A continuous rolling roller for rolling thin-walled seamless steel pipe and a manufacturing method thereof

Abstract

The present invention relates to the technical field of roll manufacturing, in particular to a continuous rolling roll for rolling thin-walled seamless steel pipes and a manufacturing method thereof. The chemical composition of a working layer and the mass percentage of each component are C 0.5-1.0%, Si 0.5-1.0%, Mn 0.5-1.0%, Cr 3.0-4.0%, Ni 0-0.5%, Mo 0.5-1.0%, P≤0.03%, S≤0.03%, and the remainder is Fe and inevitable impurities. The seamless continuous rolling roll manufactured by the present invention has high strength, high hardness, good wear resistance, and good accident resistance. After being used on a machine, there is no broken shaft or broken roll, thereby reducing the risk of rolling accidents.

Description

Technical Field

[0001] The present invention relates to the technical field of roller manufacturing, in particular to a continuous roller for rolling a thin-walled seamless steel pipe and a manufacturing method thereof. Background Art

[0002] Ultra-thin-walled tubes place higher demands on the roll's ability to withstand accidents. Conventional rolls are no longer able to meet the rolling needs of high-end seamless steel tube products. Roller and shaft breakage are common, causing significant losses and trouble for seamless steel tube manufacturers.

[0003] The present invention aims to develop a new type of forged steel roll to replace the conventional cast roll, so as to solve the problems of roll breakage and shaft breakage. Summary of the Invention

[0004] The present invention aims to develop a new type of forged steel material for seamless continuous rolling tubes used for rolling ultra-thin-wall seamless steel tubes, thereby improving the strength, hardness, uniformity, and wear resistance of the rolls and improving the accident resistance of the seamless continuous rolling rolls.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A continuous rolling roller for rolling thin-walled seamless steel pipes comprises: a working layer having the chemical composition and the mass percentage of each component being C 0.5-1.0%, Si 0.5-1.0%, Mn 0.5-1.0%, Cr 3.0-4.0%, Ni 0-0.5%, Mo 0.5-1.0%, P≤0.03%, S≤0.03%, and the remainder being Fe and unavoidable impurities.

[0007] A method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes, comprising the following steps:

[0008] Step 1: Making steel ingots. The specific steps are as follows:

[0009] Step 1.1, pig iron, scrap steel, and slag are added to an electric arc furnace in sequence according to the chemical composition requirements of each part of the new seamless continuous rolling mill to obtain molten steel;

[0010] Step 1.2: Transfer the molten steel into the LF refining ladle to make white slag, heat the deoxidizer, and adjust the final composition;

[0011] Step 1.3, transfer the LF refining bag into the VD vacuum tank and perform vacuum degassing;

[0012] Step 1.4: After vacuum degassing, transfer to the pouring station and perform argon soft blowing for 10 minutes at a pouring temperature of 1550-1570°C.

[0013] Step 2: Forging. The specific steps are as follows:

[0014] Step 2.1, placing the steel ingot into a heating furnace and heating it to 1200-1260°C;

[0015] Step 2.2, forging after exiting the furnace, using a two-stage upsetting process, requiring a forging ratio of ≥4;

[0016] Step 2.3: After the blank is formed, a stress relief annealing process at 600-700°C is performed;

[0017] Step 3, heat treatment, the specific steps are as follows:

[0018] Step 3.1, after the seamless continuous rolling roll is taken out of the furnace, it is subjected to roughing and then quenching and tempering treatment;

[0019] Step 3.2, high temperature quenching is performed on the quenched and tempered seamless continuous rolling roll, followed by three high temperature temperings;

[0020] Step 3.3: After tempering, the roll is finely processed to the finished product size to obtain a seamless continuous rolling roll.

[0021] A further improvement of the technical solution of the present invention is that in step 1.2, the white slag material is selected from silicon carbide + fluorite in a ratio of 3:1, and 2-5 kg ​​is heated per ton of steel.

[0022] A further improvement of the technical solution of the present invention is that in step 1.3, the vacuum degree is controlled below 100 Pa and maintained for 10 minutes.

[0023] A further improvement of the technical solution of the present invention is that in step 2.2, a two-stage upsetting process is adopted, and the forging ratio is ≥4.

[0024] A further improvement of the technical solution of the present invention is that in step 3.2, the high-temperature quenching process is first heating to 640-660°C and keeping it warm for 8-10 hours, and then heating to 1000-1060°C and keeping it warm for 8-10 hours.

[0025] A further improvement of the technical solution of the present invention is that in step 3.2, the three high-temperature tempering processes are to carry out the first tempering process when the continuous rolling roller furnace is cooled to 80-120°C, specifically heating from 80-120°C to 500-550°C and keeping warm for 10-12h, and then cooling to 80-120°C with the furnace; the second and third tempering processes are to repeat the first tempering.

[0026] A further improvement of the technical solution of the present invention is that the pass hardness of the prepared seamless continuous rolling roll is 60 to 70 HSD.

[0027] Due to the adoption of the above technical solution, the technical advancements achieved by the present invention are:

[0028] 1. The present invention proposes a continuous rolling roller for rolling thin-walled seamless steel pipes and a manufacturing method thereof. The seamless continuous rolling roller has high strength, high hardness, good wear resistance, and good accident resistance. After being used on the machine, there is no broken shaft or broken roller, which reduces the risk of rolling accidents.

[0029] 2. The present invention proposes a continuous rolling roller for rolling thin-walled seamless steel pipes and a manufacturing method thereof. By optimizing the smelting process parameters, the harmful elements P, S, H, O, N and other harmful elements in the roller are reduced; by optimizing the forging process parameters, the mechanical properties such as strength and toughness of the roller are further improved; by optimizing the heat treatment process parameters, the comprehensive properties such as hardness, wear resistance, and accident resistance of the roller are further improved.

[0030] 3. The present invention proposes a continuous rolling roller for rolling thin-walled seamless steel pipes and a manufacturing method thereof. The seamless continuous rolling roller is made of a new type of forged steel material, which is essentially different from the traditional cast pearlite ductile iron material; the strength of the traditional pearlite ductile iron continuous rolling roller is generally 350-450Mpa, while the material strength of the present application can reach 800-1000Mpa, and the ability to resist accidents is doubled; the prepared seamless continuous rolling roller performs well on the machine, without broken rollers, broken shafts, etc., the accident resistance is greatly improved, the wear resistance is improved by 10-20% compared with conventional materials, and the online life is increased by 20-50%. DETAILED DESCRIPTION

[0031] The present invention is described in further detail below in conjunction with the embodiments:

[0032] A continuous rolling roller for rolling thin-walled seamless steel pipes. The chemical composition of the seamless continuous rolling roller and the mass percentage of each component are C 0.5-1.0%, Si 0.5-1.0%, Mn 0.5-1.0%, Cr 3.0-4.0%, Ni 0-0.5%, Mo 0.5-1.0%, P≤0.03%, S≤0.03%, and the remainder is Fe and unavoidable impurities.

[0033] A method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes, comprising the following steps:

[0034] Step 1, steel ingot production:

[0035] Step 1.1: Pig iron, scrap steel, and slag are added to an electric arc furnace in the order specified by the chemical composition of each part of the new seamless continuous rolling mill to obtain molten steel. The purpose is to achieve decarburization and dephosphorization, so that C ≤ 0.3% and P ≤ 0.020%.

[0036] Step 1.2: The molten steel is discharged into the LF refining ladle to produce white slag and heat the deoxidizer to remove sulfur to reduce sulfur content to 0.020% or less and adjust the final product composition.

[0037] Step 1.3: Heat the LF refining bag to 1650-1680℃, transfer it to the VD vacuum tank, and perform vacuum degassing to achieve H≤1.5PPM, O≤25PPM, and N≤70PPM;

[0038] Step 1.4: After vacuum degassing, transfer to the pouring station and perform argon soft blowing for 10 minutes at a pouring temperature of 1550-1570°C to allow inclusions to float.

[0039] Step 2, forging:

[0040] Step 2.1, placing the steel ingot into a heating furnace and heating it to 1200-1260°C;

[0041] Step 2.2, forging after furnace removal, using a two-stage upsetting process with a forging ratio of ≥4, in order to refine the grains and improve their strength and toughness;

[0042] Step 2.3: After the blank is formed, a stress relief annealing process at 600-700°C is performed;

[0043] Step 3, heat treatment and processing:

[0044] Step 3.1: After the seamless continuous rolling roll is taken out of the furnace, it is subjected to roughing treatment and then quenching and tempering treatment. The quenching and tempering temperature is controlled at 850-900℃ to prepare for high temperature quenching.

[0045] Step 3.2, the seamless continuous rolling roll after quenching and tempering is subjected to high temperature quenching at a quenching temperature of 1000-1060°C, and then subjected to three high temperature temperings at a tempering temperature of 500-560°C;

[0046] Step 3.3: After tempering, the roll is finely processed to the finished product size to obtain a seamless continuous rolling roll.

[0047] Example 1

[0048] A continuous rolling roller for rolling thin-walled seamless steel pipes is used. The chemical composition of the seamless continuous rolling roller made of new forged steel and the mass percentage of each component are C 0.65%, Si 0.63%, Mn 0.82%, Cr 3.42%, Ni 0.34%, Mo 0.79%, P 0.015%, S ≤ 0.010%, and the remainder is Fe and unavoidable impurities.

[0049] A method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes, comprising the following steps:

[0050] A. Steel ingot production

[0051] A1. Pig iron, scrap steel, and offal are sequentially charged into a 30t electric arc furnace according to the chemical composition requirements of each component of the new seamless continuous rolling mill. Slag-forming materials are then added, and oxygen is blown to form slag, decarburize, and dephosphorize the slag, resulting in molten steel with a C0.1% and P0.013% content.

[0052] A2. The molten steel is transferred to an LF refining ladle, where 1 kg / t of Al deoxidizer cake is heated. 5 kg / t of lime, 2.5 kg / t of silicon carbide, and 1 kg / t of fluorite are added to create white slag, maintaining S ≤ 0.010%. The final product composition is then adjusted.

[0053] A3. Heat the LF refining bag to 1660℃, transfer it to the VD vacuum tank, and perform vacuum degassing. When the vacuum degree reaches 100 Pa, start the timer. After 10 minutes, open the vacuum valve and take a gas sample. H ≤ 1.2 PPM, O ≤ 23.8 PPM, N ≤ 68 PPM;

[0054] A4. After vacuum degassing, transfer to the pouring station and perform argon soft blowing for 12 minutes. When the temperature reaches 1563℃, open the slide and start pouring. Argon protection is implemented throughout the pouring process.

[0055] B. Forging

[0056] B1. After keeping the steel ingots at room temperature for 55 hours, unpack them and transfer them to a gas furnace, heating them to 1240°C.

[0057] B2. Forging after furnace removal is divided into two fires. In the first fire, the riser and ingot tail are removed, and a drawing process is performed. The ingot is returned to the furnace and heated to 1240℃. The second fire uses the drawing process again and corrects the blank shape. The actual forging ratio is 6.25.

[0058] B3. After the blank is formed, it is transferred to a resistance furnace and heated to 650°C for 10 hours to perform a stress relief annealing process.

[0059] C. Heat treatment and processing

[0060] C1. After the seamless continuous rolling mill is stress-relief annealed and taken out of the furnace, it is subjected to roughing. After roughing, it is subjected to quenching and tempering treatment. The quenching and tempering temperature is controlled at 880℃ to prepare for high-temperature quenching.

[0061] C2. The quenched and tempered seamless continuous rolling rolls are subjected to high-temperature quenching. The temperature is first raised to 650°C and held for 10 hours, then raised to 1030°C and held for 10 hours. After being removed from the furnace, the rolls are quenched, rapidly cooled to 300°C. The rolls are then heated to 520°C and held for 10 hours. After being removed from the furnace, they are air-cooled to 100°C for the first tempering process. The second and third tempering processes repeat the first tempering process.

[0062] C3. After the three tempering steps, the rollers are finely processed to the finished product size to obtain seamless continuous rolling rollers.

[0063] The seamless continuous rolling roller in this embodiment was used in the process of seamless ultra-thin-walled pipes and was put on the machine 20 times. During use, the shaft was broken but no cracking occurred.

[0064] Example 2

[0065] A continuous rolling roller for rolling thin-walled seamless steel pipes is used. The chemical composition of the seamless continuous rolling roller made of new forged steel and the mass percentage of each component are C 0.67%, Si 0.62%, Mn 0.80%, Cr 3.50%, Ni 0.30%, Mo 0.80%, P 0.016%, S ≤ 0.015%, and the remainder is Fe and unavoidable impurities.

[0066] A method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes, comprising the following steps:

[0067] A. Steel ingot production

[0068] A1. Pig iron, scrap steel, and offal are sequentially charged into a 30t electric arc furnace according to the chemical composition requirements of each component of the new seamless continuous rolling mill. Slag-forming materials are then added, and oxygen is blown to form slag, decarburize, and dephosphorize to produce molten steel with a C0.1% and P0.015% content.

[0069] A2. The molten steel is transferred to an LF refining ladle, where 1 kg / t of Al deoxidizer cake is heated. 5 kg / t of lime, 2.5 kg / t of silicon carbide, and 1 kg / t of fluorite are added to create white slag, maintaining S ≤ 0.015%. The final product composition is then adjusted.

[0070] A3. Heat the LF refining bag to 1665℃, transfer it to the VD vacuum tank, and perform vacuum degassing. When the vacuum reaches 100 Pa, start the timer. After 10 minutes, open the vacuum valve and take a gas sample. H ≤ 1.3 PPM, O ≤ 25 PPM, N ≤ 69 PPM;

[0071] A4. After vacuum degassing, transfer to the pouring station and perform argon soft blowing for 14 minutes. When the temperature reaches 1560℃, open the slide and start pouring. Argon protection is implemented throughout the pouring process.

[0072] B. Forging

[0073] B1. After keeping the steel ingots warm for 50 hours, unpack them and transfer them to a gas furnace, heating them to 1230°C.

[0074] B2. Forging after furnace removal is divided into two fires. In the first fire, the riser and ingot tail are removed, and a drawing process is performed. The ingot is returned to the furnace and heated to 1230℃. The second fire uses the drawing process again and corrects the blank shape. The actual forging ratio is 5.76.

[0075] B3. After forming, the blank is transferred to a resistance furnace and heated to 650°C for 8 hours for stress relief annealing.

[0076] C. Heat treatment and processing

[0077] C1. After the seamless continuous rolling mill is stress-relief annealed and taken out of the furnace, it is subjected to roughing. After roughing, it is subjected to quenching and tempering treatment. The quenching and tempering temperature is controlled at 880℃ to prepare for high-temperature quenching.

[0078] C2. The seamless continuous rolling mill rolls after quenching and tempering are subjected to high-temperature quenching. The temperature is first raised to 650°C and held at this temperature for 9 hours, then raised to 1020°C and held at this temperature for 9 hours. After being removed from the furnace, the rolls are quenched to achieve rapid cooling to 295°C. The rolls are then heated to 520°C in the furnace and held at this temperature for 9 hours. After being removed from the furnace, they are air-cooled to 102°C for the first tempering process. The second and third tempering processes are repeated for the first tempering process.

[0079] C3. After the three tempering steps, the rollers are finely processed to the finished product size to obtain seamless continuous rolling rollers.

[0080] The seamless continuous rolling roller in this embodiment was used in the process of seamless ultra-thin-walled pipes and was put on the machine 22 times. During use, the shaft was broken but no cracking occurred.

[0081] Example 3

[0082] A continuous rolling roller for rolling thin-walled seamless steel pipes is used. The chemical composition of the seamless continuous rolling roller made of new forged steel and the mass percentage of each component are C 0.66%, Si 0.66%, Mn 0.80%, Cr 3.38%, Ni 0.27%, Mo 0.78%, P 0.020%, S ≤ 0.020%, and the remainder is Fe and unavoidable impurities.

[0083] A method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes, comprising the following steps:

[0084] A. Steel ingot production

[0085] A1. Pig iron, scrap steel, and offal are sequentially charged into a 30t electric arc furnace according to the chemical composition requirements of each component of the new seamless continuous rolling mill. Slag-forming materials are then added, and oxygen is blown to form slag, decarburize, and dephosphorize the slag to produce molten steel with a C0.1% and P0.019% content.

[0086] A2. The molten steel is transferred to an LF refining ladle, where 1 kg / t of Al deoxidizer cake is heated. 5 kg / t of lime, 2.5 kg / t of silicon carbide, and 1 kg / t of fluorite are added to create white slag, maintaining S ≤ 0.020%. The final product composition is then adjusted.

[0087] A3. Heat the LF refining bag to 1659℃, transfer it to the VD vacuum tank, and perform vacuum degassing. When the vacuum reaches 100 Pa, start the timer. After 10 minutes, open the vacuum valve and take a gas sample. H ≤ 1.4 PPM, O ≤ 26 PPM, N ≤ 70 PPM;

[0088] A4. After vacuum degassing, transfer to the pouring station and perform argon soft blowing for 11 minutes. When the temperature reaches 1558℃, open the slide and start pouring. Argon protection is implemented throughout the pouring process.

[0089] B. Forging

[0090] B1. After keeping the steel ingots at room temperature for 52 hours, unpack them and transfer them to a gas furnace, heating them to 1240°C.

[0091] B2. Forging after furnace removal is divided into two fires. In the first fire, the riser and ingot tail are removed, and a drawing process is performed. The ingot is returned to the furnace and heated to 1240℃. The second fire uses the drawing process again and corrects the blank shape. The actual forging ratio is 6.24.

[0092] B3. After the blank is formed, it is transferred to a resistance furnace and heated to 650°C for 10 hours to perform a stress relief annealing process.

[0093] C. Heat treatment and processing

[0094] C1. After the seamless continuous rolling mill is stress-relief annealed and taken out of the furnace, it is subjected to roughing. After roughing, it is subjected to quenching and tempering treatment. The quenching and tempering temperature is controlled at 880℃ to prepare for high-temperature quenching.

[0095] C2. The quenched and tempered seamless continuous rolling rolls are subjected to high-temperature quenching. The temperature is first raised to 650°C and held for 10 hours, then raised to 1025°C and held for 10 hours. The rolls are then removed from the furnace for quenching, rapidly cooling to 300°C. The rolls are then heated to 520°C and held for 10 hours. After removal from the furnace, the rolls are air-cooled to 98°C for the first tempering process. The second and third tempering processes repeat the first tempering process.

[0096] C3. After the three tempering steps, the rollers are finely processed to the finished product size to obtain seamless continuous rolling rollers.

[0097] The seamless continuous rolling roller in this embodiment was used in the process of seamless ultra-thin-walled pipes and was put on the machine 21 times. During use, the shaft was broken but no cracking occurred.

[0098] The following performance test comparison data further illustrates the superior performance of this product:

[0099] Traditional product performance test data

[0100]

[0101] Performance test data of this application product

[0102]

[0103] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes, characterized in that: The steps include: Step 1: Making steel ingots. The specific steps are as follows: Step 1.1: adding pig iron, scrap steel, and slugs into an electric arc furnace in a sequence according to the chemical composition requirements of various parts of the novel seamless continuous rolling roll to obtain molten steel; the chemical composition of the working layer and the weight percentage of each component are: C 0.5-1.0%, Si 0.5-1.0%, Mn 0.5-1.0%, Cr 3.0-4.0%, Ni 0-0.5%, Mo 0.5-1.0%, P ≤ 0.03%, S ≤ 0.03%, and the remainder is Fe and unavoidable impurities; Step 1.2: Transfer the molten steel into the LF refining ladle to make white slag, heat the deoxidizer, and adjust the final composition; Step 1.3, transfer the LF refining bag into the VD vacuum tank and perform vacuum degassing; Step 1.4: After vacuum degassing, transfer to the pouring station and perform argon soft blowing for 10 minutes at a pouring temperature of 1550-1570°C. Step 2: Forging. The specific steps are as follows: Step 2.1, placing the steel ingot into a heating furnace and heating it to 1200-1260°C; Step 2.2, furnace forging, using a two-stage upsetting process, requiring a forging ratio of ≥4; Step 2.3: After the blank is formed, a stress relief annealing process is performed at 600-700℃ and kept at this temperature for 8 / 10 hours; Step 3, heat treatment, the specific steps are as follows: Step 3.1, after the seamless continuous rolling roll is taken out of the furnace, it is subjected to roughing and then quenching and tempering treatment; Step 3.2, the seamless continuous rolling roll after quenching and tempering is subjected to high temperature quenching and then three times of high temperature tempering; In step 3.2, the high temperature quenching process is to first heat the temperature to 640-660°C and keep it for 8-10 hours, then heat the temperature to 1000-1060°C and keep it for 8-10 hours; Step 3.3: After tempering, the roll is finely processed to the finished product size to obtain a seamless continuous rolling roll.

2. The method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes according to claim 1, characterized in that: In step 1.2, the white slag material is silicon carbide + fluorite, with a ratio of 3:1, and 2-5 kg ​​is heated per ton of steel.

3. The method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes according to claim 1, characterized in that: In step 1.3, the vacuum degree was controlled below 100 Pa and maintained for 10 min.

4. The method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes according to claim 1, characterized in that: In step 2.2, a two-stage piercing process is used, and the forging ratio is ≥4.

5. The method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes according to claim 1, characterized in that: In step 3.2, the three-time high-temperature tempering process is to carry out the first tempering process when the continuous rolling furnace is cooled to 80-120°C, specifically heating from 80-120°C to 500-550°C and keeping it warm for 10-12h, and then cooling to 80-120°C with the furnace; the second and third tempering processes are to repeat the first tempering.

6. The method for manufacturing a continuous rolling roller for rolling thin-walled seamless steel pipes according to claim 1, characterized in that: The seamless continuous rolling roll obtained by the manufacturing method has a pass hardness of 60 to 70 HSD.

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