JPS5822330A - Production of cold-rolled ferritic stainless steel sheet excellent in formability and surface brightness - Google Patents

Abstract

PURPOSE:To obtain the titled cold-rolled steel sheet excellent in workability and surface brightness, by subjecting a hot-rolled steel sheet to descaling, roughly grinding, primary cold-rolling with a fixed reduction ratio, recrystallization-annealing, acid-pickling, condition-rolling without a lubricant, finish cold-rolling with a fixed rolling ratio, recrystallization bright-annealing and then condition- rolling without a lubricant. CONSTITUTION:A hot-rolled steel sheet, which is dispersion-hardened or not dispersion-hardened, is subjected to descaling treatment including shot-blasting, etc. and then roughly ground. After roughly ground, the hot-rolled steel sheet is primarily cold-rolled with a rolling ratio of 75-80%, recrystallization-annealed, acid pickled and then condition-rolled without a lubricant with a rolling ratio of 0.5-5.0%. After condition-rolled, the steel sheet is finish cold-rolled with a rolling ratio of 37-44%, recrystallization bright-annealed instead of conventional recrystallization-annealing and acid-pickling, and then finally condition-rolled without a lubricant. As a result, a ferritic stainless steel sheet excellent in workability, e.g. hole-expansibility and deep-drawability, and surface brightness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method K11 for producing a cold-rolled stainless steel sheet with holes having excellent formability such as hole expansion formability and deep drawing formability, and surface gloss.

General-purpose ferritic stainless steel, represented by 8U8450, is relatively inexpensive, and its cold-rolled steel sheets are used in architectural interior materials, daily appliances, kitchen equipment, and various decorative items, such as spherical reflectors. It is used. In order for K to be suitable for applications such as ratios, the steel sheet must have good formability such as hole expansion formability and deep drawing formability, as well as excellent surface gloss.

However, from a technical standpoint of finishing a hot-rolled steel strip of ferritic stainless steel into a cold-rolled steel sheet of a predetermined thickness, the above-mentioned formability and surface gloss are characteristics that are difficult to coexist with.

In general, these two characteristics are related to the rolling rate of cold rolling, and the hole expansion ratio, which is an index of formability, is usually surface glossiness decreases as the rolling rate increases, and conversely, surface gloss improves as the rolling rate of finish cold rolling increases. Therefore, it is technically difficult to obtain a cold-rolled steel sheet that has both properties.

Nevertheless, these two incompatible characteristics are both highly K.
ll, tJ There has been a general trend in recent years to place seemingly harsh demands on products.

Ferritic stainless steel cold-rolled steel sheets obtained by conventional conventional manufacturing methods cannot be satisfactorily expanded and formed.
There were many cases where cracks occurred on the punched or cut surface when expanding the openings created by nonching + cutting with a punch, making the product unusable. Detection drawing is often carried out at the same time as or before or after the hole expansion forming process, but as is well known, ferritic stainless steel cold rolled steel sheets generally have poor deep drawability.

This poor formability is a very troublesome problem for cold-rolled ferritic stainless steel sheets, and it also ensures excellent surface gloss that can be used for applications such as the above-mentioned ornaments 1 and spherical reflectors. However, it is accompanied by further technical difficulties.

Ring treatment (pickling including mechanical descaling).

Rough sanding (usually with a belt grinder).

After performing primary cold rolling of 45-60%, recrystallization annealing and pickling, and final cold rolling of 60-8096, bright annealing and non-lubricated temper rolling (normal rolling"$0.8-1 .8%
) (see Figure FZ1). fth
In the conventional method shown in FIG. 41, the relatively recent prior art shown in FIG. 172, and the method of the present invention shown in FIG.
What they all have in common is - cold rolling,
The cold rolling of finishing cold rolling is carried out by a well-known cold tandem mill, Sendzimir mill, etc.9 The temper rolling is similarly carried out by a well-known double or quadruple rolling mill with a work roll diameter of 400 to 900 mm. It is carried out using a relatively large-diameter heavy roll and a very glossy hard roll with a surface roughness of 8.1 to 15 μm. In this case, non-lubricated temper rolling is Of course, this is well known), but the above rolling mill has zero lubrication condition II (dry condition II).
Temper rolling is a rolling process in which the work rolls and cold rolled stainless steel strips, that is, metals come into direct contact with each other, and the cold rolled steel strips are naturally tempered, but the slipping phenomenon described in rolling theory occurs. It is characterized by an increase in surface gloss. (Note that in Figure 171.f'〆2.'=3, * means a hot rolled steel strip that has undergone diffusion annealing or not.) Relatively recently, the above method has been improved, - The rolling rate of the next cold rolling was increased to 75 to 80 mm, a light polishing process (polishing with regular No. 1000 abrasive powder) was inserted before the final cold rolling, and the rolling rate of the final cold rolling was increased to 37 to 44 mm. A lowering method is used (see Figure 77"2).

With this method, a product with both of the above two properties can be obtained, but the light polishing process takes many minutes, and
It takes 24 hours to polish one ton coil.

The present inventors aim to improve this method, and as a means to replace light polishing, the present inventors used non-lubricated temper rolling (normal rolling rate of 0.5
~5. By inserting holes into holes, you can maintain superior quality and greatly improve productivity.

According to the present invention, a hot-rolled steel strip that has been diffusion annealed or has no T-holes is descaled.

Rough polishing, primary cold rolling at a rolling rate of 75 to 80 mm, recrystallization annealing and pickling, non-lubricated temper rolling, finishing cold rolling at a rolling rate of 57 to 44 mm, and re-rolling. Provided is a method for producing a cold-rolled ferritic stainless steel sheet with excellent formability and surface gloss, which comprises performing crystal bright annealing and finally non-lubricated temper rolling.

Further, according to the present invention, there is provided a method in which recrystallization bright annealing is performed in place of recrystallization annealing and pickling after the first cold rolling in the above method (see FIG. 3).

The hot-rolled steel strip, which is the starting material for the method of the present invention, is usually processed by diffusion annealing, but in some cases it is immediately descaled (pickled) and then sent to cold rolling without being subjected to diffusion annealing. (It is said that cold-rolled steel sheets with less occurrence of ripping can be obtained), so both are included. In the method of the present invention, descaling treatment means pickling that includes mechanical scale removal such as shot blasting or applying repeated bending strain using a processor-loaded leveler.

The method of the present invention is generally applicable to ferritic stainless steels in general, but its effects are particularly noticeable in 8 US 429, 4
50.45OL! , 8U8434°5U8410L.

The reason for limiting the primary cold rolling rate to 75-8C1 and the finishing cold rolling rate to 37-4496 in the method of the present invention is as follows.

When manufacturing a cold-rolled steel plate of a predetermined thickness from a hot-rolled ferritic stainless steel strip through the steps of primary cold rolling, recrystallization annealing, secondary cold rolling, and recrystallization annealing,
- A cold rolled steel sheet with improved hole expansion formability and deep drawing formability can be produced by setting the rolling rate in the secondary cold rolling to 70 to 90 - and making the cold rolling rate in the secondary cold rolling to 60 to 45g&. What could be obtained had already been envisaged by other inventors of the present applicant. (11? Kaisho 54-12842
According to research by the present inventors, No. 3) is further limited as described above, and non-lubricated temper rolling is performed within the range of the rolling rate of the next and Matsugi cold rolling, that is, finish cold rolling. This is because it has been found that by combining them during the manufacturing process, moldability and surface gloss are further improved.

In order to increase this surface glossiness, in other words, to minimize the surface roughness (unevenness), improvement of the surface texture of the hot rolled steel strip 9 Improvement of mechanical or chemical descaling treatment technology, and further simplification of rough polishing As a result of considering and improving methods such as reducing the number of passes and light polishing using as fine abrasive grains as possible, and simplifying the process, we achieved great results. The method of the present invention has been achieved which satisfies the above. By carrying out the method of the present invention based on the above effects, the surface gloss can be further increased and the customer's requirements can be satisfied.

In the method of the invention, as shown in FIGS. 1-2.

Inserting non-lubricated skin pass rolling as an alternative to light polishing before final cold rolling, which is just prior art.

As already mentioned above, the reason for inserting light polishing or non-lubricated temper rolling in place of it before finish rolling is as follows.

In the cold rolling of stainless steel, which has relatively high deformation resistance, by either rolling mills such as cold tandem mills or Senshimia mills, normal rolling oil is used. The concave part (dent) of the uneven part of the kit is caught in one work roll in the state of being stuck (or pooled). K like this 9
Due to the contact between the work roll and the material surface, the rolling oil trapped in the groove has no place to escape and continues to be rolled while being trapped, and when rolling is completed (when the above contact is broken)
The rolling oil is released, but on the other hand, this rolling oil accumulates and the shape of the large concave portion changes compared to before rolling.

Although it is slightly reduced due to the slipping phenomenon, there is almost no change.

In other words, the degree of surface roughness (unevenness) of the material before cold rolling remains almost the same after rolling, so in order to obtain the roughness of the material surface, K is set before cold rolling, especially at the manufacturing end. It is necessary to reduce the roughness of the material surface as much as possible before finishing cold rolling near the process. Light polishing or non-lubricated temper rolling is used as a means for this purpose. The rolling rate of the first non-lubricated skin pass rolling is preferably L5 to 5.0.

This is due to the reasons stated below.

As a temper rolling alternative to light polishing, at least o, 5% 1
! Although it is desirable that the surface gloss be different, the surface gloss reaches its upper limit at about 596, and no further improvement in gloss can be expected.

If this upper limit is reached, the number of nozzles will inevitably increase due to non-lubricated temper rolling where metals come into contact with each other.

Reverse Kj due to generation of metal powder or other causes.
t, the stream is lost. This temper rolling is performed in one or several passes, but it goes without saying that it is desirable to adjust it while taking into account the desired degree of gloss and productivity, and to perform the process with as few passes as possible. Nor.

The rolling rate of the final temper rolling [18 to 12% is within the conventional range, but since this is the temper rolling after the final recrystallization bright annealing (softening) is performed in the master @, In order to ensure the formability of the product, it is not preferable to use a large rolling rate for K, and it should be kept to the minimum necessary.

The basic steps of the method of the present invention are shown in FIG.

The details have been explained above, but in order to achieve both formability and surface gloss of ferritic stainless steel cold-rolled steel sheets (products), the next and final cold rolling processes, the distribution of each rolling rate, and the finishing It consists of a non-lubricated temper rolling process of cold rolling and its rolling rate, that is, a process and characteristics associated with the process.

Further, the present invention is configured in such a manner that it is necessary to adopt the shortest manufacturing process in order to maintain high productivity while providing the product with both characteristics. Conventional polishing processes require large-scale equipment.

Therefore, not only does it require a large space and a huge investment in equipment, but it also increases the number of manufacturing staff and requires a variety of materials for polishing, which is difficult to purchase, store, and manage. The work efficiency was also poor, and it took 24 hours with only 6 tons of coils. However, according to the present invention, various problems in the polishing process described above are alleviated, and above all, workability on site is improved, and a 6-ton coil can be manufactured in just 2 hours, resulting in an increase in productivity. The method of the present invention is roughly estimated.

Compared to the conventional method, the amount of bone used is approximately 1/20th, resulting in an 11-fold increase in productivity.

Next, the present invention will be specifically explained with reference to Examples.

C: Q, 05 Qi S i: [L54 'A
eM! 1: α51%.

P: 0.21 excellent, S: [LOO8*, Cr: 1
667 chi.

N: The original plate of 161111 thickness, which was diffusion annealed and descaled from 5US430 steel with α18 arrogance, was subjected to the process shown in Fig. 2 (fC and the treatment after the primary cold rolling was by normal annealing and pickling). Finally, α5 parrot cold-rolled steel sheet was produced under these conditions.

Regarding the sample cold-rolled steel sheet obtained by K in this way.

The fourth result is the result of examining the hole expansion ratio and R (Lankford value).
As shown in FIG. The hole expansion test was performed using a diameter of 10
The diameter d at which a 1-dimensional ycK crack occurs was determined by drilling a hole of m size by cutting and expanding the 1-dimensional hole with a ball lI punch to find the hole expansion ratio α = (d-10)/10. .

Looking at Figure 4, we see that the rolling rate of the next cold rolling was increased.

It can be seen that the hole expansion ratio increases as the rolling rate of finish cold rolling is lowered.

FIG. 9 shows an investigation of the relationship between the rolling ratio distribution and the R value in the subsequent and final cold rolling. As is well known, the R value is an index of deep drawability, and is determined by the ratio of the logarithmic strain in the sheet width direction to the logarithmic strain in the sheet thickness direction of a tensile test piece, and the higher the R value, the better the deep drawability. This is the result. As is clear from the results shown in Figure 6, K.

The R value is approximately 58 to 80% at the rolling reduction of the primary cold rolling.

It can be seen that the maximum value (maximum peak area) is reached when the finishing cold rolling reduction is between about 57 and about 67 minutes.

In other words, deep drawability has a maximum value or a maximum peak area, and is regulated by the rolling ratio ratio, and sufficient deep drawability cannot be obtained even if the rolling ratio is higher or lower than a certain range. There isn't.

From the results shown in FIGS. 4 and 5, the range that satisfies hole expansion formability and deep drawability at the same time is approximately 58 to 80% of the rolling ratio of the primary cold rolling that exhibits the maximum R value.

The finishing cold rolling is regulated at a rolling rate of about 37 to 67 g, and the rolling rate may be distributed within this range.

However, in terms of surface gloss, as judged by visual observation, the rolling ratio of the cold grinding wheel was less than 75%.

In the area where the finishing cold rolling reduction is 45 or higher.

It was found that the Motosawa variation was inferior to those between the above values.

The large surface roughness was determined by the JIS B O601r surface roughness measurement method, and a representative sample a of the above test.

The results of b and e are shown in the table below.

Next, the above-mentioned materials are processed through the process shown in FIG.

However, the process after cold grinding was replaced with recrystallization annealing and recrystallization bright annealing. This sample d
The results for K are also listed in the table above.

On the other hand, sample 6, which was made of the same material and processed in the same manner as sample a by the process shown in FIG. Ta. Note that light polishing for preparing this sample was performed using a No. 1000 abrasive material containing polyvinyl alcohol as a binder.

As seen here, sample e (product) obtained by the conventional method shown in Fig.
It turns out that the quality is almost the same as that of the product). On the other hand, samples A and C (products) made by the conventional method have a lower primary cold rolling rate and a higher finishing cold rolling rate compared to 9 inventive samples a and d (products) K, so there is no difference in R value. Although it is not recognized, the hole expansion ratio is low, the surface roughness is high, and the surface gloss is poor.

As mentioned above, it must be said that the industrial utility of the present invention is extremely large.

[Brief explanation of the drawing]

No. r/1. Figure I'72 is a flowchart showing the steps of the conventional method. FIG. 3 is a flowchart showing the steps of the method of the present invention. FIG. 4 is a graph showing the relationship between the rolling rate, finishing rolling rate, and Lankford (R) value in cold rolling of a cold rolled stainless steel sheet. FIG. 5 is a graph showing the relationship between the first rolling force, the finishing rolling rate, and the redundancy expansion ratio in cold rolling of a cold rolled stainless steel plate. Patent Applicant Nisshin Steel Co., Ltd. Agent Patent Attorney Masahiro Matsui (2 others) Fifth Factor F-i+<φ) Commissioner of the Japan Patent Office Shima 1) Haruki-dono 1, Indication of Case 1982 Patent Application No. No. 120632. 3 Relationship with the case of the person making the amendment Patent applicant address Name) (458) Nisshin Steel Co., Ltd. 4 Agent 5 Date of amendment order Voluntary 6 Number of inventions increased by amendment Errata with no blank On each page and line shown in , the description "Before amendment (incorrect)" will be corrected as "After amendment (correct)." 41B Fig. 2 Fig. 6 Fig. 5 6 Hard roll Hard roll 520 Polishing Polishing 7 7 (This one has been deleted) 162 Fig. 2 Fig. 6 Fig. 18 4 Flow diagram Process diagram 18 6 Flow diagram Process diagram 18 8 - Next rolling rate and finishing - Next rolling rate and rolling rate Finishing rolling rate 188-9 Lankford (R) value Hole expansion ratio (α)
1811-Next rolling rate and finishing - Arrow ball 4i-rate and rolling rate Finishing rolling rate 1811 hole expansion ratio (α) Rank four r
(R) Value■ Insert the following passage between lines 15 and 16 on page 13. [Here, the hole expansion ratio (ψ) required by the customer's processing is
There are differences depending on the customer's processing details, but if special hole expansion formability is required, the hole expansion ratio (ψ) should be approximately 0.75 or more. Therefore, the results shown in Figure 4 show that hole expansion formability varies. Considering this, the rolling ratio of primary cold rolling is about 75 inches or more,
A good product can be obtained when the rolling rate of the final cold rolling is about 44 ts or less. ” Seal Delete lines 10 to 20 on page 14, all lines on page 15, and all lines on page 17, and insert the following passage. The rolling ratio may be distributed within this range, which is regulated by the rolling ratio of about 75 to 80% for the primary cold rolling and about 67 to 44% for the finishing cold rolling. However, for surface gloss, 5U8430 shown in the table below
Judging from visual observation, the processing results show that the sample was processed using the conventional method at the factory shown in Figure 1. eFit % Tozawa Jaku on the surface is judged to be in the middle/lower rank, the rolling rate of the second cold rolling group is high, and the rolling rate of the finishing cold rolling is low. However, sample a, which was processed by recrystallization annealing and pickling after the primary cold rolling in the process shown in FIG. 5 of the present invention,
Even though the rolling rate in the primary cold rolling was higher than that of Sample C, and the rolling rate in the finishing cold rolling was lower, the surface glossiness was ranked higher. In order to quantitatively judge this surface glossiness, the surface roughness is determined by JI.
8 BO601r surface roughness" measurement method and compared, it was found that the sample treated by the process shown in Figure 1 of the conventional method had a roughness of 0.2 to 0.3μ, and sample C had a roughness of 0.6 to 0.4μ, while sample C had a roughness of 9. Sample a treated by the third WJ process of the present invention was 0.
Comparing 1 to α2μ with the surface roughness determination described above, the smaller the surface roughness, the better the surface gloss, showing the same tendency as papermaking. On the other hand, regarding the large wave ratio (ψ and R value), when processed using the process shown in Figure 3 of the present invention, there is no difference in R value compared to that processed using the process shown in Figure 1 of the conventional method. Ratio (α
) can be said to be low and excellent. In addition, sample a of the present invention was processed using the process shown in FIG. Therefore, it is judged that the present invention can replace the relatively recent prior art method of processing in the process shown in Fig. 2.In addition, in the process shown in Fig. 3, recrystallization annealing after primary cold rolling is performed. - Sample d, which was treated with recrystallization bright annealing instead of actual washing, is also shown, but since it is no different from sample a, it can be said that either method can be used for recrystallization annealing after primary cold rolling.j ■ Correct the table on page 16 of the same page to read "lower manure." ■ Correct figures 150 and 2 of the drawings to read as shown in the attached drawing.

Claims (1)

[Scope of Claims] 1. A hot-rolled steel strip that has been subjected to diffusion annealing or has not been subjected to overlapping is descaled, roughly polished, and subjected to primary cold rolling at a rolling ratio of 75 to 80, and then recrystallized. Formability, which consists of annealing and pickling, non-lubricated temper rolling, final cold rolling at a rolling reduction of 57 to 44 mm, recrystallization bright annealing, and finally non-lubricated temper rolling. A method for manufacturing ferritic stainless steel electrical testing steel plates with excellent surface gloss. 2. The method according to claim 1. A method characterized in that the rolling rate of the first non-lubricated skin pass rolling is α5 to S, OS, and the rolling rate of the final non-lubricated skin pass rolling is 0.8 to t2. 5. Descaling and rough polishing the hot rolled steel strip, which may or may not have been diffusion annealed. Primary cold rolling is performed at a rolling ratio of 75 to 80 mm, recrystallization bright annealing is performed, and non-lubricated temper rolling is performed. The method according to claim 3, wherein finish cold rolling is performed at a rolling reduction of 57 to 4496, recrystallization bright annealing is performed, and finally non-lubricated skin pass rolling is performed at a rolling rate of 4.%. The rolling ratio of the first non-lubricated skin pass rolling is Q, 5 to 50%, and the rolling ratio of the last non-lubricated skin pass rolling is α8 to 12%! How to make it into a statue.