KR100772331B1 - Method of manufacturing an austenitic stainless steel for decreasing a surface roughness defects - Google Patents

Abstract

A method of manufacturing an austenitic stainless steel with superior surface quality is provided to reduce defects in surface roughness by properly controlling a de-scaling method. A method of manufacturing an austenitic stainless steel with superior surface quality includes the steps of: separating residual scale from casting material during a continuous casting process by submerging the casting material in a water tub for more than 10 minutes; transferring the casting material to a hot rolling process; and additionally removing residual scale by spraying water onto the casting material at a de-scaling pressure over 3 bar when the thickness of a bar ranges from 94mm to 100mm during the hot rolling process.

Description

Method for manufacturing an austenitic stainless steel for decreasing a surface roughness defects}

1 is a schematic diagram of a manufacturing method of a common austenitic stainless steel sheet,

2 is a view showing the effect of the descaling method during hot rolling on the surface roughness of the present invention,

3 is a view showing the surface roughness defect reduction effect according to the present invention.

The present invention relates to a method for producing austenitic stainless steel with excellent surface quality, and more particularly, to the manufacturing conditions in the continuous casting-hot rolling process to reduce the surface roughness defects of cold-rolled products when manufacturing austenitic stainless steel, The present invention relates to a method for producing austenitic stainless steel having excellent surface quality for reducing surface roughness defects on the surface of cold rolled products by appropriately controlling the descaling conditions during continuous casting process and hot rolling.

In general, stainless steel cold rolled products are produced from cast iron, which is an intermediate material, in the casting factory, reheated in a hot rolling mill, and then rolled to produce black coils. Produced by pickling.

At this time, if the mold slag component remaining on the surface of the cast slab cannot be removed in the hot rolling process, irregularities are formed on the surface of the hot rolled coil, and finally, surface roughness is caused on the surface of the cold rolled product. Application to advanced applications is limited.

Conventionally, a method for reducing surface roughness defects remaining on the surface of a hot rolled coil.In order to remove mold slag that causes surface roughness, the desorption is increased by increasing the amount of non-aqueous quantity in the secondary refrigerating cooling basin, and the cast is placed in a water cooling tank for 1 minute. The method of immersion, the spraying of cooling water for 1 minute on the surface of cast steel, the removal of descaled residual scale on the surface of cast steel using brush and air blower For example, there has been reported a method of removing a scale using a Shot Blaster on a cast cast. However, looking at the known technology, there is no report on descaling conditions in the hot rolling process.

The present invention has been made in accordance with the above requirements, the manufacturing conditions for reducing the surface roughness defects in the final cold-rolled product in the production of austenitic stainless steel, cooling method of the casting cast after continuous casting, descaling conditions during hot rolling It is an object of the present invention to provide a method for producing austenitic stainless steel having excellent surface quality by reducing surface roughness defects of a cold rolled product by appropriately controlling appropriately.

In order to achieve the above object, the present invention provides a continuous casting process, hot rolling process, hot rolling annealing and cold rolling process of austenitic stainless steel containing 10% to 30% chromium and 5 to 15% nickel by weight. In the manufacturing method, the hot slab cut in the continuous casting process is immersed in a water cooling tank for 10 minutes or more to desorb the residual scale, and the slab is transferred to the hot rolling process to carry out the temper rolling step at the time of hot rolling. At a time when the thickness of 94 ~ 100mm, the descaling pressure on the surface of the bar is sprinkled to 3 bar or more characterized in that it provides a method for producing austenitic stainless steel having excellent surface quality to further remove the residual scale. .

In the present invention, the temperature of the cast steel in the hot state is 600 ~ 800 ℃.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

First, the present invention is to deposit the cast slab in the water cooling bath for more than 10 minutes in the reproducing process during the production of austenitic stainless steel to remove the residual mold slag, and then loaded into a hot-rolled heating furnace, the bar thickness during hot rough rolling 94 ~ 100mm In this case, descaling can be performed with an impact pressure of 3 bar or more on the surface of the bar to reduce surface roughness defects in the final cold rolled product.

1 shows a typical stainless steel manufacturing plant and unit process. first

After the molten steel manufactured in the steelmaking process is charged and reheated into a hot-rolled furnace, the cast steel is subjected to rough rolling and finishing rolling. Since the black coil (Black Coil) is a hot rolled coil is subjected to annealing and mechanical / chemical scale removal process in the hot-burning annealing plant. The hot rolled coil thus manufactured is manufactured by cold rolling and cold rolling annealing at a cold rolling mill.

At this time, if a large amount of mold slag is left in the cast slab before charging by hot rolling, or if the strength and uniformity of descaling cannot be secured during hot rolling, surface roughness defects frequently occur on the surface of the cold rolled product.

Accordingly, in the present invention, in order to reduce surface roughness defects on the surface of the cold rolled product, a method of detaching the mold slag remaining in the cast steel piece, a method of securing hot rolled descaling strength and uniformity is proposed.

Hereinafter, the present invention will be described in detail through examples.

Example 1

Performance Mold Slag Desorption method

In the present invention, a method of maximizing the scale removal effect by descaling and boiling due to thermal expansion coefficient difference during cooling in the surface layer part of the cast slab by depositing the cast slab in the water cooling tank by the detachment method of the mold slag remaining on the cast steel. The slag desorption strength according to the water cooling bath deposition time was compared and the results are shown in Table 1.

Deposition time 0 min 1 minute 5 minutes 10 minutes 30 minutes Mold Slag Retention Index 4 3 2 One One

As can be seen in Table 1, the mold slag index remaining in the cast pieces during the water cooling bath deposition is continuously reduced with the increase in the water cooling time, the mold slag residual amount was almost constant when the deposition time is more than 10 minutes. Accordingly, in order to remove the mold slag remaining in the cast steel, the water cooling tank deposition time should be set to 10 minutes or more.

Example 2

During hot rolling Descaling  Way

In order to evaluate the effect of descaling method on the surface roughness in hot rolling zone, the first, second and second descaler HSB, the first rough rolling inlet descaler R1, the second rough rolling inlet descaler R2 In the third rolling, the surface roughness defects of the products manufactured under the combination of descaling (R2-1, R2-2, R2-3) were compared and performed.

As can be seen in FIG. 2, the surface roughness defect index was the best when R2-3 descaling, and the M type defect index was also compared to R2-3 as an index to examine whether the defect was increased. Excellent defect index was shown. Accordingly, descaling should be performed once for hot rolling with R2-3 descaling, i.e., bar collision surface pressure of 3 bar or more at bar thickness 94 ~ 100mm.

By applying each of the factors configured as described above, the surface roughness defect rate before and after the present invention was compared, the results are shown in FIG. As can be seen from the graph, it can be seen that the quality rejection rate is significantly reduced compared to the conventional method when the present invention is applied.

As described above, according to the present invention, by appropriately controlling the cooling method of the cast steel and the descaling method during hot rolling, it is possible to produce a grinding cast of austenitic stainless steel having excellent surface quality with reduced surface roughness defects. have.

Claims (2)

In the method of manufacturing austenitic stainless steel containing 10% to 30% chromium and 5 to 15% nickel by weight in a continuous casting process, a hot rolling process, a hot rolling annealing and a cold rolling process, the continuous casting process In the water-cooled water bath, the hot slab cut is immersed in a water cooling tank for at least 10 minutes to desorb the residual scale, and the bar is transferred to the hot rolling process, where the thickness of the bar corresponds to 94 to 100 mm in the temper rolling step during hot rolling. A method for producing austenitic stainless steel having excellent surface quality, characterized in that the remaining scale is further removed by sprinkling the descaling pressure on the bar surface to 3 bar or more. The method of claim 1, The temperature of the cast steel in the hot state is 600 ~ 800 ℃ excellent surface quality austenitic stainless steel manufacturing method.

Images