Method for preventing surface quenching, cooling, shoulder falling and cracking of recycled supporting roller

Abstract

The invention discloses a method for preventing surface quenching, cooling, shoulder separation and cracking of a recycled supporting roller, which comprises the following steps of: before surface quenching, controlling the coverage range of water mist to be 200-500mm greater than the length of a roller body; during surface quenching cooling, the opening degree of the two nozzles on the outermost side is controlled to be 10%-70%, the opening degree of the two nozzles on the secondary outer side is controlled to be 30%-90%, and the opening degree of the other nozzles is 100%; and after surface quenching cooling is conducted for 70-150 min, the two nozzles on the outermost side are closed firstly, and the final cooling temperature of the two ends of the roller body is controlled to range from 150 DEG C to 350 DEG C. According to the method, through reasonable arrangement of the distribution of the nozzles and the distance between the nozzles and the surface of the roller body of the cyclic regeneration supporting roller, full coverage of quenching and cooling can be achieved, sufficient transformation of the end face structure of the roller body is guaranteed, the strength of the end face position of the roller body is improved, and quenching and cooling shoulder falling and cracking of the surface of the cyclic regeneration supporting roller are prevented.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycled support rolls, and particularly relates to a method for preventing shoulder cracking during surface quenching and cooling of recycled support rolls. Background Art

[0002] Large forged steel support rolls are important components in rolling mills, used to support work rolls or intermediate rolls to prevent the work rolls from flexing and deforming, which may affect the output and quality of plates and strips. The quality characteristics of large forged steel support rolls are high hardness on the roll body surface, good hardness uniformity, deep hardened layer on the roll body, and good strength and toughness in the roll neck and the core of the roll body. The performance characteristics of large forged steel support rolls are high wear resistance, good spalling resistance, and strong accident resistance.

[0003] When large forged steel support rolls are used until they reach the normal scrapped size, there will still be a relatively large weight and relatively large size specifications remaining. If they are directly disposed of as scrap steel, it will cause great waste of resources. Recycled support rolls can, through a series of technical treatments on scrapped support rolls (i.e., old support rolls), reach the service performance of new rolls again, thus realizing the recycling and maximizing the value of used rolling rolls.

[0004] Currently, during surface quenching and cooling of conventional large forged steel support rolls, the range covered by water mist is controlled to be less than 100 mm within the roll body length [see Chinese Patent Document CN105087877A]. See Figure 1 , the two outermost nozzles 22' on the quenching spraying equipment are arranged within the two end faces 11' of the large forged steel support roll 10', and the opening degrees of the two outermost nozzles 22' and all the intermediate nozzles 21' are 100%.

[0005] However, due to the poorer compactness and uniformity of the microstructure within the surface quenching layer of the roll body of recycled support rolls compared to conventional large forged steel support rolls, when using the conventional surface quenching and cooling method, there is a problem of insufficient strength at both end faces of the roll body, resulting in accidents of shoulder cracking at both ends of the roll body during the surface quenching and cooling process. Summary of the Invention

[0006] The purpose of the present invention is to solve the above problems and provide a method for preventing shoulder cracking during surface quenching and cooling of recycled support rolls.

[0007] The technical solution for achieving the purpose of the present invention is: a method for preventing shoulder cracking during surface quenching and cooling of recycled support rolls, which has the following steps: S1. Before surface quenching and cooling, control the range covered by water mist to be greater than 200 - 500 mm within the roll body length [i.e., 100 - 250 mm on each side].

[0008] S2. During surface hardening and cooling, control the opening degrees of the two outermost nozzles at 10% - 70%, the opening degrees of the two nozzles on the second outermost side at 30% - 90%, and the opening degrees of the remaining nozzles at 100%.

[0009] S3. After surface hardening and cooling for 70 - 150 minutes, first close the two outermost nozzles, and control the final cooling temperature at both ends of the roll body at 150 - 350 °C.

[0010] In the above step S1, setting the two outermost nozzles on the spray quenching equipment 50 - 180 mm outside both end faces of the recycled support roll can ensure that the range covered by the water mist is controlled to be greater than 200 - 500 mm of the roll body length.

[0011] In the above step S1, the distance between the nozzle and the surface of the roll body of the recycled support roll is 300 - 900 mm, which can ensure that the water mist ejected from each nozzle can be superimposed and covered.

[0012] In the above step S2, control the opening degrees of the two outermost nozzles at 20% - 60%, and the opening degrees of the two nozzles on the second outermost side at 40% - 80%.

[0013] In the above step S2, control the opening degrees of the two outermost nozzles at 30% - 50%, and the opening degrees of the two nozzles on the second outermost side at 50% - 70%.

[0014] The positive effects of the present invention: The method of the present invention can achieve full coverage of quenching and cooling by reasonably setting the distribution of the nozzles and the distance between the nozzles and the surface of the roll body of the recycled support roll, ensure full transformation of the structure at both ends of the roll body, thereby improving the strength at the end positions of the roll body, and preventing shoulder cracking during surface hardening and cooling of the recycled support roll. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of nozzle coverage during surface hardening and cooling of an existing conventional large forged steel support roll.

[0016] Figure 2 It is a schematic diagram of nozzle coverage during surface hardening and cooling of the recycled support roll of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] (Example 1) Refer to Figure 2 , the method for preventing shoulder cracking during surface hardening and cooling of the recycled support roll in this embodiment is as follows: S1. Before surface hardening and cooling, symmetrically set the two outermost nozzles 23 on the spray quenching equipment 100 mm outside both end faces 11 of the recycled support roll 10, that is Figure 2In the middle, L = 100 mm, which can ensure that the range covered by the water mist is controlled to be greater than the roll body length by 300 - 350 mm [150 - 175 mm on each side], ensuring full coverage cooling of the outer circumference and end face of the roll body during spray quenching cooling.

[0018] At the same time, the distance between the nozzle and the surface 12 of the roll body of the circulating and regenerative support roll 10 is controlled within 500 - 600 mm, that is Figure 2 In the middle, H = 500 - 600 mm, ensuring that the water mist ejected from each nozzle can be superimposed and covered.

[0019] S2. During surface hardening cooling, the opening degrees of the two outermost nozzles 23 are controlled at 40%, the opening degrees of the two sub-outermost nozzles 22 are controlled at 60%, and the opening degrees of the remaining nozzles 21 are 100%.

[0020] By controlling the opening degrees of the nozzles, the cooling intensity at both sides of the roll body can be effectively controlled.

[0021] S3. After surface hardening cooling for 100 min, first close the two outermost nozzles 23, and control the final cooling temperature at both ends of the roll body at 250 ± 10 °C, thereby improving the safety during the quenching cooling process.

[0022] During the entire quenching cooling process, the measurement and recording of the axial movement amount are carried out every 5 min, and the axial movement amount is controlled within the range of 0 mm - 80 mm. If the axial movement amount is greater than the required control range, the supporting rollers reverse, and then the axial movement amount during the quenching cooling process is controlled to ensure that the entire roll body is within the spray quenching coverage range during the quenching cooling process.

Claims

1. A method for preventing the surface of a recycled support roller from peeling and cracking during quenching and cooling, characterized in that The following steps are involved: S1. Before surface quenching and cooling, the range covered by the water mist should be controlled to be 200-500mm larger than the roller length; S2. During surface quenching and cooling, the opening and closing degree of the two outermost nozzles is controlled at 10% to 70%, the opening and closing degree of the two second outermost nozzles is controlled at 30% to 90%, and the opening and closing degree of the remaining nozzles is 100%; S3. After the surface quenching cooling is carried out for 70 to 150 minutes, the two outermost nozzles are closed first, and the final cooling temperature of the two ends of the roller body is controlled at 150 to 350°C.

2. The method for preventing the surface of the recycled support roller from being peeled off and cracked during quenching and cooling according to claim 1 is characterized in that: In the above step S1, the two outermost nozzles on the quenching equipment are arranged 50 to 180 mm outside the two end surfaces of the recycling support roller.

3. The method for preventing the surface of the recycled support roller from being peeled off and cracked during quenching and cooling according to claim 1 is characterized in that: In the above step S1, the distance between the nozzle and the surface of the recycling support roller body is 300-900 mm.

4. The method for preventing the surface of a recycled backup roller from being debonded and cracked during quenching and cooling according to claim 1 is characterized in that: In the above step S2, the opening and closing degrees of the two outermost nozzles are controlled within a range of 20% to 60%, and the opening and closing degrees of the two second outermost nozzles are controlled within a range of 40% to 80%.

5. The method for preventing the surface of the recycled support roller from being debonded and cracked during quenching and cooling according to claim 4 is characterized in that: In the above step S2, the opening and closing degrees of the two outermost nozzles are controlled within a range of 30% to 50%, and the opening and closing degrees of the two second outermost nozzles are controlled within a range of 50% to 70%.

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