KR101528065B1

KR101528065B1 - Heating method for hot rolling of stainless steel

Info

Publication number: KR101528065B1
Application number: KR1020130157950A
Authority: KR
Inventors: 이용헌; 서창우; 최재혁
Original assignee: 주식회사 포스코
Priority date: 2013-12-18
Filing date: 2013-12-18
Publication date: 2015-06-10

Abstract

The present invention provides a heating furnace heating method for hot rolling austenitic stainless steel sequentially having a pre-heat process and a heating process and comprises 0.04-0.07 wt% of C, 0.3-0.5 wt% of Si, 18.02-18.06 wt% of Cr, 8.02-8.4 wt% of Ni, 0.02-0.05 wt% of N, and the balance of Fe and inevitable impurities. The present invention is maintained at the temperature of the preheating process over 1120°C and less than 1150°C and has a preheating time over 70 minutes and less than 110 minutes in order to inhibit uneven delta ferrite oxidation.

Description

Technical Field [0001] The present invention relates to a heating method for hot rolling of a stainless steel,

The present invention relates to a heating furnace heating method for hot rolling a stainless steel to obtain a stainless steel having improved surface quality by removing striped stripe defects of a stainless steel.

Stainless steel has excellent mechanical properties and is widely used in industry. However, in cold-rolled products of stainless steel, there is a problem that the color of the surface of the steel becomes uneven due to band-shaped stripe defects.

Additional steel surface treatment processes, such as conventional coil grinding, have been used to remove the striated stripe defects, but additional process costs are incurred.

SUMMARY OF THE INVENTION The present invention has been devised to solve the problems described above, and it is an object of the present invention to provide a heating furnace heating method for hot rolling a stainless steel having excellent surface quality by reducing striped stripe defects without using a surface treatment process of an additional stainless steel It has its purpose.

In order to achieve the above-mentioned object, the present invention provides a method of manufacturing a semiconductor device, comprising the steps of: C: 0.04 to 0.07 wt%, Si: 0.3 to 0.5 wt%, Mn: 1.0 to 1.3 wt% in a furnace heating method for hot rolling austenitic stainless steels composed of at least one element selected from the group consisting of Fe, Fe, Fe, Fe, Ni, Fe, Ni and Fe in an amount of 8.02 to 8.4 wt%, N: 0.02 to 0.05 wt%, and Fe and other unavoidable impurities. Furnace heating method for hot rolling of stainless steel wherein the temperature of the preheating step is maintained at more than 1120 DEG C but less than 1150 DEG C and the preheating time is more than 70 minutes and less than 110 minutes.

Also preferably, the heating process can be maintained at a temperature greater than 1220 DEG C but less than 1260 DEG C for less than 70 minutes and less than 110 minutes.

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According to the heating furnace heating method for hot rolling the stainless steel of the present invention, it is possible to remove striped streaks without the need of further steps, and to have an excellent surface quality of stainless steel.

FIG. 1 is a graph showing the temperature of the preheating zone and the presence or absence of streaking according to time. FIG.
2 is a photographic view showing non-uniform oxidation of a stainless steel surface by delta ferrite.
Fig. 3 is a photograph of the surface of the cold-rolled coil where band-shaped stripes are generated.

Hereinafter, the present invention will be described in detail with reference to figures and tables.

First, in the steel composition of the present invention, the content of each element represents% by weight.

The furnace generally consists of three parts. The front part of the heating furnace is a part that rapidly raises the temperature from room temperature to the target temperature and is called as preheating. The exit side is a part that allows the metal slab to enter the rolling section at a certain temperature by keeping the temperature constant. It is called. And, the zone between the preliminary troposphere and the crack zone is called the heating zone. Here, the preheating zone corresponds to the preheating process, the heating zone and the crack zone correspond to the heating process, and the stainless steel is heated.

The heating furnace heating method for hot rolling the stainless steel of the present invention has a preheating step and a heating step in this order, and the temperature of the preheating step is maintained at a temperature higher than 1120 DEG C and lower than 1150 DEG C so as to suppress the delta ferrite nonuniform oxidation.

In the preheating step, the preheating time is preferably more than 70 minutes but less than 110 minutes.

As described above, the temperature and the time in the preheating process are important factors for the occurrence of band streaks. As shown in FIG. 1, when the temperature of the preheating zone is 1150 ° C or below 1120 ° C, banding streaks occur, If it is more than 110 minutes or less than 70 minutes, it can be known that stripe stripe occurs.

If the temperature in the preheating step is too low or too high, banding streaks occur. If the temperature of the preheating zone is too high, the oxidation rate increases to promote the occurrence of stripe patterns, and the temperature of the preheating zone If it is too low, the decomposition of the delta ferrite is disturbed, so that the occurrence of the stripe stripe can not be suppressed.

If the preheating time is too long, banding streaks become noticeable as the amount of oxidation increases, and when the preheating time is too short, the decomposition of the delta ferrite is not sufficient, resulting in the occurrence of banding streaks.

FIG. 2 is a photographic view showing non-uniform oxidation of a stainless steel surface by delta ferrite, and FIG. 3 is a photographic view of a surface of a coil in which striped stripes are generated by such nonuniform oxidation.

On the other hand, it is preferable that the heating step is maintained at a temperature higher than 1220 DEG C but lower than 1260 DEG C for less than 110 minutes and more than 70 minutes.

The range of temperature and time in the heating process is also determined as a trade-off relationship between the amount of oxidation and the decomposition of the delta ferrite.

Meanwhile, stainless steel called '304 austenitic stainless steel' among the types of stainless steels has been widely used because of its good corrosion resistance, heat resistance and mechanical properties. The present invention relates to austenitic stainless steel of the '304 type austenitic stainless steel' Applicable.

That is, the stainless steel used in the present invention may contain 0.04 to 0.07 wt% of C, 0.3 to 0.5 wt% of Si, 1.0 to 1.3 wt% of Mn, 18.02 to 18.06 wt% of Cr, 8.02 to 8.4 wt% of Ni %, N: 0.02 to 0.05 wt%, and the balance Fe and other unavoidable impurities.

The present invention will be described with reference to the following Table 1. Table 1 shows the results of checking the occurrence of banding streaks as the temperature and heating time of the preheating zone, the temperature and heating time of the heating zone and the cracking zone, and the total heating time are changed.

Example Yes Tropical
Temperature
(° C) Yes Tropical
Heating time
(minute) Heating table,
Crack base
Temperature (℃) Heating table,
Crack base
Heating time (min) gun
Heating time
(minute) String
Presence or absence of stripe Comparative Example 1 1150 100 1260 100 200 Occur Comparative Example 2 1140 70 1250 100 170 Occur Inventory 1 1140 80 1250 100 180 Not occurring Inventory 2 1140 90 1250 100 190 Not occurring Inventory 3 1140 100 1250 100 200 Not occurring Comparative Example 3 1140 110 1250 100 210 Occur Comparative Example 4 1130 70 1250 100 170 Occur Honorable 4 1130 80 1250 100 180 Not occurring Inventory 5 1130 90 1250 100 190 Not occurring Inventory 6 1130 100 1250 100 200 Not occurring Comparative Example 5 1130 110 1250 100 210 Occur Comparative Example 6 1120 100 1250 100 200 Occur Comparative Example 7 1110 100 1250 100 200 Occur

It can be seen from the above Comparative Example 1 of Table 1 that banding streaks occur when the temperature of the preheating band is more than 1150 ° C and banding streaks occur when the heating time of the preheating band is less than 70 minutes through Comparative Example 2 have.

On the other hand, in the case of Inventive Examples 1, 2 and 3, no stripe stripe occurred, but in Comparative Examples 3 and 5, it was confirmed that stripe stripe occurred when the preheating time was 110 minutes or longer.

In the case of Inventive Examples 4, 5 and 6, no stripe-like striations were observed, but in Comparative Examples 6 and 7, banding streaks were observed when the preheating temperature was 1120 ° C. or lower.

It can be seen from the results of the above examples that the heating method of the present invention has the effect that streaks do not occur in the stainless steel.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood that various changes and modifications may be made without departing from the scope of the appended claims.

Claims

A preheating step and a heating step in this order,
The steel sheet contains 0.04 to 0.07 wt% of C, 0.3 to 0.5 wt% of Si, 1.0 to 1.3 wt% of Mn, 18.02 to 18.06 wt% of Cr, 8.02 to 8.4 wt% of Ni, 0.02 to 0.05 wt% of N, A heating furnace heating method for hot rolling an austenitic stainless steel composed of Fe and other unavoidable impurities,
Wherein the temperature of the preheating step is maintained at more than 1120 DEG C but less than 1150 DEG C so as to suppress delta ferrite nonuniform oxidation and the preheating time is more than 70 minutes and less than 110 minutes.

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The method according to claim 1,
Wherein the heating step is maintained at a temperature of greater than 1220 DEG C but less than 1260 DEG C for less than 110 minutes and greater than 70 minutes.

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