JPS5916858B2 - How to make titanium slabs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing titanium slabs.

Conventionally, methods for manufacturing titanium slabs include forging a titanium ingot or press blooming.

Titanium ingots are made by casting titanium melted in a vacuum melting furnace in a round mold, or by casting titanium melted in a plasma beam furnace in a flat mold.

Round titanium ingots made by vacuum melting are formed into slabs by forging.

The slab thus formed is finished into a slab of desired size and shape by performing slab maintenance such as peeling off the black skin and removing scratches.

However, slabs manufactured by conventional methods have poor flatness and are more prone to surface flaws.

If this slab is hot rolled after being treated,
Poor surface quality of hot strip.

In order to improve the surface quality, it is necessary to increase the amount of surface peeling when cleaning the slab.

An object of the present invention is to provide a method for manufacturing titanium slabs with excellent shape and surface quality with a high yield.

The method for manufacturing a titanium slab of the present invention involves heating a round titanium ingot after melting and casting to a temperature of 700 to 980°C, and then
The ingot is forged into a flat ingot in which the tip and rear ends are gradually thinner and narrower than the center, and then the flat ingot is heated again at 700 to 980°C.
It is characterized in that it is heated to a temperature of , and then formed into a slab of a predetermined size by blooming rolling.

A conventional soaking furnace or heating furnace is used to heat the round titanium ingot.

However, since soaking furnaces in general blooming plants are used to heat steel ingots, the heating temperature is usually around 1300℃.
Therefore, when heating a titanium ingot, it is necessary to control the temperature of the furnace so that the heating temperature is 700 to 980°C.

The reason why the heating temperature was limited to 700 to 980°C is as follows.

If the heating temperature is 700° C. or lower, as will be described later, the hot workability of titanium decreases significantly, surface flaws (cracks) increase, and hot deformation resistance increases, making rolling difficult.

On the other hand, if the heating temperature is 980°C or higher for a long time, the surface of the titanium ingot will be oxidized and a hardened layer of titanium oxides, nitrides, hydrides, etc. will be generated, which will cause surface defects during rolling. This causes surface flaws due to abnormal growth of crystal grains, and at high temperatures, hot deformation resistance is small, causing indentation and oyster flaws.

Next, the method of the present invention will be explained with reference to FIG.

First, in melting and casting process 1, a round titanium ingot is manufactured.

The external titanium ingot is formed into a slab of predetermined dimensions by the method of the present invention, indicated by the block 10 surrounded by dashed lines.

The method of the present invention includes a heating step 2, a rough forging step 3, a reheating step 4, and a blooming step 5.

In the heating step 2, the round titanium ingot 11 (FIG. 2A) manufactured in the melting and casting step 1 is charged into a soaking furnace or a heating furnace and heated to a temperature of 700 to 980°C.

In the rough forging step 3, the heated round titanium ingot 1
1 is formed into a flat titanium ingot 31 of a predetermined shape (FIG. 2B) using a press forging machine or a press forging machine.

As shown in FIG. 3, the flat titanium ingot 31 is formed so that its front end and rear end become gradually thinner and narrower in width than the center.

This tapered shape is provided in order to improve the yield by reducing crop loss at the leading and trailing ends of the slab in the blooming process, which will be described later.

In the reheating step 4, the flat titanium ingot 31 is again charged into a soaking furnace or a heating furnace and heated to a temperature of 700 to 980°C.

In the blooming process 5, the flat titanium ingot 31 heated by a plate mill or universal mill is formed into a titanium slab 51 of a predetermined size (FIG. 2C).

The reduction amount per pass in blooming rolling is approximately 10 to 4011 tons.
1L is appropriate.

If the pressure is too light, shape control will be difficult, air hole-like defects will not be sufficiently crimped, and rolling efficiency will also decrease.

On the other hand, if the titanium slab 51 is subjected to strong pressure, cracks will occur on the sides of the slab. (Fig. 2D).

In the slab care process 6, surface flaws are removed from the slab 51 by mechanical cutting.

In the heating step 7, the slab 51 after treatment is heated to 930
Heat to ~950°C.

Conventional titanium slab care generally involves mechanical cutting using a plano mill, 7 rice, or brainer to recover scrap.

Therefore, if the flatness of the slab is poor, the processing yield will decrease.

In addition, surface flaws are not detected by visual color checks and develop into hot strip surface flaws.

In the method of the present invention, after forging, blooming is performed using a plate mill or a universal mill, so the flatness of the slab is significantly improved.

In the surface layer of a round titanium ingot (at a depth of 20 to 30 cm from the surface), there are small defects in the form of pores that occur during melting and casting.

These defects appear as cracks in forging and slabs, and as surface defects (heges) after the hot rolling process, and have a negative effect on the surface quality of the IJ tube after cold rolling.

For this reason, in the conventional method, it is necessary to polish the surface of the titanium hot strip to remove the flaws, which increases the work cost and causes an increase in costs such as a decrease in yield.

According to the method of the present invention, the slab is formed by blooming rolling, which not only improves the flatness but also improves the surface quality by compressing small void-like defects that occur on the surface layer of the round titanium ingot. The surface of the slab can be easily cleaned by hot stripping or cold stripping.
The surface quality of the IJ knob is also further improved.

Next, examples of the method of the present invention will be described.

<Example> (1) Round titanium ingot dimensions: Diameter 980gat x length 2000mm Composition: Based on vacuum melted titanium ingot Table 1 (2) Flat titanium ingot forged nibless Forging dimensions: See Figure 3 (left-right symmetry) ) L = 1800 ~ 2500 (forceps 0 1 = 350 (ms) T = 550 ~ 650 (ii) t = 350 (dragon) W = 1000 ~ 1350 (關) w = 1000 ~ 1350 (酩) (3) Titanium. Slab dimensions: Thickness (165-190) x width (1000-125
0 ) (mi) Rolling temperature: 500~850℃ Rolling mill: Universal Mill (4) Hot strip dimensions: Thickness (3,3~4.5) x width (100OX125
0) (1!711) Rolling temperature = 500 to 850°C Rolling mill: Semi-continuous hot strip mill (5) Product inspection results Status of occurrence of defects on slab surface by conventional method and method of the present invention and after slab cleaning Table 2 shows the product inspection results for the surface properties of the hot strip.

Here, the conventional method refers to manufacturing a slab from a round titanium ingot by omitting the blooming in step 3 and only press forging in step 2.0 The flatness and wave height of the slab manufactured by the conventional method is 5 to 10. However, the flatness and wave height of the slab obtained by the method of the present invention ranged from 2 to 2.
It decreased to 5mm.

(The number of flaws or defects per unit area of the conventional slab or hot strip surface is 100.

) As is clear from the above, in the method of the present invention, titanium slabs with excellent shape and surface quality can be produced by combining the forging process and the blooming process when manufacturing titanium slabs. Furthermore, since fish tails and the like do not occur at the front and rear ends of the slab, the yield is further improved.

Furthermore, the surface quality of the hot strip is also significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a detailed process diagram of the present invention. FIG. 2 is an explanatory diagram schematically showing the processing process of the material. FIG. 3 is a perspective view of a flat titanium ingot. 11...Round titanium ingot, 31...Flat titanium casting L51...Titanium slab, 81.
...Hot strip.

Claims (1)

[Claims] 1 After heating the round titanium ingot after melting and casting to a temperature of 700 to 980°C, the ingot is forged so that the tip and rear ends become gradually thinner and narrower in tapered shape than the center. 1. A method for producing a titanium slab, which comprises forming a titanium slab into a flat ingot, then heating the flat ingot again to a temperature of 700 to 980°C, and then forming it into a slab of a predetermined size by blooming.