Method for repairing a roll of a spiral type rolling mill
By repairing worn rolls through steps such as annealing, machining, vacuum furnace heating, and quenching, the problem of roll damage has been solved, rolls can be recycled, production costs have been reduced, and rolling efficiency and quality have been improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANGANG MINING MASCH MFG CO LTD
- Filing Date
- 2024-02-29
- Publication Date
- 2026-06-05
AI Technical Summary
Rolls are easily damaged during the rolling process, resulting in high consumption and production costs. Existing technologies are insufficient to effectively repair them and reduce consumption and costs.
The worn rolls are repaired by a combination of annealing, machining, vacuum furnace heating, isothermal quenching and low temperature tempering to ensure that the spiral die is consistent with the original and to improve hardness and wear resistance.
By repairing the rolls, the utilization rate of the rolls is improved, the production cost is reduced, the rolling efficiency and quality are enhanced, and the rolling volume is close to that of new rolls.
Smart Images
Figure CN118046176B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of round steel rolling into balls, specifically relating to a method for repairing rolls in a rolling mill. Background Technology
[0002] A steel ball rolling mill, also known as a spiral skew rolling mill, typically consists of a pair of rolls, a pair of guide plates, two sets of bearing seats, axial adjustment devices, radial adjustment devices, tilt adjustment devices, and a stand. Its working principle is as follows: two rolls with spiral holes have their axes intersecting. The rolls rotate in the same direction. Round steel enters from the mill's inlet end and, under the action of the rolls, both rotate and advance, rolling into a spherical or cylindrical shape. The radial distance between the center points of the two rolls can be adjusted. As the rolls wear down, the center point distance needs to be adjusted using an adjusting base to ensure the shape of the rolled balls.
[0003] Rolls are the most important tools in the ball forging process. They are the tools that cause round steel to undergo plastic deformation and form balls. They are also important consumable components that determine the efficiency of the rolling mill and the quality of ball forging.
[0004] Currently, rolling mill rolls mainly bear the effects of dynamic and static loads, wear, and temperature changes during rolling. During use, they are subjected to bending, twisting, shearing, contact stress, and thermal stress, making them extremely prone to damage and resulting in high consumption. They are the main consumable parts of rolling mills, and the rolling mill rolls of ball forging mills are primary consumables, leading to high production costs. Summary of the Invention
[0005] This invention aims to reduce the consumption of rolling mill rolls by repairing used rolls and enabling them to be reused, thereby improving roll utilization and reducing production costs. A repair method for spiral skew rolling mill rolls is proposed.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows:
[0007] A method for repairing a spiral skew rolling mill roll includes the following steps:
[0008] 1) Anneal the worn rolls by heating them at a rate of 80~100℃ / h to 750-850℃, holding them at that temperature for 3-6 hours, and then slowly cooling them in the furnace to reduce the surface hardness of the rolls to below HRC35.
[0009] 2) Re-machine the annealed roll hole surface to ensure that the re-machined spiral die is consistent with the spiral die before wear;
[0010] 3) After machining, the roll is heated in a vacuum furnace at a heating rate of 40-50℃ / h to 550-650℃, held at that temperature for 1.5-2.5 hours, then heated at a heating rate of 40-80℃ / h to 820-860℃, held at that temperature for 1.5-2.5 hours, and then heated at a heating rate of 40-100℃ / h to 1000-1050℃, held at that temperature for 1.0-1.2 min / mm; wherein, the holding time is proportional to the radius of the roll.
[0011] 4) After the rolls come out of the furnace, they are quickly immersed in water and isothermal quenched at 200-250℃ to obtain rolls with a hardness greater than HRC60 in the spiral die section and a hardness greater than HRC56 in the roll body.
[0012] 5) Perform low-temperature vacuum tempering at 160-180℃ on the isothermal quenched rolls for 3-6 hours.
[0013] Furthermore, the roll is made of hot work die steel, comprising the following components by weight: C 0.33-0.43%, Si 0.60-0.90%, Mn ≤0.65%, Cr 2.80-3.30%, W 1.20-1.80%, Mo 2.50-3.0%, S ≤0.03%, P ≤0.035%.
[0014] Furthermore, in step 1), when the wear of the spiral groove of the worn roll is 25%-50% higher than that of the spiral groove of the unworn roll, it is repaired.
[0015] Furthermore, in step 2), the sum of the amount of remachining of the rolls and the amount of wear after use is sufficient to ensure that the axial distance between the two rolls is within the adjustable range of the radial distance between the two roll bases, thus ensuring that the two rolls can mesh normally during use after installation.
[0016] Compared with the prior art, the advantages of the present invention are:
[0017] Spiral skew rolling mill rolls have high requirements for hardness and wear resistance, with a roll surface hardness greater than HRC60. In addition, the rolls must be impact-resistant, have strong biting ability, and have a high surface finish. At the same time, the rolls' machinability must be guaranteed. Therefore, the requirements for roll repair methods are also higher.
[0018] 1. The roll to be repaired is heated slowly at a rate of 80~100℃ / h to prevent excessive deformation of the roll, reduce hardness, and facilitate processing.
[0019] 2. The rolls of the spiral skew rolling mill are processed in three dimensions simultaneously, and need to be re-processed using a CNC machining center lathe to ensure the accuracy of the processing dimensions.
[0020] 3. Using a vacuum furnace for slow heating can prevent deformation and oxidation of the processed rolls, ensure roll precision, avoid re-finishing, and save processing costs.
[0021] 4. Isothermal quenching is adopted, which can make the spiral hole on the surface of the roller body have the characteristics of high strength, wear resistance, impact resistance and small deformation, and the roller body itself also has high strength.
[0022] 5. Low-temperature tempering is used to eliminate roll stress and stabilize the microstructure. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the roll structure of a spiral skew rolling mill;
[0024] Figure 2 This is a schematic diagram showing the installation of the rolls on a spiral skew rolling mill.
[0025] 1. Machine base; 2. Rolls; 3. Spiral die type. Detailed Implementation
[0026] The embodiments of the present invention employ medium-frequency electric furnace annealing, CNC machining center lathe processing, vacuum electric furnace quenching and tempering.
[0027] The repair method for spiral skew rolling mill rolls of the present invention includes the following steps:
[0028] 1) Anneal the worn rolls by heating them at a rate of 80~100℃ / h to 750-850℃, holding them at that temperature for 3-6 hours, and then slowly cooling them in the furnace to reduce the surface hardness of the rolls to below HRC35.
[0029] 2) Re-machine the annealed roll hole surface to make the re-machined spiral die shape consistent with the spiral die shape before wear;
[0030] 3) After machining, heat the rolls in a vacuum furnace at a heating rate of 40~50℃ / h to 550-650℃, hold at that temperature for 1.5~2.5 hours, then heat at a heating rate of 40~80℃ / h to 820-860℃, hold at that temperature for 1.5~2.5 hours, and then heat at a heating rate of 40~100℃ / h to 1000-1050℃, holding at that temperature for 1.0~1.2 min / mm.
[0031] 4) After the rolls come out of the furnace, they are quickly immersed in water and isothermal quenched at 200-250℃ to obtain rolls with a hardness greater than HRC60 in the spiral die section and a hardness greater than HRC56 in the roll body.
[0032] 5) Perform low-temperature vacuum tempering at 160-180℃ on the isothermal quenched rolls for 3-6 hours.
[0033] The specific implementation method is as follows: Example
[0034] This embodiment of a method for repairing a spiral skew rolling mill roll includes the following steps:
[0035] The φ80 ball roll has a radius of 235mm and a roll hole height of 40mm. After rolling 1160 tons of steel balls, the top of the spiral hole wears off by 12mm. The roll comprises the following components by weight: C 0.39%, Si 0.68%, Mn 0.55%, Cr 3.1%, W 1.32%, Mo 2.8%, S 0.016%, P 0.019%.
[0036] The worn roll was placed in an electric furnace and heated to 800±10℃ at a rate of 100℃ / h, held for 3 hours, and then slowly cooled in the furnace. After cooling, the surface hardness was measured to be HRC30.5. The roll was then machined on a CNC lathe, with the radial direction towards the axis of the roll surface being machined to restore the original helical bore shape. The diameter of the machined roll was reduced by 34mm compared to the original new roll. The machined roll was then placed in a vacuum furnace for heat treatment. It was slowly heated at a rate of 50℃ / h to 650℃ and held at that temperature for 2 hours. Then, it was slowly heated to 850℃ at a rate of 50℃ / h and held for 2 hours. Finally, it was slowly heated to 1030±10℃ at a rate of 50℃ / h and held for 4.7 hours (235mm x 1.2min / mm ÷ 60). Finally, it was isothermally quenched at 200-250℃. After isothermal quenching, the rolls undergo low-temperature vacuum tempering at 180℃ for 4 hours. The hardness of the helical die is HRC61.2, and the roll body hardness is HRC58. The helical die of the rolls can be polished before use. Rolls repaired using this process can roll more than 1100 tons of steel balls, which is similar to the rolling capacity of new rolls.
[0037] Example 2
[0038] This embodiment of a method for repairing a spiral skew rolling mill roll includes the following steps:
[0039] The φ20 ball roll has a radius of 150mm and a bore height of 8mm. After rolling 160 tons of steel balls, the top of the spiral bore wears off by 2.5mm. The roll comprises the following components by weight: C 0.38%, Si 0.65%, Mn 0.58%, Cr 3.3%, W 1.31%, Mo 2.6%, S 0.015%, P 0.031%.
[0040] The worn roll was heated to 760±10℃ at a rate of 100℃ / h and held for 3 hours. It was then slowly cooled in the furnace, and the surface hardness was measured to be HRC32 after cooling. The roll was then machined, with deep machining along the radial direction based on the worn spiral die to recreate the original spiral die. The diameter of the machined roll was reduced by 10mm compared to the original new roll. The machined roll was then placed in a vacuum furnace for heat treatment. It was heated to 600℃ at a rate of 40℃ / h and held isothermally for 2 hours. The temperature was then increased to 820℃ at a rate of 60℃ / h and held for 2 hours. Finally, it was heated to 1020±10℃ at a rate of 60℃ / h and held for 2.5-3 hours. Finally, it underwent isothermal quenching at 200-250℃. After isothermal quenching, the rolls undergo low-temperature vacuum tempering at 160℃ for 3 hours, achieving a hardness of HRC61.8 for the bore and HRC58.3 for the roll body. The rolls are then polished to create a spiral bore before use. Rolls repaired using this process can roll over 150 tons of steel balls, similar to the rolling capacity of new rolls.
[0041] Example 3
[0042] This embodiment of a method for repairing a spiral skew rolling mill roll includes the following steps:
[0043] The φ100 ball roll has a radius of 300mm and a roll hole height of 50mm. After rolling 1400 tons of steel balls, the top of the spiral hole wears off by 16mm. The roll contains the following components by weight: C 0.40%, Si 0.71%, Mn 0.59%, Cr 3.08%, W 1.26%, Mo 2.95%, S 0.016%, P 0.039%.
[0044] The worn roll was heated to 840±10℃ at a rate of 80℃ / h and held for 6 hours, then slowly cooled in the furnace. After cooling, the surface hardness was measured to be HRC29.5. The roll was then machined, with deep machining along the radial direction based on the worn spiral die to recreate the original spiral die. The diameter of the machined roll was reduced by 42mm compared to the original new roll. The machined roll was then heat-treated in a vacuum furnace, slowly heated at a rate of 50℃ / h to 600℃ and held for 2 hours, then heated to 850℃ at a rate of 80℃ / h and held for 2 hours, then heated to 1050±10℃ at a rate of 100℃ / h and held for 5-6 hours, followed by isothermal quenching at 200-250℃. After isothermal quenching, the roll underwent low-temperature vacuum tempering at 180℃ for 4 hours, achieving a die hardness of HRC62 and a roll body hardness of HRC58.2. The spiral die was then polished before use. The rolls repaired using this process can roll more than 1,300 tons of steel balls, which is similar to the rolling capacity of the original rolls.
Claims
1. A method for repairing the rolls of a spiral skew rolling mill, characterized in that, Includes the following steps: 1) Anneal the worn rolls by heating them at a rate of 80~100℃ / h to 750-850℃, holding them at that temperature for 3-6 hours, and then slowly cooling them in the furnace to reduce the surface hardness of the rolls to below HRC35. 2) Re-machine the annealed roll hole surface to make the re-machined spiral die shape consistent with the spiral die shape before wear; 3) After machining, the roll is heated in a vacuum furnace at a heating rate of 40-50℃ / h to 550-650℃, held at that temperature for 1.5-2.5 hours, then heated at a heating rate of 40-80℃ / h to 820-860℃, held at that temperature for 1.5-2.5 hours, and then heated at a heating rate of 40-100℃ / h to 1000-1050℃, held at that temperature for 1.0-1.2 min / mm; wherein, the holding time is proportional to the radius of the roll. 4) After the rolls come out of the furnace, they are immersed in water and subjected to isothermal quenching at 200-250℃ to obtain rolls with a hardness greater than HRC60 in the spiral die section and a hardness greater than HRC56 in the roll body. 5) Perform low-temperature vacuum tempering at 160-180℃ on the isothermal quenched rolls for 3-6 hours.
2. The repair method for spiral skew rolling mill rolls according to claim 1, characterized in that, The rolls are made of hot work die steel, comprising the following components by weight: C 0.33-0.43%, Si 0.60-0.90%, Mn ≤0.65%, Cr 2.80-3.30%, W 1.20-1.80%, Mo 2.50-3.0%, S ≤0.03%, P ≤0.035%.
3. The repair method for spiral skew rolling mill rolls according to claim 1, characterized in that, In step 1), when the wear of the spiral groove of the worn roll is 25%-50% higher than that of the spiral groove of the unworn roll, it is repaired.
4. The repair method for spiral skew rolling mill rolls according to claim 1, characterized in that, In step 2), the sum of the amount of remachining of the rolls and the amount of wear after use is such that the distance between the centerlines of the two rolls is within the adjustable range of the radial distance between the two roll bases.