JPS61217562A - Manufacture of titanium hot-rolled plate - Google Patents

Abstract

PURPOSE:To inhibit the occurrence of surface wrinkles in high efficiency under a wide range of rolling conditions and to manufacture a high-quality titanium hot-rolled plate by carrying out lubricating rolling in hot-rolling a titanium plate. CONSTITUTION:In manufacturing the titanium plate by a continuous hot rolling machine, hot lubricating oil is formed into the state of emulsion together with water in a mixing nozzle, which is jetted to work rolls or backing-up rolls. In this way, a coefficient of friction between the rolls and the titanium plate can be sharply reduced and the wrinkles of titanium plate attendant upon the rolling of large rolling reduction and be inhibited; the effect of inhibiting wrinkles is heightened when the above coefficient of friction is <=about 0.25.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing high-quality titanium hot-rolled sheets and cold-rolled materials.

(Prior art) The conventional ρ technology for manufacturing titanium plates is disclosed in Japanese Patent Application Laid-open No. 53-
As shown in Japanese Patent No. 112246, it is hot rolled at a lower temperature than steel materials.

Therefore, the winding temperature is generally 650° C. or lower, and hot-rolled sheet annealing is often required to improve cold rollability.

In order to omit hot-rolled sheet annealing, it is preferable to set the winding temperature to around 650°C, but in order to avoid coarsening of the initial grain size and acceleration of the rate of scale formation, the current heating temperature (950° C., preferably 880° C. or below, which is below the α/β transformation point), it is difficult to roll the material at around 650° C. with a normal rolling schedule.

In particular, when the finished plate thickness is 3u or less, it is difficult to roll it up at a temperature of 600°C or higher.

One possible way to increase the winding temperature is to increase the individual rolling reduction rates and shorten the rolling time. Note that when a large reduction is applied, the driving force for recrystallization increases due to the temperature increase due to processing heat generation and the increase in the introduced dislocation density, which lowers the recrystallization temperature and promotes complete recrystallization during winding. .

However, in conventional hot rolling methods for titanium plates, large reduction rolling is usually not performed. The main reason for this is that applying a large reduction causes wrinkle-like flaws to occur on the surface of the titanium plate. These scratches may occur even in normal light reduction rolling, although to a small extent, and cause deterioration in the quality of the titanium plate.

(Problems to be Solved by the Invention) Research by the present inventors has revealed that the cause of the wrinkle defects that degrade the surface quality described above is large shear deformation acting on the surface layer. A possible reason why wrinkles are more likely to occur in titanium materials than in steel materials is the difference in the coefficient of friction between the roll and the rolled plate.

The coefficient of friction between the roll and the plate during hot rolling is μ for titanium plates.
=0.35~0.48, μ of ordinary steel: 0.25~o
640, and therefore shear deformation near the surface occurs more significantly in the titanium plate. That is, in order to suppress the occurrence of wrinkle defects on the titanium plate, it is necessary to reduce the coefficient of friction between the roll and the plate.

Light reduction rolling is another effective method for reducing shear deformation near the surface, but when using current continuous hot rolling mills, it is essential to reduce the initial plate thickness or increase the number of passes. resulting in increased operating costs.

The object of the present invention is to efficiently suppress the occurrence of surface wrinkles under a wide range of rolling conditions and to produce a high-quality titanium hot-rolled sheet.

(Means for Solving the Problems) This object of the present invention is achieved by performing lubricated rolling when hot rolling a titanium plate. Suppression of wrinkle defects by lubricated rolling becomes more effective when the friction coefficient is 0.25 or less.

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

The present inventors succeeded in significantly lowering the coefficient of friction between the roll and the titanium plate by mixing hot lubricating oil with water in an emulsion state in a nozzle and injecting it onto the work roll or backup roll.

It was also confirmed that a similar lubrication effect could be obtained by applying glass lubrication to the surface of the titanium plate or applying a solid lubricant to the roll.

The friction coefficient can be obtained by actually measuring the plate speed and roll circumferential speed, and using rolling theory from the previous week's rate calculated from the measurements. The friction coefficient is affected by the amount of oil, the mixing ratio of oil and water, plate speed, rolling temperature, plate thickness, etc. There is a clear correlation between surface wrinkle defects and the friction coefficient; as the friction coefficient decreases, the frequency of occurrence of wrinkle defects decreases, and when μ=0.25 or less, wrinkle defects hardly occur.

Although the present invention does not require any special limitations on rolling conditions such as heating temperature, rolling temperature, and rolling schedule, it has been confirmed that low-temperature, high-speed rolling has a good gutter lubrication effect. In addition, in suppressing wrinkle defects, the effect of lubrication becomes more pronounced during rolling at a high reduction rate.

(Example) Figure 1 shows the friction coefficient when a titanium material having the composition range shown in Table 1 was subjected to one-stage rolling by changing the heating temperature in the range of 800 to 1100°C and the rolling temperature in the range of 1050 to 650°C. Indicates the frequency of wrinkle defects. Here, the wrinkle flaw frequency is the length of wrinkles observed in 1 square meter, and the unit is /-.

FIG. 2 shows the presence or absence of lubrication and the occurrence of wrinkle defects in actual rolling. In the case of lubricated rolling, the friction coefficient was 0.25 or less in all stands, and no scratches occurred at all. (Number of rolls rolled: 12) In addition, wrinkle defects occurred in normal wet rolling (number of rolls rolled: 8).

The non-lubricated rolled material in which wrinkle defects did not occur was due to light reduction rolling (6 rolls per roll), which required a reduction in the initial plate thickness or an increase in the number of passes, leading to an increase in operating costs. On the other hand, by carrying out lubricated rolling, the rolling load and torque are significantly increased (effects of the invention).The present invention makes it possible to produce hot-rolled titanium sheets with excellent surface quality without any special restrictions on the rolling schedule. Since rolling can be performed with less processing energy, it is possible to reduce manufacturing costs by saving energy.

[Brief explanation of drawings]

FIG. 1 is a chart showing the relationship between the friction coefficient and wrinkle frequency, and FIG. 2 is a chart showing the relationship between the occurrence of wrinkle flow depending on the lubrication condition and the number of rolled sheets. 17p Negative (A 3 Amount 2 Figure 1 Sucho 5 Tomi I Soaked) Procedural Amendment (Voluntary) April 22, 1980

Claims (1)

[Scope of Claims] 1. A method for producing a hot-rolled titanium plate, which comprises rolling the titanium plate while applying lubrication when producing the titanium plate using a continuous hot rolling mill. 2. The friction coefficient between the roll and the titanium plate during hot rolling is 0.
2. The method for producing a hot-rolled titanium sheet according to claim 1, wherein the titanium hot-rolled sheet is lubricated rolled in a state of 25 or less.