WO2009030105A1

WO2009030105A1 - Manufacturing technique of seamless steel pipe

Info

Publication number: WO2009030105A1
Application number: PCT/CN2008/001518
Authority: WO
Inventors: Huaiwen Liu; Yubao Zhu; Xiaomei Ma; Dekuan Sun; Jianfeng Zhu; Xiaogui Li; Lanqing Gao; Jingjing Xuan
Original assignee: Huaiwen Liu; Yubao Zhu; Xiaomei Ma; Dekuan Sun; Jianfeng Zhu; Xiaogui Li; Lanqing Gao; Jingjing Xuan
Priority date: 2007-08-30
Filing date: 2008-08-22
Publication date: 2009-03-12
Also published as: CN101376204B; CN101376204A

Abstract

A manufacturing technique of seamless steel pipe comprises process steps as follows, producing a hollow blank pipe(1) with annular cup bottom(2) at one end by centrifugal casting, executing machinework on the inner and outer surface of the hollow blank pipe(1), then heating said hollow blank pipe(1), rolling the heated hollow blank pipe(1) by a push bench rolling method so as to produce satisfied pipe diameter, length and wall thickness, cutting and sizing the pipe after loosing and removing rod from said pipe, finally certified pipe being finished. This process can economize energy and cost.

Description

Production process of seamless steel pipe

Technical field

The present invention relates to a manufacturing technique for seamless steel pipes, and more particularly to a manufacturing technique for a large-diameter medium-thick-wall seamless steel pipe. Background technique

Large-diameter seamless steel pipes, especially large-diameter medium-thickness seamless steel pipes with a diameter of more than 500 mm and a diameter-to-wall ratio of 25 or less, have a wide range of applications in many important industrial fields. Such as: the main steam pipeline for nuclear power generation and the loop pipeline for nuclear power, as well as the CNG tow truck, the high pressure gas cylinder for the gas station and the cylinder block of various high pressure vessels. Because of the wide-ranging use of large-diameter thick-walled seamless steel pipes, their mechanical properties and physical and chemical properties are different, and the choice of materials and processing methods is also different. For the energy industry, natural gas pipelines, nuclear power circuits, fire main steam pipes, large gas cylinders for trailers, accumulator pipes and other high-pressure vessel pipes, most of them must have a diameter of more than 500 mm and a certain length (some long) Up to 13 meters) large-diameter medium-thick-wall seamless pipe, because the medium in the pipe is basically high temperature, high pressure, and some are also radioactive, highly corrosive, etc., the use environment is very harsh, the physical and chemical of the pipe Performance, length and dimensional accuracy, surface quality and metallurgical organization all place high demands. Therefore, for large-diameter medium-thick-wall seamless steel pipes used in special fields such as the above-mentioned energy industry, not only stainless steels and various alloy steels, such as 304, 316, 30CrMoA, 35CrMo, 30CrMnSiA, etc., which are difficult to process, are required. It has to be forged or rolled to have a reasonable forged or as-rolled metallurgical structure.

In order to meet the above requirements, some traditional production methods have been unable to produce large-diameter medium-thick wall seamless steel pipes that meet the requirements. However, under the strong market demand, various countries have developed a variety of methods for producing large-diameter medium-thick-wall seamless steel pipes, and have been successful in the United States, Japan, Italy, France, the United Kingdom, and Venezuela, the Czech Republic, India and other countries. Applications. According to the current rough statistics, many sets of units have been built in the world to produce large-diameter medium-thick wall seamless steel pipes. There are three main types: extrusion method, pipe jacking method and diameter expansion (tube) method. One type is the extrusion method. As early as the 1980s, the United States had three large-scale extruders of 20,000 to 30,000 tons, which could produce pipes of Φ 500 to Φ 1200 mm, and the weight of the blanks could reach 16 tons. The extrusion process steps were as follows. Figure 1 shows. Because large-scale extrusion equipment has high investment and complicated technology, and the method has long process, many equipments, and difficult process stability, and the length of the processed pipe is limited, the promotion is limited.

The other type is the expansion (tube) method. That is, the Φ 600 can be produced through various pipe expansion processes (such as oblique expansion, drawing and expansion, push-pull, etc.) by adopting an automatic pipe rolling machine, or a semi-finished pipe rolled by a cycle rolling mill or a cross-rolling piercing machine. ~Φ 800mm seamless steel pipe. At present, the representative manufacturer in China is the original Chengdu Seamless Steel Tube Plant. The production process is shown in Figure 2. In addition to the above-mentioned extrusion method, the above-mentioned extrusion method has many defects, high investment and maintenance cost defects, and the most fatal defect of the diameter expansion method is that it has no tolerance capability and easily expands surface defects, so the expansion amount is limited. , and the expansion process is difficult to control. Therefore, the application of this method has obvious deficiencies.

Another type is the pipe jacking method. In the United States, Japan, France, and the United Kingdom, there are useful billets for punching blanks with cup bottoms, and then producing Φ 500~ Φ 1500 mm finished steel pipes on pipe jacking machines. The billet can weigh up to 22 tons, and the pipe length can be Up to 9 meters. At present, the representative manufacturer in China is Wuhan Heavy Industry Casting & Forging Co., Ltd. The actual production process is shown in Figure 3. The limitations of this processing method are also obvious: First, the method has a long process, many equipment, and high investment and maintenance costs. Among them, at present, Wuhan Heavy Industry Casting & Forging Co., Ltd. is used for pressure setting, which is a large-scale hydraulic press for punching out the material with cup bottom blank. The cost is very high. Secondly, the length of the processed pipe is limited because of the limitation of the stamping die; Especially in the process of punching, the inner hole of the workpiece is prone to cracks and other defects, and these defects are difficult to be overcome by the subsequent processes and may be further expanded by the subsequent processes, resulting in an increase in subsequent trimming amount and a yield rate. high. This method is currently the most widely used method for processing large-diameter medium-thick-wall forged or rolled seamless steel tubes.

In order to overcome the shortcomings of the prior art, especially in order to process large-diameter medium-thick-wall seamless pipes that meet the urgently needed high-quality stainless steel or special alloy steels such as energy, gas, nuclear power, thermal power, and national defense, people have been researching and exploring. A better processing method, in which ZL00112551. No. 6 Chinese invention patent discloses a use of "centrifugal casting + cold drawing" The method to produce "ultra-low carbon duplex stainless steel seamless pipe" method. Compared with the above three methods, although the method can produce special steel pipes containing elements such as Cr, Ni, Mo, N, etc., the method still requires an expensive cold pipe drawing machine, and requires multiple cycles of cold drawing, and each After the cold drawing, solution treatment, pickling treatment and lubrication treatment are also carried out. There are also defects such as high equipment cost and many processing procedures, and this method is difficult to adopt for the production of large-diameter medium-thickness seamless steel tubes. Summary of the invention

The invention is to overcome the defects of the above background art, and the new process method for seamless steel pipe production after years of trial and research and development is especially suitable for the production of energy industry, natural gas pipeline, nuclear power primary circuit, thermal power main steam. High-quality, difficult-to-machine and extra-large-diameter medium-thick-wall seamless steel pipes required for pipes and high-pressure gas cylinders. Specifically:

A new process for producing seamless steel pipes, comprising the following process steps:

In the first step, a hollow shell blank is produced by centrifugal casting;

In the second step, machining the inner and outer surfaces of the hollow shell;

In the third step, the hollow tube blank after machining is heated;

In the fourth step, the heated hollow shell is subjected to pipe jacking processing to obtain a pipe member having a wall thickness, a diameter and a length;

In the fifth step, the pipe fitting after the pipe rolling process is cut and finished to obtain a qualified finished pipe.

The centrifugal casting of the first step is carried out on a tilting centrifugal casting machine with a horizontal axis of the mold and a horizontal angle of inclination of 15 to 30 degrees. The hollow tube blank is centrifugally cast into a hollow tube blank having an inner diameter of one end. The hollow shell is made into a hollow shell with an annular cup bottom at one end.

Alternatively, the centrifugal casting of the first step is performed on a horizontal centrifugal casting machine with a rotation axis of the mold and a horizontal angle of 0 degrees, and the hollow tube blanks obtained by centrifugal casting are transparent at both ends of the same wall thickness. Hollow tube blank.

Further, an annular cup bottom is welded to one end of the hollow tube blank which is transparent at both ends, so that the hollow tube blank becomes a hollow tube blank with an annular cup bottom at one end. The welding is gas-shielded automatic welding, and the annular cup bottom can be made of ordinary carbon steel.

The machining described in the second step is the cutting of the inner and outer surfaces of the hollow shell having the annular cup bottom at one end.

The inner surface of the hollow shell having the annular cup bottom at one end has a cutting thickness of not less than 5 mm, and the outer surface of the hollow shell having the annular cup bottom at the one end has a cutting thickness of not less than 2 mm.

Also included between the second step and the third step is a defect inspection step that excludes the hollow shell that is still unsatisfactory after being repaired by the defect.

The heating of the third step is performed in accordance with a pre-selected temperature range of the direction of the high temperature plasticity diagram of the material of the hollow shell.

Alternatively, the hollow tube blank transparent to the two ends obtained above further comprises an in-line cuffing step between the third step and the fourth step, the step being the two ends obtained by centrifuging the centrifugal casting on the closing machine One end of the large-diameter thick-walled hollow tube that is permeated is closed, so that the large-diameter thick-walled hollow tube blank becomes a hollow tube blank with an annular cup bottom at one end.

The jacking process of the fourth step is to insert the mandrel into the heated hollow shell at the end with the annular cup bottom, and then feed the top of the plurality of roll rings by the advancement of the mandrel. Rolling deformation in the pipe machine.

Inserting the mandrel into the hollow hollow shell with the annular cup bottom at the end of the heating, and then feeding the metal rod into the pipe jacking machine with 3~7 roll rings for rolling deformation. The hole diameters of the 3 to 7 roll rings are arranged in order from small to large.

The maximum elongation coefficient (μ _ΜΜ ) of the hollow shell on the single roll ring is 1.35, and the average elongation coefficient is (4 is (0.85-0.95) μ _Μ , and the diameters of the holes are arranged from small to large. The elongation coefficient on each roller ring is distributed according to the "mountain" shape, that is, the extension coefficient on the front and rear roller rings is small, and the extension coefficient on the intermediate roller ring is large.

The pipe jacking machine is a pipe jacking machine having five roll rings, and the elongation coefficient of the hollow tube blank on each roll ring is (0.92-0.96) μ ₃ , (1.00-1.08) from front to back. μ ₃ , (1.10-1.18) μ ₃ , (0.98-1.04) μ _a , (0.88-0.92) μ _a . Further, between the fourth step and the fifth step, a core rod releasing step is performed, and the pipe member rolled out from the pipe jacking machine is sent to a loose rod machine together with the core rod to perform a loose rod. The tube is then transported along with the mandrel to a rod puller, and the mandrel is withdrawn from the tube.

The rotational speed n of the inclined centrifugal casting machine is:

Where: n - speed;

L-tube length;

The thickness of the wall at an inner diameter cuff;

a pipe body nominal wall thickness;

Z). The outer diameter of a tube;

A—inclination factor.

The angle of inclination A is greater than 0 and less than or equal to 0.716.

When the inclination is 15 degrees, A = 0. 1853; when the inclination is 20 degrees, A = 0. 2449, when the inclination is 25 degrees, A = 0. 3026; When the inclination is 30 degrees, A = 0. 3580 .

The wall thickness H of the annular cup bottom at the inner diameter of the one end of the hollow shell is:

Where: H—the thickness of the annular cup bottom sufficient to withstand the top thrust of the mandrel during jacking; F—the top thrust during steady rolling;

Dx—core rod diameter;

Σ—high temperature tensile strength of steel;

^ The elongation coefficient calculated after rolling the bottom portion of the annular cup at the inner diameter end.

The elongation coefficient calculated after rolling the annular bottom portion of the inner diameter end cup is:

- the diameter of the inner hole of the annular cup bottom ring;

The outer diameter of an annular cup bottom ring; By adopting the above processing method of the invention, the high-quality centrifugal casting is firstly established with a process connection between the top tube rolling with less investment, relatively simple technology and ideal deformation conditions, and is particularly suitable for producing large diameters. Thick-walled seamless steel tubes can not only produce high-quality, difficult-to-process stainless steel and special seamless steel tubes, but also overcome the shortcomings of the prior art, forming an energy-saving, high-quality, economical and different production method. Short process and new process of seam steel pipe.

The above method of the present invention has the following advantages over the existing three processing techniques:

1. Compared with the extrusion method, the patented method can produce large-diameter thick-walled pipes with heavier tonnage and longer length, and the patented method has less equipment investment, short process, low technical complexity and easy process stability. The physical and chemical properties of the product are better;

2. Compared with the expansion method, the products produced by the patented method have higher precision and surface quality, the organizational state is more ideal, the deformation process is easy to control, and the patented method has less investment and shorter process;

3. The advantages of this patented method are more prominent than the currently used jacking method:

(1) The patented method adopts a billet, an octagonal billet or a solid round billet which is usually used in the jacking method, but a hollow billet which is obtained by a unique process and has a cup bottom. In addition, it is also possible to inspect the quality of the hollow billet before hot working, and then enter the heating and jacking process of the next pass to facilitate the quality control of the finished product. However, the pipe jacking method cannot detect the quality of the workpiece before the punching (perforation) and the pipe heating process before the lower pipe heating process and the pipe jacking process, so that the workpiece with good quality and poor quality passes through the next process, and the product quality is not controlled;

(2) Using the patented method to produce pipes, there is no need to specially arrange in-line punching (perforation) and pre-extension processes that are prone to various surface defects, thereby not only reducing at least one reheating step, but also saving energy by about 10%. Processing some difficult-to-deformed metals that are not easily punched (perforated) into high-quality, large-diameter seamless pipes; (3) This patented method is a short-flow pipe-making process that can reduce 2 to 3 links and does not require expensive large-tonnage hydraulic presses, thereby significantly reducing equipment investment and operating costs and field area of the pipe-making workshop. ;

(4) This patented method can obtain centrifugally cast tube blanks with less dense structure, better mechanical properties, fewer defects such as pores, shrinkage holes, slag inclusions, and coarse grains. Under the same deformation conditions, the patented method can be obtained. Special pipe with superior surface quality and comprehensive performance for some important occasions (such as primary circuit of nuclear power);

(5) It is precisely because the patented method can carry out the quality control of the intermediate link as described above, thereby creating conditions for improving the product qualification rate and reducing the workload of the finishing process;

(6) The patented method can also weld an annular cup bottom at one end of a centrifugally cast hollow tube blank, so that the hollow tube blank becomes a hollow tube blank with a cup bottom at one end, and the cup bottom for welding can be ordinary carbon. It is made of plain steel, so that not only the precious billet metal but the ordinary carbon steel is cut off at the last cutting head, so that the purpose of saving precious billet metal can be achieved, and the saving can be about 3%. BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 is a process flow diagram of the extrusion method;

Figure 2 is a process flow diagram of the diameter expansion method;

Figure 3 is a process flow diagram of the pipe jacking method;

4 is a process flow diagram of Embodiment 1 of the present patent;

Figure 5 is a hollow end of the cup with one end in the first embodiment of the present patent

6 is a process flow diagram of Embodiment 2 of the present patent;

Figure 7 is a hollow end of the cup at the end of the second embodiment of the present patent

8 is a process flow diagram of Embodiment 3 of the present patent;

Figure 9 is a hollow end of the cup end of the third embodiment of the present patent

Figure 10 is a high temperature plasticity diagram of lCrl8Ni9Ti metal; As shown in FIG. 4, according to a first embodiment of the present invention, the following process steps are included:

In the first step, a large-diameter medium-thick-wall hollow tube blank is produced by centrifugal casting; the centrifugal casting is performed on a tilting centrifugal casting machine with a horizontal axis of the mold and a horizontal angle of inclination of 15 to 30 degrees. The large-diameter thick-walled hollow tube blank which is centrifugally cast is a hollow tube blank having an inner diameter of one end, that is, an end with an annular cup bottom, that is, a radially inner closed mouth is formed at the end, and a hollow tube blank with a cup bottom 2 is formed. 1. This cup bottom 2 has a hollow portion 21 as shown in FIG. The provision of the above structure can facilitate the post-topping process, and the end of the mandrel of the pipe jacking machine can abut against the inner surface of the cup bottom 2 so that the mandrel pushes the hollow shell. The hollow tube blank 1 with the cup bottom 2 can be processed conveniently and with high quality by the inclined centrifugal casting machine, and the inclined centrifugal casting machine has been popularized and applied in the field of cast iron pipe production, and the specific structure is not here. Let me repeat.

In the second step, the inner and outer surfaces of the hollow shell are machined; the machining is performed on the inner and outer surfaces of the hollow shell having the annular cup bottom at one end prepared in the first step. The cutting thickness of the inner surface of the hollow shell is not less than 5 mm, and the cutting thickness of the outer surface of the hollow shell is not less than 2 mm. This machining step can remove the rough inner and outer surface layers of the hollow tube blank and the deposited impurities, and remove other defects such as cracks and bubbles on the inner and outer surface layers to ensure the smoothness of the inner and outer surfaces of the hollow tube blank and improve the quality of the finished product after processing.

In the third step, the machined hollow mandrel with an annular cup bottom at one end is heated; the heating is performed according to a pre-selected temperature range of the high temperature plastic pattern of the tube material. The high temperature plasticity diagram of the lCrl8Ni9Ti metal as shown in Fig. 10; the shaded portion in this figure is the temperature range of heating. Only heating according to this predetermined temperature range can guarantee the post-rolling process and produce a qualified finished product.

In the fourth step, the heated hollow shell is subjected to pipe jacking to obtain a pipe fitting that meets the requirements of wall thickness, diameter and length; and the jacking process of the jacking is to insert the mandrel into the heated The hollow tube blank with the bottom of the cup at one end is then fed into the pipe jacking machine with multiple roll rings by the advancement of the mandrel for rolling deformation. The pipe jacking machine is an existing device, which is described here. The number of the upper roller rings can be changed as needed, and the patent preferably uses 3 to 7 roller rings, and The diameters of the 3~7 roll rings are arranged in order from small to large. The maximum elongation coefficient of the hollow shell on the single roll ring is _Ma J3⁄41.35, the average elongation coefficient j^(0.85~0.95) μ and the elongation coefficient of the pipe on each roll ring from front to back according to the "mountain" The regular distribution of the glyphs, that is, the elongation coefficient on the front and rear roller rings is small, and the elongation coefficient on the intermediate roller rings is large. It should be noted here that the "mountain" shape rule means that the extension coefficient on the front roller rings is small, and then gradually increases, and the extension coefficient is the largest when reaching the middle roller rings, and reaches the maximum after extending. The coefficient starts to gradually become smaller, which is similar to the "mountain" shape: the middle is high and the two sides are small.

For example, in a pipe jacking machine of five roll rings, the elongation coefficient of the hollow shell blank on each roll ring is (0.92-0.96) μ _a , ( 1.00-1.08) μ _a , ( 1.10-1.18) μ ₃ , (0.98-1.04) μ _a , (0.88-0.92) μ _a . The total elongation factor is between 3-4. The specific elongation coefficients on each roll ring are 0.94μ, 1.06 a, 1.12μ, 1. οομ&, 0.90μ&, and the total elongation factor can be 3 - 3.5ο. The fifth step is the rolling process of the top tube. The latter pipe is cut and finished to produce a qualified finished pipe. This step is mainly to cut off the bottom of the tube, and finish the tube body, and process the inner and outer surfaces of the tube as needed to meet the requirements of different environments.

Referring to Fig. 4, a defect inspection step is further included between the second step and the third step, and the hollow tube blank in which the defect is still not in compliance with the repair is excluded from the process step. This can ensure that the hollow tube blanks used for processing in the later stage are all qualified blanks, which can greatly save costs and reduce the generation of waste products.

Referring to FIG. 4, a core rod releasing step is further included between the fourth step and the fifth step, and the pipe rolled out from the pipe jacking machine, together with the core rod, is sent to a loose rod machine for loosening. a rod, the tube is transported to the rod machine together with the mandrel, and the mandrel is drawn from the tube

Formula requirements:

Where: n - speed;

L-tube length;

The thickness of the wall at an inner diameter cuff;

a pipe body nominal wall thickness;

Z). The outer diameter of a tube;

A—inclination factor.

The above-mentioned inclination coefficient A is greater than 0 and less than or equal to 0. 716, when the inclination is 15 degrees, A = 0. 1853; when the inclination is 20 degrees, A = 0. 2449, when the inclination is 25 degrees, A = 0. 3026 When the inclination is 30 degrees, Α = 0. 3580 ο

In the above embodiment given by the present invention, the mandrel is inserted into the heated hollow shell with the bottom of the cup and fed into the plurality of roll rings by the advancement of the mandrel for rolling deformation, in the process of jacking The bottom of the cup is subjected to the load of pushing the mandrel. On the first few roller rings, the top thrust of the mandrel mainly acts on the bottom of the cup due to the limited holding force between the hollow tube blank and the mandrel. After the wall-reducing deformation has become the absolute dominant deformation on the subsequent rolls, the holding force between the hollow tube blank and the mandrel suddenly rises, thereby offsetting the load that should be applied to the bottom of the cup, making it axial. As the force decreases, the increase in total thrust is also slowing. The bottom of the cup is cut off after the tube has been processed, and it becomes waste. If the bottom of the cup is too thick, it will cause waste of material, but if it is too small, the strength of the top thrust is not enough. Therefore, it is important to prepare the bottom of the cup of the corresponding thickness. The thickness of the bottom of the cup can be determined by the following formula:

H =

3.611 * Dx * a * μ _ά where: Η - sufficient to withstand the thickness of the bottom of the mandrel at the top of the mandrel;

F—top thrust during stable rolling;

Dx—core rod diameter;

Σ—high temperature tensile strength of steel;

The elongation coefficient calculated after rolling the bottom portion of the annular cup at the inner diameter end is:

Wherein, the diameter of the inner hole of an annular cup bottom ring;

3⁄4—the outer diameter of the annular cup bottom ring;

J. The total elongation factor of a hollow shell.

The above production method of the present invention is particularly suitable for producing a seamless steel pipe having a diameter of 500 mm or more and a diameter to wall ratio of 25 or less, because the first method of the present invention uses centrifugal casting to prepare a hollow shell, so if the diameter of the pipe is small, for example Below 100 mm, the advantages of centrifugal casting cannot be realized; if it is used for the production of thinner wall thickness, the thickness of the machined cutting is large because of the precipitation of impurities on the inner and outer surfaces after centrifugal casting, and it is not economical. Therefore, it is generally not used for the production of seamless steel tubes with a wall-to-wall ratio greater than 25.

As shown in FIG. 6, a second embodiment according to the present invention includes the following process steps:

In the first step, a hollow tube blank is produced by centrifugal casting; the centrifugal casting is carried out on a horizontal centrifugal casting machine in which the rotation axis of the mold is parallel to the horizontal line, and the hollow tube blank which is centrifugally cast is two equal wall thicknesses. Hollow tube blank that is transparent at the end. After centrifugal casting, a welding step is added, in which an annular cup bottom 2 is welded to one end of the hollow shell 1 obtained by centrifugal casting, so that the hollow shell 1 becomes a hollow shell with a cup bottom 2 at one end. . The cup bottom 2 has a hollow portion 21 as shown in FIG. The welding is a gas shielded automatic welding, and the annular cup bottom may be made of ordinary carbon steel. The main function of the bottom of the cup is to withstand the top thrust of the mandrel during the post-top processing. In the finished product, the bottom of the cup is to be cut off, which becomes waste. The material of the tube blank is made of precious metal material. In order to save cost, a low-cost common metal cup bottom can be welded at one end of the thick-walled hollow tube blank, thereby saving precious metals. The automatic welding with gas protection can ensure the connection strength between the bottom of the cup and the hollow tube blank, which is beneficial to the later processing. After the above treatment, the hollow shell is processed into a hollow shell having an annular cup bottom.

In the second step, the inner and outer surfaces of the hollow shell of the one end with the bottom of the cup are machined; the machining is performed on the inner and outer surfaces of the hollow shell produced in the first step. Cutting the inner surface of the hollow shell blank to a thickness of not less than 5 mm, to the thick wall The outer surface of the hollow shell blank has a cutting thickness of not less than 2 mm. The machining step can remove the rough inner and outer skin layers and other defects of the hollow shell, ensure the smoothness of the inner and outer surfaces of the hollow shell, and improve the quality of the finished product after processing.

In the third step, the machined hollow tube blank is heated; the heating is performed according to a pre-selected temperature range of the high temperature plastic pattern of the tube material. The high temperature plasticity diagram of the lCrl8Ni9Ti metal as shown in Fig. 10; the shaded portion in this figure is the temperature range of heating. Only heating according to this predetermined temperature range can guarantee the final topping process and produce a qualified finished product.

In the fourth step, the heated hollow shell is subjected to a topping process to obtain a pipe fitting that meets the requirements of wall thickness, diameter and length; and the top processing is also to insert the mandrel into the heated one end with the bottom of the cup The hollow tube blank is then fed into the pipe jacking machine of the multiple roll rings by the advancement of the mandrel for rolling deformation. The pipe jacking machine is the same as that of the first embodiment, and the elongation coefficient on each roller ring is also the same as that in the first embodiment.

In the fifth step, the pipe fitting after the topping process is cut and finished to obtain a qualified finished pipe. This step is mainly to cut off the bottom of the tube and finish the tube to obtain a qualified finished tube.

Referring to FIG. 6, a defect inspection step is further included between the second step and the third step to exclude the hollow shell having defects from being inconsistent with the process step. This can ensure that the hollow tube blanks used for processing in the later stage are all qualified blanks, which can greatly save costs and reduce the generation of waste products.

Referring to Fig. 6, between the fourth step and the fifth step, a core rod releasing step is further included, and the pipe rolled out from the pipe jacking machine is sent to the pine bar machine together with the mandrel rod for loosening. The rod is then transported along with the mandrel to a rod puller, and the mandrel is withdrawn from the tube. The loose rod machine and the rod pump are both existing equipment and are commercially available, and are not described herein.

As shown in FIG. 8, a third embodiment according to the present invention includes the following process steps:

In the first step, a hollow tube blank is produced by centrifugal casting; the centrifugal casting is carried out on a horizontal centrifugal casting machine in which the rotation axis of the mold is parallel to the horizontal line, and the hollow tube blank which is centrifugally cast is two equal wall thicknesses. Hollow tube blank that is transparent at the end. In the second step, the wall hollow tube blank is machined, and the machining is performed on the inner and outer surfaces of the hollow tube blank which is transparent at both ends. The cutting thickness of the inner surface of the hollow shell is not less than 5 mm, and the cutting thickness of the outer surface of the hollow shell is not less than 2 mm. The machining step can remove the rough inner and outer skin layers and other defects of the hollow shell, ensure the smoothness of the inner and outer surfaces of the hollow shell, and improve the quality of the finished product after processing.

In the third step, the machined hollow shell is heated. This step is the same as the above-described Embodiment 1 and Embodiment 2.

Referring to FIG. 8 , after heating the tube blank, the tube blank is not directly entered into the pipe jacking machine for pipe jacking, but the online capping step is performed before the jacking tube is rolled, that is, the wall thickness is two. The end of the hollow tube blank closing machine is closed at one end thereof, so that one end of the large-diameter thick-walled hollow tube blank is closed to form a hollow tube blank with an end of the annular cup bottom, as shown in FIG. . The closing machine is an existing sizing device and is commercially available, and will not be described herein.

In the fourth step, the hollow tube blank having the bottom of the cup at one end prepared in the above-mentioned manner is immediately subjected to pipe rolling, and the steps are the same as those in the first embodiment and the second embodiment.

The fifth step is the same as the first embodiment and the second embodiment.

As shown in FIG. 8, as in the first embodiment and the second embodiment, a defect inspection step is further included between the second step and the third step; in the fourth step and the fifth step The core rod release step is also included.

The foregoing detailed description of the preferred embodiments of the invention, It is obvious to those skilled in the art that the various modifications of the specific embodiments of the present invention are within the scope of the claims and the equivalents of the invention.

Claims

Claim

1. A new process for the production of seamless steel pipes, including the following process steps:

In the first step, a hollow shell blank is produced by centrifugal casting;

In the second step, machining the inner and outer surfaces of the hollow shell;

In the third step, the hollow tube blank after machining is heated;

In the fourth step, the heated tube blank is subjected to pipe jacking processing to obtain a pipe member having a wall thickness, a diameter and a length;

2. The new production process according to claim 1, wherein: the centrifugal casting of the first step is performed on a tilting centrifugal casting machine having a rotation axis of the mold and a horizontal angle of inclination of 15 to 30 degrees. The hollow tube blank which is centrifugally cast is a hollow tube blank having an inner diameter of one end, and the hollow tube blank is a hollow tube blank having an annular cup bottom at one end.

3. The new production process according to claim 1, wherein: the centrifugal casting of the first step is performed on a horizontal centrifugal casting machine having a rotation axis of the mold and a horizontal angle of 0 degrees, centrifugal casting The hollow tube blank is a hollow tube blank which is transparent at both ends of the same wall thickness.

4. The new production process according to claim 3, further comprising: a welding step between the first step and the second step, the step being a hollow through the two ends obtained by centrifugal casting An annular cup bottom is welded to one end of the tube blank, so that the hollow tube blank becomes a hollow tube blank with an annular cup bottom at one end.

A new production process according to claim 4, wherein: said welding is gas-shielded automatic welding, and said annular cup bottom is made of ordinary carbon steel.

6. The new production process according to any one of claims 2 or 4, wherein: the machining according to the second step is performed on the inner and outer hollow shells with the annular cup bottom at one end. Surface machining.

7. The new production process according to claim 6, wherein: the inner surface of the hollow tube blank having an annular cup bottom at one end has a cutting thickness of not less than 5 mm, and the end portion has an annular cup bottom. The outer surface of the hollow tube blank has a cutting thickness of not less than 2 mm.

8. The new production process according to any one of claims 2 or 4, characterized in that: a defect inspection step is further included between the second step and the third step, and the defect remains after the repair process The hollow shell blanks that do not meet the requirements exclude the process steps.

9. A new production process according to any one of claims 2 or 4, wherein: said heating in said third step is carried out according to a preselected temperature range of the direction of the high temperature plasticity diagram of the material of said hollow shell. heating.

10. The new production process according to claim 3, wherein: the machining according to the second step is a cutting process of the inner and outer surfaces of the hollow shells which are transparent to the two ends.

11. The new production process according to claim 10, wherein: the cutting thickness of the inner surface of the hollow shell is not less than 5 mm, and the cutting thickness of the outer surface of the hollow shell is not less than 2 mm. .

12. The new production process according to claim 11, wherein: a defect inspection step is further included between the second step and the third step, and the defect is still not satisfied after the repair process is performed. The hollow shell blank excludes the process steps.

13. A new process for producing according to claim 12, characterized in that said heating in said third step is carried out in accordance with a preselected temperature range of the direction of the high temperature plasticity diagram of the material of said hollow shell.

14. The new production process according to claim 13, wherein: between the third step and the fourth step, an online closing step is further included, wherein the step is to obtain the two ends of the centrifugal casting on the closing machine. One end of the hollow hollow tube is closed to make the hollow shell into a hollow shell with an annular cup bottom at one end.

A new production process according to any one of claims 2, 4 or 14, wherein: said jacking process of said fourth step is to insert a mandrel into said one end with an annular cup The bottom hollow shell is then fed by a pusher of a mandrel into a pipe jacking machine having a plurality of roll rings for rolling deformation.

16. The new production process according to claim 15, wherein: said mandrel is inserted into said hollow mandrel with an annular cup bottom at one end, and then advanced by said mandrel. Rolling deformation is carried out in a pipe jacking machine having 3 to 7 roll rings, and the diameters of the 3 to 7 roll rings are arranged in order from small to large.

17. The new production process according to claim 16, wherein: the maximum elongation coefficient (μ Μ _Μ ) of the hollow shell blank on a single roll ring is 1.35, and the average elongation coefficient (4 is (0.85 to 0.95). ) μ _Μ , and the elongation coefficient on each of the roll rings of the roll ring whose diameter is from small to large is distributed according to the "mountain" shape, that is, the elongation coefficient on the front and rear roll rings is small, the middle frame The elongation coefficient on the roller ring is large.

18. The new production process according to claim 17, wherein: said pipe jacking machine is a pipe jacking machine having five roll rings, and the elongation coefficient of said hollow tube blank on each roll ring is from front to bottom The order is (0.92-0.96) μ ₃ , (1.00- 1.08) μ ₃ , (1.10-1.18) μ ₃ , (0.98-1.04) μ ₃ , (0.88-0.92) μ _a .

19. The new production process of claim 18, further comprising: a core rod releasing step between said fourth step and said fifth step, said step of rolling from said pipe jacking machine The tube, together with the mandrel, is fed to a loose bar machine for loosening the rod, and the tube is transported along with the mandrel to a rod puller, and the mandrel is withdrawn from the tube.

20. The new production process according to claim 2, wherein: the rotational speed n of the inclined centrifugal casting machine is:

Where: n - speed;

L-tube length;

The thickness of the wall at an inner diameter cuff;

a pipe body nominal wall thickness;

Z). The outer diameter of a tube;

A—inclination factor.

21. The new production process according to claim 20, wherein: the number of inclination angles A is greater than 0 and less than or equal to 0.716.

22. The new production process according to claim 21, wherein: when the inclination is 15 degrees, A = 0.185; when the inclination is 20 degrees, A = 0. 2449, when the inclination is 25 degrees , A = 0. 3026; When the inclination is 30 degrees, A = 0. 3580.

23. The new production process according to claim 2, wherein: the thickness H of the annular cup bottom at the inner diameter of the one end of the hollow shell is:

H = F—

3.611 * Dx * a * μ _ά where: Η - the thickness of the annular cup bottom sufficient to withstand the top thrust of the mandrel during jacking; F - the top thrust during steady rolling;

Dx—core rod diameter;

Σ—high temperature tensile strength of steel;

24. The new production process according to claim 23, wherein: the elongation coefficient calculated after the annular cup bottom portion of the inner diameter closing end is: d

Wherein, the diameter of the inner hole of an annular cup bottom ring;

A—the outer diameter of the bottom ring of the annular cup;

μ ₀ The total elongation factor of a hollow shell.

A new production process according to any one of claims 2, 4 or 14, wherein: said step of cutting said pipe member in said fifth step is to cut said ring of said pipe member by a cutting machine At the bottom of the cup, the pipe fittings after cutting the bottom of the annular cup are finished, and a qualified finished pipe is obtained.