JPH09268357A - Method of heating cylindrical billets of pure titanium and titanium alloys - Google Patents

Abstract

(57) An object of the present invention is to provide a heating method for reducing the bending of a billet when rolling a cylindrical billet of pure titanium and a titanium alloy into a rod, a wire and a pipe material. SOLUTION: In a heating step before rolling, a holding temperature of pure titanium is 680 to 850 using a walking beam type heating furnace in which a cylindrical billet is rotationally conveyed around an axis.
C., α + β type alloy is 780 to 900 ° C., α or β type alloy is 950 to 1150 ° C., and one or more rotations at a rotation speed of 6 to 36 ° / min. You can Furthermore, by raising the processing temperature in the induction heating furnace to a processing temperature higher than the heating temperature in the walking beam type heating furnace within 10 minutes, it is possible to suppress oxidation and reduce defects after rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating method for rolling a cylindrical billet of pure titanium and titanium alloy into a bar, a wire and a tube.

[0002]

2. Description of the Related Art Since pure titanium and titanium alloys have excellent corrosion resistance and high specific strength, rods and wires are used for aircraft members and eyeglass frames, and pipes are used for chemical plants.

A billet having a long total length with respect to a cross-sectional area is generally used for a material to be rolled such as a rod, a wire or a pipe. In general, a radiant heating furnace is often used to heat the material, and a pusher type or a walking beam type is used as the transportation method. In the case of the pusher type, when it is pushed out by the pusher, it violently rubs against the hearth, causing hearth flaws.
A walking beam method is used to prevent this hearth flaw. However, when a material having a bend is used, the bend remains as it is at a low temperature, and at a high temperature, the bend increases because the front and rear ends of the material to be heated are held on only one side. In some cases, it may be difficult to convey the material during rolling. Therefore, limit the bending of the material used,
A material having a bend exceeding the limit needs to be corrected, which has a drawback that the number of steps is increased.

Also, Japanese Patent Publication No. 56-20330 discloses a method of preventing a bending due to uneven heat and uneven thickness by rotating and transporting a cylindrical material (billet) around an axis. On the other hand, the heating temperature of titanium is extremely low compared to the heating temperature of steel of around 1000 ° C., in order to suppress oxidation,
Japanese Patent Application Laid-Open No. 6-269836 discloses a method of performing primary heating at a low temperature of 680 ° C. or less for pure titanium and 780 ° C. or less for titanium alloy, and then performing secondary heating using an induction heating furnace in order to prevent oxidation. Has been done. In such a low temperature range, the bending due to uneven heating is small, but the initial bending remains, so it was difficult to reduce the bending in the walking beam type heating furnace.

[0005]

In view of the current state of the art, the present invention provides a method for heating a cylindrical billet made of pure titanium or titanium alloy into a bar, wire, or pipe material by rolling the billet. It is an object of the present invention to provide a temperature and a transportation method to be reduced, and further to provide a method for reducing bending and heating by reducing oxidation to a high processing temperature.

[0006]

Means for Solving the Problems That is, the present invention is as follows: (1) In a heating method for rolling a cylindrical billet of pure titanium into a rod, a wire, or a pipe material, a walking in which the cylindrical billet is rotationally conveyed about an axis. Using a beam type heating furnace, holding temperature 680-850 ° C, rotation speed 6-36 ° /
A method of heating a columnar material made of pure titanium, which comprises rotating one or more revolutions per minute. (2) A cylindrical billet of α + β type titanium alloy is used as a rod, wire,
In a heating method for rolling into a pipe material, a walking beam type heating furnace that rotates and transports a cylindrical billet around an axis is used, and a holding temperature is 780 to 900 ° C. and a rotation speed is 6
A method for heating a cylindrical material of α + β type titanium alloy, characterized by rotating at least 36 ° / min for one rotation or more, and (3) a cylindrical billet of α or β type titanium alloy, a rod,
In a heating method for rolling into a wire or pipe, a walking beam type heating furnace that rotates and transports a cylindrical billet around an axis is used to make one rotation at a holding temperature of 950 to 1150 ° C and a rotation speed of 6 to 36 ° / min. A method for heating a cylindrical material of α or β type titanium alloy, which is characterized by rotating as described above. (4) After heating as described in 1 above, heating to a higher processing temperature within 10 minutes using an induction heating furnace. A method for heating a pure titanium columnar material, which comprises: (5) A method for heating a cylindrical raw material of an α + β titanium alloy, which is characterized in that after the heating according to the above 2 is heated to a higher processing temperature within 10 minutes using an induction heating furnace, and (6) The above 3 After heating as described above, the method is a method for heating a cylindrical raw material of α or β type titanium alloy, which is characterized by heating to a higher processing temperature within 10 minutes using an induction heating furnace.

FIG. 1 shows the relationship between the number of revolutions and the bending at various holding temperatures when a cylindrical billet of pure titanium was conveyed at a rotation speed of 18 ° / min using a walking beam type heating furnace. Here, the billet rotation speed is 18 ° / in the case of conveyance in which the billet rotates 36 ° after being held for 2 minutes and advances to the next pocket.
Minutes, and if it rotates 18 degrees after holding for 2 minutes, 9 degrees /
Minutes. The billet used has a diameter of 156 mm, a length of 6 m, and a bend of 45 to 55 mm. Here, the bending was performed at room temperature at 45 ° intervals in the circumferential direction of the billet by horizontally stretching a thread between both ends of the billet, and making the distance most distant in the radial direction.

From FIG. 1, when the reference value of the bending that does not hinder the conveyance is 10 mm, the holding temperature is 870,900.
When the temperature is as high as ℃, since the deformation resistance is too small, the bending becomes large, and the bending remains even if the number of rotations is increased, and does not fall below the reference value. On the other hand, even when the holding temperature is as low as 600 and 650 ° C., the deformation resistance is too high, so that the initial bending remains and the bending resistance does not fall below the reference value. On the other hand, holding temperature 68
In the case of 0,750,850 ° C., the number of rotations is one rotation or more, and the bending becomes less than the reference value. Therefore, the number of rotations is set to one rotation or more. It is preferably 1.5 times or more.

FIG. 2 shows the relationship between the rotational speed and bending at various holding temperatures when a pure titanium cylindrical billet is rotated twice using a walking beam type heating furnace. The billet used here has a diameter of 156 mm, a length of 6 m, and is 45-
It has a bend of 55 mm. From FIG. 2, when the reference value of the bending that does not hinder the conveyance is 10 mm and the holding temperature is as high as 900 ° C., the deformation resistance is too small.
The bend becomes large, and the bend remains even if the rotation speed is increased, and does not fall below the standard value.

Even when the holding temperature is as low as 600 ° C., since the deformation resistance is too high, the initial bending remains and it does not fall below the reference value.

On the other hand, when the holding temperature is 750 and 850 ° C., the bending is less than the reference value when the rotation speed is 6 ° / min or more, but the rotation speed is slow when the rotation speed is less than 6 ° / min, so that the state becomes constant. Since the holding time is long, the bend becomes large and does not fall below the standard value. When the rotation speed is 680 ° C., the bending becomes less than the reference value when the rotation speed is 36 ° / min or less, and when the rotation speed is higher than 36 ° / min, the rotation is fast, and therefore the rotation is performed before the initial bending is corrected. The bend does not fall below the standard value. Therefore, the rotation speed is set to 6 to 36 ° / min. It is preferably 10 to 25 ° / min.

FIG. 3 shows pure titanium and Ti which is an α + β type alloy.
-6Al-4V (abbreviation 64), α type alloy (more precisely, Ne
ar α type alloy) Ti-6Al-2Sn-4Zr
-2Mo (abbreviation 6242), Ti-3A which is a β type alloy
1-8 shows a relationship between a holding temperature and bending when a cylindrical billet was rotated twice at a rotation speed of 18 ° / min using a walking beam type heating furnace in 1-8V-6Cr-4Mo-4Zr (abbreviation βC). The billets used here all have a diameter of 156 mm, a length of 6 m, and a bend of 45 to 55 mm.

From FIG. 3, when the reference value of the bending that does not hinder the conveyance is set to 10 mm, pure titanium is 680 to 85.
0 ℃, 780-900 ℃ at 64, 6242 and βC are 9
At 50 to 1150 ° C, the bending becomes less than the reference value. On the lower temperature side than the above temperature range, the deformation resistance is high, so that the initial bending remains, and on the high temperature side, the bending resistance is low, so the bending amount becomes large, and the bending amount does not fall below the reference value. Further, the temperature range in which the bend is below the reference value is the same for each type of alloy (α, α + β, β type). Since titanium alloy has higher strength than pure titanium, the temperature range where the bending is below the reference value is shifted to the higher temperature side than pure titanium, and the high alloy β type titanium alloy and α type titanium with high creep strength are used. Alloy is α +
It is shifted to a higher temperature side than β type. Therefore, the holding temperature is 680 to 850 ° C. for pure titanium, 780 to 900 ° C. for α + β type alloys, and 950 to 1150 for α and β type alloys.
° C. Preferably, pure titanium is 700 to 800 ° C.,
800 to 880 ° C for α + β type alloys, 9 for α and β type alloys
It is 50 to 1000 ° C. Here, pure titanium is industrial pure titanium. The α-type alloy also includes a Near α-type alloy, and the β-type alloy also includes a Near β-type alloy.

FIG. 4 shows the range of the holding temperature and the rotation speed suitable for reducing the bending in the cylindrical billet of various titanium. Pure titanium less than 680 ° C, α + β type alloy 780 ° C
If less than 950 ° C for α and β type alloys, the deformation resistance is too high, so initial bending remains, and pure titanium exceeds 850 ° C, α + β type alloys exceeds 900 ° C, α and β type alloys When the temperature exceeds 1150 ° C., the deformation resistance is too small, so that the bending becomes large, and none of them fall below the reference value. Also, if the billet rotation speed is less than 6 ° / min, the rotation speed is slow, so the time for which it is held in a constant state becomes long and the bend becomes large. Since the speed is high, the time in which it is held in a constant state is short, and rotation occurs before the initial bending is reduced.
Therefore, the holding temperature is 680 to 850 ° C. for pure titanium,
780-900 ° C for α + β type alloys, 9 for α and β type alloys
Rotation speed 6 to 3 around the billet axis at 50 to 1150 ° C
It was decided to rotate once or more at 6 ° / min.

Further, when titanium is heated at a high temperature in an oxidizing atmosphere, it reacts with oxygen to form a scale or a hardened layer having a poor hot deformability, so that flaws or cracks are generated. Therefore, when heating to a higher processing temperature after heating using a walking beam type heating furnace, if the temperature is maintained near the β transformation point or higher, for more than 10 minutes,
Since the diffusion rate of oxygen becomes faster, the scale and the hardened layer become thicker, and a flaw or crack of 100 μm or more occurs after rolling. Therefore, the yield in the peeling process for removing flaws and cracks decreases. Therefore, it was decided to raise the temperature in the induction heating furnace within 10 minutes. It is preferably within 5 minutes.

[0016]

The present invention will be described in more detail with reference to the following examples. Industrial JIS Class 1 pure titanium, 6
4,6242, βC diameter 156 mm, length 6 m, 45-45
Cylindrical billet having a bend of 55 mm was measured using a walking beam type heating furnace, when the billet was conveyed and heated at various holding temperatures, rotation speeds and rotation speeds.
Tables 1-1 and 1-2 show the holding temperature, rotation speed, number of rotations (total number of rotations from reaching the holding temperature to exiting the walking beam heating furnace) and billet bending in the walking beam heating furnace. Show.

[0017]

[Table 1]

[0018]

[Table 2]

Pure titanium of Table 1, No. In Examples 1 to 30, billets within the scope of the present invention in the walking beam heating furnace have a bend of 10 mm or less, and billets outside the scope of the present invention have a bend of more than 10 mm for the reason described above. Further, in the case of titanium alloys 64, 6242 and βC (Nos. 31 to 45 in Table 1), similar results are shown in a temperature range higher than that of pure titanium.

Table 2 shows the depth of flaws on the surface of a wire rod having a diameter of 9.0 mm after being heated in a walking beam type heating furnace and then heated to a higher temperature in an induction heating furnace for various heating times. Shows

[0021]

[Table 3]

For pure titanium, 64, 6242, βC, No. 2 in Table 2 in which the temperature rising time in the induction heating furnace was within 10 minutes. 46, 47, 49, 50, 52, 53, 55, 5
No. 6 has a maximum flaw depth of 80 μm or less, while there is a deep flaw of 100 μm or more when the temperature rising time is 15 minutes.

[0023]

EFFECT OF THE INVENTION In a heating method for rolling a cylindrical raw material billet of pure titanium and titanium alloy into a bar, a wire and a pipe material, it is possible to reduce the bending of the billet by setting a temperature and a conveying method to predetermined conditions. You can Furthermore, it is possible to reduce bending and reduce oxidation to a high processing temperature and heat.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the number of revolutions and bending in a walking beam type heating furnace for a pure titanium cylindrical billet.

FIG. 2 is a view showing a relationship between a rotation speed and a bending of a walking beam type heating furnace for a pure titanium cylindrical billet.

FIG. 3 is a diagram showing a relationship between a holding temperature and bending in a walking beam type heating furnace.

FIG. 4 is a diagram showing a range of a holding temperature and a rotation speed in a walking beam type heating furnace in which the bending of a cylindrical billet is corrected.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshitaka Nakamura 3434 Shimada, Hikari City, Yamaguchi Prefecture Shin Nippon Steel Co., Ltd.

Claims (6)

[Claims] 1. A heating method for rolling a pure titanium cylindrical billet into rods, wires, and pipes, using a walking beam type heating furnace for rotating and transporting the cylindrical billet around an axis, and a holding temperature of 680 to 680. 850 ℃, rotation speed 6 ~
A method for heating a columnar material made of pure titanium, which comprises rotating at 36 ° / min for one rotation or more. 2. A heating method for rolling a cylindrical billet of an α + β type titanium alloy into a rod, wire or pipe material,
Using a walking beam type heating furnace that rotatably conveys a cylindrical billet around an axis, it is rotated one or more times at a holding temperature of 780 to 900 ° C. and a rotation speed of 6 to 36 ° / min. How to heat a cylindrical material. 3. A heating method for rolling a cylindrical billet of an α or β type titanium alloy into a rod, a wire or a pipe material, using a walking beam type heating furnace for rotating and transporting the cylindrical billet around an axis. Holding temperature 950 to 1150
A method for heating a columnar material of α- or β-type titanium alloy, which comprises rotating at least one rotation at a rotation speed of 6 to 36 ° / min. 4. A method for heating a pure titanium columnar material, which comprises heating to a higher processing temperature within 10 minutes after the heating according to claim 1 by using an induction heating furnace. 5. A method for heating a cylindrical raw material of an α + β titanium alloy, which comprises heating to a higher processing temperature within 10 minutes after the heating according to claim 2 by using an induction heating furnace. 6. A method for heating a cylindrical raw material of α- or β-type titanium alloy, which comprises heating to a higher processing temperature within 10 minutes after the heating according to claim 3 by using an induction heating furnace. .