JP2001262232A - Manufacturing method of stainless steel strip - Google Patents

Abstract

(57) [Abstract] [Problem] To provide a method for producing a stainless steel strip having high strength and hardness, excellent punching properties and surface properties by a simple process. SOLUTION: A stainless steel strip is subjected to cold rolling, degreasing, annealing and pickling, and then the rolling reduction is reduced without using rolling oil.
Perform temper rolling satisfying the range of 2.0 to 5.2%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a stainless steel strip having high strength and hardness and excellent punching properties and surface properties used for a leaf spring material.

[0002]

2. Description of the Related Art Generally, in order to manufacture a stainless steel strip having high strength and hardness, which is used as a leaf spring material, and has excellent punching properties and surface properties, a cold-rolled stainless steel strip is degreased and rolled. After removing oil and the like, annealing and pickling are performed. Next, temper rolling is performed to correct the distortion caused by the annealing and to smooth the surface.

[0003] When a rolling oil is used in the temper rolling, the rolling oil is caught between the stainless steel strip and the work roll during the temper rolling, so that a pit-shaped surface defect (hereinafter, referred to as a "defect") is formed.
Oil pit). When oil pits occur during temper rolling, the surface of the stainless steel strip must be polished to remove the oil pits, and a degreasing treatment is required to remove rolling oil attached to the stainless steel strip. is there.

[0004] As described above, when temper rolling (hereinafter referred to as wet temper rolling) is performed using a liquid lubricant such as rolling oil, degreasing treatment, polishing, and the like are required after wet temper rolling. Therefore, there is a problem that the working process becomes complicated. Therefore, various techniques have been proposed for performing temper rolling (hereinafter, referred to as dry temper rolling) without using a liquid lubricant such as rolling oil.

[0005] For example, JP-A-52-70966 and JP-A-7-9001 disclose a temper rolling method for a stainless steel strip. According to these methods, in two passes of temper rolling after cold rolling, annealing and pickling of a stainless steel strip, a first pass performs dry temper rolling and then a second pass.
The pass is intended to prevent lateral stripes or scratches by performing wet pass rolling. However, this method has a problem that oil pits are generated because the second pass is wet pass rolling, and polishing and degreasing treatment after pass pass rolling is required.
In addition, due to the low elongation, sufficient hardness for punching could not be obtained.

Japanese Patent Application Laid-Open No. 6-182403 discloses a stainless steel strip having excellent flatness and a method for producing the same. This technology is intended to suppress the burn-in pattern called heat streak pattern to an area ratio of 35% or less by cold rolling a stainless steel strip, annealing and pickling, and then performing dry pass rolling. It is. However, this method has a problem that seizure occurs when the reduction ratio of dry pass rolling is large.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a method for producing a stainless steel strip having high strength and hardness, excellent punching properties and surface properties by a simple process. The purpose is to:

[0008]

As a result of various experiments, the inventors of the present invention have found that not only oil pits are generated when wet passivation rolling is performed, but also that a rolling oil pool formed on the roll entry side is formed. Since the metal powder is trapped, it has been found that the metal powder bites into the stainless steel strip and surface flaws occur. Therefore, in the case where wet temper rolling is performed, after the wet temper rolling, degreasing treatment for removing rolling oil and polishing for removing oil pits and surface defects are required.

On the other hand, since rolling oil is not used in dry pass rolling, no oil pits are generated in dry pass rolling, and no surface flaw is generated. In the present invention, a stainless steel strip is cold-rolled, subjected to a degreasing treatment, further subjected to annealing and pickling, and then to a reduction ratio of 2.0 to 5.2%.
This is a method for producing a high-strength and high-hardness stainless steel strip which is subjected to dry pass rolling that satisfies the above range.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS During cold rolling of a stainless steel strip, rolling oil, metal powder and the like adhere to the surface of the stainless steel strip. Since these deposits cause defects related to the surface quality of the stainless steel strip, a degreasing treatment is performed after cold rolling to remove the deposits. As the degreasing treatment, chemical degreasing and electrolytic degreasing using an alkaline aqueous solution are generally known. In the present invention, the degreasing treatment is not limited to a specific configuration, and it is only necessary to remove rolling oil, metal powder and the like adhering to the surface of the stainless steel strip.

Since the cold-rolled stainless steel strip is hard and has poor workability, annealing is performed after the degreasing treatment. Annealing is desirably performed in a reducing atmosphere such as bright annealing in order to obtain good gloss of the stainless steel strip.
After annealing, pickling is performed to remove scale generated on the surface of the stainless steel strip. Annealing the stainless steel strip causes wrinkles due to the stretcher strain. Therefore, dry temper rolling is performed to correct wrinkles of the stainless steel strip and improve the surface properties. In the dry pass rolling, no rolling oil is used, so that no oil pits are generated. Further, since metal powder is easily discharged to both sides of the stainless steel strip, no surface flaw is generated.

However, if oil pits and surface defects generated during cold rolling remain after dry pass rolling, polishing must be performed after dry pass rolling. Since the surface flaws are shallow, the polishing depth is shallow. The rolling reduction of dry pass rolling is in the range of 2.0 to 5.2%. If the rolling reduction is less than 2.0%, work hardening is not sufficient, so that burrs at the time of punching become large, and if the rolling reduction exceeds 5.2%, the stainless steel sheet is seized on the roll. The rolling reduction is a value calculated by the following equation.

Reduction ratio (%) = 100 × (t ₁ −t ₂ ) / t ₁ t ₁ : Thickness before temper rolling (mm) t ₂ : Thickness after temper rolling (mm)

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A stainless steel strip (JI
S standard SUS304 and SUS430) were manufactured. That is,
2.0-4.0mm thickness, 1016-1237mm width by cold rolling
After the steel strip was manufactured, alkali degreasing was performed, further annealing and pickling were performed in a stainless steel continuous annealing pickling line having a temper rolling mill, and then dry temper rolling was performed in a temper rolling mill. . The rolling reduction of dry temper rolling is 2.0 to 5.
The range of 2% was satisfied.

The Vickers hardness (Hv) of the stainless steel strip thus obtained, the presence or absence of biting of metal powder, the presence or absence of seizure, the polishing depth, the gloss (the presence or absence of unevenness), and the punching property (size of burrs). investigated. The results are shown in Tables 1 and 2 as Invention Examples 1 to 14. Inventive Examples 1 to 7 in Table 1
This is an example of SUS304, and Invention Examples 8 to 14 in Table 2 are examples of SUS430.

As a comparative example, dry temper rolling with a rolling reduction of less than 2.0% and wet temper rolling with a rolling reduction of 2.0 to 5.2% were performed to obtain Vickers hardness (Hv), presence or absence of metal powder biting, and seizure. The presence / absence, polishing depth, gloss (presence / absence of unevenness), and punchability (size of burrs) were investigated.
The results are shown in Tables 1 and 2 as Comparative Examples 1 to 10.
Comparative Examples 1 to 6 in Table 1 are examples of SUS304, and Comparative Examples 7 to 10 in Table 2 are examples of SUS430.

[0017]

[Table 1]

[0018]

[Table 2]

As is clear from Table 1, Inventive Examples 1 to 7 of SUS304 had sufficient hardness as a leaf spring material. In addition, metal biting and seizure do not occur, and the polishing depth is
It was suppressed to 0.5 μm or less, and the punching properties and gloss were good. On the other hand, Comparative Examples 1 and 2 are examples in which dry pass rolling is performed. However, since the rolling reduction is less than 2.0%, the burrs of punching are large and the punching properties are inferior. Comparative Examples 3 to 6
Although the rolling reduction satisfies the range of 2.0 to 5.2%, the surface properties of the stainless steel strip are inferior due to wet temper rolling. That is, in Comparative Examples 3 to 6, oil pits occurred because the rolling oil was used in the wet temper rolling.
In particular, in Comparative Examples 3 and 5, the metal powder was caught in the rolling oil pool on the roll entry side, and surface flaws were generated due to the metal powder being caught. Therefore, in Comparative Examples 3 to 6, since the oil pits and surface flaws generated by the wet temper rolling had to be polished, the polishing depth exceeded 0.5 μm.

Moreover, in Comparative Examples 3 to 6, since the rolling oil was used in the wet temper rolling, it was necessary to perform a degreasing treatment after the wet temper rolling. However, in Invention Examples 1 to 7, since dry pass rolling was performed, it is not necessary to perform degreasing after dry pass rolling. Next, as is clear from Table 2, Inventive Examples 8 to 14 of SUS430 showed sufficient hardness as a leaf spring material. In addition, metal biting and seizure did not occur, the polishing depth was suppressed to 0.5 μm or less, and the punching properties and gloss were good.

On the other hand, Comparative Example 7 is an example in which dry temper rolling is performed. However, since the rolling reduction is less than 2.0%, the burrs of punching are large and the punching properties are poor. Comparative Examples 8 to 10
Although the rolling reduction satisfies the range of 2.0 to 5.2%, the surface properties of the stainless steel strip are inferior due to wet temper rolling. In other words, in Comparative Examples 8 to 10, oil pits occurred because the rolling oil was used in wet temper rolling.
In particular, in Comparative Examples 8 and 9, the metal powder was caught in the rolling oil pool on the roll entry side, and surface flaws were generated due to the metal powder being caught. Therefore, in Comparative Examples 8 to 10, the oil pits and surface flaws generated by wet temper rolling had to be polished, and the polishing depth was 1.0 μm or more.

Moreover, in Comparative Examples 8 to 10, since the rolling oil was used in the wet temper rolling, it was necessary to perform a degreasing treatment after the wet temper rolling. However, in Invention Examples 8 to 14, dry passivation rolling was performed, so that it is not necessary to perform degreasing after temper rolling.

[0023]

According to the present invention, a stainless steel strip having high strength and hardness, and excellent punching properties and surface properties can be manufactured. Moreover, since the degreasing treatment after the temper rolling can be omitted, the productivity is improved, and the polishing depth is shallow, so that the yield is improved, which is economically advantageous.

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Claims (1)

[Claims] (1) After cold rolling a stainless steel strip, the stainless steel strip is subjected to a degreasing treatment, further subjected to annealing and pickling, and then to a dry temper rolling in which a reduction ratio satisfies a range of 2.0 to 5.2%. Method for producing high-strength, high-hardness stainless steel strip.