JPH0262323B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is applicable to cold rolling of two or three layers of cladding material (hereinafter simply referred to as "cladding material") to a predetermined thickness. The present invention particularly relates to a method for preventing the occurrence of chattering (also referred to as "chattering") that appears as minute undulations on the surface of a rolled thin plate cladding material.

Such clad materials are made by cladding stainless steel, nickel, copper, titanium, or alloys thereof to base materials of mild steel, stainless steel, nickel, copper, titanium, or alloys thereof, There are two-layer clad materials that are clad on only one side of the base material and three-layer clad materials that are clad on both sides of the base material.

(Prior art) Conventionally, for example, in order to manufacture thin plate cladding material with a thickness of 6 mm or less, the thick cladding material is generally hot rolled, heat treated and descaled, and then warm or cold rolled ( They are manufactured by rolling them to a predetermined thickness using a method called "cold rolling" hereinafter.

During this cold rolling, a chattering phenomenon in which minute waviness appears on the surface of the plate in a direction perpendicular to the rolling direction is observed even in a single layer material. In the case of clad wood,
This tendency was especially strong, and the occurrence of chattering with a pitch width of about 1 mm and a peak height of about 1 μm to about 10 μm was inevitable.

Conventionally, measures to prevent such vibrations were to perform cold rolling in a way that prevents the vibrations themselves from occurring, and to correct the vibrations once they have occurred.

Methods for correcting the vibrations that have occurred include applying skin pass rolling while applying a large tension after cold rolling, and stretching each sheet with a stretcher after shearing.
Alternatively, there is a method of polishing a product that has been subjected to processing such as bending with a coarse abrasive to make chattering less visible.

However, for thin plate cladding materials, for example, when the total plate thickness is 1
For thin cladding materials with a cladding ratio of 10%, the thickness of the composite material is 0.1mm, and the conventional method described above, which removes cracked cladding by polishing it with the final product, is not possible. In industrial production lines, excessive grinding is sometimes carried out, and there is a risk that the composite material will be scraped off and the base material will be exposed. Therefore, it is necessary to avoid abrasive grinding of the finished product as much as possible. For these reasons, products made of thin cladding materials are only polished to give them a glossy shine, and as a result, materials with chattering become more noticeable, significantly impairing the aesthetic appearance of the finished surface, and reducing the quality of thin cladding materials. This will reduce the product value.

However, on the other hand, it is difficult to completely prevent chattering by straightening by skin pass rolling or stretcher, and the cost is high.

Thus, as a measure to prevent the occurrence of chattering in thin plate cladding materials, it has been strongly desired to develop a method that prevents the occurrence of chattering itself, rather than a method of eliminating the chattering that has already occurred.

By the way, in JP-A-58-110104, it is proposed to specify the cold rolling conditions, particularly the total rolling reduction rate, for the purpose of preventing the occurrence of chattering in stainless steel strips. In other words, the cause of chattering can be reduced by 50 to 90%.
This is because cold rolling was performed at a single total reduction rate, but it consists of dividing rolling at a total reduction rate of 40% or less each time while adding an annealing and pickling process prior to each cold rolling. The method is disclosed. In this example, the material is first rolled at a total reduction of 37.5%, then annealed and pickled, and then rolled at a reduction of 40%.

This method is for single-layer stainless steel materials, and is not always satisfactory, as it requires annealing and pickling each time, resulting in an expensive process, and the content provided by the present invention is largely unsatisfactory. They are different.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a method for preventing the occurrence of chattering itself during cold rolling when producing a two-layer or three-layer thin plate clad material. be.

Another object of the present invention is to provide a rolling method that does not cause chattering during cold rolling of two- or three-layer thin plate cladding materials.

Furthermore, another object of the present invention is to provide a method for preventing the occurrence of chattering itself while continuing cold rolling without requiring an annealing step during cold rolling of a two-layer or three-layer thin plate clad material. That's true.

(Means for Solving the Problems) In order to solve the problems of the above-mentioned prior art, the present inventors have conducted various studies and have found that, in general, in the case of thin plate clad materials as well as in the case of single-layer materials, focused on the occurrence of chattering during cold rolling, and conducted various studies to determine the cause of this in the rolling process and to see if it is possible to prevent the occurrence of chattering itself by changing rolling conditions.

Here, 304L/mild steel/
We investigated the reduction rate per pass and the degree of chattering during cold rolling of a 304L three-layer clad material with a total thickness of 4.0 mm. The results are summarized graphically in Figure 1. When the initial rolling reduction is 0%, that is, when rolling from 4 mm, and when the rolling reduction is 50%, that is, 2 mm.
When changing the reduction rate from 4mm to 2mm (the reduction amount per pass was reduced to prevent vibration from occurring), the previous reduction rate was 70%,
That is, the relationship between the rolling reduction rate and the occurrence of chattering was shown when the rolling reduction rate per pass was changed from 1.2 mm.

According to the illustrated results, if the initial rolling reduction rate is 0%, if the rolling reduction rate in one pass exceeds 25%, it will be rejected due to vibration, and if the rolling reduction rate up to that point is 50%, the rolling reduction rate per pass will be rejected. If it exceeds 21%, it will be rejected.
Furthermore, if the rolling reduction rate up to that point was 70%, chattering occurred when the rolling reduction rate per pass exceeded 18%.

From this, it can be seen that the working conditions for preventing vibration during cold rolling, that is, the rolling reduction rate, are greatly influenced by the previous cold working history.

As a result, the present inventors found that there is a certain correlation between the amount of reduction and the occurrence of chattering when cold rolling thin clad materials to a predetermined thickness, similar to single-layer materials. At the same time, I learned that there was a certain correlation with the previous machining history, and after further research, I found that the rolling strain per pass was within the area surrounded by points A, B, C, and D in Figure 2.
The present invention was completed based on the discovery that the occurrence of chattering can be effectively prevented by desirably making the amount of rolling strain at each rolling process at least not larger than that of the previous rolling.

Thus, the gist of the present invention is to calculate the amount of rolling strain per pass on the vertical axis (y-axis) when rolling a two- or three-layer cladding material to a target thickness using a cold rolling mill. Rolling strain amount ε per pass
, the horizontal axis (x-axis) is the total cold rolling strain ε〓, and the point (0, 0.288) surrounded by the straight line shown by the formula y = -0.082x + 0.288, the x-axis, and the y-axis, B (0,
0), C (2.5, 0), and D (2.5, 0.083).

In other words, the present invention attempts to perform cold rolling continuously and regulate each rolling operation by the amount of rolling strain, and in that case, it is possible to control the rolling reduction without inserting an annealing process in the middle of rolling. This is always regulated by the amount of total rolling strain. Therefore, according to the present invention, the occurrence of vibration, which has been a problem in the past, can be completely prevented even by the inexpensive means of designing the pass schedule.

In the past, cold rolling was only carried out at a rolling reduction of 40% or less after the rolling history was removed by annealing each time.

Here, the above rolling strain amount ε per pass is defined by the following formula.

ε=Int ₀ /t ₁ ......Formula However, t ₀ and t ₁ each indicate the plate thickness before and after cold rolling.

(Function) Using various types of clad thin plate cladding materials with a thickness of 3 to 10 mm, the maximum total cold rolling reduction amount was determined in terms of true strain by various combinations of rolling strain per pass in a small rolling mill. After rolling to 3.0 (95% reduction),
A thin plate of clad material is manufactured through the usual processes such as heat treatment and pickling, and the height of the cracks is measured using a roughness meter while the plate is still flat, and the surface is lightly polished with #1000 abrasive paper. visually inspected the degree of occurrence of chattering.

Furthermore, these materials were subjected to cylindrical drawing (punch diameter: 40 mm), the side walls of the cylindrical products were polished with #1000 abrasive paper, and the occurrence of chattering was determined by visual observation.

The graph in FIG. 2 summarizes the results of a series of tests using mild steel as the base material and stainless steel plate as the composite material in terms of the amount of rolling strain per pass. In the figure, by regulating the amount within the range surrounded by points A, B, C, and D, and preferably decreasing the amount of rolling strain in sequence, no vibration occurs during cold rolling. .

It was also confirmed that a similar tendency is not limited to a specific combination of composite material and base material, but is observed in general two-layer or three-layer clad materials. Examples of these clad materials are two-layer clad materials such as titanium plate and mild steel, titanium plate and stainless steel (430), aluminum plate and stainless steel (304), copper plate and stainless steel (304), or titanium plate/mild steel/titanium plate. It is a three-layer clad material such as plate, 25Cr-50Ni alloy/stainless steel (304)/25Cr-50Ni.

Visual observation of the flat plate and cylindrical drawing sidewall revealed that cold-rolled plates with a poor degree of vibration had a large peak height of vibration, reaching 3 to 10 μm. The height of the peaks was 1 μm or less for those that passed the visual observation, and the height of the peaks was about 0.5 μm or less for those that had no problems at all.

By the way, the vibration evaluation should be expressed by the height of this peak, but the height of the peak of 1 μm or less, which is considered good, is actually affected by the surface roughness, so even if the vibration height is accurately measured, it will not be very accurate. There is no meaning, and in the present invention, vibration evaluation was carried out as a four-level evaluation of large vibration, small vibration, extremely small vibration, and no vibration. Two levels of minimal vibration and no vibration were considered to have passed.

In addition to the above examples, nickel plate and stainless steel plate (316L), copper plate and stainless steel plate (304),
Alternatively, we investigated two-layer cladding such as 25Cr-50Ni alloy plate and stainless steel plate (304L), and three-layer cladding of stainless steel plate (430)/mild steel/stainless steel plate (430), and a similar tendency was observed. It has been found that chattering can be almost completely prevented by performing cold rolling within the range surrounded by points A, B, C, and D in the figure.

Here, the amount of rolling strain y (true strain) per pass in Fig. 2 is y≦-0.082x+0.288 (where X is the total amount of cold rolling strain ε〓) This is a numerical value expressed in true strain.For example, when rolled from 4 mm to 2 mm in multiple passes, the total cold rolling strain amount ε〓 becomes In4/2 = 0.693). Therefore, according to the present invention, by repeating cold rolling within a range that satisfies the formula and in a manner that successively reduces the amount of rolling strain, chattering can be almost completely prevented.
On the other hand, if the total cold rolling strain amount ε〓 exceeds 2.5, the rolling reduction per pass becomes 8% or less, which is too small and the number of rolling passes increases significantly, which is economically unfavorable. It was out of range. If the rolling reduction ratio becomes small in this way, it is a good idea in industrial production to soften the cladding material again by heat treatment before reaching the specified thickness, and then restart rolling under the conditions specified in the formula. .

Next, an embodiment of the present invention will be explained using an example using a 20-high cold rolling mill and a 4-high reversible rolling mill. In addition,
These examples are merely illustrative and do not limit the invention.

Example 1 Stainless steel plate (304L)/mild steel/stainless steel (304L) clad material (thickness: 4.5 mm) that has gone through the normal hot rolling process is rolled in a 20-high Sendzimer rolling mill.
Reduction rate per pass is 20%, 15%, 15 respectively
%, 15%, 15%, 15%, 15%, 15%, 13%, 11
%, 10%, and the amount of rolling strain is Fig. 2 A, B,
It was rolled using a reduction pass schedule Z within the area surrounded by points C and D, and then subjected to conventional processes such as heat treatment and pickling to produce a three-layer thin plate clad material product with a thickness of 0.8 mm.

The pass schedule Z of this example is summarized in FIG. In the figure, points A, B, C, and D are the same as those in FIG.

The thus obtained product was polished with #1000 abrasive paper and visually inspected for vibration, and the vibration was found to be good. In addition, a cylindrical drawing product was finished polished by sisal cloth polishing and visually observed, but no problem of chattering occurred.

Example 2 The same material as in Example 1 was used in a four-high reversible rolling mill to keep the amount of rolling strain per pass constant at 0.198 (rolling ratio 18%) from the first pass to the final pass as shown in pass schedule R1 in Figure 4. In the same case, as in the case of pass schedule R2, the amount of rolling strain was gradually lowered.The thin clad material was cold rolled to 0.8 mm, and then heat treated and pickled as usual. The process produced a thin plate clad material product. These vibration evaluations showed that there were no problems at all in the case of Pass Schedule R2, but when they were conducted with Pass Schedule R1, significant vibration occurred in the obtained clad material, making it difficult to commercialize it.

In the case of pass schedule R1, chattering occurred because the rolling strain per pass exceeded the range surrounded by points A, B, C, and D in Figure 2, which is the permissible rolling limit, in the latter half of rolling. This is because clad materials are used on actual production lines. Points A, B, C, and D in FIG. 4 are the same as those in FIG. 2.

(Effects of the Invention) As explained above, according to the present invention, it is possible to prevent the occurrence of chattering during cold rolling of thin plate cladding materials without the need for special equipment or equipment, and therefore it is possible to This method not only eliminates the need for a chattering correction process using a grinder, but also provides excellent effects such as eliminating the need for heavy grinding of thin plate clad material products.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between the rolling reduction per pass in cold rolling and the vibration evaluation; Fig. 2 is a graph showing the relationship between the total cold rolling reduction strain amount and one pass which regulates the cold rolling conditions in the present invention. A graph showing the relationship with the amount of rolling strain per hit; and FIGS. 3 and 4,
3 is a graph showing pass schedules of Examples 1 and 2 of the present invention, respectively.

Claims (1)

[Claims] 1. When rolling a two-layer or three-layer cladding material to a target thickness using a cold rolling mill, the amount of rolling strain per pass is plotted on the vertical axis (y-axis) per pass. Taking the amount of rolling strain ε and the total amount of cold rolling strain ε on the horizontal axis (x-axis), point A (0 , 0.288), B
A method for preventing vibration in cold rolling of clad material, characterized by regulating the amount within the range of (0, 0), C (2.5, 0), and D (2.5, 0.083).