JPH06190402A - Manufacture of cold rolled stainless steel strip - Google Patents

Abstract

PURPOSE:To improve the efficiency of a processing and to maintain the surface quality of a cold rolled stainless steel strip by constituting a continuous line of annealing-grinding-cold rolling-annealing and carrying out the surface grinding at a specialized temperature of above. CONSTITUTION:A hot rolled stainless steel coil or a thin ingot coil 2 is treated through a process containing solution heat treatment 6, surface grinding 8, cold rolling 12. In this case, the surface layer is softened by grinding the surface at 80-550 deg.C, especially, in metastable austenite stainless steel, a worked surface is made of a single phase of gamma phase and can restrain the generation of martensite. Further, the surface is leveled sufficiently by performing cold rolling at a draft exceeding 40% to obtain a good surface luster. Furthermore, after the solution heat treatment, the shape of the hot rolled coil or the thin ingot coil 2 is straightened to level the surface and after the surface is ground, the surface is cleaned to remove the foreign matter such as shavings attached to the surface.

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 cold rolled stainless steel strip having good surface gloss.

[0002]

2. Description of the Related Art In the manufacturing process of a strip-shaped metal body, oxide scale and surface flaws are generated on the surface of the strip-shaped metal body due to heating of the slab and subsequent hot rolling or continuous casting of thin slabs. In addition, a process for finishing the surface into a glossy surface is required.

Conventionally, these methods include shot blasting in which a steel ball having a diameter of 0.2 to 0.6 mm is projected on the surface of a strip-shaped metal body to perform surface layer cleaning to cause cracks or peeling of the scale. Then, descaling is performed by pickling with nitric hydrofluoric acid, sulfuric acid, hydrochloric acid, etc., and then cold rolling is performed to correct the shape of the strip-shaped metal body.After that, the surface of the strip-shaped metal body is scratched by belt grinding on another line. It has been considered to be a typical method.

However, in this conventional process, the pickling process is a continuous line with the annealing process, and since the grinding line and the rolling line or the dummy plate welding line are separately arranged, the oxide scale of the strip-shaped metal body and the In order to remove the surface flaws, it is necessary to pass 2 to 4 lines, which causes a problem of extremely poor efficiency. The annealing pickling line is inefficient because descaling is performed by pickling, and there are various problems from the viewpoint of productivity, cost, and labor saving, such as a large amount of waste liquid generated due to pickling. It was
On the other hand, in order to perform surface flaw removal by belt grinding, it is necessary to straighten the shape of the coil by cold working, but this straightening work is often performed using a normal cold rolling mill, and therefore In addition to the gauge down work (thickness reduction work), an additional shape correction work must be performed, so that not only the efficiency is not improved, but also the cost is increased. Furthermore, in the grinding line, the method of grinding the surface of the strip-shaped metal body with a rotary endless belt is the main method, but this method has a low plate passing speed,
Workability is poor because the belt life is short and frequent belt replacement is required. In addition, there is a problem that uniform grinding cannot be performed unless the plate shape before grinding is flat.

Therefore, for the purpose of improving the efficiency of descaling and improving the surface quality of the hot-rolled steel strip, a plurality of pickling treatment steps are provided after the pretreatment step of the tension leveler, and the plurality of pickling treatment steps are performed. Japanese Unexamined Patent Publication No. 59-41482 discloses descaling in which a grinding process for mainly removing metal residues and smut is combined with the above.
However, although this descaling improves the surface quality of the steel strip to some extent, its effect is limited, and since most of the descaling is performed by pickling treatment, a considerably large pickling treatment facility is required. Since it is necessary, the initial investment is large, and a large amount of waste liquid associated with large-scale pickling is required to be treated. Further, since the grinding process provided between each pickling process is not for actively removing the surface flaws of the steel strip, the steel strip that has been subjected to this descaling is different from that for removing the surface flaw. The problem arises that the plate has to be passed through the grinding line.

By the way, although the steel strip is conventionally ground at room temperature, in particular, SUS301, SUS304 and S are used.
In a stainless steel strip typified by US430, a hard working layer having a thickness of about 5 to 10 μm is formed on the surface, and this occurs as fine cracks on the surface during cold rolling, which deteriorates the surface gloss. There was a problem.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by improving the efficiency of processing work and maintaining the surface quality of a strip-shaped metal body, especially a stainless cold-rolled steel strip. The purpose is to plan.

[0008]

In order to solve the above problems, the present inventor constructed a continuous line of annealing-grinding-cold rolling-annealing to improve the efficiency of the processing work and to grind a steel strip. In particular, it was found that a hard working layer is formed on the working surface when grinding the stainless steel strip at room temperature as in the past, and in order to solve this, the surface grinding treatment can prevent an increase in work hardening. The above problems have been solved by carrying out at temperature.

That is, the present invention provides a method for producing a stainless cold-rolled steel strip, which comprises carrying out a solution heat treatment, a surface grinding treatment, and a cold rolling treatment on a stainless hot-rolled coil or a thin cast coil, The surface grinding treatment is performed at a temperature of 8
The cold rolling treatment is performed at 0 ° C to 550 ° C and the rolling reduction is 4
The present invention provides a method for manufacturing a stainless cold-rolled steel strip, which is characterized in that it is performed at 0% or more. After the solution treatment, it is preferable to correct the shape of the hot rolled coil or the thin slab coil for surface flattening. After the surface grinding treatment, it is preferable to wash the hot rolled coil or the thin cast coil to remove foreign matter such as grinding powder adhering to the surface. Furthermore, it is preferable to perform bright annealing after the cold rolling treatment.

In the present invention, the reason why the surface grinding treatment is performed in the temperature range of 80 ° C. to 550 ° C. is that the temperature is 80 ° C.
When the temperature is lower than 0 ° C, the work hardening inhibiting ability of the surface layer by grinding is low, and particularly in the metastable austenitic stainless steel, a large amount of martensite phase is induced, so that the surface hardening proceeds remarkably. On the other hand, if the temperature exceeds 550 ° C., a temper color is generated after grinding and the surface gloss is impaired, so the temperature of the surface grinding treatment was set in the range of 80 to 550 ° C.

The reason why the cold rolling treatment is carried out at a rolling reduction of 40% or more is that if the rolling reduction is less than 40%, the linear indentations due to the abrasive grains during grinding are not sufficiently smoothed and good surface gloss is obtained. Because I can't.

[0012]

In the present invention, since the surface grinding treatment is carried out at a temperature of 80 ° C. or higher, the surface layer is soft, and particularly in the case of metastable austenitic stainless steel, the processed surface becomes a γ phase single phase and suppresses the generation of martensite phase. can do. Further, by setting the rolling reduction to 40% or more, the surface is sufficiently smoothed and good surface gloss can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated apparatus. FIG. 1 is a schematic view showing the method of the present invention in the order of steps. That is, the method for producing a stainless cold-rolled steel strip according to the present invention is roughly constituted by a continuous line of annealing treatment 6-grinding treatment 8-cold rolling treatment 12.

More specifically, 1 is a pay-off reel for rewinding and feeding a strip-shaped metal body, 2 is strip-shaped stainless steel that has been hot-rolled or continuously cast into thin-walled slabs, and 3 is a dummy plate for the strip-shaped stainless steel 2. , Leader) and welding between leaders. For example, a submerged arc welder, a TIG welder, a plasma welder, or a spot welder is used. 4 is a trimmer for cutting and removing edge flaws and hot cracks generated in the band-shaped stainless steel 2 at the time of hot rolling or continuous casting of thin slabs, and 5 is a relatively small one among such flaws and cracks. It is an edge grinder for grinding and removing.
Reference numeral 6 denotes a solution treatment apparatus provided as necessary, of which 6a is a heating furnace for annealing the band-shaped stainless steel 2, for example, a heating furnace using heavy oil or gas heating, or induction heating, direct current heating. It is an electric furnace. Further, 6b is a cooling zone for cooling the strip-shaped stainless steel 2 after heating, and for example, gas cooling, spray cooling, spray cooling, or roll cooling can be used. Reference numeral 7 is a shape correcting device for treating the band-shaped stainless steel 2 as necessary, for promoting the progress of cracks and peeling on the surface of the band-shaped stainless steel 2 and facilitating uniform grinding / polishing. Bending and warping are corrected.

Numeral 8 is an in-line warm grinding apparatus, which is one of the features of the present invention, to which the band-shaped stainless steel 2 in the temperature range of 80 to 550 ° C. is supplied. The temperature of the strip-shaped stainless steel 2 is controlled by controlling the cooling after the heat treatment.
The temperature can be maintained by another heating means. The warm grinding device 8 includes, for example, a plurality of stands, each of which is composed of an elastic grindstone roll 8a and a pressing roll 8b.
The belt-shaped stainless steel 2 is placed and subjected to heavy grinding on both front and back surfaces. Here, the elastic grindstone roll is a grindstone in a roll shape having elasticity to some extent in order to easily fit the shape of the plate, and is formed into a roll shape by laminating disks coated with abrasive grains (lamination Type), a roll wheel formed by laminating flap wheels (flap type), and a roll-shaped nylon resin containing abrasive grains (integrated type).
Either may be adopted. In an in-line grinding machine having such an elastic grindstone roll, at least 3 elastic grindstone rolls 8a for grinding one surface of the band-shaped stainless steel 2 are used.
It is desirable to use an elastic grindstone roll which is arranged so as to form a body and has an abrasive grain count of # 240 or more on the final stand for grinding each surface. Further, the grinding device 8 has
It is preferable to place the laminated elastic whetstone rolls on at least the first stand.

That is, since the thickness of the scale and the depth of the surface flaw, which are generally generated by annealing in the hot rolling or subsequent steps, continuous casting of thin slabs, etc., are at least about 5 to 10 μm, the scale and the surface flaw are removed. Therefore, it is necessary to grind at least 10 μm or more, and it is desirable to grind more than 20 μm for more reliable grinding. Further, when Rmax exceeds 30 μm in the surface roughness after heavy grinding, deep grinding marks such as scratches occur, and in order to sufficiently remove this, the load of the surface conditioning in the subsequent step increases. Therefore, it is desirable that Rmax ≦
20 μm is preferable, for which the grinding is performed on one side in a plurality of passes, preferably 3 passes or more, as described above, to reduce the load per pass, and further, the abrasive grain count of the final pass is # 240 or more. As a result, the surface roughness can be adjusted.

Reference numeral 9 denotes a degreasing / cleaning device which is arranged after the grinding device 8 as required, and, for example, a plurality of stands, each pair of which consist of a brush roll 9a and a press roll 9b, are arranged, or a brush roll. 9a are provided so as to face both the front and back surfaces of the strip-shaped stainless steel 2. The brush roll 9a may be, for example, a roll formed of a brush made of nylon fiber containing abrasive grains. In addition, a warm water spray 9c is provided on the second half of the degreasing / cleaning device 9.
Are placed.

Reference numeral 10 is a light acid cleaning device selectively provided. A cleaning device 11 is, for example, a brush roll 11a.
A plurality of stands, each of which is paired with the press roll 11b, are arranged in a plurality of stages, or the brush rolls 11a are provided so as to face both front and back surfaces of the belt-shaped stainless steel 2. A hot water spray 11c is arranged in the latter half of the cleaning device 11.

Reference numeral 12 is a cold rolling apparatus, and for example, a multi-stage rolling mill comprising work rolls 12a and backup rolls 12b can be used. Here, the band-shaped stainless steel 2 that has been ground is subjected to cold rolling at a rolling reduction of 40% or more to flatten the ground surface and form a beautiful glossy surface.

Reference numeral 13 is a device for performing bright annealing equipped with a degreasing / cleaning device, and this device performs annealing of the strip-shaped stainless steel 2 in a stream of reducing or non-oxidizing gas or in a vacuum furnace. The purpose is to prevent oxidative decarburization on the surface of the strip-shaped stainless steel 2 and maintain the metallic luster.

Reference numeral 14 is a temper rolling mill, and for example, a multi-stage rolling mill comprising work rolls 14a and backup rolls 14b can be used. This temper rolling is carried out as necessary in order to correct the shape and not to output the Luders wire, and the strip-shaped stainless steel 2 has a reduction rate of 1 to 5%.
A slight rolling is performed. Reference numeral 15 is a tension reel for winding up the manufactured cold rolled stainless steel strip.

The apparatus shown in FIG. 1 is an example for carrying out the method for producing a stainless cold-rolled steel strip according to the present invention, and in some cases, the shape correcting apparatus 7 and a series of cleaning apparatuses (degreasing / cleaning). Device 9, light acid cleaning device 10, cleaning device 1
1), the bright annealing device 13, the temper rolling device 14 and the like may be appropriately or partially omitted.

[0023]

【Example】

[Example 1] SUS304, 2.5 mm thick sheet of metastable austenitic stainless hot rolled coil, 1100 ℃
The temperature of this hot-rolled coil was adjusted to 105 ° C, and then the hot-rolled coil was made to bite into a roll-type flaw removal grinding machine, and the grinding amount was set to 45
Grinding was performed so that the surface roughness (Rmax) was 8 μm. Then, the hot-rolled coil was cold-rolled with a multi-roll mill having a work roll diameter of 50 mm to obtain a cold-rolled steel strip having a plate thickness of 0.8 mm. Then, after degreasing treatment, bright annealing was performed and temper rolling was performed at a rolling reduction of 0.5%, and the surface gloss of the obtained metastable austenitic stainless cold-rolled steel strip was measured. As a result, the glossiness (Gs 45 °) was 860, and it was confirmed that the film had good surface properties.

[Comparative Example 1] SUS304, plate thickness 2.5 mm
The metastable austenitic stainless hot-rolled coil of No. 2 was kept at a temperature of 1100 ° C. for 30 seconds for solution treatment, and then air-cooled, and the temperature of this hot-rolled coil was set to 25
Allowed to cool to ° C. Then, it was bitten into a roll-type flaw removing grinder, the grinding amount was 40 μm, and the surface roughness (Rmax): 7
Grinding was performed to obtain a thickness of μm. Subsequently, this hot rolled coil was cold rolled by a multi-roll mill having a work roll diameter of 50 mm to obtain a cold rolled steel strip having a plate thickness of 0.8 mm. After degreasing,
Bright annealing was performed, temper rolling was performed at a rolling reduction of 0.5%, and the surface gloss of the obtained metastable austenitic stainless cold-rolled steel strip was measured. As a result, glossiness (Gs 45 °)
Was 795, and the surface was whitish and the gloss was insufficient.

[Example 2] SUS430LX, plate thickness 3.
0mm ferritic stainless steel hot rolled coil
The temperature of this hot rolling coil was kept at 00 ° C for 30 seconds for solution treatment for 30 seconds and then cooled by air, and the temperature of this hot rolling coil was adjusted to 450 ° C.
Grinding was performed so that the surface roughness (Rmax) was 9 μm. Then, the hot-rolled coil is worked roll diameter 60
A cold-rolled steel strip having a plate thickness of 0.8 mm was obtained by cold rolling with a mm multi-stage rolling mill. Then, after degreasing treatment, bright annealing was performed, temper rolling was performed with a rolling reduction of 1.1%, and the surface gloss of the obtained ferritic stainless cold-rolled steel strip was measured. As a result, it was confirmed that the glossiness (Gs 45 °) was 855, and that it had good surface properties.

[Comparative Example 2] SUS430LX, plate thickness 3.
0mm ferritic stainless steel hot rolled coil
The solution was heat-treated at a temperature of 00 ° C for 30 seconds, then air-cooled, and the temperature of the hot-rolled coil was cooled to 25 ° C. Then, it was bitten into a roll-type flaw removal grinder, and grinding was performed with a grinding amount of 45 μm and a surface roughness (Rmax): 8 μm. Subsequently, this hot rolled coil was cold rolled by a multi-stage rolling mill having a work roll diameter of 60 mm to obtain a cold rolled steel strip having a plate thickness of 0.8 mm. Then, after degreasing treatment, bright annealing was performed, temper rolling was performed with a rolling reduction of 1.1%, and the surface gloss of the obtained ferritic stainless cold-rolled steel strip was measured. As a result, the glossiness (Gs 45 °) was 780, and the surface gloss was insufficient.

[0027]

As described in detail above, according to the present invention,
By constructing a continuous line of annealing-grinding-cold rolling-annealing, it is possible to improve the efficiency of the treatment work, and since the surface grinding treatment is performed at a temperature of 80 ° C or higher, hardening of the worked surface is suppressed, and particularly Stable austenitic stainless steel can prevent the generation of martensite phase, and by setting the rolling reduction in cold rolling to 40% or more, the surface is sufficiently smoothed and has good surface gloss. A metastable austenitic stainless cold-rolled steel strip can be obtained.

[Brief description of drawings]

1 shows an apparatus for carrying out the method according to the invention, 1
The schematic diagram shown in an example.

[Explanation of symbols] 1 ... Pay-off reel 2 ... Band metastable austenitic stainless steel 3 ... Welding machine 4 ... Trimmer 5 ... Edge grinder 6 ... Solution treatment device 7 ... Shape correction device 8 ... In-line grinding device 9 ... Degreasing / cleaning device 10 ... Light acid cleaning device 11 ... Cleaning device 12 ... Cold rolling device 13 ... Bright annealing device 14 ... Temper rolling device 15 ... Tension reel

Claims (4)

[Claims] 1. A method for producing a stainless cold-rolled steel strip, wherein a stainless hot-rolled coil or a thin cast coil is treated through a process including a solution treatment, a surface grinding treatment, and a cold rolling treatment. Treatment at a temperature of 80 ° C to 550
And a cold rolling treatment at a rolling reduction of 40% or more. 2. The method for producing a stainless cold-rolled steel strip according to claim 1, wherein after the solution treatment, the hot-rolled coil or the thin slab coil is shape-corrected for surface flattening. 3. The stainless cold-rolled steel according to claim 1, wherein after the surface grinding treatment, the hot-rolled coil or the thin slab coil is washed to remove foreign matters such as grinding dust on the surface. Method of manufacturing obi. 4. The method for producing a stainless cold-rolled steel strip according to claim 1, wherein bright annealing treatment is performed after the cold rolling treatment.