KR20120057221A - Austenitic stainless steel and Method of manufacturing it - Google Patents

Abstract

According to the present invention, in the cold rolling process of the material, the cold rolling process includes a TRM (tandom rolling mill) rolling step and a ZRM (zendsimir rolling mill) rolling step, wherein the ZRM rolling step has an initial rolling reduction of 9% to It relates to an austenitic stainless steel having a good surface shape, including 15% and having a total number of passes of 5 to 9 times, and a method of manufacturing the same.

Description

Austenitic stainless steel and method of manufacturing the same

The present invention relates to a method for producing austenitic stainless steel, and more particularly to a method for producing austenitic stainless steel that can control the shape of the thin object.

Stainless steel is an alloy steel resistant to corrosion by adding elements having strong corrosion resistance and heat resistance such as alloys (nickel (Ni) and chromium (Cr)) to iron. Such stainless steels can be broadly divided into ferrite, austenite, martensite and duplex systems according to their composition. Among these, the most commonly used steels are iron-chromium ferritic stainless steels and iron-nickel-chromium austenitic stainless steels.

Ferritic stainless steel dissolves a lot of chromium in a body-centered cubic crystal, which is a crystal system of iron at room temperature, and protects the inside by forming both oxide films of iron and chromium on the surface when oxidized.

Typically ferritic stainless steel contains at least 13% chromium. In addition, steel containing 12 to 13% of low chromium is called martensite stainless steel because it becomes martensite by quenching. The austenitic stainless steel is stabilized to room temperature by adding a large amount of nickel and chromium to a face-centered cubic crystal that is stable at 900 to 1400 ° C of iron.

In the conventional manufacturing method of austenitic stainless steel, winding defects such as coils are crushed in the cold rolling annealing process frequently occur, and the production time is increased to deal with this, and it is difficult to implement a continuous process. there was.

An object of the present invention devised to solve the above problems is to provide an austenitic stainless steel having no surface defects in the cold rolling annealing process.

Another object of the present invention is to provide a method for producing austenitic stainless steel using a novel cold rolling process without surface defects.

According to a feature of the present invention for achieving the object as described above, the present invention in the cold rolling process of the material, the cold rolling process TRM (tandom rolling mill) rolling step and ZRM (zendsimir rolling mill) rolling step The ZRM rolling step relates to a method for producing an austenitic stainless steel having excellent surface shape, including an initial rolling reduction of 9% to 15% and a total number of passes of 5 to 9 times.

The TRM rolling step may be made of first to fourth stands.

In addition, the rolling reduction rate of the first stand of the TRM rolling step may be 22% to 28%, and the reduction ratio of the second to fourth stands may be 20% to 25%.

The ZRM rolling step may be characterized in that the rolling speed is performed at 150 m / min to 250 m / min.

The ZRM rolling step may be performed after the TRM rolling step.

In the ZRM rolling step, the initial reduction ratio is 12%, and the total number of passes may be performed nine times.

The material may be composed of 8% to 10.5% by weight of Ni, 18% to 20% of Cr, 0.08% of C, 1.0% or less of Si, 2.0% or less of Mn, and the remainder of Fe.

The cold rolling process of the material may further include an annealing process, and the annealing process may be performed after the cold rolling process.

In addition, the present invention in the process of cold-rolling the material material consisting of 8 to 10.5% by weight, 18 to 20% Cr, 0.08% or less, 0.0% or less Si, 2.0% or less Mn, 2.0% or less, Fe is composed of, The cold rolling may include a TRM (tandom rolling mill) rolling step and a ZRM (zendsimir rolling mill) rolling step, wherein the ZRM rolling step has an initial rolling reduction of 9% to 15%, and a total number of passes is performed 5 to 9 times. The present invention relates to an austenitic stainless steel having excellent surface shape.

According to the present invention as described above, it is possible to provide an austenitic stainless steel that is easy to control the shape of the thin film without any defects.

In addition, according to the present invention it is possible to provide a method for producing austenitic stainless steel capable of controlling the shape of the thin metal using a novel cold rolling process.

1 is a schematic flowchart of a method of manufacturing austenitic stainless steel according to a preferred embodiment of the present invention.
Figure 2a is a schematic diagram of a tandom rolling mill (TRM) rolling step.
Figure 2b is a schematic view of the ZRM (zendsimir rolling mill) rolling step.
3A is a view showing a coil form of austenitic stainless steel in which false odor is generated according to a comparative example;
Figure 3b is a view showing the coil form of austenitic stainless steel according to a preferred embodiment of the present invention.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms. In the following description, it is assumed that a part is connected to another part, But also includes a case in which other elements are electrically connected to each other in the middle thereof. In the drawings, parts not relating to the present invention are omitted for clarity of description, and like parts are denoted by the same reference numerals throughout the specification.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

In the manufacturing method of the austenitic stainless steel according to the preferred embodiment of the present invention in the cold rolling process of the material, the cold rolling process includes a TRM (tandom rolling mill) rolling step and ZRM (zendsimir rolling mill) rolling step The ZRM rolling step includes a method for producing an austenitic stainless steel having an excellent surface shape including an initial rolling reduction of 9% to 15% and a total number of passes of 5 to 9 times.

1 is a schematic flowchart of a method for producing austenitic stainless steel according to a preferred embodiment of the present invention, Figure 2a is a schematic diagram of a tandom rolling mill (TRM) rolling step, Figure 2b is a ZRM (zendsimir rolling mill) rolling step Schematic diagram of.

The method for producing austenitic stainless steel according to the present invention includes a process of cold rolling a material material, and the cold rolling process may include both a TRM rolling step and a ZRM rolling step.

Referring to FIG. 1, the austenitic stainless steel having an excellent surface shape is subjected to a cold rolling process (S2) of a hot rolled thin material (S1), and an intermediate material having undergone the cold rolling process (S3) is subjected to a pickling annealing process (S4). It can be produced by cold rolled material (S4).

In general, austenitic stainless steel may be first manufactured by hot rolling a slab to produce a hot rolled thin material, and then cold rolled the hot rolled thin material to produce a cold rolled thin material. The cold rolled material thus produced may be sold to the outside by surface treatment or the like to have a predetermined physical property. In this case, the cold rolling process is a process for more precisely adjusting the physical properties such as the thickness and surface gloss of the hot-rolled thin material, it may be carried out by one or more of the TRM rolling step or ZRM rolling step.

In the conventional cold rolling process, the cold rolling process is performed as a single process using only the ZRM rolling step. After performing the cold rolling process, the austenitic stainless steel formed by the annealing pickling process is wound and formed in a coil form. . At this time, surface defects such as coils crushed and wound frequently occurred during winding. The present invention was performed in conjunction with the TRM rolling step and the ZRM rolling step in order to prevent such a surface defect, and optimized each TRM rolling step and ZRM rolling step. In addition, the cold rolling process of the material may further comprise an annealing pickling process, the annealing pickling process may be performed after the cold rolling process.

The manufacturing method of the austenitic stainless steel according to the present invention may include both a TRM rolling step and a ZRM rolling step in the cold rolling process, by adjusting the conditions to perform rolling in each rolling step, the austenitic stainless steel having excellent surface quality Stainless steel can be produced.

Referring to FIG. 2A, the TRM rolling step 100 constituting the cold rolling process includes a working roll 110, an intermediate roll 120, and a backup roll each having a thin material 10 therebetween. 130) may include a stand. In addition, the TRM rolling step 100 may be made of the first to fourth stands (100a, 100b, 100c, 100d).

The material 10 may be rolled through the first stand 100a and continuously passed through the second, third and fourth stands 100b, 100c, and 100d. The rolled material 10 may be wound through the tension reel 140 to facilitate storage and movement. In this case, the rolling reduction rate of the first stand 100a of the TRM rolling step 100 is 22% to 28%, and the reduction ratio of the second to fourth stands 100b, 100c, and 100d is 20% to 25%. Can be. The material 10 is rolled through each stand, and if the reduction ratio is not appropriate, it may be difficult to obtain a desired thickness and surface quality.

Referring to FIG. 2B, the ZRM rolling step 200 constituting the cold rolling process provides beauty to the surface of the material 10 discharged from the TRM rolling step 100 and also reduces the final thickness to the target dimension. Can be provided for. Thus, the ZRM rolling step 200 may be composed of a working roll 210 in contact with the surface of the material 10, the working roll 210 may be supported by a plurality of backup rolls.

The ZRM rolling step 200 may include a working roll 210 and a plurality of backup rolls, a left tension reel 240a and a right tension reel 240b provided at both sides of the rolls, and include a motor or a reducer (not shown). ), The thin material 10 is wound and repeatedly rolled until the thin material 10 has a predetermined thickness.

At this time, ZRM rolling step 200 is the initial rolling reduction is 9% to 15%, it is preferable that the total number of passes is carried out 5 to 9 times. In addition, it is particularly preferable that the ZRM rolling step 200 has an initial rolling reduction of 12% and a total number of passes of nine.

When the initial rolling reduction is less than 9%, the fixing that can be performed by the ZRM rolling step 200 is limited, so that process efficiency may be lowered. In addition, when the initial rolling reduction exceeds 15%, the thickness may be thin, while the surface quality may be degraded. Therefore, it is preferable that the initial reduction rate is 9% to 15%, but it may be particularly preferable that the initial reduction rate is 12% in consideration of productivity and surface quality at the same time.

The ZRM rolling step 200 may be performed after the TRM rolling step 100, and it is preferable that the ZRM rolling step 200 is composed of only one stand, unlike the TRM rolling step 100. As such, the ZRM rolling step 200 may control the thickness by reversibly reciprocating the thin material 10 manufactured through the TRM rolling step 100 through the working roll 210.

As described above, the ZRM rolling step 200 is rolled by repeatedly reciprocating the material 10, wherein the total number of passes is preferably 5 to 9 times. When the total number of passes is less than five times, it is difficult to obtain a predetermined thickness of the material 10, and when the total number of passes exceeds nine times, the production time can be reduced because the processing time is increased. In addition, the material 10 has a total pass number of nine times, so the best surface quality, it may be particularly preferable that the total number of passes is nine times.

At this time, the ZRM rolling step 200 may be performed at a rolling speed of 150 m / min to 250 m / min. In addition, the thin material may be 8% to 10.5% Ni, 18% to 20% Cr, 0.08% C or less, 1.0% Si or less, 2.0% or less Mn, and the remainder may be Fe.

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the scope of the present invention is not limited by the following examples.

(Comparative Example)

Hot rolled material material hot-rolled using a material material consisting of Ni 8 ~ 10.5%, Cr 18 ~ 20%, C 0.08% or less, Si 1.0% or less, Mn 2.0% or less, Fe 66.42% or less Cold rolling was performed using. At this time, the cold rolling process is made of only ZRM rolling step. The ZRM rolling step was performed directly using the hot rolled material, wherein the initial rolling rate is 150 m / min to 250 m / min, the total number of passes is 13 times, and the initial rolling rate is 22%. ZRM rolling step was performed. Subsequently, the surface quality of the austenitic stainless steel wound in the form of a coil, which was carried out by annealing and pickling, was visually inspected.

As a result of ten tests in this manner, it was confirmed that surface defects occurred in all tests and surface quality was poor.

3A is a view showing a coil form of austenitic stainless steel having surface defects according to the present comparative example.

As a result of ten tests in this manner, it was confirmed that surface defects occurred in all tests.

(Example)

Hot rolled material material hot-rolled using a material material consisting of Ni 8 ~ 10.5%, Cr 18 ~ 20%, C 0.08% or less, Si 1.0% or less, Mn 2.0% or less, Fe 66.42% or less Cold rolling was performed using. At this time, the cold rolling process consists of a TRM rolling step and ZRM rolling step. The hot rolled natural material was subjected to the TRM rolling step continuously with a first reduction rate of 22% to 28% and a second reduction rate of 20% to 25% of the second to fourth stands. Subsequently, a ZRM rolling step was performed, in which the initial rolling reduction was set at a rolling speed of 150 m / min to 250 m / min, the total number of passes was nine times, and the initial rolling reduction was 12%. .

Figure 3b is a view showing the coil form of austenitic stainless steel according to a preferred embodiment of the present invention.

As a result of ten tests in this manner, it was confirmed that no surface defects occurred in all the tests.

In the case of performing the annealing operation using austenitic stainless steel having no shape control of the edge portion in the annealing operation that follows the cold rolling, deformation of the austenitic stainless steel may occur over the entire width, in particular, the center. It can cause negative distortion, resulting in poor surface quality.

In addition, in the ZRM rolling step performed after the TRM rolling step, in the case of a full hard material (rolled material), since the hardened material is rolled, rolling may not be performed when the conventional pass method is applied. In addition, it may cause an adverse effect on the surface quality of the austenitic stainless steel. In addition, when the pass method is set without considering the rolling capability, excessive rolling causes a rolling load, which may lower rolling stability and adversely affect the rolling shape. Therefore, in the ZRM rolling step, the initial rolling reduction was 12%, and the total number of passes was 9 times, and it is preferable to roll the austenitic stainless steel hardened primarily by the TRM rolling step.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the scope of the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalent concept are included in the scope of the present invention. Should be interpreted.

10: Museum
100: TRM rolling stage
100a, 100b, 100c, 100d: first to fourth stands
110: walking roll 120: intermediate roll
130: backup roll 140: tension reel
200: ZRM rolling step 210: working roll
240a: left tension reel 240b: right tension reel

Claims (9)

In the cold rolling process of the material, the cold rolling comprises a TRM (tandom rolling mill) rolling step and ZRM (zendsimir rolling mill) rolling step, the ZRM rolling step has an initial rolling reduction of 9% to 15%, A method for producing austenitic stainless steel having an excellent surface shape, including a total number of passes of five to nine times. The method of claim 1,
The TRM rolling step is a method for producing austenitic stainless steel consisting of the first to fourth stands. The method of claim 2,
The rolling reduction rate of the first stand of the TRM rolling step is 22% to 28%, and the reduction rate of the second to fourth stands is 20% to 25%. The method of claim 1,
The ZRM rolling step is a method for producing austenitic stainless steel, characterized in that the rolling speed is carried out at 150 m / min to 250 m / min. The method of claim 1,
The ZRM rolling step is a method for producing austenitic stainless steel, characterized in that carried out after the TRM rolling step. The method of claim 1,
The ZRM rolling step has an initial rolling reduction of 12% and a total number of passes of nine times, characterized in that the austenitic stainless steel manufacturing method. The method of claim 1,
The material is a weight% Ni 8 ~ 10.5%, Cr 18 ~ 20%, C 0.08% or less, Si 1.0% or less, Mn 2.0% or less, the remainder is made of austenitic stainless steel. The method of claim 1
The cold rolling process of the material further comprises an annealing pickling process, wherein the annealing pickling process is performed after the cold rolling process. In the process of cold rolling a material composed of Ni 8-10.5%, Cr 18-20%, C 0.08% or less, Si 1.0% or less, Mn 2.0% or less, and the remainder Fe by weight, the cold rolling is TRM (tandom rolling mill) rolling step and ZRM (zendsimir rolling mill) rolling step, the ZRM rolling step is the initial rolling reduction is 9% to 15%, the surface shape is produced by performing a total number of passes of 5 to 9 times This excellent austenitic stainless steel.

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