Straight seam steel pipe machining method, straight seam steel pipe manufactured through machining method, welding core and welding flux
By employing a two-stage forming and welding process, combined with high-toughness welding materials and flux, the problem of bulging on both sides of the weld seam in straight seam steel pipes was solved, achieving high-precision control of the roundness and straightness of the steel pipes.
Patent Information
- Application Number
- CN202411661416.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2026-05-22
AI Technical Summary
In the existing straight seam steel pipe forming process, there are often problems of inner or outer bulges on both sides of the weld, especially in thick-walled steel pipes, which affect the quality indicators such as the roundness and straightness of the steel pipe.
The process involves two forming and welding steps. After the first rolling, a straight section is reserved and high-toughness welding material and multi-layer, multi-pass submerged arc automatic welding are used. During the second rolling, the straight edge is eliminated by RB three-roll forming. Combined with special welding core and flux, the weld is made consistent with the base material.
It effectively eliminates straight edges on both sides of the weld, improves the roundness and straightness of the steel pipe, and achieves precise control. The weld bead is controlled within 1mm, the roundness of the steel pipe is controlled within 0.4%D, and the straightness is controlled within 2mm.
Smart Images
Figure CN122071082A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of straight seam steel pipe processing technology, specifically relating to a straight seam steel pipe processing method, a straight seam steel pipe prepared by the processing method, as well as a welding core and welding flux. Background Technology
[0002] Currently, the main forming processes for straight seam steel pipes include JCOE, UOE, and RB three-roll forming. These processes typically involve pre-bending the edges before forming. Therefore, all these forming methods suffer from weld seam bulging issues, especially for thick-walled steel pipes. The greater the wall thickness, the more difficult the pre-bending of the plate edges becomes. After forming, the weld seam will inevitably have a certain length of straight edge on both sides, leading to internal or external bulging of the weld seam, severely affecting the roundness, straightness, and circumferential weld joints of the steel pipe. This problem has long remained unresolved, causing significant difficulties for engineers in the industry and hindering the improvement of quality indicators such as roundness and straightness of steel pipes.
[0003] Therefore, how to improve and enhance the forming quality of both sides of the weld seam in steel pipes has always been one of the most critical technical bottlenecks in the pipe manufacturing industry.
[0004] Generally, welding materials consist of two parts: the welding core and the welding flux.
[0005] The welding core is the metal core of the welding electrode. In order to ensure the quality and performance of the weld, there are strict regulations on the content of each metal element in the welding core, especially the content of harmful impurities (such as sulfur and phosphorus), which should be strictly limited.
[0006] During the welding process, flux decomposes and melts to form gas and slag, which provide mechanical protection, metallurgical treatment, and improve process performance. Flux is a crucial factor determining weld quality. Summary of the Invention
[0007] In order to solve the above-mentioned problems in the prior art, namely the problem of the forming quality of both sides of the weld seam of steel pipe, the present invention provides a method for processing straight seam steel pipe.
[0008] The present invention also provides a straight seam steel pipe prepared by the above processing method.
[0009] The present invention also provides a welding core and a welding flux for the above-described processing method.
[0010] The technical solution of the present invention includes:
[0011] A method for processing straight seam steel pipes, characterized by comprising the following steps: (1) First rolling: The precast steel plate is initially rolled into a tube shape directly using a tube rolling forming equipment. At this time, a straight section is reserved at the joint of the rolled tube. (2) For the first welding, high toughness welding materials are used for the first welding of the steel pipe weld. The weld morphology must be strictly controlled during the first welding. The weld height should be lower than or level with the base material, and there should be no obvious grooves or lack of fusion at the fusion line between the weld and the base material. (3) Second rolling: The pipe body that has been welded for the first time is rolled into shape by the RB three-roll forming equipment. In particular, after the straight section that has been welded for the first time is rolled for the second time, there are no obvious straight edges or obvious bulges on both sides of the weld seam of the steel pipe, and the outline of all parts in the circumferential direction of the steel pipe is consistent. (4) Second welding: Perform a second welding on the pipe body weld that has been rolled a second time. Ensure that the weld morphology and performance quality meet the relevant specifications after the weld is completed.
[0012] As an optional technical solution, the high-toughness welding material mentioned in step (2) has a core material of high-toughness, high-alloy low-carbon steel. The high-toughness, high-alloy low-carbon steel core material has a nickel content of 3.5-4.5%, a chromium content of 0.2-0.25%, a molybdenum content of 0.15-0.20%, a carbon content of 0.045-0.055%, a manganese content of 1.2-1.6%, a silicon content of 0.045-0.055%, a copper content of 0.08-0.12%, a sulfur content of ≤0.008%, and a phosphorus content of ≤0.01%. The core material has an impact toughness of ≥60J at -45℃.
[0013] As an optional technical solution, the high-toughness welding material mentioned in step (2) is composed of an A+B type alkaline welding flux combination, wherein the manganese oxide content in alkaline welding flux A is ≤10%, the silicon dioxide content in alkaline welding flux B is 5-15%, and the mixing mass ratio of alkaline welding flux A and alkaline welding flux B is 2-2.5:1.
[0014] As an optional technical solution, the welding method described in step (2) is multi-layer multi-pass submerged arc automatic welding (SAW), with a welding current of 450-500A, a welding voltage of 30-34V, and a welding speed of 500-550mm / min. After the first welding is completed, the weld height should be lower than the base material.
[0015] As an optional technical solution, in step (4), the welding heat input during the welding process should be ≤18KJ / cm. 2 Furthermore, the interpass temperature should be controlled between 20-80℃ during the welding process.
[0016] As an optional technical solution, in step (1), straight sections are reserved on both sides of the joint of the tube after the first rolling, and the transverse length of each straight section is 250-400mm.
[0017] A straight seam steel pipe, characterized in that: the straight seam steel pipe is manufactured by the above-mentioned straight seam steel pipe processing method.
[0018] A welding core, characterized in that: the welding core is a high-toughness, high-alloy low-carbon steel welding core material, wherein the nickel content is 3.5-4.5%, the chromium content is 0.2-0.25%, the molybdenum content is 0.15-0.20%, the carbon content is 0.045-0.055%, the manganese content is 1.2-1.6%, the silicon content is 0.045-0.055%, the copper content is 0.08-0.12%, the sulfur content is ≤0.008%, the phosphorus content is ≤0.01%, and the welding core material has an impact toughness ≥60J at -45℃.
[0019] A flux, characterized in that: the flux is a composition of alkaline flux A and alkaline flux B, wherein the manganese oxide content in alkaline flux A is ≤10%, and the silicon dioxide content in flux B is 5-15%.
[0020] As an optional technical solution, the mass mixing ratio of alkaline flux A and alkaline flux B is 2-2.5:1.
[0021] The beneficial effects of this invention are:
[0022] (1) In the technical solution of this invention, the straight seam steel pipe is formed in two stages. The first stage can be formed by RB three-roll rolling or other forming methods. However, after the first stage, the shape of the steel pipe must be an approximate "peach" shape with a certain allowance at both ends of the joint, and the transverse length of the straight edge on each side of the weld should be controlled between 250-400mm. The second stage of forming of the steel pipe must be carried out by RB three-roll rolling. During the second stage, the focus is on controlling the straight edge on both sides of the weld and eliminating the straight edge on both sides of the weld. At the same time, the inner or outer bulge of the weld is reduced to achieve precise control of the roundness of the steel pipe. In addition, the straightness of the steel pipe can also be improved during the second RB three-roll rolling process.
[0023] In conventional steel pipe rolling processes, most of them adopt a one-time rolling process. Due to the rolling process, there is always an unrolled "excess edge" at the joint after rolling. This excess edge is a defect of the traditional pipe rolling process. The traditional understanding is that the smaller the "excess edge", the better. The smaller the "excess edge" after rolling, the more advanced the rolling process and the higher the rolling performance.
[0024] However, this invention deliberately leaves straight sections of a considerable size on both sides of the joint of the rolled tube to form a cross-section of the tube after the initial rolling that is approximately "peach" shaped. Combined with the first welding process, after the first welding, a second rolling is performed to finally solve the problem of straight edges on both sides of the weld, reduce weld protrusion, and improve the roundness and straightness of the steel pipe.
[0025] (2) In the technical solution of the present invention, a secondary welding process is designed in combination with the characteristics of the secondary rolling process. The first welding adopts a specially designed high-toughness, high-alloy, low-carbon steel core material, and is combined with the multi-layer multi-pass submerged arc automatic welding (SAW) process. The straight sections reserved on both sides of the weld after the first welding process are combined to form a "complete" steel plate. After the second RB three-roll rolling, the weld inner or outer bulge that exists in the traditional steel pipe rolling process is basically perfectly avoided. At the same time, the roundness of the steel pipe is accurately controlled. In addition, the straightness of the steel pipe can also be improved during the second RB three-roll rolling process.
[0026] (3) In the technical solution of the present invention, the reason for adopting two rolling and two welding alternating settings to comprehensively improve the accuracy of steel pipe roundness, weld bead, straightness and other aspects is mainly due to two reasons. First, the traditional rolling process has a blind spot for pre-bending the plate edge at the weld. Due to the rolling equipment and process, the steel plate edge range of 50-100mm cannot be pre-bent when the steel plate is pre-bent. Only after the second rolling can the straight edge and bead on both sides of the butt weld be eliminated to a certain extent. Second, the weld reinforcement has a great influence on the steel pipe forming. If the weld reinforcement is higher than the base material, it will inevitably lead to the formation of a certain straight edge on both sides of the base material when the steel pipe is formed, and it is impossible to achieve the consistency of the forming size accuracy of the weld and the base material.
[0027] In the second forming process, in order to eliminate the influence of weld reinforcement on the forming dimensional accuracy and achieve consistency between the forming dimensions of the steel pipe weld and the base material, the second forming process is carried out.
[0028] (4) In the technical solution of the present invention, in order to ensure that the weld does not crack while being subjected to large stress deformation during the first rolling process, and to ultimately achieve the roundness of the steel pipe to meet the technical specifications, and after the first welding is completed, the weld reinforcement must be slightly lower than or flush with the base material, and there must be no undercut or lack of fusion at the fusion part of the weld and the base material, a special welding material with high toughness is designed. Through specially designed core material and flux, and combined with the use of multi-layer multi-pass submerged arc automatic welding (SAW) process, the process of alternating two rolling and two welding in the technical solution of the present invention is realized. Attached Figure Description
[0029] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0030] Figure 1 This is a schematic diagram of the structure of the steel pipe after its first rolling and forming according to the present invention;
[0031] Figure 2 This is a schematic diagram of the weld structure after the first welding of the steel pipe according to the present invention;
[0032] Figure 3 This is a schematic diagram of the steel pipe structure before the second rolling of the present invention;
[0033] Figure 4 This is a schematic diagram of the structure of the steel pipe after the second rolling of the present invention;
[0034] Figure 5 This is a schematic diagram of the weld structure after the second welding of the steel pipe according to the present invention; Detailed Implementation
[0035] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.
[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.
[0037] This invention provides a method for processing straight seam steel pipes, the method comprising:
[0038] (1) First rolling: The precast steel plate is initially rolled into a tubular shape directly using a tube rolling forming equipment. At this time, a straight section is reserved at the joint of the rolled tube. After forming, the steel pipe is approximately "peach" shaped. See [link to documentation]. Figure 1 Except for the 250-400mm straight sections reserved on both sides of the weld, the rest of the steel pipe is basically formed.
[0039] (2) For the first weld, high-toughness welding materials should be used for the steel pipe weld. The weld morphology must be strictly controlled during the first weld; the weld must not be higher than the base metal, and there should be no obvious grooves or lack of fusion at the fusion line between the weld and the base metal. See [reference needed]. Figure 2 The process employs multi-layer, multi-pass submerged arc welding (SAW) technology, in accordance with... Figure 2 The welding sequence shown is applied sequentially.
[0040] In the first welding process, the welding material used is a high-toughness, high-alloy, low-carbon steel core and an alkaline combined flux provided by this invention.
[0041] This high-toughness, high-alloy, low-carbon steel welding core material contains 3.5-4.5% nickel, 0.2-0.25% chromium, 0.15-0.20% molybdenum, 0.045-0.055% carbon, 1.2-1.6% manganese, 0.045-0.055% silicon, 0.08-0.12% copper, ≤0.008% sulfur, and ≤0.01% phosphorus. Furthermore, the welding core material is required to have an impact toughness ≥60J at -45℃.
[0042] The alkaline combined flux is a combination of alkaline flux A and alkaline flux B, wherein the manganese oxide content in alkaline flux A is ≤10%, the silicon dioxide content in flux B is 5-15%, and the mass mixing ratio of alkaline flux A and alkaline flux B is 2-2.5:1.
[0043] (3) Second rolling: The tube body that has undergone the first welding is placed into the RB three-roll forming equipment for rolling. See [link to relevant documentation]. Figure 3 .
[0044] During the second rolling process, the straight sections welded in the first round need to be rolled repeatedly. The requirement is that after the second rolling, there should be no obvious straight edges or noticeable bulges on either side of the weld seam, and the overall outline of all parts of the steel pipe should be consistent along its circumference. (See [reference needed]). Figure 4 .
[0045] (4) For the second welding, conventional welding materials and ordinary welding processes can be used to ensure that the weld morphology and performance quality meet the relevant specifications after the weld is completed.
[0046] As a preferred embodiment, the second welding can also employ a multi-layer, multi-pass submerged arc welding (SAW) process, during which the welding heat input should not exceed 18 kJ / cm². 2 During welding, the interpass temperature should be controlled between 20-80℃, and in accordance with... Figure 5 The welding sequence shown is applied sequentially.
[0047] The forming and processing method for straight seam steel pipes provided by this invention is particularly suitable for straight seam steel pipe products with stringent requirements for technical indicators such as roundness, weld bead, and straightness.
[0048] The straight seam steel pipe processing method provided by this invention can effectively eliminate the straight edges on both sides of the steel pipe weld, reduce the problem of internal or external bulges in the weld, and control the internal or external bulges in the weld within 1mm. After the steel pipe is finally formed, its roundness can be controlled within 0.4%D (D is the diameter of the steel pipe), and the straightness of every 3 meters of steel pipe can be controlled within 2mm. The table below shows the statistical results of the product dimensions of straight seam steel pipes (D1524×16mm) produced in a certain project using the processing method of this invention:
[0049] In the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0050] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0051] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.
[0052] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.
Claims
1. A method for processing straight seam steel pipes, characterized in that, Includes the following steps: (1) First rolling: The precast steel plate is initially rolled into a tubular shape directly using a tube rolling forming equipment. At this time, straight sections are reserved at the joints of the rolled tubes; (2) For the first weld, high-toughness welding materials should be used for the steel pipe weld. During the first weld, the weld morphology must be strictly controlled; the weld height should be lower than or level with the base material. There must be no obvious grooves or lack of fusion at the fusion line between the weld and the base metal; (3) Second rolling: The pipe body that has been welded for the first time is rolled into shape by the RB three-roll forming equipment. In particular, after the straight section that has been welded for the first time is rolled for the second time, there are no obvious straight edges or obvious bulges on both sides of the weld seam of the steel pipe, and the outline of all parts in the circumferential direction of the steel pipe is consistent. (4) Second welding: The weld seam of the pipe body that has been rolled a second time is welded a second time. Ensure that the weld morphology and performance quality meet the relevant specifications after the weld is completed.
2. The method for processing straight seam steel pipes as described in claim 1, characterized in that: The high-toughness welding material mentioned in step (2) has a core material of high-toughness, high-alloy low-carbon steel. The high-toughness, high-alloy low-carbon steel core material contains 3.5-4.5% nickel, 0.2-0.25% chromium, 0.15-0.20% molybdenum, 0.045-0.055% carbon, 1.2-1.6% manganese, 0.045-0.055% silicon, 0.08-0.12% copper, and sulfur content ≤ [missing information]. The content of phosphorus is ≤0.008%, and the core material has an impact toughness of ≥60J at -45℃.
3. The method for processing straight seam steel pipes as described in claim 2, characterized in that: The high-toughness welding material mentioned in step (2) is composed of an A+B type alkaline welding flux combination, wherein the manganese oxide content in alkaline welding flux A is ≤10%, the silicon dioxide content in alkaline welding flux B is 5-15%, and the mixing mass ratio of alkaline welding flux A and alkaline welding flux B is 2-2.5:
1.
4. The method for processing straight seam steel pipes as described in claim 3, characterized in that: The welding method described in step (2) is multi-layer multi-pass submerged arc automatic welding (SAW), with a welding current of 450-500A, a welding voltage of 30-34V, and a welding speed of 500-550mm / min. After the first welding is completed, the weld height should be lower than the base material.
5. The method for processing straight seam steel pipes as described in claim 4, characterized in that: In step (4), the welding heat input should be ≤18KJ / cm² during the welding process. 2 Furthermore, the interpass temperature should be controlled between 20-80℃ during the welding process.
6. The method for processing straight seam steel pipes as described in claim 1, characterized in that: In step (1), straight sections are reserved on both sides of the joint of the tube after the first rolling, and the transverse length of each straight section is 250-400mm.
7. A straight seam steel pipe, characterized in that: The straight seam steel pipe is manufactured by any one of the straight seam steel pipe processing methods according to claims 1-6.
8. A welding core, characterized in that: The welding core is a high-toughness, high-alloy low-carbon steel welding core material, wherein the nickel content is 3.5-4.5%, the chromium content is 0.2-0.25%, the molybdenum content is 0.15-0.20%, the carbon content is 0.045-0.055%, the manganese content is 1.2-1.6%, the silicon content is 0.045-0.055%, the copper content is 0.08-0.12%, the sulfur content is ≤0.008%, and the phosphorus content is ≤0.01%, and the welding core material has an impact toughness ≥60J at -45℃.
9. A flux, characterized in that: The flux is a composition of alkaline flux A and alkaline flux B, wherein the manganese oxide content in alkaline flux A is ≤10% and the silicon dioxide content in flux B is 5-15%.
10. The flux as described in claim 9, characterized in that: The mass mixing ratio of alkaline flux A and alkaline flux B is 2-2.5:1.