JPS6044041B2 - Cold rolling method of titanium plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for cold rolling a titanium plate, in particular a method for effectively preventing seizure during cold rolling by forming an oxide film on the surface of the titanium material prior to cold rolling. The present invention relates to a rolling method that enables efficient rolling operations at low rolling pressure and ensures good surface properties, dimensional accuracy, etc. of rolled products.

In general, active metals such as titanium, zirconium, tantalum, etc. tend to seize due to friction between the metals. Titanium or titanium alloy (hereinafter referred to as "titanium material").
), there is a serious problem in that seizing occurs between the rolls and the rolling rolls, making the rolling operation difficult and worsening the surface quality of the product. In order to suppress this tendency of seizure, rolling must be performed at a low rolling pressure.

The rolling pressure increases as the ratio of the roll diameter to the thickness of the rolled material increases, and in order to roll the material in a rolling mill with large diameter rolls, the rolling reduction must be kept small. Therefore, the number of buses increases to approximately 2 to 4% per bus, and rolling efficiency is significantly reduced. Therefore, it is generally rolled using a Sendzimir rolling mill (multi-stage mill), which is a small diameter roll.
Although the rolling reduction per bath is, for example, about 10%, this is not satisfactory when compared with the original rolling efficiency and equipment cost of a large diameter roll mill. In order to increase the rolling efficiency, rolling with a high rolling speed and a high reduction ratio is required.

Therefore, in order to increase the rolling efficiency of titanium materials, it is necessary to take some effective measures to prevent seizure even if the rolling speed and reduction ratio are increased.The present invention solves the above-mentioned problems in rolling titanium materials. This was developed to overcome this problem, and was completed based on the knowledge that it is extremely effective to form a dense oxide film on the surface of titanium material through appropriate treatment.

That is, the present invention provides, prior to cold rolling of titanium material,
A dense oxide film is formed on the surface of the titanium material by heating in an oxidizing atmosphere such as the air at a temperature of 200°C or more and less than 700°C, and then cold-rolled with rolling oil. By coating the titanium material with a very thin oxide film on the surface of the titanium material, which is different from the so-called passive film, the titanium material loses its easy-to-seizure properties and retains the inherent lubricity of rolling oil during rolling. This makes it possible to achieve highly efficient and stable rolling operations and good surface texture.

The method of the present invention will be explained in detail below.

The surface of active metals such as titanium, zirconium, and tantalum can be coated with a dense oxide film by heating in an oxidizing atmosphere such as the air or by anodic oxidation. By appropriately adjusting the film forming conditions and forming an oxide film having a thickness within a certain range, it is possible to effectively prevent seizure. The attached drawing shows a pure titanium rolled annealed plate (thickness: 2wm, width: 30wft)
1 length 250Tf$L) is heated in the atmosphere at various temperatures to form an oxide film, and the rolled material is made into a rolled material with a diameter of 15
In a two-high roll rolling mill with a diameter of 0.0 mm, a raw solution of beef tallow and mineral oil was used as the rolling oil, and the rolling speed was 6.8.
This is a graph showing the measurement results of the relationship between the average rolling pressure (Kg/w!IL) and the total rolling reduction (%) when cold rolling is performed up to 7 buses at a rolling reduction of about 15% per m/Minl bus. be.

In the figure, mark 8 indicates the heating temperature of 200℃, and mark ROJ indicates the heating temperature of 300℃.
゜CJ-Δ is 400℃, 1ro is 500℃, 0
◇The mark is 600'C. ．． rAJ mark is 700℃,
In each case, one powder was heated and maintained at each temperature to form an oxide film.

The 1× mark indicates that no oxide film formation treatment was performed (although a normal, extremely thin oxide film is present).

In addition, in the figure, the area surrounded by the broken line has a heating temperature of 200°C.
The curve shows the material treated at ~600°C, the dashed line shows the material treated at 700'C, and the solid line shows the material not subjected to film forming treatment. As shown in the figure, in the case where the oxide film formation treatment was not performed (marked with Cx), the total rolling reduction rate increased. In both cases, the rolling pressure increases rapidly, whereas in the case where an oxide film is formed, the increase in rolling pressure is slow, indicating that the presence of an oxide film has a large effect on reducing the rolling pressure.

In particular, those heated in the atmosphere at a temperature of 200 to 600°C (dotted line area) are excellent; for example, when the total reduction rate is 70
The average rolling pressure in % is for those without oxide film (sigma)
This shows a good value that is about 40% lower than that of the previous model. In addition, in the case of 700℃ (heating time 1 powder) (1A mark),
At the same time as the thickness of the film formed becomes excessively thick, a porous and brittle film called scale is partially formed, so the rolling pressure increases, especially in the first half of the number of baths, and the effect of reducing the same pressure decreases. . The thickness of the oxide film of the titanium material (heated at 200 to 6000 C) that showed good results in reducing the rolling pressure in the above rolling test was approximately 5.
It is 0-50A.

The reference photo shows the effect of preventing roll seizure due to the formation of an oxide film. Photo A shows the reduction per bath of a titanium material that has been heated in the atmosphere at 50°C to form an oxide film. Photo B shows the roll surface condition when rolled at a rate of about 15% for 7 baths, and Photo B shows the seizure condition of the roll when a titanium material without oxide film treatment is rolled under the same conditions a. It can be seen that in the case where no oxide film is formed (photo B), seizure occurs, whereas in the case where a sufficient oxide film is formed, no seizure occurs at all (in the same photograph). A). Note that the effect of the oxide film lasts up to a high total rolling reduction ratio, so once the film is formed, a low rolling pressure can be maintained until the end of rolling without having to repeat it during rolling. The method for forming the oxide film is not limited to the above-mentioned heating method in an oxidizing atmosphere, but may also include other methods such as anodic oxide film treatment.

The limit for the thickness of the oxide film, which is dense and hard to seize, varies depending on the formation method, and in the case of anodic oxidation treatment, it is 2,000 mm thick.
The current may be less than A, and may be 1000 A if the method uses heating in the atmosphere. As described above, according to the present invention, seizure during rolling can be effectively prevented by coating the surface of a titanium material with an oxide film of an appropriate thickness, and as a result, the following effects can be obtained.

(1) Good surface quality of board products is guaranteed.

(2) Since the rolling pressure is lower, the rolling reduction ratio can be increased, and as a result, the number of rolling baths can be reduced, and rolling efficiency is improved. Therefore, rolling with large diameter rolls is also facilitated. (3) Since there is no change in the roll surface due to seizure, there is no fluctuation in rolling pressure, a stable rolling operation is maintained, and good dimensional accuracy of the product is guaranteed. (4) In thin plate rolling, intermediate annealing is required multiple times due to the increase in rolling pressure associated with work hardening, but according to the present invention, the number of intermediate annealing can be reduced or completely omitted.
(5) Since there is little seizure, there is less damage to the roll surface.
Extends lifespan.

(6) Deterioration of rolling oil caused by seizure is eliminated.

This is especially effective when the rolling oil is supplied using a circulating system.
In this way, it brings about effects such as improving the quality of rolled products, stabilizing operations, and reducing operating costs.

[Brief explanation of drawings]

The drawing is a graph showing the relationship between the average rolling pressure and the total rolling reduction of the rolled material that has been subjected to the oxide film forming treatment.

Claims (1)

[Claims] 1. When cold rolling a titanium material, it is heated in an oxidizing atmosphere at a temperature of 200°C or more and less than 700°C to form an oxide film on the surface of the material before rolling, and then cold rolled with rolling oil. A method for cold rolling a titanium plate, characterized in that seizure occurring between the rolls and the rolls is prevented.