JPS6123696A - Method for cold rolling dense hexagonal metal sheet - Google Patents

Abstract

PURPOSE:To obtain a metal sheet having a good surface quality with good productivity without forming oil pitch, by cold rolling a dense hexagonal metal sheet by using an emulsion type lubricant contg. an oil disperse phase having a specified median particle size and a specified degree of saponification. CONSTITUTION:A dense hexagonal metal sheet is cold-rolled by using an emulsion type lubricant contg. an oil disperse phase haing a median particle size of 6mu or below and a degree of saponification of 80 or above. The emulsion lubricant having a median particle size of 6mu or below can be prepd. by adding an anionic, cationic or ampholytic hydrophilic group-contg. surfactant to oil to thereby form an emulsion contg. oil particles uniformly dispersed therein. When the lubricant has a degree of saponification of less than 80, rolling pressure is too high and difficulty ariser in carrying out rolling, while when the degree of saponification is 80 or above, an increase in rolling pressure is relatively gradual and the average rolling pressure reaches its peak at a pressure of 170kg/mm.<2> or below and is no longer increased, even when rolling reduction is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cold rolling a dense hexagonal metal plate, and particularly to a method for manufacturing the same metal plate with almost no oil pits and good surface quality with high productivity. It is.

The close-packed hexagonal metal plate to be subjected to cold rolling in the present invention is a general term for metal plates having a close-packed hexagonal crystal structure, such as Ti5Ti alloy, Zr, and Zr alloy.

In the cold rolling of metal plates, it is essential to use rolling oil to prevent seizure, but on the other hand, if too much rolling oil is supplied, fluid lubrication will occur between the rolling rolls and the material to be rolled, and the high-pressure rolling oil will It is known that unevenness (so-called oil pits) is produced on the free surface of the rolled material in contact with the rolling material. In particular, in metals such as the dense hexagonal metals, which have significantly different deformation resistance depending on the crystal orientation, oil pits are likely to occur because crystals in orientations with lower deformation resistance are easily deformed. It is not uncommon for the depth to reach more than ten microns. These oil pits significantly impede the surface precision of the final product, so how to reduce the size of the oil pits that occur during the rolling process is an important issue in the cold rolling of this type of difficult-to-work metal sheet. It has become. The allowable limit of this oil pit varies depending on the required surface accuracy depending on the product's use, but the depth is 1 to 2.
It is often required that the thickness be less than μm.

By the way, as mentioned above, oil pits are thought to be caused by an excessive amount of lubricating oil intervening between the rolls and the rolled material, and the amount of lubricating oil drawn in must be minimized and made uniform. If this is possible, it is thought that the oil pit can be made as shallow as possible. However, in this case, if the oil film runs out during rolling, a seizure problem will occur, so when rolling metal sheets that are prone to seizure, such as Ti+Zr or their alloys, it is important to apply only the minimum amount of oil necessary. It is extremely important to ensure uniform adhesion over the entire surface of the processed plate. However, with conventional lubricants, if an amount of lubricant that does not cause seizure occurs, oil bits will occur, whereas if the lubricant supply amount is reduced to the extent that oil pits do not occur, the oil film will run out and cause seizure. A problem arose, and it was not possible to solve the above two problems at the same time.

The present inventors focused on these circumstances, and aimed to solve two problems simultaneously: occurrence of oil bits due to excessive supply of lubricant and occurrence of seizure due to lack of oil film of lubricant, targeting dense hexagonal metal plates. In an attempt to establish a cold rolling method that would enable this, various studies have been conducted, focusing on the particle size, saponification value, rolling speed, etc. of emulsion lubricants. This product was completed as a result of the research conducted by the present invention, and its composition uses an emulsion-type lubricant containing an oil-based dispersoid with a center particle size of 6 μm or less and a saponification value of 80 or more, and has a dense hexagonal structure. The gist is that a crystalline metal plate is cold rolled.

In the present invention, as described above, the particle size and saponification value of the dispersoid constituting the emulsion cutting lubricant are strictly specified, and the reason for this is as detailed below. In other words, according to various preliminary experiments conducted by the present inventors, the lubricating ability a of emulsion-type lubricating oil and the emulsion concentration are ``significantly affected by the saponification value and particle size of the dispersoid.'' This was because of the knowledge gained, and we proceeded with research to quantitatively clarify these points. Then, emulsion-type lubricants (concentration 1 T or 0.5%) containing various tallow-based oils with different saponification values as dispersoids were prepared, rolling experiments were conducted using each lubricant, and rolling reduction Ct I =/ n
(b, o/h i )) and the average rolling pressure (Pm) were investigated. However, the rolling conditions are as follows: work roll diameter 254 mm + rolling speed 12 m/m, rolling reduction per pass of 10 inches, and thickness 1.0 I! A pure titanium plate of lff1 was rolled to a thickness of 0.5+++mt. The result is the first
As shown in the figure, the tendency for the average rolling pressure to increase as the rolling reduction rate increases varies markedly depending on the saponification value of tallow-based oil. It is thought that the rolling pressure will suddenly increase to a high t-force and the rolling operation will become substantially difficult. The higher the saponification value of tallow-based oil, the smaller the tendency for the rolling pressure to increase.The rolling pressure observed when using a lubricant with a saponification value of 80 is the limit for actual operation. If 4 is less than 80, the rolling pressure will be too high, making actual operation difficult. For those using tallow-based oil with a rating of 80 or higher, the above-mentioned increasing trend becomes relatively slow, and the average rolling pressure plateaus at about 170ψ or less, and even if the rolling reduction rate is increased, the average rolling pressure increases even more. Rolling pressure does not increase. As is clear from these results, in order to suppress the threading resistance during rolling and smoothly perform cold threading, it is necessary to have a saponification value of 80 AL or higher as the oil-based dispersoid that makes up the emulsion-type lubricant. It turns out that you should choose one.

Next, we conducted higher-level experiments to clarify the effects of oily dispersoid particle size and concentration on lubrication performance. However, the central particle size of the oil-based dispersoid referred to in the present invention refers to the particle size at the peak position in the emulsion particle size distribution as shown in Figure 2, for example, and the particle size distribution is measured using a Coulter counter (using a 50 μm aperture tube). Measured by

In the experiment, tallow-based oil (saponification value: 185) was used as the oil-based dispersoid, and emulsion-type lubricants with different center particle diameters and concentrations of the dispersoid were prepared.
The oil bit depth was compared with that of a Ti plate (crystal grain size: about 5 μm) cold rolled using a rolling roll at various rolling speeds.

The results are as shown in Table 1, and the central particle size of the dispersoid is 6.
By using an emulsion type lubricant having a diameter of 1 to 2 .mu.m or less, the oil bit depth can be kept to 1 to 2 .mu.m or less regardless of the emulsion concentration or rolling speed. On the other hand, if an emulsion type lubricant with a center particle diameter exceeding 10 μm is used, the oil bits cannot be made smaller even when the rolling speed is lowered to 50 m/min. Furthermore, if an emulsion lubricant with a center particle size of 6 to 10 μm is used, oil bits can be kept to a small level when the rolling speed is lowered, but when the rolling speed is lower than 200 m/min or more, which is used in actual cold rolling. At speed the oil bit becomes extremely deep. When using an emulsion type lubricant with a center particle size of 6 μm or less, the oil bit depth should be 200 mm.
A saturation state of #l is reached at a rolling speed of m/min, and even if the rolling speed is increased further, the oil bits do not become deeper. In other words, if an emulsion-type lubricant that meets the specified requirements of the present invention is used, the depth of the oil bit can be made extremely small regardless of the rolling speed, and this will fully meet the demand for improved productivity by increasing the rolling speed. You can go there.

In addition, Figures 3 and 4 are micrographs (all magnified at 400x) showing the surface properties of T (rolled plates). When using the emulsion type lubricant of H (comparative example), Figure 4 shows that the dispersoid is also made of tallow oil and the central particle size is 2 to 3 μm.
The cases in which an emulsion type lubricant having a concentration of 2-0 (invention example) is used are shown. Comparing these photographs, it is clear that when an emulsion type lubricant with a large center particle size is used, the oil bits generated on the surface of the rolled plate are extremely significant (Fig. 3), but this satisfies the specified requirements of the present invention. When an emulsion lubricant with a small center particle size is used, the number of oil bits is significantly smaller and the depth is shallower, at 1 to 2 μm (g, Figure 4).

Unit: 2 μm Another criterion for determining the particle size structure of an emulsion is to divide particles with a specific particle size as a boundary and divide them into particles with a content exceeding that particle size and particles with a content below that particle size, and calculate their content ratio ( Volume ratio: E, D, P, I: Emul-eion Dist
One possible method is to compare the results using the distribution profile index). Therefore, the present inventors conducted the following experiments in order to clarify the preferred particle size configuration based on these judgment factors. That is, based on 6 μm, where the amount and depth of oil bits suddenly change, we prepared various emulsion-type lubricants with different ratios of [(content of oil bits exceeding 6 μm)/(content of oil bits of 6 μm or less)]. A Ti plate was cold rolled using each lubricant (rolling speed: 200m/
The relationship between the depth of oil bits formed on the surface of the rolled plate and the ratio was investigated.

As a result, in the through hole shown in Figure 5 [the numbers indicated by 0 in the figure indicate the center particle diameter], when the ratio exceeds 1, there is a tendency for the oil bit to deepen rapidly; If it is less than 1, the oil bit depth can be suppressed to 1 to 2 μm or less.

In this way, it is also meaningful to employ the above ratio as a determining factor for emulsion type lubricants.

As described above, in the present invention, the saponification value and central particle size of the oil-based dispersoid are strictly defined in order to achieve the object, but other requirements are not particularly special. For example, the concentration of the emulsion type lubricant is almost the same as the preferred concentration of the emulsion type lubricant known since Kaji, 0.5 to 10%,
It is preferably in the range of 0.5 to 5%. In addition, in the above explanation, an example was given in which the most common tallow-based oil is used as the oil-based dispersoid, but the oil-based dispersoid is not limited to tallow-based oil that has the above-mentioned preferred saponification value, Of course, it is also possible to use other fats and oils, fatty acids, etc. (specifically, natural fats and oils such as palm oil and lard oil, or synthetic fatty acid fragments such as Dimer Shun).

Furthermore, the method for producing an emulsion lubricant having the above-mentioned center particle size is not particularly limited. ) can be added to oil to form an emulsion in which the oil particles are surrounded by water and the oil particles are uniformly dispersed in water. The desired emulsion particle size can be obtained by changing the type and amount of the emulsifier) or by appropriately selecting the stirring conditions after forming the emulsion.

The present invention is constructed as described above, and its effects can be summarized as follows.

■Oil-based lubricants have a high saponification value and good affinity with metals, so they easily form a thin oil film on the surface of the workpiece. Therefore, in combination with the fine central grain size, it is possible to reliably form a homogeneous, ultra-thin oil film at the bite portion of the pressure roll, and to suppress the occurrence of oil pits due to excessive lubricant as much as possible. Moreover, since the oil film is less likely to run out, seizure phenomena are less likely to occur, and the cold rolling of dense hexagonal metal plates can be carried out without any problems.

■As shown in Table 1 above, even if the rolling speed is increased, the oil pit remains shallow, and seizing is less likely to occur under high-speed rolling, so cold rolling with good surface accuracy can be achieved. Boards can be manufactured with high productivity.

■For cold pressing of Ti plates, etc., as disclosed in Japanese Patent Application Laid-open No. 165502/1983,
In order to prevent oil pits, it is necessary to make the diameter of the rolling rolls as small as possible to narrow the bite area, and it was thought that it would be difficult in practice to use rolls with large diameters, but this If an emulsion lubricant that satisfies the specified requirements of the invention is used, cold rolling can be carried out without any problem even if a rolling wheel with a large diameter is used, contributing to improved productivity.

[Brief explanation of the drawings] Figure 1 shows the reduction ratio (ti-1ln) when beef tallow-based emulsion lubricants with different concentrations and saponification values are used.
(ho/hi): A graph showing the relationship between l and average rolling pressure (Pm), Figure 2 is a diagram to explain the meaning of central grain size,
Figures 3 and 4 are micrographs used as drawings showing the surface properties of Ti plates obtained in cold rolling experiments. This is a graph showing the influence on

Claims (1)

[Claims] A method for cold rolling a dense hexagonal metal plate, characterized in that an emulsion type lubricant containing an oily dispersoid having a center particle size of 6 μm or less and a saponification value of 80 or more is used.