JPH0542302A - Pack rolling - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve shape characteristics such as flatness of core material during pack rolling. [Structure] When the easy-to-process material is laminated on both sides of the difficult-to-process material and pack-rolled, the surface is cooled to increase the deformation resistance value of the easy-to-process material, and the difference in deformation resistance value from the core material is 5 kg.
/ Mm ² or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of pack-rolling a hard-to-work material such as titanium alloy or high alloy steel.

[0002]

2. Description of the Related Art Difficult-to-work materials such as titanium alloy and high alloy steel have been formed into a predetermined shape by forging. But,
Since productivity is poor in forging, a method of superposing a difficult-to-process material on an easily-processable material and performing pack rolling has been partially adopted. That is, single or plural raw plates of the target titanium alloy, Inconel or the like are used as the core material, and easily workable materials such as carbon steel are stacked as the cover material on the upper and lower surfaces thereof. Further, the core material is surrounded by a spacer material. The assembled laminated body is heated to a high temperature at which the deformation resistance of the core material becomes small, and then subjected to pack rolling. After rolling, the core material is separated from the cover material and taken out.

In this pack rolling, if there is a temperature difference between the materials, the deformation resistance is different, which causes variations in the finished plate thickness and deteriorates the plate thickness accuracy. Therefore, JP-A-63-7
According to Japanese Patent No. 2405, when a plurality of core materials are overlapped and pack-rolled, the outer core materials are heated in advance so as to be higher than the inner core material, and the core materials are mutually heated due to the temperature drop during rolling. It prevents the temperature difference between them from increasing.

[0004]

In pack rolling, as described above, a laminate in which a material that is difficult to process and a material that is easy to process are superposed is rolled. Therefore, the cover material having a smaller deformation resistance than the core material is preferentially rolled. At this time, when the thickness of the cover material is extremely reduced, the cover material is corrugated or broken, and this is transferred to the core material. As a result, the thickness of the rolled core material varies, and the flatness becomes poor.

Therefore, the object of the present invention is to pack-roll the laminate under stable conditions by increasing the deformation resistance value of the cover material to bring it closer to the core material, and to manufacture a product having excellent shape characteristics. And

[0006]

In order to achieve the object, the pack rolling method of the present invention is carried out by pack rolling a laminate in which easily workable materials are laminated on the upper and lower surfaces of a difficult-to-process material.
The surface of the laminate is cooled, the deformation resistance value of the easily processable material is increased, and the difference from the deformation resistance value of the hardly processable material is maintained at 5 kg / mm ² or less.

[0007]

Function: The deformation resistance of a metal material generally decreases as the temperature rises. Therefore, the present invention utilizes the relationship between the temperature and the deformation resistance to bring the deformation resistance of the cover material close to the deformation resistance of the core material and to roll both under substantially the same conditions.

For example, titanium alloy (6Al-4V-T
In i) and carbon steel SS41, the deformation resistance changes with temperature as shown in FIG. The deformation resistance of titanium alloy at a temperature of 900 ° C. is 13 kg / mm ² , which is 9
It is almost equal to the deformation resistance of carbon steel at 00 ° C. When materials having the same deformation resistance are rolled with the same rolling force, basically both the titanium alloy and the carbon steel should show the same elongation.

When this relationship between temperature and deformation resistance is applied to the material for pack rolling, the following advantages are obtained. That is, since the core material and the cover material show the same rolling characteristics,
The cover material will not be rolled and thinned preferentially as compared with the core material. Therefore, the thickness of the cover material is secured until the core material is rolled to a predetermined plate thickness, and corrugation, breakage, etc. do not occur in the cover material. Further, since the core material and the cover material are stretched in substantially the same manner, slippage that occurs between the core material and the cover material is eliminated, and pack rolling can be performed under stable conditions. Further, since the deformation resistance of the cover material is increased, the laminate is prevented from being irregularly curved or buckled during rolling. As a result, the obtained product has excellent flatness and a uniform wall thickness.

As a means for lowering the temperature of the cover material below the temperature of the core material, a method of spraying cooling water on the cover material forming the surface layer portion of the laminate is adopted. In this cooling method, the surface temperature of the cover material can be freely controlled by adjusting the amount of cooling water to be injected. Further, since the temperature of only the surface layer portion which receives the rolling force of the rolling roll is lowered, the cooling effect can be efficiently utilized.

Furthermore, the sprayed cooling water also has a function of removing oxide scale and the like on the surface of the cover material. Therefore, foreign matter is not caught in the rolling roll, and defects such as rolling defects are suppressed.

When the deformation resistance value is increased by cooling the cover material, the cooling conditions are controlled so that the difference between the deformation resistance value of the cover material and the deformation resistance value of the core material is 5 kg / mm ² or less. Specifically, the temperature of the carbon steel as the cover material is kept lower by 50 to 100 ° C. than the temperature of the titanium alloy as the core material. When the difference in deformation resistance value is within this range, the core material and the cover material are stretched in a substantially similar manner during rolling, and preferential thinning of the cover material is eliminated. When the difference in deformation resistance value exceeds 5 kg / mm ² , the above-mentioned effect due to cooling cannot be sufficiently exerted, and the rolled product is apt to have variations in plate thickness and corrugation.

[0013]

EXAMPLES The features and effects of the present invention will be specifically described below with reference to examples.

Plate thickness 16 mm, width 1900 mm, length 15
A 00 mm titanium alloy (6Al-4V-Ti) base plate was prepared as a core material. On the other hand, plate thickness 16 mm, width 1
A carbon steel plate SS41 having a length of 980 mm and a length of 1600 mm was used as a cover material. Two core materials are overlapped, a cover material is applied to both upper and lower surfaces thereof, the periphery of the core material is surrounded by a spacer material of the same material as the cover material, and the cover material and the spacer material are welded to form a laminated body having a total thickness of 64 mm. Assembled

After holding this laminated body at a temperature of 900 ° C. for 1 hour, it was rolled in 8 passes while spraying cooling water to obtain a total thickness of 1
A rolled material having a length of 6 mm and a length of 6400 mm was obtained. At this time,
The temperature T of the core material inside the laminated body is estimated by a simulation test, the amount of cooling water injected into the laminated body is adjusted according to the change of the temperature T of the core material, and the temperature t of the cover material is constantly kept at the temperature T. Kept lower than.

FIG. 2 shows the temperature difference Δt (T-t) at this time.
It is a graph which showed the relationship between and a thickness reduction ratio. The thickness reduction ratio in FIG. 2 is expressed as follows. That is, when the material thickness of the cover material is t ₁ and the thickness after rolling is t ₂ ,
The thickness reduction rate α of the cover material is expressed by (t ₁ −t ₂ ) / t ₁ . On the other hand, when the material thickness of the core material is t ₃ and the thickness after rolling is t ₄ , the thickness reduction rate β of the core material is (t ₃ −t ₄ ) /
It is represented by t ₃ . The ratio of this thinning rate, that is, α / β =
_{[(T 1 -t 2) / t} 1 ] / _{[(t 3 -t 4) / t} 3 ]
Is the thinning ratio. The closer the metal thinning ratio is to 1, the more the metal thinning ratios α and β become equal, indicating that the cover material is subjected to the same rolling process as the core material.

When the amount of cooling water sprayed onto the laminated body during rolling is increased, the temperature t of the cover material is greatly reduced and the difference from the temperature T of the core material is increased. For example, for a laminate having a surface temperature of 900 ° C., a water amount of 50 liter / m ² ·
When spraying room temperature cooling water in seconds, the surface temperature is 820
The temperature was lowered to ℃. In addition, the temperature T of the core material inside the laminated body
Was estimated to be 870 ° C. from the simulation test, and the temperature difference Δt (T−t) was 50 ° C. By this temperature decrease, the deformation resistance of the cover material approaches the deformation resistance of the core material as described in FIG. As a result, as shown in FIG. 2, both the cover material and the core material exhibit the same elongation for the same rolling force, and the cover material is not preferentially thinned.

As shown in FIG. 1, when the temperature difference Δt (T−t) is 50 ° C. or more, the cover material is cooled with cooling water so that the difference in deformation resistance between the cover material and the core material is 5 Kg /
It becomes within mm ² , and the effect becomes remarkable. For example,
When pack-rolled at a temperature difference Δt = 10 ° C., the core material (material thickness 16 mm) was rolled to 6.4 mm and the cover material (material thickness 16 mm) was rolled to 1.6 mm. At this time, the thickness reduction ratio is about 1.5, and the cover material is extremely thin as compared with the core material. On the other hand, when rolled at a temperature difference Δt = 70 ° C., a cover material and a core material having similar material thicknesses were rolled to 3.8 mm and 4.2 mm, respectively.
At this time, the thickness reduction ratio was almost 1, and both the cover material and the core material showed similar elongation.

Thus, the cover material was rolled in a state where the deformation resistance was increased, and the wall thickness of the cover material could be ensured to be a necessary value or more until the end of rolling. Further, in combination with the deformation resistance, that is, the increased rigidity, the laminated body is not curved or buckled during rolling. As a result, the obtained product was free from defects such as corrugation and thickness variation, and a thin plate material excellent in shape characteristics was obtained.

[0020]

As described above, in the present invention, by positively cooling the cover material, the deformation resistance of the cover material is increased to approach the deformation resistance of the core material. As a result, the cover material and the core material are similarly thinned by the same rolling force, and only the cover material is not preferentially thinned. Therefore, the rolling conditions are stabilized, and defects such as bending and buckling do not occur in the laminated body. The product thus obtained has excellent shape characteristics free from defects such as corrugation and defective thickness.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between temperature and deformation resistance of a metal material for explaining the operation of the present invention.

FIG. 2 Temperature difference Δ between core material temperature and cover material temperature
It is a graph showing the effect of t on the thickness reduction ratio of the core material and the cover material.

Claims (1)

[Claims] 1. When pack-rolling a laminate in which an easily-processable material is layered on the upper and lower surfaces of a difficult-to-machine material, the surface of the laminate is cooled to increase the deformation resistance value of the easily-processable material.
The difference from the deformation resistance value of the hard-to-process material is 5 kg / mm ²
A pack rolling method characterized by maintaining the following.