JP2001121206A - Pack rolling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pack rolling method for manufacturing a product small in thickness difference at end parts of a core by solving a problem that the thickness at the ends of the core is increased in the pack rolling, in particular, a problem that the thickness at the ends in the longitudinal direction is increased. SOLUTION: In the pack rolling method in which one or a plurality of plate- like cores are covered by a cover material and a spacer to form a pack slab, and the pack slab is rolled to manufacture a sheet for the core, an AGC is operated after the rolling of the core is started. The elongation of the spacer is estimated for each pass, the rolling start timing of the core is calculated from the number of revolutions of a roll, and the operation timing of the AGC is set to the rolling start timing of the core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pack rolling (lamination rolling) method for producing wide and thin materials by hot rolling of alloys which are difficult to hot work, such as heat-resistant alloys and titanium alloys. .

[0002]

2. Description of the Related Art In general, heat-resistant alloys and titanium alloys have a large temperature dependency of deformation resistance, and a processing load is increased due to a decrease in temperature during processing, so that processing is difficult. Further, there are materials having poor hot workability such as boron-added austenitic stainless steel. These are usually called difficult-to-machine materials.

[0003] As a thin plate rolling technique for these difficult-to-process materials,
Conventionally, a pack rolling (lamination rolling) method has been implemented. The pack rolling method is a rolling method using a pack slab as shown in FIG. The core material 1 which is one or a plurality of materials to be rolled is covered with a spacer material 2 on four sides. The core member 1 and the spacer member 2 are sandwiched between upper and lower cover members 3. FIG. 1 is an example showing a cross section of a pack slab in which two core materials 1 are covered with a spacer material 2 and sandwiched by a cover material 3.

As described above, when the core material, which is the material to be rolled, is covered with the spacer material and the cover material and rolled, the surface of the core material does not come into direct contact with a medium, such as outside air or a roll, which is colder than the material. The reduction can be prevented, and the production of a thin plate material becomes possible.

For example, a Ti-6Al-4V alloy, which is well known as an α + β type titanium alloy, needs to be subjected to hot working in the α + β region in order to ensure cold workability and superplasticity. Temperature dependence of resistance is very large, deformation resistance rises significantly below 800 ° C, exceeds the allowable load of the rolling mill, further rolling cannot be performed, and deformation resistance does not increase so much below β transformation point 8
It is ideal to perform rolling in a temperature range of 00 ° C. to 950 ° C., and pack rolling in which a decrease in temperature is small is applied.

[0006] Further, between the core materials, and between the core material and the cover material, press-fitting of the core materials and the core material and the cover material by rolling is prevented. A release agent is applied for the purpose of preventing a temperature drop. Reference numeral 4 in FIG. 1 indicates a release agent. A moderate space 5 is usually provided between the core material and the spacer material. After surrounding the core material with the spacer material and the cover material, the spacer material and the cover material are joined to complete the assembly of the pack slab. The pack slab thus assembled is hot rolled to obtain a rolled pack. Thereafter, the rolled material is disassembled, and the core material obtained by rolling the thin plate is taken out.

In such a pack rolling method, it is difficult to control the thickness of the product at the time of rolling because the core material as the product and the rolling roll are not in direct contact with each other. Japanese Patent Laid-Open No. 5-42302 discloses a technique for controlling the deformation resistance ratio and the temperature of the core material and the cover material.
No. 6,009,036.

In connection with this problem, the pack rolling method has a problem that the thickness of the end portion of the core material becomes large. FIG. 2 is an example of a plate thickness distribution when a Ti-6Al-4V alloy is used for the core material and SS330 is used for the cover material. At the end of the core material, the plate thickness is increased, which leads to a decrease in yield. Japanese Patent Application Laid-Open No. Hei 10-216807 proposes a technique for preventing this deviation in thickness by managing the space between a core material and a spacer material during assembly.

[0009]

Problems to be Solved by the Invention
The method disclosed in Japanese Patent Application Publication No. 07-07207 is effective for eliminating the thickness deviation at the end in the width direction, but is not very effective especially for the deviation in thickness at the end in the longitudinal direction when the reduction ratio in the longitudinal direction is large.
As the rolling progresses, the crop at the tip becomes larger, so it is necessary to set a space in anticipation of the amount of crop generation. However, even if such a large space is provided, it has been confirmed that the reduction in the thickness of the upper and lower cover members during rolling is small and the space is closed. Obviously, once the space is closed, the effect will obviously be lost.

The present invention has a problem that the thickness of the end portion of the core material in the above-described pack rolling is increased.
In particular, an object of the present invention is to provide a pack rolling method capable of solving the problem of thickness deviation at the longitudinal end and producing a product having a small thickness deviation at the end of the core material.

[0011]

The above object is achieved by the following invention. The first invention of the present application is a pack rolling in which one or a plurality of plate-shaped core materials are covered with a cover material and a spacer material to form a pack slab, and the pack slab is rolled to produce a thin plate of the core material. A pack rolling method, characterized in that AGC is activated after the core material starts rolling.

The second aspect of the present invention is to predict the amount of elongation of the spacer material for each pass, calculate the roll start timing of the core material from the number of roll rotations, and adjust the AGC operation timing to the roll start timing of the core material. A pack rolling method according to the first aspect of the invention.

The present inventors have found that the cause of the thickness deviation in the rolled pack is due to AGC (automatic thickness control). The principle of AGC will be briefly described.
FIG. 3 shows the relationship between the sheet thickness, the rolling load, and the roll gap during rolling. The straight line rising to the right represents the amount of elastic deformation of the rolling mill, and the curve rising to the left is called the plastic curve because of the relationship between the sheet thickness and the rolling load. When the material to be rolled having the entry side plate thickness H1 is rolled with a load P1 and a roll gap S1,
The exit side plate thickness is h1. When the incoming side plate thickness becomes H2 due to variation or the like, the rolling load increases to P2, so that the amount of elastic deformation of the rolling mill changes, and the outgoing side plate thickness becomes h2. In this case, the finished plate thickness varies within the plate. Therefore, AGC detects such load fluctuations and plate thickness fluctuations and automatically adjusts the roll gap according to the fluctuations. In the case of FIG. 3, when the roll gap is set to S2, the output side plate thickness becomes h1 with respect to the input side plate thickness H2, and a product having a uniform thickness over the entire length can be obtained.

However, if AGC is applied to pack rolling as it is, it is not possible to obtain a product having a uniform thickness over the entire length. FIG. 4 (a) shows the results of measuring variations in the exit side plate thickness (total thickness), roll gap, and core material thickness when AGC is applied to pack rolling. At the start of core material rolling,
The plate thickness suddenly increases at the position where the core material bites. FIG. 4B shows the relationship between the thickness of the rolled material, the rolling load, and the roll gap. Since the spacer material does not eventually become a product, inexpensive mild steel is generally used, and the spacer material has a lower deformation resistance than the core material. 4 (a) and 4 (b) show that the core material is Ti-6Al-4V alloy and the cover material is SS330.
It is an example of the case of general pack rolling, especially in the region where the temperature at which the thickness of the sheet near the finished thickness has decreased is reduced.
The deformation resistance of the spacer material may be about half that of the core material. For this reason, the plastic curve in the spacer material portion has a shape lying down as compared with the core material portion.

FIG. 4 shows a case where AGC is used for pack rolling.
Considering in (b), the roll gap set before rolling is set to S0 so that the exit side thickness becomes h0 at the rolling load P0 based on the plasticity curve of the core material so that the core portion has the target thickness. Is set. However, at the time of biting, it corresponds to a core portion having low deformation resistance, so that the rolling load is as low as P1 and the exit side plate thickness is h1, which is smaller than the target plate thickness. When AGC is activated,
The roll gap is opened to S1, and the roll gap is changed to S1 so that the exit side plate thickness becomes h0.

When the core gap is engaged with the roll gap being S1, the plastic curve shifts to that of the core zone and the rolling load increases to P2. Also get thicker. In response to this load variation, the roll gap is changed to S0, and the exit side plate thickness is adjusted to the target plate thickness h0. Sheet thickness distribution of core material at this time (core material thickness)
Is as shown in FIG. 4 (a), and the plate thickness is large in the portion where the roll gap is open.

That is, when AGC is used for pack rolling as in the case of rolling a normal material (integral material), the AGC operates at the spacer portion having low deformation resistance, which causes an increase in the end plate thickness. Understand. Therefore, if the AGC is operated after the rolling of the core material is started, the roll gap does not open before the rolling of the core material starts, and the increase in the thickness of the end can be reduced. .

The timing for starting the rolling of the core material is determined by estimating the amount of elongation of the spacer material for each pass, calculating from the number of roll rotations, or monitoring the load transition during rolling.
The time when the load is increased can be determined as the start of the rolling of the core material.

[0019]

Embodiments of the present invention will be described below. As in the case of using the normal pack rolling method, the material to be rolled is covered with a spacer material and a cover material and joined to produce a pack slab. The pack slab is heated to a predetermined temperature in a heating furnace or the like, and hot rolled by a rolling mill.
The roll gap at the start of rolling is adjusted to the optimum roll gap when rolling the core material portion, and the AGC is not operated. The AGC is operated simultaneously with or after the start of the rolling of the core material portion to control the roll gap. The rolling start position of the core material portion is calculated as follows. By multiplying the spacer length at the time of assembly by the rolling reduction ratio, the spacer length in that pass can be predicted. Since the time required for rolling the spacer can be calculated from the length and the number of roll rotations, the AGC is operated after the time required for rolling the spacer has passed since the start of rolling. Thereafter, the pass is rolled while the AGC is operated. The rolling pass is repeated in this manner to obtain a rolled pack. Then, the rolled material is disassembled, the core material obtained by rolling the thin plate is taken out, and cut into a predetermined size to obtain a product.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to embodiments. Ti-6
A thin plate of an Al-4V alloy was manufactured by a pack rolling method. SS-330 is used for the cover material and the spacer material.
A pack slab having a structure similar to that of FIG. 1 was produced by stacking two 6Al-4V alloy core materials. The core material of Ti-6Al-4V alloy is 20 mm thick, 2050 mm long, and 250 mm wide.
0 mm, the thickness of the cover material laminated one by one above and below the core material is 50 mm, the thickness of the spacer material is 40 mm, and the width is 50 mm
It is. The pack slab having a thickness of 140 mm was rolled for 11 passes according to the pass schedule shown in Table 1 to produce a rolled pack having a final thickness of 21 mm. In addition, the elongation amount of the spacer was estimated for each pass, and the start timing of AGC was set. As a comparative example, similarly to the conventional case, a rolled rolled material that was rolled in such a manner that AGC was started from the time when the rolled material was bitten into a rolling mill was also manufactured.

[0021]

[Table 1]

The rolled pack produced as described above was cut and disassembled to obtain a product having a thickness of 3.0 mm, a length of 12200 mm and a width of 2440 mm. FIG. 5 shows the measurement results of the roll gap fluctuation in the final pass and the total thickness of the product and the core material thickness when the start timing of the AGC is adjusted. Compared to FIG. 4A corresponding to the case of the comparative example, the roll gap does not greatly open at the time of rolling the spacer material portion, and the roll gap fluctuation at the time of rolling the core material portion also disappears. When the thickness deviation was measured, the product of the comparative example had a thickness deviation of about 1.80 mm, but the product of the example of the present invention was remarkably reduced to 0.02 mm. The thickness accuracy was ensured only by this method, and the yield increased.

[0023]

As described above, by starting AGC after starting rolling of the core material portion during pack rolling and rolling, the thickness deviation occurring at the end in the longitudinal direction is reduced. This eliminates the problem that the thickness of the end portion is increased, improves the yield, and eliminates the need for machining for adjusting the thickness of the end portion after rolling, thereby improving production efficiency and economy. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a pack slab used for pack rolling.

FIG. 2 is a diagram showing an example of a thickness distribution in conventional pack rolling.

FIG. 3 is an explanatory diagram of a relationship between a roll gap and a sheet thickness during general rolling.

FIG. 4 (a): Measurement results of thickness and roll gap during conventional pack rolling. (B): Explanatory drawing of the relationship between roll gap and sheet thickness during pack rolling.

FIG. 5 shows the measurement results of the thickness and roll gap when the present invention is used.

[Explanation of symbols]

 1 core material 2 spacer material 3 cover material 4 release agent 5 space

Claims (2)

[Claims] 1. A pack rolling method for forming a pack slab by covering one or more plate-shaped core materials with a cover material and a spacer material, and rolling the pack slab to produce a thin sheet of the core material. 3. The pack rolling method according to claim 1, wherein the AGC is operated after the core material starts rolling. 2. Predicting the amount of elongation of the spacer material for each pass,
2. The pack rolling method according to claim 1, wherein the core material rolling start timing is calculated from the number of roll rotations, and the AGC operation timing is matched with the core material rolling start timing.