A method of recycling a titanium alloy coil rolling mill roll

Abstract

The application discloses a method for recycling and rolling titanium alloy coil rolls, and belongs to the field of roll remanufacturing.The method comprises the following steps: taking a 55Cr medium-carbon alloy forged steel roll as a main shaft, setting a double-transmission end on the main shaft, fusing wear-resistant welding material on the main shaft to form a working layer, performing passivation treatment on the working layer, rolling the titanium alloy coil roll, designing a primary rolling pass on the roll, rolling the roll, repairing and transforming the roll according to the position of the roll after rolling wear, transforming the surface pass of the roll after rolling wear, continuing to roll the roll after transforming the surface pass into a secondary rolling pass, turning the working layer as a whole to leave the main shaft, fusing the main shaft, and repeating the above steps.The method can effectively roll the titanium alloy coil and reduce the rolling cost per ton.

Description

Technical Field

[0001] This invention relates to the field of roll remanufacturing, and in particular to a method for recycling rolled titanium alloy coil rolls. Background Technology

[0002] With the continuous development of aerospace and medical technologies, titanium alloy products are increasingly in demand due to their advantages such as high strength, high wear resistance, high temperature resistance, and light weight. Titanium alloy bars and coils are widely used in the production of aero-engines and medical devices. Due to the high wear resistance of titanium alloys, the roll hardness, wear resistance, and rolling volume required for roll forming are subject to strict requirements. Billets produced by conventional forging often contain numerous "impurity bubbles" due to the high temperature and oxide scale during forging. While this has no impact on ordinary steel, it is considered substandard for aerospace materials. Research shows that titanium alloy coils and bars rolled using low-temperature rolls exhibit better internal microstructure. In actual production, due to the different dimensions of the bars before and after rolling, generally, φ1150, φ850, and φ650 rolling mills are sufficient for most bar rolling tasks. However, due to the relatively low hardness and high wear resistance of titanium alloys, steel sticking often occurs during rough rolling, and roll pass wear is severe during finish rolling, resulting in significant roll wear. The current roughing rolls are generally made of 60CrMnMo, which is relatively expensive.

[0003] Therefore, a method for recycling rolling mill rolls for titanium alloy coils and bars is needed. This method involves purchasing low-cost forged steel rolls as the main shaft and depositing a high-performance material that is non-adhesive and has good wear resistance as the wear-resistant working layer. By repeatedly depositing and remanufacturing the material, the method can save on roll purchases, avoid the use of rigidity, and continuously roll titanium alloys, effectively maintaining production progress and ensuring production results. Furthermore, the deposited working layer can be fully utilized through welding and cutting, further reducing costs. Summary of the Invention

[0004] The technical problem this invention aims to solve is to provide a method for recycling rolling mill rolls for titanium alloy coils. It has solved the problem of choosing the right forged steel material for the rolling spindle of titanium alloy coils and bars, ensuring long-term use and maintaining good straightness despite repeated machining, turning, and heat treatment. Simultaneously, it has developed a welding material with better wear resistance and better "steel removal" (non-adhesion) properties, and maximized the utilization of the working layer made from the welding material to reduce costs.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for recycling rolling mill rolls for titanium alloy coils, the specific steps of which are as follows:

[0006] Step 1: Select low-cost 55Cr medium carbon alloy forged steel rolls as the main shaft for rolling titanium alloy coil rolls;

[0007] Step 2: Configure the spindle with dual drive ends;

[0008] Step 3: Apply wear-resistant welding material to the spindle to form a working layer;

[0009] Step 4: Passivate the working layer with concentrated sulfuric acid to form an antioxidant layer on the surface; the rolling of titanium alloy coil rolls is completed;

[0010] Step 5: Design the rolling pass pattern on the surface of the rolling titanium alloy coil roll in a comprehensive manner, and set the roughing large pass pattern and the finishing small pass pattern in descending order from the drive end to the non-drive end;

[0011] Step 6: Roll the titanium alloy coil using multiple rolls with pre-designed die patterns;

[0012] Step 7: After rolling for a period of time, if the wear of the rolling pass exceeds 20mm, reverse the position of the rolls and repair the surface pass as needed; continue rolling after repair.

[0013] Step 8: After rolling for a period of time, if the wear of the repaired primary rolling pass exceeds 20mm, repair and machine the surface pass as needed to convert it into a secondary rolling pass; continue rolling after conversion.

[0014] Step 9: After rolling for a period of time, if the wear of the secondary rolling hollow core exceeds 20mm, the working layer is scrapped. The entire welded working layer is machined, leaving the spindle. The spindle is then welded again, and steps 3-8 are repeated to achieve continuous rolling of titanium alloy coils and recycling of the rolls. A further improvement of the technical solution of this invention is that the 55Cr medium carbon alloy forged steel roll used as the spindle in step 1 meets the first-level ultrasonic testing standard of JB / T5000.15-2007.

[0015] A further improvement to the technical solution of the present invention is that: the dual transmission end setting in step 2 is specifically as follows: the two ends of the 55Cr medium carbon alloy forged steel roll, which serves as the main shaft, are transmission ends and non-transmission ends adapted to the rolling mill. The dimensions of the transmission end and the non-transmission end are different. A plum blossom support ring is set with the same outer diameter as the transmission end and the inner diameter adapted to the outer diameter of the non-transmission end. After the non-transmission end is fitted with the plum blossom support ring, its dimensions are consistent with those of the transmission end.

[0016] A further improvement of the technical solution of the present invention is that: the chemical composition and weight percentage of the wear-resistant welding material in step 3 are as follows: C 0.18-0.22%, Mn 1-1.6%, Si 0.2-0.35%, P≤0.03%, S≤0.03%, Cr 0.3-0.5%, Mo 0.25-0.5%, Ni≤0.7%, Bo<0.03%, and the remainder are unavoidable impurities.

[0017] A further improvement of the technical solution of the present invention is that: in step 4, the thickness of the passivation layer after passivation exceeds 2 mm.

[0018] A further improvement of the technical solution of the present invention is that: in steps 5 and 8, the size of each hole in the secondary rolling pass is larger than the size of each hole in the primary rolling pass.

[0019] A further improvement to the technical solution of the present invention is that step 7 specifically includes:

[0020] Step 7.1: Remove the rolled titanium alloy coil rolls from the rolling mill;

[0021] Step 7.2: Repair the worn roughing mill large pass on the working layer by sequential small-area welding, and transform it into the corresponding finishing mill small pass;

[0022] Step 7.3: The worn finish rolling pass on the working layer is directly machined into the corresponding rough rolling pass by turning.

[0023] Step 7.4: After attaching the plum blossom support ring to the non-drive end, connect it to the drive end of the rolling mill to realize the position change of the roll.

[0024] A further improvement to the technical solution of this invention is that step 8 specifically includes:

[0025] Step 8.1: Remove the rolled titanium alloy coil rolls from the rolling mill;

[0026] Step 8.2: Repair and machine each hole of the primary rolling pass on the roll to transform it into a secondary rolling pass with a larger hole size.

[0027] Step 8.3: Install the modified rolls onto the machine.

[0028] The technological advancements achieved by this invention, due to the adoption of the above technical solutions, are as follows: By selecting 55Cr medium-carbon alloy forged steel rolls as the main shaft, the overall cost-effectiveness is highest, the price is moderate, and the product service life can exceed 300,000 cycles. Through adjustments to the metal composition of the fused layer and metal passivation reaction, the problems of steel adhesion and significant die wear during the rolling of titanium alloy coils and bars are solved. The dual-drive-end main shaft design, with the addition of a perforated support ring, enables roll interchangeability, increasing the utilization rate of the roll working layer. Combined with the roughing and finishing die interchangeability and turning-processing fused layer solution, the utilization rate of the fused metal layer (working layer) is maximized, reducing the cost per ton of rolling. This improves roll service life and reduces the cost per ton of rolling. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the rolling pass pattern of the rolls in this invention;

[0031] Figure 2 This is a schematic diagram of the secondary rolling pass of the rolls in this invention; Detailed Implementation

[0032] The present invention will be further described in detail below with reference to embodiments:

[0033] A method for recycling rolling mill rolls for titanium alloy coils, comprising the following specific steps:

[0034] Step 1: Select low-cost 55Cr medium carbon alloy forged steel rolls as the spindle for rolling titanium alloy coils; conduct a detailed survey of the use of forged steel support rolls, covering 12 materials with diameters between φ500-1200mm and rolling temperatures between 800-1100℃. This operating condition is basically consistent with the rolling temperature of titanium alloy bars. Ultimately, 55Cr medium carbon alloy forged steel rolls were determined to have the highest overall cost-effectiveness, moderate price, and a product service life exceeding 300,000 cycles. To ensure the stability of the forged steel spindle, ultrasonic testing must meet the JB / T5000.15-2007, Level 1 testing standard.

[0035] Step 2: Configure the main shaft with dual drive ends. The 55Cr medium carbon alloy forged steel roll used as the main shaft is a conventional roll with drive ends and non-drive ends adapted to the rolling mill. The drive ends and non-drive ends have different dimensions, so an additional plum blossom support ring is installed. The outer diameter of the support ring is the same as that of the drive end, and the inner diameter is adapted to the outer diameter of the non-drive end. After the plum blossom support ring is fitted onto the non-drive end, its dimensions are consistent with those of the drive end. This achieves the dual drive end configuration.

[0036] Step 3: The wear-resistant welding material is deposited onto the spindle to form a working layer. By adjusting the Cr and Ni content in the wear-resistant welding material, five types of high-Cr and low-Ni welding materials are prepared based on the original wear-resistant welding material. Simulated steel adhesion tests, wear resistance tests, and passivation layer measurements are conducted using high-temperature rollers. Finally, one wear-resistant welding material is determined to have no steel adhesion problem and the best wear resistance. The chemical composition and weight percentage of the wear-resistant welding material are: C 0.18-0.22%, Mn 1-1.6%, Si 0.2-0.35%, P≤0.03%, S≤0.03%, Cr 0.3-0.5%, Mo 0.25-0.5%, Ni≤0.7%, Bo<0.03%, with the remainder being unavoidable impurities.

[0037] Step 4: Passivate the working layer with concentrated sulfuric acid to form an anti-oxidation layer on the surface; the rolling of titanium alloy coils is completed; due to the low hardness and high wear resistance of titanium alloy, its bars are prone to sticking during rolling. By controlling the billet at a low temperature through a water cooling system, an anti-oxidation layer is formed on the surface of the rolls through a metal passivation reaction, which can reduce the problem of metal sticking; at the same time, the anti-oxidation layer produced by the passivation reaction also has a certain degree of wear resistance, and the passivation layer thickness exceeds 2mm. The combination of welding material preparation and passivation layer can effectively solve the problem of metal sticking.

[0038] Step 5: Design the primary rolling pass pattern comprehensively on the surface of the rolling mill rolls for titanium alloy coils. Arrange the large roughing pass pattern and the small finishing pass pattern sequentially from largest to smallest, from the drive end to the non-drive end. The specific structure of the primary rolling pass pattern is as follows: Figure 1 As shown, from the drive end to the non-drive end, there are square coarse rolling large-diameter holes and circular fine rolling small-diameter holes, respectively.

[0039] Step 6: Roll the titanium alloy coil using multiple rolls with pre-designed pass patterns; the rolling mill uses, for example... Figure 1 The multiple rolls shown are used to roll the titanium alloy coil in a combined process.

[0040] Step 7: After rolling for a period of time, if the surface of the working layer of the rolls shows wear and the wear of the rolling pass exceeds 20mm in a single pass, reverse the roll positions and repair the surface pass as needed; after repair, continue rolling; from Figure 1It is known that the non-drive end has a smaller pass size and a thicker working layer, resulting in less wear during rolling and a greater amount of retained working layer material. Therefore, to fully utilize the thicker working layer at the non-drive end, the original unrolled position is utilized by swapping the roll positions. The small finish pass on the original non-drive end is then machined into a large rough pass on the original drive end without additional welding, allowing for further rolling and full utilization of the working layer. The specific steps are as follows:

[0041] Step 7.1: Remove the rolled titanium alloy coil rolls from the rolling mill;

[0042] Step 7.2: Repair the worn roughing mill large pass on the working layer by sequential small-area welding, and transform it into the corresponding finishing mill small pass;

[0043] Step 7.3: The worn finish rolling pass on the working layer is directly machined into the corresponding rough rolling pass by turning.

[0044] Step 7.4: After attaching the plum blossom support ring to the non-drive end, connect it to the drive end of the rolling mill to realize the position change of the roll.

[0045] Step 8: After rolling for a period of time, if the wear on the working layer surface of the roll exceeds 20mm after repair, the surface roll pass is repaired and machined as needed to convert it into a secondary rolling pass; rolling continues after the conversion; the secondary rolling pass is as follows. Figure 2 As shown in the figure, the dimensions of each hole in the secondary rolling pass are larger than those in the primary rolling pass. Therefore, the worn working layer of the primary rolling pass is still relatively thick after rolling, allowing for the modification of the secondary rolling pass to create a larger pass. The specific steps are as follows:

[0046] Step 8.1: Remove the rolled titanium alloy coil rolls from the rolling mill;

[0047] Step 8.2: Repair and machine each hole of the primary rolling pass on the roll to transform it into a secondary rolling pass with a larger hole size.

[0048] Step 8.3: Install the modified rolls onto the machine.

[0049] Step 9: After rolling for a period of time and undergoing multiple modifications, the working layer on the spindle is almost completely depleted. After the wear from the secondary hollow rolling exceeds 20mm, the working layer is scrapped. The remaining working layer is machined as a whole, leaving only the spindle. The working layer is then deposited onto the spindle, and steps 3-8 are repeated to achieve continuous rolling of titanium alloy coils and recycling of the rolls. The design allows a single spindle to be remanufactured and used more than 30 times, significantly reducing roll procurement costs.

[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for recycling rolling mill rolls for titanium alloy coils, characterized in that: The specific steps are as follows: Step 1: Select low-cost 55Cr medium carbon alloy forged steel rolls as the spindle for rolling titanium alloy coil rolls; Step 2: Configure the spindle with dual drive ends; Step 3: Apply wear-resistant welding material to the spindle to form a working layer; Step 4: Passivate the working layer with concentrated sulfuric acid to form an antioxidant layer on the surface; the rolling of titanium alloy coil rolls is completed; Step 5: Design the rolling pass pattern on the surface of the rolling titanium alloy coil roll in a comprehensive manner, and set the roughing large pass pattern and the finishing small pass pattern in descending order from the drive end to the non-drive end; Step 6: Roll the titanium alloy coil using multiple rolls with pre-designed die patterns; Step 7: After rolling for a period of time, if the wear of the rolling pass exceeds 20mm, reverse the position of the rolls and repair the surface pass as needed; continue rolling after repair. Step 8: After rolling for a period of time, if the wear of the repaired primary rolling pass exceeds 20mm, repair and machine the surface pass as needed to convert it into a secondary rolling pass; continue rolling after conversion. Step 9: After rolling for a period of time, if the wear of the secondary rolling pass exceeds 20mm, the working layer is scrapped. The entire working layer is machined to leave the spindle, and then the spindle is welded again. Repeat steps 3-8 to achieve continuous rolling of titanium alloy coils and recycling of the rolls.

2. The method for recycling rolling mill rolls for titanium alloy coils according to claim 1, characterized in that: The 55Cr medium carbon alloy forged steel rolls used as the main shaft in step 1 met the first-class testing standard of JB / T5000.15-2007 through ultrasonic testing.

3. The method for recycling rolling mill rolls for titanium alloy coils according to claim 1, characterized in that: In step 2, the dual-drive end setup is as follows: the two ends of the 55Cr medium carbon alloy forged steel roll, which serves as the main shaft, are drive ends and non-drive ends adapted to the rolling mill. The drive ends and non-drive ends have different dimensions. A plum blossom support ring with the same outer diameter as the drive end and an inner diameter adapted to the outer diameter of the non-drive end is set. After the plum blossom support ring is fitted onto the non-drive end, its dimensions are consistent with those of the drive end.

4. The method for recycling rolling mill rolls for titanium alloy coils according to claim 1, characterized in that: The chemical composition and weight percentage of the wear-resistant welding material in step 3 are as follows: C 0.18-0.22%, Mn 1-1.6%, Si 0.2-0.35%, P≤0.03%, S≤0.03%, Cr 0.3-0.5%, Mo 0.25-0.5%, Ni≤0.7%, Bo<0.03%, and the remainder are unavoidable impurities.

5. A method for recycling rolling mill rolls for titanium alloy coils according to claim 1, characterized in that: In step 4, the thickness of the passivation layer after passivation exceeds 2 mm.

6. The method for recycling rolling mill rolls for titanium alloy coils according to claim 1, characterized in that: In steps 5 and 8, the size and depth of each hole in the secondary rolling pass are greater than those in the primary rolling pass.

7. A method for recycling rolling mill rolls for titanium alloy coils according to claim 3, characterized in that: Step 7 specifically includes: Step 7.1: Remove the rolled titanium alloy coil rolls from the rolling mill; Step 7.2: Repair the worn roughing mill large pass on the working layer by sequential small-area welding, and transform it into the corresponding finishing mill small pass; Step 7.3: The worn finish rolling small pass on the working layer is directly machined into the corresponding rough rolling large pass by turning. Step 7.4: After attaching the plum blossom support ring to the non-drive end, connect it to the drive end of the rolling mill to realize the position change of the roll.

8. A method for recycling rolling mill rolls for titanium alloy coils according to claim 6, characterized in that: Step 8 specifically includes: Step 8.1: Remove the rolled titanium alloy coil rolls from the rolling mill; Step 8.2: Repair and machine each hole of the primary rolling pass on the roll to transform it into a secondary rolling pass with a larger hole size; Step 8.3: Install the modified rolls onto the machine.

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