JPH084807B2 - Method for producing ultrathin abrasive-finished austenitic stainless steel strip with good workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing an improved ultra-thin abrasive finish austenitic stainless steel strip.

[Conventional technology]

Austenitic stainless steel sheets used for building exterior steel sheets and the like are often subjected to polishing finish for reasons of appearance. In the past, this type of polished steel strip was most commonly one having a thickness of about 1 mm to 3 mm due to its application. However, in recent years, thin steel strips have been desired in order to reduce manufacturing costs and improve workability, and in particular, the abraded finish austenitic stainless steel sheets used as outer panels of cladding steel sheets for building exteriors have a sheet thickness of 0.3. It is required to be very thin, less than mm. Similar to the conventional polishing finish process for plate thickness (1 mm to 3 mm), when performing ultra-thin (0.3 mm or less) austenitic stainless steel strip like this, hot rolling → annealing pickling → cold rolling → The manufacturing process was annealing pickling → polishing. That is, the soft steel strip having good workability after the pickling by annealing was subjected to the polishing finish.

[Problems to be solved by the invention]

However, when it is attempted to manufacture an ultrathin polished finish austenitic stainless steel strip by such a manufacturing process, there are the following problems.

(1) Since the plate thickness is thin and soft, defects such as foreign matter indentation occur on the surface of the steel strip during polishing and the surface quality deteriorates.

(2) In order to avoid the above-mentioned surface flaws, a hard material that has been subjected to an abrasive finish reduces surface flaws, but the workability of the product is poor, and bending cracks etc. occur when processed by the user. .

(3) If the soft material is polished and then annealed and pickled to soften the material, the surface condition deteriorates.

[Object of the Invention]

Therefore, it is an object of the present invention to provide a method for producing an ultrathin, polished finish austenitic stainless steel strip having good surface quality and good workability.

[Means for solving problems]

In order to achieve such an object, the present invention adjusts the hardness of the steel strip by temper rolling before polishing and finishing to an appropriate hardness that does not allow surface flaws, and further improves workability. After polishing finish, strain relief annealing is performed in a reducing atmosphere.

[Structure of Invention]

The present invention provides a method for producing an ultrathin abrasive finish austenitic stainless steel strip, which is characterized by performing temper rolling before polishing finish and performing strain relief annealing in a reducing atmosphere after polishing finish. .

The present invention is mainly intended for steel strips of austenitic stainless steel such as SUS 304, SUS 301, SUS 304L, but is not limited thereto. Temper rolling is performed before polishing finish, and after polishing finish, strain relief annealing is performed in a reducing atmosphere.

Performing temper rolling before polishing finish is to reduce surface defects such as intrusion of foreign matter into the surface of the steel strip that occurs during polishing finish. It is important not to increase the hardness of the steel strip. Therefore, it is necessary to set the minimum required hardness of the steel strip in order to reduce surface defects.

SUS 30 as a typical austenitic stainless steel
Regarding the relationship between the surface flaw occurrence rate and hardness of 4 and SUS 304L, if the hardness is HMv250 or more, the surface flaw occurrence rate can be limited to a level that does not cause a problem as a product. Therefore, it is necessary to adjust the temper rolling performed before the polishing finish so that the hardness of the steel strip is HMv250 or more.

By adjusting the hardness in this way, the polished finish austenitic stainless steel strip with reduced surface defects,
In addition to adjusting the hardness by temper rolling, the hardness is further increased by the surface processing in the polishing finishing process, and the workability is poor.

Therefore, it is necessary to add strain relief annealing to the steel strip to improve the workability, and at that time, it is necessary to deal with the following conditions.

Since it has already been polished, it must be annealed so as not to change the surface texture.

Since austenitic stainless steel undergoes sensitization in a specific temperature range and its corrosion resistance deteriorates, it is necessary to avoid the sensitization temperature range and perform sufficient annealing to improve workability.

Regarding the above, by performing annealing in a reducing atmosphere, strain relief annealing can be performed without generating oxide scale due to annealing on the surface of the steel strip and without changing the surface texture.

Regarding the above, it is necessary to set an annealing temperature at which sensitization is not caused and workability is improved.

SUS 30 which is a typical austenitic stainless steel
No. 4 does not cause sensitization by annealing at 950 ° C. or higher, and sufficient workability can be obtained. However, if the temperature exceeds 1100 ° C, the shape of the steel strip may deteriorate during striping, and the effect of improving workability does not change even if annealing is performed at higher than 1100 ° C, so the upper limit of the annealing temperature is set to 1100 ° C.

In the case of SUS 304L, it does not cause sensitization by annealing at 800 ℃ or more, and sufficient workability can be obtained. However, if the temperature exceeds 1100 ° C, the shape of the steel strip may deteriorate during passing, as in the case of SUS 304, and the workability does not change even if annealing exceeds 1100 ° C, so the upper limit of the annealing temperature is 1100 ° C. And

In this way, by setting a temperature range that does not cause sensitization for each steel type and that sufficient workability is obtained, an ultrathin austenitic stainless steel strip that is polished and has good workability is obtained. be able to.

(Specific description of the invention)

The present inventors investigated the relationship between surface flaws and hardness in the polishing finish of SUS 304 steel strip, and obtained the results shown in FIG. According to this figure, if the hardness is 250 HMv or more,
It can be seen that the occurrence of surface defects can be suppressed within the product collection limit.

The annealing temperature, hardness elongation and sensitization temperature range were investigated for SUS 304 and SUS 304L steels. The results are shown in Fig. 2 (SUS 30
4) and Fig. 3 (SUS 304L). According to this, SUS 3
It can be seen that when 04 is annealed at a temperature of 950 ° C or higher and SUS 304L is annealed at a temperature of 800 ° C or higher, no sensitization is caused and sufficient workability is obtained.

Example As material, plate thickness of SUS 304 and SUS 304L steel 0.15 m
A steel strip with a width of 1000 mm and a strip width of 1000 mm was processed in the order of temper rolling → polishing finish → strain relief annealing.

The strain relief annealing was performed at 1000 ° C. for SUS 304 and 900 ° C. for SUS 304L in an atmosphere of H ₂ + N ₂ mixed gas.

Table 1 shows the hardness of the steel strip after temper rolling and the surface flaw occurrence rate at the time of polishing finish. As shown in Table 1, if the hardness after temper rolling is about HMv250 to 400, the surface flaw occurrence rate is low and the product can be sufficiently used. If it is less than HMv250, the defect occurrence rate becomes high and it cannot be collected as a product.

Table 2 shows the hardness and elongation before strain relief annealing and the hardness and elongation after strain relief annealing. As shown in Table 2, sufficient workability was obtained by strain relief annealing.

The steel strip passed through the above-mentioned manufacturing process had a good surface condition, and the workability evaluation when used by the user was good.

[Effect] As described above, the present invention achieves the above-mentioned object and has the following effects.

(A) By performing temper rolling before polishing and controlling the hardness of the steel strip, it is possible to reduce flaws due to indentation during polishing and obtain a good surface condition.

(B) By performing strain relief annealing in a reducing atmosphere, strain relief annealing can be performed without deteriorating the surface condition.

(C) By performing strain relief annealing after polishing finish, it is possible to obtain an ultrathin polished finish austenitic stainless steel strip with good workability of the product.

[Brief description of drawings]

FIG. 1 shows the relationship between hardness and the occurrence rate of surface defects. Fig. 2 shows changes in hardness and elongation depending on the sensitization temperature range and the annealing temperature in SUS 304 steel. FIG. 3 shows changes in hardness and elongation depending on the sensitization temperature range and the annealing temperature in SUS 304L steel.

Claims (3)

[Claims] 1. A method for producing an ultra-thin abrasive finish austenitic stainless steel strip, which comprises temper rolling before polishing finish, and performing strain relief annealing in a reducing atmosphere after polishing finish. 2. An ultra-thin SUS 304 steel strip is used, and the hardness is adjusted to HMv250 or more by temper rolling before polishing finish, and after polishing finish, 950 ° C or more 1100 at 950 ° C. in a reducing atmosphere in a bright annealing furnace.
The method for producing an ultrathin, polished finish austenitic stainless steel strip according to claim 1, wherein strain relief annealing is performed at a temperature of ℃ or less. 3. An ultra-thin SUS 304L steel strip is used, and the hardness is adjusted to HMv250 or more by temper rolling before polishing finish, and after polishing finish, 800 ° C or more 1100 in a reducing atmosphere in a bright annealing furnace.
The method for producing an ultrathin, polished finish austenitic stainless steel strip according to claim 1, wherein strain relief annealing is performed at a temperature of ℃ or less.