# US 2009/0260728 A1 · Method and installation for producing hot-rolled strip from austenitic stainless steels

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- Number: US 2009/0260728 A1
- Document ID: US20090260728A1
- Status: Published application
- Kind: A1
- Application number: 12/454,318
- Filed: 2009-05-15
- Published: 2009-10-22
- Earliest claimed: 2002-01-31
- Assignees: SMS Siemag Aktiengesellschaft
- Inventors: Ingo Schuster; Manfred Albedyhl
- Web page: https://patentgrep.com/patent/US20090260728A1

## CPC

- C21D 8/0226: {Hot rolling}
- B21B 1/26: by hot-rolling {, e.g. Steckel hot mill}
- B21B 1/466: {in a non-continuous process, i.e. the cast being cut before rolling}
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- B21B 1/18: in a continuous process
- B21B 3/02: Rolling special iron alloys {, e.g. stainless steel}
- B21B 37/74: Temperature control, e.g. by cooling or heating the rolls or the product (B21B37/32, B21B37/44 take precedence)
- B21B 45/004: {Heating the product}
- C21D 6/004: {containing Cr and Ni}
- C21D 8/021: involving particular fabrication steps or treatments of ingots or slabs
- C21D 8/0263: {following hot rolling}
- 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)
- B21B: ROLLING OF METAL (auxiliary operations used in connection with metal-working operations covered in B21, see B21C; bending by rolling B21D; manufacture of particular objects, e.g. screws, wheels, rings, barrels, balls, by rolling B21H; pressure welding by means of a rolling mill B23K20/04)

## Abstract

A method for producing hot-rolled strip from austenitic stainless steels. In a first step, a cast product is subjected to a rolling operation in a rolling mill with a finishing train, and, in a second step, a heat treatment is carried out to prevent susceptibility to corrosion, especially intergranular corrosion due to chromium carbide precipitation. To establish the final rolling temperature (Twe), a run-in temperature (Tein) of the cast product into the finishing train of the rolling mill that is above 1,150° C., and preferably above 1,200° C., is established by a multistage heating process, especially a two-stage heating process, which comprises a preheating stage and an intensive heating stage, and the heat treatment is carried out by directly utilizing the rolling heat.

## Claims

### Claim 1

Method for producing hot-rolled strip from austenitic stainless steels, in which, in a first step, a cast product (6) is subjected to a rolling operation in a rolling mill with a finishing train and, in a second step, a heat treatment is carried out to prevent susceptibility to corrosion, especially intergranular corrosion due to chromium carbide precipitation, wherein, to establish the final rolling temperature (Twe), a run-in temperature (Tein) of the cast product into the finishing train of the rolling mill that is above 1,150° C., and preferably above 1,200° C., is established by a multistage heating process, especially a two-stage heating process, which comprises a preheating stage and an intensive heating stage, and the heat treatment is carried out by directly exploiting the rolling heat.

### Claim 2 (depends on 1)

Method in accordance with claim 1, wherein the final rolling temperature (Twe) of the rolling stock (15) is adjusted to values at which complete dynamic recrystallization of the steel still occurs, and that after the last pass in the finishing train, the rolling stock (15) is quenched from the final rolling temperature (Twe) to a temperature (Ta) to prevent precipitation of chromium carbides.

### Claim 3 (depends on 2)

Method in accordance with claim 2, wherein the final rolling temperature (Twe) of the rolling stock is adjusted to temperatures above 1,000° C., and preferably above 1,050° C., and that the rolling stock is then quenched to temperatures (Ta) below 600° C., and preferably below 450° C., within 20 s.

### Claim 4 (depends on 1)

Method in accordance with claim 1, wherein the temperature of the cast product is adjusted to values of 1,000-1,150° C. in the preheating stage and is raised to values above 1,200° C. in the subsequent intensive heating zone.

### Claim 5 (depends on 1)

Method in accordance with claim 1, wherein the preheating stage is carried out in a gas-fired or oil-fired furnace (7), and the subsequent intensive heating stage is carried out in an inductive heating zone (10).

### Claim 6 (depends on 1)

Method in accordance with claim 1, wherein a descaling is carried out between the preheating stage and the intensive heating stage.

### Claim 7 (depends on 1)

Method in accordance with claim 1, wherein additional heating of the rolling stock, preferably by induction, is carried out in the last section of the finishing train (13), so that the temperature is maintained in the dynamic recrystallization range during the rolling operation.

### Claim 8 (depends on 1)

Method in accordance with claim 1, wherein the rolling stock is conveyed at the defined final rolling temperature (Twe) through a heating zone that follows the finishing train in order to continue maintaining it at temperatures at which complete recrystallization of the rolling stock occurs, and that it is quenched only subsequently.

### Claim 9 (depends on 1)

Method in accordance with claim 1, wherein the rolling heat is directly exploited to carry out the heat treatment for preventing susceptibility to corrosion on a near-net-shape cast product (6) coming from the casting heat.

### Claim 10 (depends on 1)

Method in accordance with claim 1, wherein the rolling heat is directly exploited to carry out the heat treatment for preventing susceptibility to corrosion on a rolled product that has been continuously cast and rolled on a hot wide-strip rolling train.

### Claim at position 11

-16. (canceled)