW steel pipe: cold-formed, so the outer diameter control is accurate and the fluctuation range is small.
Seamless steel pipe: The hot rolling forming process, the raw material composition of the steel pipe, the cooling condition and the cooling state of the roll have a great influence on the outer diameter, so the outer diameter control is difficult to be accurate and the fluctuation range is large.
Differences between Stainless Seamless Steel Pipe and Carbon Seamless Steel Pipe
The so-called the difference between stainless seamless steel pipe and carbon seamless steel pipe, mainly refers to the stainless steel and carbon steel in the design rules of the difference, that is to say that the two steel design rules can not be universal. These differences are summarized as follows:
The design rules for stainless steel can not be used for carbon steel because there are three fundamental differences between stainless steel and carbon steel:
First, the cold processing of stainless steel to produce hardening, for example, when bending anisotropy, namely: horizontal and vertical performance is different. It is possible to use an increased strength by cold working, but if the bending area is smaller than the total area, the increase in the strength can increase the safety factor to a certain extent.
Second, the stress / strain curve shape is different, the elastic limit of stainless steel is about 50% of the yield stress, the standard specified in the minimum value, the yield stress value is lower than the carbon steel yield stress value.
Third, the stainless steel has no yield point, usually with ó0.2 to indicate that the yield stress is considered equivalent.
Difference between Seam Stainless Steel Pipe and Seamless Stainless Steel Pipe
Stainless steel tube is a hollow long circular steel, mainly used in petroleum, chemical, medical, food, light industry, mechanical instruments and other industrial pipelines and mechanical structural components. So what are the main differences between seam stainless steel pipes and seamless stainless steel pipes?
1, Concentricity
The manufacturing process of the seamless steel pipe is to punch out a hole in the stainless steel billet at a temperature of 2200 ° f, at which the tool steel is softened and spirally formed from the hole by pressing and drawing. So that the wall thickness of the pipe is not uniform and the eccentricity is high. Thus astm allows the wall thickness difference of the seamless pipe to be larger than the wall thickness of the grooved pipe. The seam pipe is made by means of an accurate cold rolled plate (each roll width of 4-5 feet). These cold rolled plates typically have a maximum wall thickness difference of 0.002 inches. The steel plate is cut into the width of πd, where d is the outer diameter of the pipe. The tolerances of the wall thickness are small and the wall thickness of the entire circumference is very uniform.
2, Welding performance
Generally there are some differences in the chemical composition of the seam and the seamless tube. Production of seamless steel composition of steel is only to meet the basic requirements of astm. While the production of sewn steel is suitable for welding the chemical composition. Such as silicon, sulfur, manganese, oxygen and triangular ferrite and other elements in a certain proportion of mixing can be produced in the welding process is easy to pass a heat of the weld, so that the entire weld penetration. The lack of the above chemical composition of the steel pipe, such as seamless pipe, in the welding process will produce a variety of unstable factors, not easy to weld and welding thoroughly.
3, Grain size
The grain size of the metal is related to the heat treatment temperature and the time at which the same temperature is maintained. The annealed seamed stainless steel pipe and seamless stainless steel tube have the same grain size. If the seam is machined with minimal cooling, the grain size of the weld is smaller than the grain size of the metal being welded, otherwise the grain size is the same.
4, Pipeline strength
The strength of the pipe depends on the composition of the alloy, and thus the same alloy and the same heat treatment of seam stainless steel pipe and seamless stainless steel tube is essentially the same intensity. After tension testing and three-dimensional vibration test, the tearing of the sewn stainless steel pipe occurs almost far away from the welding point or the heated area. This is because the weld less impurities and nitrogen content is slightly higher, so the strength of the weld better than other parts. However, the ASME (American Society of Mechanical Engineers) believes that sewn stainless steel tubes can only withstand 85% of the allowable pressure, mainly due to the data collected earlier than the use of improved welding equipment.
ASME stipulates that 100% of the sewn stainless steel tubes tested by ultrasonic tests are fully tolerated. Similarly, Europe and Asia also require the use of eddy current test of seamless stainless steel pipe to ensure the quality of its welding performance, eddy current testing is subject to legal procedures and holders of the permit institutions. TRENT’s eddy current test passed the permission of the Swedish power department. ASME believes that the small current loss is based on the quality of the seam pipe.
5, Corrosion resistance
The corrosion resistance is also dependent on the composition of the alloy. The same chemical composition of seamless stainless steel tube and completely heat-treated seamless steel pipe corrosion resistance is consistent. ASTM’s supplemental test proves that the corrosion resistance at the weld is equivalent or better than the metal being welded. In the acidic chloride environment, the corrosion of the welded joints of the incomplete heat treatment is accelerated, but this is only the need for corrosion testing. In fact, the environment is not so bad.
6, Bending and extensibility
The extension of the weld can be verified by the following tests specified by ASTM: bending 45 °and bending to 90 °and flattening along the weld; then turn the stainless steel seam to repeat the above steps to make the weld bend to 180 °. The quality of the weld passes through the standard is 40 times the magnification of the case does not allow tear or intergranular separation. Pipeline bending radius is controlled by the composition of the alloy, the general minimum bending radius of 2d. The ideal welding condition is that the weld is in a neutral or pressurized state. Moreover, the pipe should be annealed to reduce its hardness, thereby improving the bending performance.
7, The price
The price of sewn stainless steel pipe is usually only half of the stainless steel seamless pipe.
8, Wall thickness / diameter
Thickness / diameter of small thin-walled stainless steel pipe is best to use welding production; thickness / diameter of the thick-walled tube is best made of stamping method.
9, Integrated quality
In general, the quality of the sewn stainless steel pipe is superior to that of a seamless stainless steel tube because the sewn stainless steel pipe is made of an accurate cold rolled plate which is tested so that any defects are limited to the weld. The seamless pipe is made of stainless steel billet punching, resulting in a lot of tearing in the wall formed by extrusion. The vortex test shows that the defective rate of the sewn stainless steel pipe is usually lower than that of the seamless stainless steel tube. With ultrasonic testing, the background noise of seamless stainless steel tubes is so large that it is difficult to find defects. While the background noise of the sewn stainless steel tube is very low, easy to find defects.
How to Deal with The Surface of Stainless Seamless Steel Pipe
Stainless seamless steel pipe surface treatment is mainly in the following ways:
Chemical cleaning: Chemical cleaning pipe refers to the temporary conversion of the use of chemical chemicals pipeline, the use of temporary pipes and circulating pump from the pipeline at both ends of the use of chemical ring cleaning. The technology has the features such as flexibility, speed, thorough cleaning, and the shape of the pipe is not required, such as chemical cleaning is completed, but the residue to be cleaned. Otherwise, will be running in the future effect.
PIG operation: Pig industry technology to rely on the pump to drive the fluid to promote PIG in the tube to promote the power, in the pipeline discharge dust, so as to achieve the purpose of cleaning. The technology is widely used to clean pipes of various processes, oil and oil pipelines, especially for long-distance transmission of fluid piping cleaning, with the advantage that other technologies can not be replaced.
High-pressure water cleaning: the use of high-pressure water jet that is more than 50 MPa for stripping cleaning the surface of high-pressure water jet dirt. The technology is mainly used for short-distance piping and pipe diameter must be greater than 50 cm or more. It has such as high speed and low cost and so on.
How to Rust for Stainless Seamless Steel Pipe
There are two methods to rust for stainless seamless steel pipe. The first direct use of anti – rust oil, oil film rust, also known as physical rust. The other is the chemical rust, and very stainless steel passivation rust is chemical passivation rust. And physical rust is different, the physical rust is to make stainless seamless steel pipe and air isolation, and stainless steel passivation is the surface of the stainless seamless steel pipe chemical reaction, so that the workpiece to achieve a high degree of anti-rust effect, better than the effect of anti-rust oil Of the more, but does not pollute the surface of stainless steel tube.
The traditional anti-rust oil rust effect is too bad, time is also very short, not only that, with it will pollute the surface of stainless seamless steel pipe, but also affect the appearance, so we support the use of the second method of anti-rust. This method is also relatively speaking to operate, can greatly extend the life of stainless steel pipe. Unless under certain conditions, or we do not recommend that everyone use oil film rust.
Stainless steel rust-proof principle and the principle of physical rust, of course, there is a big difference. The traditional anti-rust oil principle is to form a closed oil film, to prevent air oxidation, chemical rust is a series of chemical reactions on the stainless steel tube to produce a relatively hard and more vulnerable to corrosion of the material, the anti-rust effect several times.
In fact, stainless seamless steel pipe is not no rust, but the probability of rust is relatively low, even to the naked eye usually do not see the situation. Stainless seamless steel pipe is not rusty is not a very simple question, he and the material environment and many other are related. 200 series of stainless steel rust effect is relatively poor, exposed in the air, then it will be very easy to rust, which can prove that the rusty stainless steel tube is also and its environment is closely related.
How to Prevent Seamless Steel Pipe Crack
Domestic high-precision seamless steel pipes generally improve the properties of materials by adding alloys to metals. After cold drawing, seamless steel pipes need to be subjected to stress relief annealing to eliminate residual stress of materials, improve material structure and improve materials. Plasticity, so as to prevent the occurrence of fracture failure of seamless steel pipe.
At present, the material of China’s stainless steel seamless steel pipe is ordinary 45# or 20# steel 27SiMn steel, which improves the strength of the metal by cold drawing deformation; however, it is at the expense of plasticity and toughness of the sacrificial metal. High-precision cold-drawn seamless steel pipe is based on its high dimensional accuracy and high strength performance. It must ensure that the deformation amount is within a certain range to maximize the performance of the material and reduce the material. Negative Effects.
The deformation of the seamless steel pipe is too small to meet the requirements of surface finish and dimensional accuracy, and the strength index of the component cannot be achieved; the deformation is too large, the plasticity and toughness of the seamless steel pipe are reduced too much, and the crystal grains are excessively elongated. The fibrous structure is formed and the metal will have significant anisotropy. The axial direction of the cold drawn seamless steel pipe is parallel to the elongation direction of the grain, and the strength is increased; the radial direction of the cold drawn seamless steel pipe is perpendicular to the elongation direction of the grain, and the strength is instead decreased, and the maximum stress of the hydraulic cylinder It is present in the radial direction of the seamless steel pipe, so the deformation is too large to be detrimental to the performance of the cold drawn pipe.
How to Distinguish between Precision Seamless Steel Pipe and Industrial Seamless Steel Pipe
Precision seamless steel pipe and industrial seamless pipe can be compared from the following aspects:
1, Industrial seamless pipe material is stainless steel tube, that is, the tube, after cold drawing or cold rolling after the annealing pickling, is the finished stainless steel seamless pipe. Industrial stainless steel seamless pipe is characterized by no welding seam, can withstand greater pressure, and the surface of the steel pipe through the solid solution (that is, we usually say that the annealing process) steel pipe can be bent, reaming and other processing.
2, Precision seamless steel pipe products in recent years, mainly the hole, the outer wall size has strict tolerance requirements, and steel surface finish has a high demand.
In addition, precision seamless steel pipe has the following characteristics:
1. Diameter smaller, in general, the diameter of precision seamless steel pipe is generally more than 6 mm.
2. High precision can do small batch production.
3. Precision seamless steel pipe is relatively high accuracy, 6 to 60 steel pipe bore and the outer diameter of the tolerance is generally controlled in plus or minus 3 to 5 silk or less.
4. Precision seamless steel pipe surface finish is good, inside and outside the tube surface finish Ra ≤ 0.8μm, and can be made to wall thickness 0.5mm. And then through the polishing tube inside and outside the surface finish up to Ra ≤ 0.2-0.4μm (such as mirror).
5. Steel pipe performance is superior, the metal is relatively dense, the steel pipe can withstand the pressure also becomes larger.
Comprehensive view, precision seamless steel pipe is in the ordinary industrial grade stainless steel tube for deep processing, in the precision and finish have obvious strengths, but its cost is relatively high, is the high-end stainless steel tube.

How to packing the seamless steel pipes

There are probably hundreds of different methods for packing a pipe, and most of them have merit, but there are two principles that are vital for any method to work prevent rusting and Sea transportation security.

• Plastic caps plugged at the two sides of pipe ends
• Should be avoided by the steel strapping and transport damage
• Bundled signs should be uniform and consistent
• The same bundle(batch) of steel pipe should be came from the same furnace.
• The steel pipe has the same furnace number, the same steel grade, the same specifications.

Our packing can meet any needs of the customers.

Source: China Seamless Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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Please notice that you might be interested in the other technical articles we’ve published:

• How to get high quality steel pipes
• What is the difference between a steel pipe and a steel tube
• How to get high quality stainless steel pipes
• How to get high quality carbon steel pipes
• How To Distinguish Inferior Steel Pipe
• How to get high quality alloy steel pipes
• What is a steel pipe
• What Is A LSAW Steel Pipe
• What is a spiral steel pipe

References:

• https://www.yaang.com