# US 12,760,381 B2 · Method for manufacturing equal-hardness CR5 back up roll

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- Number: US 12,760,381 B2
- Document ID: US12760381B2
- Status: Granted
- Kind: B2
- Application number: 18/336,062
- Filed: 2023-06-16
- Published: 2023-10-19
- Granted: 2026-10-13
- Earliest claimed: 2020-12-16
- Assignees: Sinosteel Xingtai Machinery & Mill Roll Co., Ltd.
- Applicants: Sinosteel Xingtai Machinery & Mill Roll Co., Ltd.
- Inventors: Di Liu; Yudong Yang; Weiguo Han; Junxin Su
- Web page: https://patentgrep.com/patent/US12760381B2

## CPC

- C21D 1/25: Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
- B21J 1/003: {Selecting material}
- B21J 1/04: Shaping in the rough solely by forging or pressing
- C21D 8/10: during manufacturing of tubular bodies
- C21D 9/38: for roll bodies
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- B21J: FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES (rolling of metal B21B; making particular products by forging or pressing B21K; cladding or plating B23K; finishing surfaces by hammering B23P9/04; compacting surfaces by blasting with particulate material B24C1/10; general features of presses, presses for consolidating scrap B30B; furnaces in general F27)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

The present disclosure discloses a method for manufacturing an equal-hardness Cr5 back up roll. The method comprises the following steps: 1) preparing a steel raw material according to chemical components and weight percentage contents in a Cr5 back up roll material, and preparing a steel ingot according to a smelting procedure production process; 2) preparing a roller blank from the steel ingot according to a forging procedure production process; 3) performing thermal treatment on the roller blank; and 4) processing and detecting the roller blank to obtain an equal-hardness forged steel back up roll. The present disclosure solves problems that a hardness, an abrasion resistance, and a contact fatigue of a conventional forged steel back up roll are rapidly reduced in a middle and later use period, and prolongs a comprehensive use period and a service life of the back up roll.

## Claims

### Claim 1

A method for manufacturing an equal-hardness Cr5 back up roll, comprising the following steps:
1) Preparing steel raw materials according to chemical components in weight percentages for a Cr5 back up roll, and obtaining a steel ingot according to a smelting procedure production process;
2) Preparing a roller blank from the steel ingot according to a forging procedure production process;
3) Performing thermal treatment on the roller blank; and
4) Processing and detecting the roller blank to obtain the equal-hardness Cr5 back up roll;
wherein the thermal treatment of the roller blank in step 3) comprises the following specific steps:
(1) preheating: preheating the processed roller blank in a trolley furnace at a preheating temperature in a range of 400~500° C., and heat-preserving the roller blank for 10~20 h;
(2) transferring the preheated roller blank into an induction-type differential-temperature quenching device, wherein the induction-type differential-temperature quenching device has a surface temperature measurement precision of 0.1° C. and a surface temperature uniformity of ≤2° C., rapidly heating a steel blank to 950~1,050° C. in the induction-type differential-temperature quenching device at a speed of 15~20° C./min, and heat-preserving the steel blank for 100~150 min;
(3) transferring the heated roller blank into a quenching device with a continuously controllable cooling speed for quenching, opening a pipeline by adjusting an electromagnetic valve, simultaneously detecting a flow rate and a pressure of the pipeline according to a flowmeter and a pressure gauge respectively, wherein the roller blank is rapidly cooled within an initial 20~30 min, water cooling is used in the rapid cooling stage, the flow rate is controlled to be 300~600 cubic meters/hour, then the flow rate is reduced, and the flow rate is controlled to be 150~250 cubic meters/hour, such that a working layer is a fully quenched martensite structure; and
(4) tempering the quenched roller blank at a tempering temperature in a range of 300~500° C.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the chemical components in weight percentages for the Cr5 back up roll are:
0.40%~0.70% of C, 0.20%~0.80% of Si, 0.20%~0.80% of Mn, 4.00%~5.00% of Cr, 0.20%~0.60% of Ni, 0.10%~0.80% of Mo, 0.10%~0.50% of V, P≤0.015%, S≤0.015%, and the balance Fe and an inevitable impurity.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the chemical components in weight percentages for the Cr5 back up roll material are:
0.55%~0.60% of C, 0.40%~0.45% of Si, 0.35%~0.38% of Mn, 4.50%~5.00% of Cr, 0.20%~0.60% of Ni, 0.60%~0.70% of Mo, 0.20%~0.30% of V, P≤0.015%, S≤0.010%, and the balance Fe and an inevitable impurity.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the smelting procedure for the steel ingot in step 1) comprises the following specific steps:
A. smelting the steel raw materials by using an electric arc furnace and a ladle furnace, testing chemical components and weight percentages of molten steel in the ladle furnace, and performing degassing in vacuum after the molten steel is tested to be qualified; and
B. injecting molten iron into a steel ingot mold in a vacuum environment to form the steel ingot.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the steel ingot is heated and preserved for a period of time before the forging procedure in step 2), then transferred to an 80MN oil press for forging, and prepared into a forging blank through upsetting and drawing-out forging; during the forging process, methods of high-temperature forging, medium-temperature forging, and low-temperature forging are used; and the forging blank is turned after being subjected to a post-forging thermal treatment to obtain a fine-grain roller blank.

### Claim 6 (depends on 5)

The method according to claim 5, wherein
the steel ingot is heated at a temperature in a range of 1,200~1,300° C. before the forging for 20~30 h; and during the forging process, the high-temperature forging is performed at a temperature in a range of 1,100~1,300° C.; the medium-temperature forging is performed at a temperature in a range of 900~1,100° C.; and the low-temperature forging is performed at a temperature in range of 750~900° C.

### Claim 7 (depends on 5)

The method according to claim 5, wherein the post-forging thermal treatment comprises the following specific processes: the forging blank is heated to 750~850° C., preserved for 10~20 h, then cooled to 680~720° C., preserved for 30~40 h, and then annealed.

### Claim 8 (depends on 1)

The method according to claim 1, wherein a surface hardness and a hardness drop of a roller body are detected by using a D-type mechanical Shore hardness tester in step 4), a hardness within 80 mm of a surface of the roller body is in a range of 60~75 HS, a hardness uniformity is ≤2 HS, a working layer is detected according to a metallographic detection method, and a metallographic structure within 80 mm of the surface of the roller body is a quenched tempered martensite structure.