WO2008061452A1

WO2008061452A1 - Roller for welding pipe mill

Info

Publication number: WO2008061452A1
Application number: PCT/CN2007/003299
Authority: WO
Inventors: Houzhi Yuan; Ning Zhang; Xingyi Liu; Ping Wang
Original assignee: Houzhi Yuan; Ning Zhang; Xingyi Liu; Ping Wang
Priority date: 2006-11-22
Filing date: 2007-11-21
Publication date: 2008-05-29
Also published as: CN101015836A; CN100423858C

Abstract

A high Cr casting iron or steel roller is applicable to a mill for rolling welded pipe. The composition of the high Cr casting iron roller contains (by wt%): 1.8-2.8% C, ≤1.0% Si, ≤1.0% Mn, ≤0.05% P, ≤0.05% S, 12-22% Cr, 0.5-3.0% Ni, 0.8-3.0% Mo, 0-0.3% Ti, 0-1.0% V, 0-1.0% Cu, 0.01-0.5% RE, and balance Fe. The composition of the high Cr casting iron roller contains (by wt%): 0.7-1.2% C, ≤1.0% Si, ≤1.0% Mn, ≤0.05% P, ≤0.05% S, 8-12% Cr, 0.5-2.0% Ni, 0.8-3.0% Mo, 0-0.3% Ti, 0-1.0% V, 0-0.8% W, 0.01-0.5% RE, and balance Fe. With the roller for welding pipe mill, as being producing by casting, the material organization of the roller is consistent throughout the roller, toughness and wear resistance are very high, thereby having a service life of 2-5 times more than a forged roller.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe ritual roll, and more particularly to a casting roll for rolling a spliced steel pipe, the material of which is cast high chrome iron or cast high chrome steel. BACKGROUND OF THE INVENTION Rolls are the main components consumed in the production of flat steel tube rolling mills. The quality and life of the rolls directly affect the quality and production efficiency of the welded steel tubes. The rolls are in direct contact with the rolling stock and complete the rolling process. While subjecting to the action of large compressive stress, it is also subject to rolling and sliding friction, and some are also affected by the chilling heat, so the wear is severe and needs to be replaced frequently. At present, there are various grades of rolls for welded steel tube rolling mills representing the international advanced level, such as X165CrMoV12KU produced by German manufacturers X165CrMoV12 or X155CrMoV12, American manufacturer D2 and SKD11, SKD61 alloy tool steel forging rolls produced by Japanese manufacturers. Domestically introduced welded steel pipe production lines such as Baosteel, Shanghai Zhongyou, Shengli Oilfield, etc., are basically used for forging rolls of alloy tool steel produced by German and Japanese manufacturers. The material used in the domestic advanced welded steel tube rolling mill is close to the above-mentioned foreign grade Cr ₁₂ MoV cold work die steel. The use of this steel has high requirements on the purity of the material, and the difficulty in forging and heat treatment is very large. Manufacturers can produce forged Cr ₁₂ MoV rolls with smaller diameters, and the yield is very low and the price is relatively expensive. Forged Cr ₁₂ MoV rolls with a diameter greater than φ 500 are currently not produced in China, and depend on imports, and there are few foreign manufacturers. The manufacturers of large-diameter forged alloy tool steel welded steel pipe are mainly Italian EURO company and Sakamoto Sanyo Seiki Co., Ltd. For domestic welding of steel pipe, the production of forged alloy tool steel such as GCr ₁₅ , 3Cr ₂ W ₈ V, Cr ₁₂ (YB/T 128 ) and 9Cr ₂ Mo is basically used. Due to many factors such as the performance of the material, the level of production technology, etc. Some of the rolls perform poorly in terms of wear resistance and the like, and in particular, they cannot adapt to the working conditions and technical requirements of the introduction of foreign rolling pipe production lines, and there is still a certain distance compared with international advanced level products. 'The above various rolls for welding steel tube rolling mills, all of which are currently used in the forged alloy tool steel process, have the following obvious shortcomings and shortcomings in the production of forging rolls:

1 The above-mentioned alloy tool steel forging roll production process is more complicated, the process is more difficult, and the process is long: usually requires steelmaking, refining, vacuum degassing, (there is also vacuum decarburization in foreign countries, the total non-metallic inclusions are required to be less than 0.10) %) Casting, forging, roughing, heat treatment, refinishing can be delivered.

2Because of the wide variety of rolls for alloy tool steel welded steel tube mills, the batch size of the same specification is too small, and only one to two pieces are required to be manufactured in the same specification. The cost of processing forgings is difficult to form die forging, and most of them are free forging. Due to the large difference between the forging blank and the actual required size, the subsequent machining volume is large, and the material utilization rate is low, generally 50 to 60%, and only 30% for individual.

'3 alloy tool steel welded steel pipe mill with large diameter rolls, in addition to the reasons mentioned in the above 1, but also because of the large volume, it is difficult to improve the internal structure of the steel through forging to achieve good performance indicators.

4 alloy tool steel welded steel pipe rolls must be heat treated to obtain the required high hardness working layer. However, the hardness of the forged steel of the alloy tool is obtained by quenching the metallographic structure. Because of the limited depth of the quenching, the formed high-hardness working layer is relatively thin, and the microstructure is uneven, resulting in a hardness gradient from the surface. In order to ensure the accuracy of the roll during the work, it is necessary to perform multiple dressing. When the wear exceeds the effective quenching layer, the hardness is greatly reduced, and the use cannot be continued, which greatly affects the service life of the roll. In the past ten years, domestic and foreign research on high chromium cast iron or high chromium cast steel new materials has made great progress. There are also examples and reports on the application of high chromium casting rolls in strip production at home and abroad, but it has not been seen yet. Reports or examples of the application of cast high chromium iron or cast high chromium steel rolls to the production of welded steel tube mills. SUMMARY OF THE INVENTION The object of the present invention is to apply a casting roll to a welded steel tube rolling mill to provide a casting High-chromium iron or cast high-chromium steel rolls, which can overcome the shortcomings of poor wear resistance, low service life and poor performance and poor performance of alloy tool steel forging rolls. It also solves the current use of welded steel tube rolling mills. The forging rolls are difficult to forge, long in process flow, and low in material utilization. The invention adopts the following technical solutions to achieve the purpose: The casting roll is used on the welded steel tube rolling mill, and the material of the roll is selected from high chromium iron or high chromium steel. The composition of the cast high chromium iron roll is (% by weight): C: 1.8-2.8%, Si: <1.0%, Mn: <1.0%, P: <0.05%, S: <0.05%, Cr: 12-22% Ni: 0.5 ~ 3.0%, Mo: 0.8-3.0%, Ti: 0 - 0.3%, V: 0~1.0%, Cu: 0~1.0%, RE: 0.01 ~ 0.5%, and the rest is Fe. The composition of the cast high chromium steel roll is (% by weight): C: 0.7-1.2%, Si: 1.0%, Mn: <1.0%, P: <0.05%, S: 0.05%, Cr: 8-12%, Ni: 0.5 - 2.0%, Mo: 0.8 to 3.0%, Ti: 0-0.3%, V: 0 to 1.0%, W: 0 to 0.8%, RE: 0.01 to 0.5%, and the balance being Fe. Compared with the prior art, the invention has the following advantages: 1. The invention adopts cast high chromium iron or cast high chromium steel roll on the welded steel tube rolling mill, especially the large diameter casting roll, and the metallographic structure is better than the forged alloy tool steel roll. To be reasonable, its strength, hardness and wear resistance are better than that of forged alloy tool steel rolls, so its use effect and service life are better than forged alloy tool steel rolls; 2 when manufacturing cast high iron or high chromium steel rolls The casting molding process has a shorter process than the forging process, simple process and low cost. 3 The casting molding process is closer to the finished roll size than the forging forming process, which can greatly reduce the processing amount and improve the material utilization rate. The cast high-chromium or high-chromium steel roll provided by the invention is made by casting, high-chromium or high-chromium steel by conventional smelting, casting, roughing, heat treatment and finishing, and is made into a cast high-chromium or high-chromium steel roll. , applied to rolling mills for rolling welded steel pipes. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side extrusion roll for welding a straight seam steel pipe. FIG. 2 is a lower roll for welding a rectangular steel pipe. 3 is an embodiment of an upper extrusion roll for welding a straight seam steel pipe. The present invention will be described in more detail below with reference to the accompanying drawings and embodiments. The invention applies a cast high chromium iron or high chromium steel roll to a welded steel tube rolling mill to replace the forged alloy tool steel rolls of different materials. The roll can be used on a straight seam welded steel pipe mill of various shapes such as a circular welded steel pipe rolling mill, a spiral welded steel pipe rolling mill, and a rectangular welded steel pipe rolling mill. The cast high chromium iron roll of the present invention has the following composition (% by weight): C: 1.8-2.8%, Si: < 1.0%, Mn: < 1.0%, P: <0.05%, S: <0.05%, Cr: 12 — 22%, Ni: 0.5 - 3.0%, Mo: 0.8 - 3.0%, Ti: 0 - 0.3%, V: 0 - 1.0%, Cu: 0~1.0%, RE: 0.01-0.5%, and the balance being Fe. The preferred composition of the cast high chromium iron roll is (% by weight): C: 1.8-2.1%, Si: <0.8%, Mn: <0.8%, P: 0.04%, S: 0.04%, Cr: 17 - 20%, Ni: 0.8 to 1.8%, Mo: 1.4 to 2.5%, Ti: 0 to 0.3%, V: 0 to 0.5%, Cu: 0 to 0.5%, RE: 0.01 to 0.2%, and the balance being Fe. The composition of the cast high chromium steel roll of the present invention is as follows (% by weight): C: 0.7-1.2%,

Si: <1.0%, Mn: < 1.0%, P: <0.05%, S: <0.05%, Cr: 8-12%, Ni: 0.5-2.0%, Mo: 0.8-3.0%, Ti: 0~0.3 %, V: 0~.1.0%, W: 0~0.8%, RE: 0.01-0.5%, and the rest are Fe. Its preferred composition is (% by weight): C: 0.9-1.1%, Si: 0.4 - 0.8%, Mn: 0.5-0.9%, P: <0.04%, S: <0.04%, Cr: 9-11%, Ni : 0.8 ~ 1.6%, Mo: 1.0 ~ 2.5%, Ti: 0~0.3%, V: 0~0.6%, W: 0~0.5%, RE: 0.01 ~ 0.2%, the rest is Fe. The present invention incorporates a rare earth alloying element RE in a cast high chromium iron or cast high chromium steel roll. The rare earth alloy elements can form sulfides, oxides and other inclusion compounds in the molten steel, and the melting point is higher than the solidification temperature of the molten steel. Therefore, the rare earth compound particles act as nucleation during the casting solidification process, thereby effectively refining the casting rolls. The crystal structure reduces the degree of dendrite, especially for high chromium cast iron or cast steel rolls. Due to the addition of rare earth elements, the grains of high chromium cast iron or high chromium cast steel rolls are refined, and the plasticity and impact toughness of high chromium cast iron or cast steel rolls are improved; the surface quality of the castings is improved, and the yield is improved. The hot cracking tendency of the rolls is reduced.

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Correction page (Article 91) The invention uses the corresponding ferroalloy, scrap steel and other raw materials for conventional smelting to obtain the required molten iron or molten steel, adopts conventional casting to obtain the required blank, and then performs conventional heat treatment and car, grinding and the like to produce a welded steel pipe rolling mill for casting. High chrome iron or cast high chrome steel rolls. Embodiment 1 Referring to FIG. 1, according to the present invention, a casting high-chromium iron roll is applied to a rolling-welded steel pipe rolling mill. In this embodiment, a set of 2 pieces of φ 530.0 welded steel pipe is manufactured by a casting production process. The side extrusion rolls for rolling mills are made of the following high chromium iron components (% by weight): C: 1.8%, Si: 0.8%, Mn: 0.8%, P: 0.038%, S: 0.034%, Cr: 13%, Ni: 1.0%, Mo: 1.4%, Ti: 0.2%, V: 0.2%, Cu: 0.5%, RE: 0.05%, and the balance being Fe. According to the above composition requirements, the raw material ratio is selected, and the raw material is smelted and cast in a medium frequency induction electric furnace to obtain a desired blank, and then subjected to heat treatment, car, grinding, etc., to produce a side extrusion roll for a welded steel pipe rolling mill. The side extrusion roll for the welded steel tube rolling mill of the first embodiment has a weight of 1657 kg/piece, a finished product weight of 1292.5 kg/piece, and a material utilization rate of 78%. Since the hole type of the embodiment is deep, that is, the outer diameter of the outer diameter is large, the maximum diameter of the two ends is φ 856 mm, the minimum diameter of the intermediate hole type concave is φ 589.63 mm, the height is 575 mm, and the inner hole is φ 330 mm, if The free forging method obtains the blank, and the material utilization rate can only reach about 50%. The finished product of the side extrusion roll of this embodiment has a hardness of HRC 59.5 ~ 62. The test life of the Φ 610 welded steel tube rolling mill introduced in China has reached and exceeded the level of the imported imported forged alloy tool steel spliced steel pipe. It has been proved by experiments that casting high-chromium iron rolls can be applied to the welded steel tube rolling mill to provide high-level and long-life casting rolls for welded steel tube rolling mills. Example 2 The shape of Example 2 is shown in Fig. 2. The following high chromium iron components (% by weight) were selected: C: 2.8%, Si: 0.6%, Mn: 1.0%, P: 0.031%, S: 0.035%, Cr: 22%, Ni: 2.5%, Mo: 2.0% , Ti: 0.1%, V: 0.3%, Cu: 0.5%, RE: 0.1%, and the rest is Fe. A set of two 500 x 500mm welded rectangular steel tube mills are used for casting. According to the above composition requirements, the ratio of raw materials is selected, and smelting and casting are carried out in a medium frequency induction furnace. The desired blank is then subjected to heat treatment, car, grinding, etc. to produce a lower roll for a welded rectangular steel tube mill. Example 2 is a lower roll for a 500 X 500 mm welded rectangular steel tube rolling mill. The weight of the blank is 3513 kg/piece, the weight of the finished product is 2780 kg/piece, and the material utilization rate is 79.1%. The maximum outer diameter (M350mm, minimum outer diameter cj) of the roll is 660mm, the height is 530mm, and the inner hole is 4350mm. In this embodiment, if the blank is obtained by free forging, the material utilization rate can only reach about 55%. The hardness of the finished product of this embodiment is HRC55 ~ 58, the experiment on the largest welded square steel tube rolling mill in China, the service life of the finished steel is more than 3 times that of the domestic forged alloy tool steel roll, and the service life after each repair can exceed More than three times that of domestic forged alloy tool steel rolls, it also exceeds the life of imported forged alloy tool steel welded steel pipe rolls. Example 3 In Example 3, a lower roll for a Φ 219 welded steel tube rolling mill was produced by a casting production process, and the composition thereof was selected from the following high chromium iron components (% by weight): C: 1.75%, Si: 0.5%, Mn: 0.7% , P: 0.037%, S: 0.035%, Cr: 17.5%, Ni: 0.8%, Mo: 0.8%, Ti: 0.2%, V: 0.4%, Cu: 0.8%, RE: 0.02%, and the balance being Fe. According to the selected ingredients, the raw material ratio is selected, and smelting and casting are performed in an intermediate frequency induction furnace to obtain a desired blank, and then heat treatment, car, grinding, etc. are performed to manufacture a lower roll for a welded steel pipe mill. The lower roll of Example 3 had a weight of 122 kg/piece, a finished product weight of 91.5 kg/piece, and a material utilization rate of 75%. Due to the complicated shape of the embodiment, the maximum diameter of the central convex portion is Φ 401.52 ιηηι, and the thickness is 106 mm, the diameter of the convex portions on both sides is φ 250 mm, the thickness of one side is 47 mm, and the inner hole is Φ 160 ΙΉΠΙ. If the blank is obtained by free forging The material utilization rate can only reach about 49%. The hardness of the finished product of this embodiment is HRC 58.8 ~ 61. The test on the Φ 250 welded steel tube rolling mill introduced in China has reached the service life of the imported forged alloy tool steel welded steel pipe. Its performance is superior to that of forged rolls and its life is higher than that of forged rolls. Example 4 In Example 4, a lower roll for a Φ 168 welded steel tube rolling mill was produced by a casting production process, and the composition thereof was selected from the following high chromium iron components (% by weight): C: 2.1%, Si: 0.8%, Mn: 0.6% , P: 0.033%, S: 0.030%, Cr: 21%, Ni: 1.8%, Mo: 2.2%, Ti: 0.3%,

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Correction page (Article 91) V: 0.5%, Cu: 0.2%, RE: 0.2%, and the balance being Fe. According to the selected components selected above, the raw material ratio is selected, and smelting and casting are performed in a medium frequency induction electric furnace to obtain a desired blank, and then heat treatment, car grinding, and the like are performed to produce a lower roll for a welded steel pipe rolling mill. The lower roll of Example 4 had a weight of 92 kg/piece, a finished product weight of 68 kg/piece, and a material utilization rate of 74%. Due to the complicated shape of the embodiment, the maximum diameter of the central protruding portion is φ 380 mm and the thickness is 86 mm, the diameter of the convex portions on both sides is φ 200 mm, the thickness of one side is 38 mm, and the inner hole is φ 160 mm. If the blank is obtained by free forging, The material utilization rate can only reach about 50%. The hardness of the finished product of this embodiment is HRC59 ~ 61. The test on the Φ 168 welded steel tube rolling mill introduced in China has reached the service life of the imported forged alloy tool steel welded steel pipe. Its performance is superior to that of forged rolls and its life is higher than that of forged rolls. Example 5 In Example 5, two extrusion rolls for a φ 168 welded steel tube rolling mill were produced by a casting production process, and the composition thereof was selected from the following high chromium iron components (% by weight): C: 2.0%, Si: 0.4%, Mn: 0.5 %, P: 0.039%, S: 0.035%, Cr: 20%, Ni: 1.5%, Mo: 2.5%, Ti: 0.3%, V: 0.3%, Cu: 0.4%, RE: 0.15%, and the balance is Fe . According to the selected components selected above, the raw material ratio is selected, and smelting and casting are performed in an intermediate frequency induction furnace to obtain a desired blank, and then heat treatment, car, grinding, and the like are performed to produce a squeeze roll for a welded steel pipe rolling mill. The extrusion roll of Example 5 had a weight of 103 kg/piece, a finished product weight of 74 kg/piece, and a material utilization rate of 72%. The maximum diameter of the roll is φ 408 ηηπι, the thickness is 105 mm, and the inner hole is Φ 155 mm. If the blank is obtained by free forging, the material utilization rate can only reach about 50%. The hardness of the finished product of this embodiment is HRC 58.8 ~ 61. The test life of the φ 168 welded steel tube rolling mill introduced in China has reached the service level of the imported forged alloy tool steel welded steel pipe. Its performance is superior to that of forged rolls and its life is higher than that of forged rolls. Example 6. The shape of Example 6 is shown in Fig. 3. For a set of 2 φ 273.1 welded steel tube mills, the upper extrusion rolls are made of the following high chromium steel components (% by weight): C: 0.9%, Si: 0.8%, Mn: 0.8%, P: 0.029%, S: 0.031%, Cr: 10%, Ni: 0.8%, Mo: 0.8%, Ti: 0.3%, V: 0.5%, W: 0.3%, RE : 0.015%, the rest is Fe. According to the above composition requirements, the raw material ratio is selected, and the raw material is smelted and cast in a medium frequency induction electric furnace to obtain a desired blank, and then heat treatment, car, grinding, and the like are performed to produce an upper extrusion roll for a welded steel pipe. The weight of the blank of Example 6 was 91.6 kg/piece, the weight of the finished product was 65.5 kg/piece, and the material utilization rate was 71.5%. In this embodiment, if the blank is obtained by free forging, the material utilization rate can only reach about 55%. The hardness of the finished product of this embodiment is HRC 55.5 ~ 57. The experiment was carried out on the domestically introduced Φ 325 welded steel tube rolling mill, and its service life reached and exceeded the level of imported forged alloy tool steel rolls. After 4 times of turning repair, the amount of turning is about 2mm, and the hardness is kept at HRC55 ~ 57 after the outer diameter is reduced by 16mm. Example 7 Example 7 is a set of 2 Φ 610 welded steel tube rolling mill upper extrusion rolls, the composition of which is selected from the following high chromium steel composition (% by weight): C: 1.2%, Si: 0.6%, Mn: 0.7% , P: 0.033%, S: 0.029%, Cr: 8%, Ni: 2.0%, Mo: 1.8%, Ti: 0.1%, V: 0.2%, W: 0.5%, RE: 0.1%, The rest is Fe. According to the above composition requirements, the raw material ratio is selected, and the raw material is smelted and cast in a medium frequency induction electric furnace to obtain a desired blank, and then heat treatment, car, grinding, and the like are performed to produce an upper extrusion roll for a welded steel pipe. The blank weight of Example 7 was 268 kg/piece, the finished product weight was 193 kg/piece, and the material utilization rate was 72%. In this embodiment, if the blank is obtained by free forging, the material utilization rate can only reach about 55%. The hardness of the finished product of this embodiment is HRC 55.5 ~ 57. Experiments were carried out on the domestically introduced Φ 610 welded steel tube rolling mill, and its service life reached and exceeded the level of imported forged alloy tool steel rolls. After 5 times of turning repair, the amount of turning is about 2mm, and the hardness is kept at HRC55 ~ 57 after the outer diameter is reduced by 20mm. Example 8 Example 8 is a set of two side squeezing rolls for a φ 610 welded steel tube rolling mill whose composition is selected from the following high chromium steel components (% by weight): C: 0.7%, Si: 0.5%, Mn: 1.0 %, P: 0.041%, S: 0.038%, Cr: 9%, Ni: 0.5%, Mo: 2.5%, Ti: 0.2%, V: 0.8%, W: 0.8%, RE: 0.08%, the rest For Fe. According to the above ingredients

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Correction page (Article 91) The raw material ratio is smelted and cast in a medium frequency induction furnace to obtain a desired blank, and then heat treatment, car, grinding, etc. are performed to produce a side extrusion roll for a welded steel pipe. Example

The weight of the blank of 8 is 5032kg/piece, the weight of the finished product is 3975kg/piece, and the material utilization rate is 79%. Since the hole type of the embodiment is 4 艮 deep, that is, the outer diameter difference is large, the maximum diameter of both ends is Φ 952.6 mm, the minimum diameter of the intermediate hole type recess is φ 600.5 mm, the height is 690 mm, and the inner hole is Φ 325ππη, If the blank is obtained by free forging, the material utilization rate can only reach about 50%. The hardness of the finished product of this embodiment is HRC 58 ~ 61. The actual inspection was carried out on the domestically introduced Φ 610 welded steel tube rolling mill, and its service life reached and exceeded the level of imported imported forged alloy tool steel rolls. Example 9 Example 9 is a set of rolls for a 500 X 500 splicing rectangular steel tube mill, the composition of which is selected from the following high chromium steel components (% by weight): C: 0.8%, Si: 1.0%, Mn: 0.5% , P: 0.037%, S: 0.034%, Cr: 11%, Ni: 1.0%, Mo: 1.0%, Ti: 0.3%, V: 1.0%, W: 0.1%, RE: 0.15%, The rest is Fe. According to the above composition requirements, the ratio of raw materials is selected, and the raw material is smelted and cast in a medium frequency induction furnace to obtain a desired blank, and then heat treatment, car, grinding, etc. are performed to produce a side extrusion roll for welded steel pipe. Example

The weight of the blank of 9 is 104kg/piece, the weight of the finished product is 73.5kg/piece, and the material utilization rate is 76%. In this embodiment, if the blank is obtained by free forging, the material utilization rate can only reach about 50%. The hardness of the finished product of this embodiment is HRC 58 ~ 61. The experiment was carried out on a 500 x 500 welded steel tube rolling mill imported from China, and its service life reached and exceeded the level of imported forged alloy tool steel rolls. Embodiment 10 Embodiment 10 is a set of two rolls of 500 X 500 welded rectangular steel tube rolling mill, the composition of which is selected from the following high chromium steel components (% by weight): C: 1.1%, Si: 0.4%, Mn: 0.9%, P: 0.038%, S: 0.036%, Cr: 12%, Ni: 1.6%, Mo: 2.0%, Ti: 0.2%, V: 0.6%, W: 0.1%, RE: 0.01%, the rest For Fe. According to the above composition requirements, the raw material ratio is selected, and smelting and casting are performed in an intermediate frequency induction electric furnace to obtain a desired blank, and then heat treatment, car, grinding, and the like are performed to produce a side extrusion roll for a welded steel pipe. Implementation The blank weight of Example 10 was 107 kg/piece, the finished product weight was 79 kg/piece, and the material utilization rate was 74%. In this embodiment, if the blank is obtained by free forging, the material utilization rate can only reach about 55%, and the outer diameter is cj 450mm and the thickness is only 75mm, and the forging is difficult. The hardness of the finished product of this embodiment is HRC 58 ~ 61. The experiment was carried out on a 500 x 500 welded steel tube rolling mill imported from China, and its service life reached and exceeded the level of imported forged alloy tool steel rolls. After many experiments, the present invention selects high chromium iron or high chromium steel as the material for the roll of the welded steel tube rolling mill. Due to its good alloying material ratio, the casting rolls can obtain a uniform metallographic structure inside and outside, thereby obtaining consistent strength, hardness and wear resistance. The invention overcomes the shortcomings of the foregoing alloy tool steel forging rolls because the thickness of the hardened layer is limited, the surface and the inner structure are uneven, and the hardness gradient is formed, which is difficult to meet the practical use requirements. The production process is simple, the production cycle is short, and the production cost is also low. The invention is used on a welded steel tube rolling mill. Because of its material structure, the wear resistance and toughness are greatly improved, the strength reaches 6 _b > 500 MPa, the hardness reaches HRC 55 ~ 65, and the service life is doubled. The disposable service life of the invention can reach 2~3 times of the domestic forged alloy tool steel welded steel pipe roll, and the service life after each repair can reach 2~3 times of the domestic forged alloy tool steel roll, and can reach More than Germany, Italy, Japan and other international advanced level forged alloy tool steel spliced steel pipe roll life, after grinding many times lower production costs.

Claims

Claim

1. A roll for a welded steel tube rolling mill, characterized in that a casting roll is used on a welded steel tube rolling mill, and the material of the roll is high chromium iron or high chromium steel.

2. A cast high chromium iron roll for a welded steel tube rolling mill, characterized in that the composition of the cast high chromium iron roll is (% by weight): C: 1.8-2.8%, Si: < 1.0%, Mn: < 1.0%, P : <0.05%, S: <0.05%, Cr: 12~22%, Ni: 0.5 - 3.0%, Mo: 0.8 ~ 3.0%, Ti: 0~0.3%, V: 0~1.0%, Cu: 0~ 1.0%, RE: 0.01 ~ 0.5%, the rest is Fe.

3. A cast high chromium iron roll according to claim 2, characterized in that the preferred composition of the cast high chromium iron roll is (% by weight): C: 1.8-2.1%, Si: 0.8%, Mn: < 0.8%, P: <0.04%, S: <0.04%, Cr: 17-20%, Ni: 0.8 - 1.8%, Mo: 1.4-2.5%, Ti: 0-0.3%, V: 0 - 0.5%, Cu: 0 - 0.5%, RE: 0.01 - 0.2%, the rest is Fe.

4. A cast high chromium steel roll for a welded steel tube rolling mill, characterized in that the composition of the cast high chromium steel roll is (% by weight): C: 0.7-1.2%, Si: < 1.0%, Mn: <1.0%, P : <0.05%, S: <0.05%, Cr: 8~12%, Ni: 0.5 ~ 2.0%, Mo: 0.8 ~ 3.0%, Ti: 0-0.3%, V: 0~1.0%, W: 0~ 0.8%, RE: 0.01 ~ 0.5%, the rest is Fe.

5. A cast high chromium steel roll for a welded steel tube rolling mill according to claim 4, characterized in that the preferred composition of the cast high chromium steel roll is (% by weight): C: 0.9-1.1%, Si: 0.4 - 0.8%, Mn: 0.5-0.9%, P: <0.04%, S: <0.04%, Cr: 9-11%, Ni: 0.8-1.6%, Mo: 1.0-2.5%, Ti: 0-0.3%, V: 0 ~0.6%, W: 0 ~ 0.5%, RE: 0.01-0.2%, and the rest is Fe.

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Correction page (Article 91)