CN113543901B - Method for manufacturing seamless square steel tube - Google Patents
Method for manufacturing seamless square steel tube Download PDFInfo
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- CN113543901B CN113543901B CN202080018676.7A CN202080018676A CN113543901B CN 113543901 B CN113543901 B CN 113543901B CN 202080018676 A CN202080018676 A CN 202080018676A CN 113543901 B CN113543901 B CN 113543901B
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- square
- steel pipe
- seamless
- square steel
- pipe
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B17/00—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling
- B21B17/08—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling with mandrel having one or more protrusions, i.e. only the mandrel plugs contact the rolled tube; Press-piercing mills
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B17/00—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling
- B21B17/14—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling without mandrel, e.g. stretch-reducing mills
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/15—Making tubes of special shape; Making tube fittings
Abstract
The invention provides a method for manufacturing a seamless square steel pipe, which can reduce equipment load and simultaneously obtain a seamless square steel pipe with a corner S value equal to that of the prior art. In the method for producing a seamless square steel pipe, a square billet is perforated to form a cylindrical raw pipe, the cylindrical raw pipe is hot-rolled by a sizing mill having a plurality of square pipe forming frames to form a square pipe, the number n of square pipe forming frames in the sizing mill is 3 or more, and the external diameter reduction ratio Δr1 of the 1 st square pipe forming frame, the external diameter reduction ratio Δr2 of the 2 nd square pipe forming frame, and the external diameter reduction ratio R of the total square pipe forming frame satisfy the following formulas (1) and (2). (Deltar1+Deltar2)/R is more than or equal to 0.70 … (1) Deltar2-0.01 is less than or equal to Deltar1 is less than or equal to Deltar2+0.01 … (2).
Description
Technical Field
The present invention relates to a method for producing a seamless square steel pipe (seamless square steel pipe or tube), and more particularly to a method for producing a seamless square steel pipe capable of producing a seamless square steel pipe having a corner S value equivalent to that of the prior art while reducing the load on equipment.
Background
In recent years, square steel pipes have been used for various applications such as general structural use and construction materials. Among them, the seamless square steel pipe has a feature that it can be made thicker than the square welded steel pipe, and a high strength can be obtained. Therefore, seamless square steel pipes have been used particularly for building material applications.
As a method for manufacturing a seamless square steel pipe, a method using thermal seamless forming is proposed. In this method, first, a billet as a starting material is heated in a heating furnace, and then perforated by a perforator to prepare a cylindrical billet. Then, the cylindrical billet is treated with an elongation mill (for expanding), a mandrel mill (for elongation), a leveling mill (for grinding), etc., heated in a reheating furnace, and then hot-rolled in a sizing mill (sizing mill) to obtain a seamless square steel pipe.
Fig. 1 is a schematic view showing an example of a rolling stand configuration of a sizing mill 10 used for manufacturing a seamless square steel pipe. The sizing mill 10 is a mill in which a plurality of rolling stands are arranged in series, and a stand 11 having a roll with a circular hole pattern (caliber) is arranged in the front section (upstream side) of the sizing mill 10, and a square tube forming stand 12 having a roll with a square hole pattern is arranged in the rear section (downstream side). Then, the rolling is performed by the front stage of the frame 11 so as to have a circular cross section of a predetermined outer diameter, and then the square tube forming frame 12 of the rear stage is formed into a square cross section. The sizing mill 10 illustrated in fig. 1 is composed of 2 rolls and 8 stands, and the latter 4 stands are square tube molding stands.
In this way, since the round cross section is formed into the square cross section by roll forming, the corners of the seamless square steel pipe have a certain degree of roundness as shown in fig. 2. Further, as one of the indexes for evaluating the roundness of the corner, an S value specified as "corner dimension" in JIS G3466 is used.
Generally, from the viewpoints of designability, performance in connecting joints of beams and columns, and the like, a seamless square steel pipe is required to have a sharp corner shape, that is, a small S value. Therefore, a method for manufacturing a seamless square steel pipe having a small S value has been studied.
For example, patent document 1 proposes a method of obtaining a seamless square steel pipe having a small curvature at the corner and a flat side by controlling rolling conditions so that the external diameter reduction ratios (outside diameter reduction) of a plurality of square pipe forming frames of a sizing mill satisfy a predetermined relationship.
Further, patent document 2 proposes a method of obtaining a seamless square steel pipe having a small curvature at the corner and a flat side by controlling rolling conditions so that the reduction ratio (perimeter reduction rate) of the circumference of the first square pipe forming stand, the S value, and the wall thickness t of the shaping mill satisfy a predetermined relationship.
Technical literature
Prior art literature
Patent document 1: japanese patent laid-open No. 11-104711
Patent document 2: japanese patent laid-open No. 10-258303
Disclosure of Invention
By using the techniques proposed in patent documents 1 and 2, a seamless square steel pipe having a small S value can be obtained. However, in the conventional techniques such as patent documents 1 and 2, in order to reduce the S value, the reduction ratio (reduction in diameter) of the square tube forming stand (1 st) of the sizing mill must be made significantly larger than that of the other stands.
The solid line in fig. 3 is a line for extracting the experimental results of wall thickness t=20 to 30mm in fig. 4 of patent document 2. Here, the horizontal axis in fig. 3 represents the outside diameter reduction ratio Δr1 of the 1 st square tube molding frame, and the vertical axis (left side) represents the ratio (S/t) of the S value to the wall thickness t. The value of S/t decreases as Δr1 increases. That is, the above-described experimental results indicate that in order to reduce the S value, the outside diameter reduction ratio Δr1 of the 1 st square tube molding frame must be increased.
On the other hand, the dotted line of fig. 3 indicates the load ratio that the rolling stand is subjected to at this time. Here, the load ratio is a relative value of the load received by the rolling stand, where the load when Δr1 is 0.2 is set to 1. From this curve, it is also clear that if Δr1 is increased, S/t can be reduced, but with this, the load to which the rolling stand is subjected increases considerably.
Further, with the enlargement of the application, further increase in diameter and thickness of seamless square steel pipes have been demanded. The cross-sectional area of the steel pipe (the area of the portion occupied by the steel material in the cross-section) increases by increasing the diameter and increasing the thickness, and accordingly, the load required for rolling increases.
Therefore, in order to cope with the above-described needs for the increase in diameter and thickness, the reduction in S value is required to greatly increase the rolling load. However, since a significant increase in rolling load causes a significant increase in load on manufacturing equipment, conventional manufacturing equipment cannot cope with further increases in diameter and thickness. In order to cope with such an increase in load on manufacturing facilities, it is necessary to replace the main motor of the rolling mill with a larger capacity, and to replace the housing with a high-strength housing, and so on, which is a large-scale equipment investment.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a method for producing a seamless square steel pipe, which can produce a seamless square steel pipe having a large cross-sectional area without increasing rolling load and can realize a sufficiently small S value.
The inventors of the present invention studied the influence of the rolling load and the S value on the rolling schedule of the sizing mill in detail in order to solve the above problems. As a result, it has been found that the above problems can be solved by controlling rolling conditions based on a concept completely different from conventional techniques in which the S value is reduced by increasing Δr1 as much as possible. That is, the gist of the present invention is as follows.
1. A method for manufacturing a seamless square steel pipe comprises perforating a square billet to form a cylindrical billet, hot-rolling the cylindrical billet by a sizing mill having a plurality of square pipe molding frames to form a square pipe,
the number n of square tube forming frames of the sizing mill is more than 3,
the external diameter reduction ratio Δr1 of the 1 st square tube molding frame, the external diameter reduction ratio Δr2 of the 2 nd square tube molding frame, and the external diameter reduction ratio R of the total square tube molding frame satisfy the following formulas (1) and (2).
(Δr1+Δr2)/R≥0.70…(1)
Δr2-0.01≤Δr1≤Δr2+0.01…(2)
2. The method for producing a seamless square steel pipe according to the above 1, wherein the temperature of the rolled material is 600 to 1100 ℃ during the hot rolling of the square pipe forming machine frame.
According to the present invention, even a seamless square steel pipe having a large cross-sectional area can be manufactured without increasing rolling load, and a sufficiently small S value can be realized. Since an increase in rolling load can be suppressed, the method of the present invention can be used to produce a seamless square steel pipe having a larger cross-sectional area and a favorable corner shape, which is industrially extremely significant.
Drawings
Fig. 1 is a schematic view showing an example of a rolling stand configuration of a sizing mill used for manufacturing a seamless square steel pipe.
Fig. 2 is a schematic diagram showing the definition of the corner shape and S value of a seamless square steel pipe.
Fig. 3 is a graph showing the relationship between the ratio of the S value to the wall thickness t (S/t) and the load ratio and the outside diameter reduction ratio Δr1 of the 1 st square tube molding frame.
Detailed Description
Next, a method for carrying out the present invention will be specifically described. The following description is given of preferred embodiments of the present invention, and the present invention is not limited to the following description.
In the present invention, a square billet is perforated to form a cylindrical billet, and the cylindrical billet is hot-rolled by a setting mill having a plurality of square tube forming stands to form a square tube, thereby producing a seamless square steel tube.
The method of perforating the square billet to obtain the cylindrical billet is not particularly limited, and any method may be used. For example, the square billet may be heated in a heating furnace and then perforated by a perforator to produce a cylindrical billet. When heating is performed by the above-mentioned heating furnace, the temperature of the outlet side of the heating furnace is preferably set to 700 to 1200 ℃.
The tubular billet is preferably optionally expanded by an elongation mill, elongated by a mandrel mill, and milled by a leveling mill before the next hot rolling by a sizing mill.
Next, the cylindrical blank pipe is hot-rolled by a sizing mill having a plurality of square pipe forming frames to form a square pipe. The seamless square steel pipe having the final size and cross-sectional shape is obtained by the above-mentioned hot rolling.
As the above-mentioned sizing mill, any square-shaped forming machine can be used as long as the number n of square-shaped forming frames is 3 or more. The upper limit of the number n of square tube molding frames is not particularly limited. However, n is usually preferably 3 or 4, more preferably 4.
The number of rolls of each square tube molding frame is not particularly limited, and may be any number. However, it is generally preferably 2 or 3, more preferably 2. As shown in fig. 1, the rollers of the square tube molding frame are disposed on a surface perpendicular to the pipe direction so as to be rotated by 90 ° with respect to the rollers of the square tube molding frames adjacent to each other.
As shown in fig. 1, the sizing mill may include, for example, the following stands on the upstream side of the square tube forming stand: a frame having a roll with a circular hole pattern (circular hole pattern roll). The number of frames provided with the circular grooved roll is not particularly limited. However, it is generally preferably 3 or 4, more preferably 4.
In the present invention, it is important to control the rolling conditions so that the external diameter reduction ratio Δr1 of the 1 st square tube forming frame, the external diameter reduction ratio Δr2 of the 2 nd square tube forming frame, and the external diameter reduction ratio R of the total square tube forming frame satisfy the following formulas (1) and (2).
(Δr1+Δr2)/R≥0.70…(1)
Δr2-0.01≤Δr1≤Δr2+0.01…(2)
Here, the outer diameter reduction ratios Δr1, Δr2, and R are defined as follows.
Δr1＝(D0-D1)/D0
Δr2＝(D1-D2)/D1
R＝(D0-Dn)/D0
D0: outside diameter of tube before rolling of 1 st square tube forming frame
D1: outside diameter of rolled tube of 1 st square tube forming frame
D2: outside diameter of rolled tube of 2 nd square tube forming frame
Dn: external diameter of rolled tube of final square tube forming frame
The outer diameter of the tube before rolling in the square tube forming stand is the outer diameter of the tube on the inlet side of the stand. Similarly, the outer diameter of the rolled tube of the square tube forming stand is the outer diameter of the tube on the outlet side of the stand. Therefore, as shown in fig. 1, D0 is equal to the outer diameter of the cylindrical blank pipe before square pipe molding is performed. Dn is the distance between the outer surfaces of the flat portions facing each other in the cross section of the square steel pipe. Similarly, D1 and D2 are distances between outer surfaces of flat portions facing each other in a cross section of the steel pipe during molding.
By satisfying the relationship between the above expression (1) and expression (2), the rolling load can be reduced without increasing the S value. It is preferable that (Δr1+Δr2)/R be 0.75 or more. On the other hand, the upper limit of (Δr1+Δr2)/R is not particularly limited, but is preferably 0.85 or less, more preferably 0.83 or less.
The present invention is not particularly limited, and can be applied to the production of seamless square steel pipes having arbitrary outer diameters and arbitrary wall thicknesses. However, as described above, the problem of the load on the equipment is deeply the case of a large cross-sectional area. Therefore, the present invention can be applied particularly to the production of seamless square steel pipes having a large cross-sectional area. Specifically, the outer diameter of the manufactured seamless square steel pipe is preferably 250mm or more. The thickness of the seamless square steel pipe to be produced is preferably 25mm or more. On the other hand, the upper limit of the outer diameter and the wall thickness of the seamless square steel pipe is not particularly limited, but the outer diameter of the seamless square steel pipe is preferably 360mm or less. The wall thickness of the seamless square steel pipe is preferably 40mm or less.
The temperature of the material to be rolled in the hot rolling of the square tube molding frame is not particularly limited, and may be any temperature. However, if the temperature is 600 ℃ or higher, strain remaining due to cold working can be suppressed. Therefore, from the standpoint of material properties, it is preferable to set the temperature of the steel pipe as the material to be rolled during hot rolling to 600 ℃. On the other hand, the upper limit of the temperature is not particularly limited, and if the temperature is 1100 ℃ or lower, the generation of scale on the outer surface of the steel pipe can be suppressed. As a result, the scale is prevented from being pushed in during the square tube molding, and the occurrence of scratches can be prevented. Therefore, from the viewpoint of improving the appearance quality, the temperature is preferably 1100 ℃ or lower.
Here, the temperature of the material to be rolled refers to the surface temperature of the material to be rolled (steel pipe).
Examples
The present invention will be described in further detail with reference to examples.
A seamless square steel pipe was manufactured in the order set forth below. First, a square billet is perforated to produce a cylindrical billet tube. The cylindrical billet is heated in a heating furnace, and then hot-rolled by a shaping mill having a plurality of square tube forming frames to form a square tube, thereby producing a seamless square steel tube. In the heating, the temperature at the outlet side of the heating furnace was set at 1000 ℃.
As the sizing mill, a sizing mill having 2 square tube forming stands with double rolls was used. The upstream side of the 2 square tube forming frames is the 1 st frame, and the downstream side is the 2 nd frame.
The molding conditions (outer diameter reduction ratio) of the square tube molding frame are shown in table 1. The rolling loads of the 1 st and 2 nd stands at this time were measured, and the corner dimensions (S values) of the finally obtained seamless square steel pipes were measured. The measurement results are collectively shown in Table 1. The temperature of the rolled material during hot rolling in the square tube forming stand is 1000 to 900 ℃.
The seamless square steel pipe has an outer diameter (side length): 300mm, wall thickness t:30mm. The outer diameter D0 of the cylindrical blank tube was 418mm.
The load was determined based on the following criteria, and the results thereof are collectively shown in table 1.
Load of the 1 st rack: less than 150tonf: o (circle)
Load of the 1 st rack: 150tonf or more and less than 160tonf: and (V)
Load of the 1 st rack: 160tonf or more: x-shaped glass tube
The S value was determined based on the following criteria, and the results thereof are collectively shown in table 1.
S value: less than 30.0mm: excellent (L.) Excellent
S value: 30.0mm or more and 37.5mm or less: o (circle)
S value: exceeding 37.5mm: x-shaped glass tube
Here, 37.5mm is the wall thickness t: the standard S value of the 30mm steel pipe is set to be 0.75, and the allowable range of the S value is set to be 0.5 t. As shown in fig. 2, there are 2S values for 1 corner of the square steel pipe. Therefore, the above determination uses the total 8 arithmetic mean values of the S values of the 4 corners of the obtained seamless square steel pipe.
Comparative example No.1 adopts conventional rolling conditions in which reduction of S value is achieved by increasing Δr1 as much as possible. In this No.1, the S value is a pass determination, but the condition of the expression (2) is not satisfied, so the rolling load is extremely large. That is, when the rolling conditions are selected so that the S value becomes low based on the conventional idea, the rolling load becomes excessive and the production facility receives a significant load.
In addition, comparative example No.2 has a decrease in Δr1 as compared with No. 1. In this No.2, the S value is judged to be acceptable as in No.1, but the condition of the expression (2) is not satisfied, so the rolling load is still large.
In contrast, in invention example No.3 satisfying the conditions of the present invention, the load of the 1 st rack can be significantly reduced to about 31% as compared with comparative example No. 1. In addition, although the diameter reduction ratio of the outer diameter of the 1 st frame is greatly reduced, the increase of the S value is sufficiently suppressed to be a satisfactory level contrary to the prior art.
In comparative example No.4, Δr1 was further reduced from No. 3. No.4 satisfies the condition of formula (2), but does not satisfy the condition of formula (1). As a result, the load on the 1 st rack is low, but the S value increases greatly. From the results, it is clear that the load is reduced by simply reducing Δr1, and a good corner shape cannot be achieved. That is, in order to obtain a seamless square steel pipe having a corner S value equivalent to that of the conventional one while reducing the load on the equipment, both the conditions of formulas (1) and (2) must be satisfied.
In this way, the technique of the present invention can meet the opposite demands of reduction of the S value and suppression of the rolling load by controlling the rolling conditions based on a completely different technical idea from the conventional technique, while overcoming the prejudice of the conventional technique.
Symbol description
1. Cylindrical blank pipe
2. Seamless square steel pipe
10. Shaping mill
11. Frame with round hole pattern
12. Square tube forming frame
Claims (2)
1. A method for producing a seamless square steel pipe, wherein a square billet is perforated to form a cylindrical billet, the cylindrical billet is hot-rolled by a sizing mill having a plurality of square pipe forming frames to form a square pipe,
the number n of square tube forming frames of the sizing mill is more than 3,
the external diameter reduction ratio Deltar 1 of the 1 st square tube forming frame, the external diameter reduction ratio Deltar 2 of the 2 nd square tube forming frame and the external diameter reduction ratio R of the total square tube forming frame satisfy the following formulas (1) and (2),
(Δr1+Δr2)/R≥0.70…(1)
Δr2-0.01≤Δr1≤Δr2+0.01…(2)。
2. the method for producing a seamless square steel pipe according to claim 1, wherein the temperature of the rolled material is set to 600 to 1100 ℃ during the hot rolling of the square pipe forming machine frame.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019048291 | 2019-03-15 | ||
| JP2019-048291 | 2019-03-15 | ||
| PCT/JP2020/006235 WO2020189140A1 (en) | 2019-03-15 | 2020-02-18 | Method for manufacturing seamless square steel tube |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113543901A CN113543901A (en) | 2021-10-22 |
| CN113543901B true CN113543901B (en) | 2023-08-04 |
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| CN202080018676.7A Active CN113543901B (en) | 2019-03-15 | 2020-02-18 | Method for manufacturing seamless square steel tube |
Country Status (4)
| Country | Link |
|---|---|
| KR (1) | KR102476860B1 (en) |
| CN (1) | CN113543901B (en) |
| TW (1) | TWI731615B (en) |
| WO (1) | WO2020189140A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114733911A (en) * | 2022-04-15 | 2022-07-12 | 衡阳华菱钢管有限公司 | Pipe processing method |
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| JPH11104710A (en) * | 1997-10-03 | 1999-04-20 | Yoshitomi Onoda | Making of seamless square steel pipe |
| JPH11104711A (en) * | 1997-10-03 | 1999-04-20 | Yoshitomi Onoda | Production method for seamless square shaped steel pipe |
| CN102245320A (en) * | 2008-12-24 | 2011-11-16 | 住友金属工业株式会社 | Process for production of seamless metal pipe by cold rolling |
| JP2016196040A (en) * | 2015-04-06 | 2016-11-24 | Ｊｆｅスチール株式会社 | METHOD OF PRODUCING MARTENSITIC HIGH Cr STEEL SEAMLESS STEEL TUBE |
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| JPH04224022A (en) * | 1990-12-27 | 1992-08-13 | Nippon Steel Corp | Formation of square steel tube |
| JPH08164416A (en) * | 1994-12-12 | 1996-06-25 | Kawasaki Steel Corp | Production of forge welded square tube |
| JPH10258303A (en) | 1997-03-18 | 1998-09-29 | Kawasaki Steel Corp | Manufacture of square seamless steel tube |
| JP3308848B2 (en) * | 1997-03-24 | 2002-07-29 | 川崎製鉄株式会社 | Seamless rectangular steel pipe and method of manufacturing the same |
| JPH11123452A (en) * | 1997-10-24 | 1999-05-11 | Nkk Corp | Square tube production method from round tube |
| JP3496554B2 (en) * | 1999-01-06 | 2004-02-16 | 住友金属工業株式会社 | Manufacturing method of channel steel, rough universal rolling mill and finish universal rolling mill |
| JP2001353520A (en) * | 2000-06-14 | 2001-12-25 | Nippon Steel Corp | Forming method for square steel tube |
| JP4650747B2 (en) * | 2004-03-29 | 2011-03-16 | 住友金属工業株式会社 | Pipe manufacturing method and constant diameter rolling apparatus |
| EP1738839B1 (en) * | 2005-06-28 | 2009-08-26 | Sumitomo Metal Industries, Ltd. | Cold rolling process for metal tubes |
| AU2006312544B8 (en) * | 2005-11-11 | 2010-12-23 | Jfe Steel Corporation | Method of manufacturing electric resistance welding pipes having excellent characterization of welded seams |
| AU2006324717B2 (en) * | 2005-12-16 | 2010-09-23 | Jfe Steel Corporation | Method of manufacturing electric resistance welding pipe having excellent characterization of welded seam |
| RU2411095C2 (en) * | 2006-10-12 | 2011-02-10 | ДжФЕ СТИЛ КОРПОРЕЙШН | Equipment for producing tubes by contact welding with high-quality welded seam |
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- 2020-02-18 CN CN202080018676.7A patent/CN113543901B/en active Active
- 2020-02-18 KR KR1020217030004A patent/KR102476860B1/en active IP Right Grant
- 2020-02-18 WO PCT/JP2020/006235 patent/WO2020189140A1/en active Application Filing
- 2020-03-09 TW TW109107583A patent/TWI731615B/en active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH11104710A (en) * | 1997-10-03 | 1999-04-20 | Yoshitomi Onoda | Making of seamless square steel pipe |
| JPH11104711A (en) * | 1997-10-03 | 1999-04-20 | Yoshitomi Onoda | Production method for seamless square shaped steel pipe |
| CN102245320A (en) * | 2008-12-24 | 2011-11-16 | 住友金属工业株式会社 | Process for production of seamless metal pipe by cold rolling |
| JP2016196040A (en) * | 2015-04-06 | 2016-11-24 | Ｊｆｅスチール株式会社 | METHOD OF PRODUCING MARTENSITIC HIGH Cr STEEL SEAMLESS STEEL TUBE |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2020189140A1 (en) | 2020-09-24 |
| KR102476860B1 (en) | 2022-12-12 |
| CN113543901A (en) | 2021-10-22 |
| TW202039109A (en) | 2020-11-01 |
| TWI731615B (en) | 2021-06-21 |
| KR20210127238A (en) | 2021-10-21 |
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