KR20210030640A - Rolling method of titanium sheet - Google Patents

Abstract

The present disclosure relates to a rolling method of a titanium sheet, which comprises: a step of preparing a titanium core material; a step of covering both surfaces of the core material by a cover material and sealing a slope in a thickness direction to manufacture a pack; a step of reheating the pack at temperature of 850-900°C; and a step of rolling the reheated pack. In the step of manufacturing the pack, the pack has thickness of at least 80 mm, and the rolling disclosing temperature is 800-900°C and the rolling finishing temperature is 700-800°C in the step of rolling the reheated pack. A ratio of the thickness of the core material to the entire thickness of the pack can be same with or lower than 0.3.

Description

Rolling method of titanium plate {ROLLING METHOD OF TITANIUM SHEET}

It relates to a method of rolling a titanium plate. More specifically, it relates to a method of rolling a titanium plate using existing steel manufacturing equipment.

Titanium alloys have a high temperature dependence of deformation resistance and a large processing load due to a decrease in temperature during processing, making it difficult to manufacture a thin plate.

If the thickness of the titanium alloy is controlled to be less than 2mm, the utilization value of the plate is further increased. In general rolling, the control is difficult due to the heat loss and springback phenomenon of the material. These materials are manufactured using pack rolling technology, and pack rolling is a manufacturing technology to obtain thin plates by hot rolling by vacuum welding by covering the top and bottom and slopes of one or several sheets as a core material and covering the top and bottom and slopes with a cover material. .

Conventionally, there has been a technique for obtaining a sheet material having a good shape by rolling in a temperature range having the same elongation rate of the cover material and the core material using a relatively small hot rolling machine, and reheating when a temperature drop occurs during rolling. In addition, a method for controlling the sheet thickness of a rolled pack rolled material has been proposed in which a core material is selected in consideration of the ratio of the deformation resistance value of the core material and the cover material, and the thickness of the core material is determined by a change in rolling load or a change in gamma ray output. In addition, in the pack rolling manufacturing method, a rolling method has been proposed in which a core material and a cover material are selected so that the core material deformation resistance value is less than or equal to the cover material deformation resistance value, and the total thickness ratio of the core material thickness and the granulated material is controlled. .

However, in the prior art, there has been a problem that existing steel facilities cannot be used using a small hot rolling mill, and heavy reheating is required, resulting in an increase in manufacturing cost.

Therefore, there is a need for a titanium rolling method with high productivity and low unit cost, as there is no need for intermediate reheating while using existing steel facilities.

In order to solve the problems of the prior art, the present invention is to provide a method of rolling a titanium or titanium alloy thin plate by using a continuous facility for manufacturing existing steel. Specifically, it is intended to provide a method of rolling a titanium alloy thin plate in which the occurrence of wrinkles in the width direction or the length direction is suppressed by using the existing continuous equipment for manufacturing steel.

A method of manufacturing a titanium thin plate according to an embodiment of the present invention includes the steps of preparing a titanium core material; Manufacturing a pack by covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction; Reheating the pack at 850 to 900°C; And rolling the reheated pack. Including, the reheated pack put into the rolling mill in the step of rolling the reheated pack has a thickness of 80 mm or more, the rolling start temperature in the step of rolling the reheated pack is 800 to 900°C, and the rolling ends The temperature is 700 to 800°C, and the ratio of the thickness of the core material to the total thickness of the pack may be 0.3 or less.

In the step of manufacturing a pack by covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction; In, the thickness of the cover material may be 30 mm or more.

Rolling the reheated pack; In, it may not be necessary to reheat during the rolling process.

In the step of manufacturing a pack by covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction; In, the inside of the pack may be in a vacuum state.

Preparing the titanium core material; may include pickling the titanium plate.

Preparing the titanium core material; may further include applying a release agent to the titanium plate.

Covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction to manufacture a pack; In the core material, two or more titanium plates may be stacked.

Rolling the reheated pack; In the rolling may consist of two or more rolling passes.

The two or more rolling passes may have a reduction ratio of 10 to 20% per pass.

The surface roughness (Ra) of the titanium thin plate manufactured by the method of manufacturing the titanium thin plate may be 4 μm or less.

According to one embodiment of the present invention, it is possible to provide a method of rolling a titanium or titanium alloy thin plate using an existing steel manufacturing continuous facility.

In addition, according to an embodiment of the present invention, it is possible to provide an optimal method of pack rolling a titanium or titanium alloy thin plate.

In addition, according to an embodiment of the present invention, it is possible to provide a titanium or titanium alloy thin plate with reduced shape defects.

In addition, according to an embodiment of the present invention, it is possible to provide a method of rolling a titanium or titanium alloy thin plate having high yield by rolling using an existing continuous steel manufacturing facility and not reheating, which is economical.

1 shows the dependence of the deformation resistance according to the temperature of the core material and the cover material according to an embodiment of the present invention.
Figure 2 shows the temperature drop during the existing process of the core material and the cover material according to an embodiment of the present invention.
3 is a graph showing the ratio of the extent of elongation of the core material and the cover material according to the ratio of the core material to the total thickness of the pack according to an embodiment of the present invention.

Terms such as first, second and third are used to describe various parts, components, regions, layers and/or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only for referring to specific embodiments and is not intended to limit the present invention. Singular forms as used herein also include plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising" as used in the specification specifies a particular characteristic, region, integer, step, action, element and/or component, and the presence of another characteristic, region, integer, step, action, element and/or component, or It does not exclude additions.

When a part is referred to as being "on" or "on" another part, it may be directly on or on another part, or other parts may be involved in between. In contrast, when a part is referred to as being "directly above" another part, no other part is interposed between them.

In addition, unless otherwise specified,% means% by weight, and 1 ppm is 0.0001% by weight.

Although not defined differently, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms defined in a commonly used dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal meaning unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In pack rolling of a metal material, since a cover material that is easy to process is laminated and rolled on a core material having low workability, when the selection or combination of the core material and the cover material is inappropriate, there arises a problem that a good product cannot be obtained. That is, when the elongation of the core material is greater than the elongation of the cover material, a buckling phenomenon in which wrinkles are generated in the core material may occur. Conversely, when the elongation rate of the core material is less than the elongation rate of the cover material, the buckling phenomenon does not occur in the core material, but the thickness hit rate decreases. In addition, even when the thickness and width ratio of the core material and the cover material are not appropriate, a poor product with low strength or no spheroid structure is obtained.

In general, a method of manufacturing a titanium or titanium alloy thin plate having a high temperature dependence of the deformation resistance can be classified into a method of obtaining a thin plate by removing the surface oxide layer by performing pack rolling at 980°C or lower or reheating during rolling. At this time, in the case of pack rolling, a small rolling mill that is smaller than that of existing steel facilities is required, which may incur equipment investment. In the case of non-pack rolling, a surface oxide layer may be generated, resulting in a poor product.

In this regard, the present invention aims to reduce manufacturing cost by using a continuous hot rolling facility for steel manufacturing in order to pack-roll a titanium plate, and controls the total thickness of the pack to be rolled to be applied to the steel manufacturing facility, and the thickness of the cover material To provide a rolling method that controls the thickness to a thickness that does not require reheating.

As described above, titanium has a high temperature dependence of the deformation resistance. 1 is a graph showing a change in deformation resistance according to temperature of a titanium alloy (Ti-6Al-4V) that can be used as a core material and a carbon steel that can be used as a cover material.

)와 커버재의 변형저항 (

)가 동일한 온도가 존재한다. 이 온도에서 압연하면 기본적으로는 코어재와 커버재는 동일한 정도로 신장할 것이다. 그러나,

인 조건에서는 코어재가 커버재보다 연신이 용이하여 코어재에 주름이 발생하게 된다. 그러므로, 코어재에 주름이 발생하지 않도록 하기 위하여는

가 되도록 하여야 한다.

인 조건에서는 압연 중에 커버재는 온도 저하가 일어나고 코어재는 복열이 존재하여 온도가 유지된다. 따라서 도 1에서 커버재의 온도가 T_A 이고 코어재의 온도가 T_B인 경우, 두 재료의 변형 저항은 유사한 수준이 되어 주름 발생 가능성이 낮다. According to Figure 1, the deformation resistance of the core material (

) And the deformation resistance of the cover material (

) Exist at the same temperature. When rolling at this temperature, the core material and the cover material will basically elongate to the same extent. But,

In the phosphorus condition, the core material is more easily stretched than the cover material, so that wrinkles occur in the core material. Therefore, to prevent wrinkles from occurring in the core material,

Should be.

In the phosphorus condition, the temperature of the cover material decreases during rolling, and the core material has double heat to maintain the temperature. Therefore, in FIG. 1, when the temperature of the cover material is T _A and the temperature of the core material is T _B , the deformation resistance of the two materials is at a similar level, so that the possibility of occurrence of wrinkles is low.

= 0.3으로 하여 일반적인 팩 압연 개시온도인 950℃에서 압연을 개시한 경우 압연 중 온도 저하를 나타낸 것이다. 도 2에서 나타나듯이 압연 중 커버재는 약 750℃까지 온도가 저하되는 반면에 코어재는 약 930℃까지만 온도가 저하된다. 이는 코어재의 경우 압연 중 발생되는 복열과 팩 내부의 진공 조건으로 인하여 대류가 발생하지 않아 온도 감소가 완만한 것으로 파악되고, 이러한 조건에서

를 만족시키기는 어렵다.Figure 2 shows the ratio of the core material to the total thickness of the pack

When rolling is started at 950°C, which is a general pack rolling start temperature with = 0.3, the temperature decreases during rolling. As shown in FIG. 2, during rolling, the temperature of the cover material decreases to about 750°C, while the temperature of the core material decreases only to about 930°C. In the case of the core material, it is understood that convection does not occur due to the reheat generated during rolling and the vacuum condition inside the pack, so that the temperature decrease is moderate.

It is difficult to satisfy.

조건을 만족하도록 제어되므로, 코어재를 소정의 두께로 압연할 때까지 커버재의 두께도 확보되고 파단이 발생하지 않으며, 압연 중 코어재가 불규칙하게 만족되거나 좌굴하는 것이 방지된다. 따라서 평탄성이 우수하고 균일한 두께를 가지는 티타늄 또는 티타늄 합금 판재를 얻을 수 있다. Accordingly, in the present invention, in order to solve these difficulties, the thickness of the entire pack, the thickness of the cover material, and the temperature range during the process are controlled. That is, according to the present invention, the deformation resistance of the core material and the cover material is

Since it is controlled to satisfy the condition, the thickness of the cover material is also secured until the core material is rolled to a predetermined thickness, no fracture occurs, and the core material is prevented from being randomly satisfied or buckling during rolling. Therefore, it is possible to obtain a titanium or titanium alloy plate having excellent flatness and a uniform thickness.

Hereinafter, each step will be described in detail.

The method of manufacturing a titanium thin plate of the present invention comprises the steps of preparing a titanium core material; Manufacturing a pack by covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction; Reheating the pack at 850 to 900°C; And rolling the reheated pack. It may include.

The cover material may be a carbon steel plate. As the cover material, a carbon steel plate having a carbon content of 0.2 to 0.5% by weight may be used. Specifically, S45C (carbon content: 0.40 to 0.50% by weight) or SS400 (carbon content: 0.2 to 0.3% by weight) may be used.

The reheating temperature may be equal to or less than the β transformation temperature, and in the reheating step, the reheating temperature may be maintained for an appropriate time so that the temperature becomes uniform from the temperature to the inside of the pack.

Covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction to manufacture a pack; In the sealing of the slopes, the sealing may be a weld seal using a spacer.

Rolling the reheated pack; The reheated pack introduced into the rolling mill may have a thickness of 80 mm or more. Specifically, the pack may have a thickness of 80 to 140 mm. More specifically, the pack may have a thickness of 80 to 122 mm. If the pack thickness is less than 80 mm, it cannot be used in existing steel facilities and productivity decreases.If the pack thickness is too thick, the reheating time before rolling increases, and the number of rolling passes increases, resulting in a decrease in temperature during rolling, which prevents reheating during rolling. There is a problem that the workability becomes poor, such as when it should be.

In the step of rolling the reheated pack, a rolling start temperature may be 800 to 900°C, and a rolling end temperature may be 700 to 800°C.

The ratio of the thickness of the core material to the total thickness of the pack may be 0.3 or less. Specifically, the ratio may be 0.1 to 0.3, more specifically 0.12 to 0.3, and more specifically 0.12 to 0.25.

If the core material thickness ratio does not satisfy the proper ratio range, there is a risk that quality defects of the rolled core material may occur due to different degrees of elongation between the cover and the core. In particular, the degree of rollability of the cover and the core varies greatly based on the core material thickness ratio of 0.3. Referring to FIG. 3, when the core material thickness ratio is 0.3 or less, the ratio of the degree of rolling of the cover and the core (degree of cover rolling/degree of core rolling) is 1.0 or less, and it can be seen that rolling of the core is performed better than that of the cover.

However, if the thickness ratio of the core material exceeds 0.3, the ratio of the degree of rolling between the cover and the core exceeds 1.0. Therefore, the core material is not sufficiently rolled and must pass through a number of rolling passes. There may be a problem of having to reheat the pack to a rollable temperature to compensate.

In addition, when the reheating temperature, rolling start temperature, rolling end temperature, pack thickness, and core material thickness ratio are all controlled, it is possible to obtain a titanium plate material having excellent flatness while using existing steel facilities.

In the step of manufacturing a pack by covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction; In, the thickness of the cover material may be 30 mm or more. Specifically, the thickness of the cover material may be 30 to 50mm. If the thickness of the cover material is too thin, there is a problem in that the flatness is not maintained unless reheated due to a decrease in the temperature of the cover material, and accordingly, reheating is required, thereby increasing the manufacturing cost. If the thickness of the cover material is too thick, the rolling pass increases, causing a large temperature drop during the rolling process, and accordingly, there is a problem that the workability is degraded out of the rollable temperature.

Rolling the reheated pack; In, no reheating is required during the rolling process.

In the step of manufacturing a pack by covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction; In, the inside of the pack may be in a vacuum state. The inside of the pack may be a vacuum ^{of 10 -3 torr or more.}

Preparing the titanium core material; A method of manufacturing a titanium thin plate comprising the step of pickling a titanium plate material. The pickling may be a step for removing an oxide layer present on the titanium surface.

Preparing the titanium core material; may further include applying a release agent to the titanium plate. The release agent is to prevent solid-state diffusion bonding between the titanium core material and the cover material.

Covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction to manufacture a pack; In the core material, two or more titanium plates may be stacked.

Rolling the reheated pack; In the rolling may consist of two or more rolling passes. The reheating step may not be included between the two or more rolling passes.

The two or more rolling passes may have a reduction ratio of 10 to 20% per pass.

The surface roughness (Ra) of the titanium thin plate manufactured by the method of manufacturing the titanium thin plate may be 4 μm or less. Specifically, the surface roughness may be 1 to 4 μm, more specifically, the surface roughness may be 1.4 to 4 μm, more specifically 1.5 to 4 μm, and more specifically 1.4 to 1.5 μm.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are for illustrative purposes only, and the present invention is not limited thereto.

Experimental Example 1-Control of reheating temperature, rolling start temperature, and rolling end temperature

Table 1 below shows the pack reheating temperature, rolling start temperature, and rolling end temperature for manufacturing a titanium alloy thin plate through the pack rolling method.

In this experimental example, titanium alloy (Ti-6Al-4V) was used as the core material, and carbon steel (S45C) was used as the cover material. The total pack thickness was 80 mm, and the cover material was laminated on the upper and lower surfaces of the core material so that the ratio of the core material to the total pack thickness was as shown in Table 1 below. After that, the four sides of the laminated core material and the cover material were spacer-welded to prepare a pack. Thereafter, the pack was reheated to the temperature disclosed in Table 1, and the surface roughness of the titanium plate prepared by rolling was measured to evaluate the flatness of the plate.

division Reheating temperature Rolling start temperature Rolling end temperature T _core /T _total asperity
(Ra, ㎛) Comparative Example 1 980 975 925 0.17 27 Comparative Example 2 960 955 890 0.17 26 Comparative Example 3 940 920 840 0.17 8 Example 1 900 880 800 0.25 4 Example 2 860 840 770 0.17 1.5 Example 3 900 880 800 0.17 4 Example 4 850 850 700 0.17 1.4 Example 5 880 850 770 0.12 1.5 Comparative Example 4 900℃ 860℃ 790℃ 0.38 5 Comparative Example 5 900℃ 855℃ 770℃ 0.6 5

Although the Comparative Examples 1 to 3 _{satisfies the T core} /T _total , it can be seen that the temperature range is out of the range controlled by the present invention and the surface roughness value is large. Comparative Examples 4 and 5 satisfies the temperature range during the reheating and rolling process, but _{did not satisfy T core} /T _total , so that the surface roughness value was larger than that of the example and the flatness was also poor. In particular, in the case of Comparative Example 4, the flatness was not good, so that the rolling could not be performed without reheating.

Therefore, it can be seen that in order to obtain a titanium plate having excellent flatness even without reheating during the rolling process, the temperature and T _core /T _total range during pack rolling must be controlled within the range of the present invention.

Experimental Example 2-Control of plate thickness and cover thickness

Table 2 below shows the results of measuring flatness by controlling the total thickness of the pack and the thickness of the cover material during pack rolling to obtain a titanium plate.

In this experimental example, titanium alloy (Ti-6Al-4V) was used as the core material, and carbon steel (S45C) was used as the cover material. A cover material was laminated on the upper and lower surfaces of the core material so that the total pack thickness and the cover material thickness are as shown in Table 2. The thickness of the cover material in Table 2 means the thickness of one cover material. After that, the four sides of the laminated core material and the cover material were spacer-welded to prepare a pack. Thereafter, it was reheated to 860°C, and during rolling, the rolling start temperature was 840°C and the rolling end temperature was 770°C to manufacture a titanium plate. The flatness of the prepared titanium plate was evaluated and shown in Table 2.

Pack thickness (mm) Cover thickness (mm) T _core /T _total Reheating (times) flatness Comparative Example 6 80 20 0.50 2 Good Comparative Example 7 80 20 0.50 X Bad Comparative Example 8 80 25 0.38 2 Good Comparative Example 9 80 25 0.38 x Bad Example 6 80 30 0.25 x Good Example 7 90 35 0.22 x Good Example 8 115 42 0.27 x Good Example 9 122 50 0.18 x Good

) 조건이 되어 주름이 발생되기 때문으로, 이를 방지하기 위하여는 재가열이 필요한 것으로 파악된다.As can be seen from Table 2, in the case of Comparative Examples 1 to 4 in which the thickness of the cover material is 30 mm or less even if the pack thickness of 80 mm is satisfied, a titanium plate material having poor flatness is obtained without reheating, and in order to obtain a titanium plate material having good flatness, It can be seen that reheating is required. This is because the thickness of the cover material is thin, so that the temperature of the cover material decreases significantly during the rolling process, whereas the temperature of the core material does not decrease significantly due to reheating, so that the deformation resistance of the cover material is greater than the deformation resistance of the core material (

) It is believed that reheating is necessary to prevent wrinkles due to conditions.

)조건이 만족하기 때문으로 재가열 없이도 평탄도가 양호한 티타늄 판재를 얻을 수 있음을 알 수 있다.On the other hand, it can be seen that the flatness of the rolled titanium plate is excellent even without reheating under the condition that the pack thickness is 80 mm or more and the thickness of the cover material is 30 mm or more. This is because the thickness of the cover material is thick and the temperature does not drop significantly during the rolling process, so that the deformation resistance of the cover material is less than or equal to the deformation resistance of the core material (

) Because the condition is satisfied, it can be seen that a titanium plate with good flatness can be obtained without reheating.

The present invention is not limited to the embodiments, but may be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains may use other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented. Therefore, it should be understood that the embodiments described above are illustrative and non-limiting in all respects.

Claims (10)

Preparing a titanium core material;
Manufacturing a pack by covering both surfaces of the core material with a cover material and sealing the slopes in the thickness direction;
Reheating the pack at 850 to 900°C; And
Rolling the reheated pack;
Including,
In the step of rolling the reheated pack, the reheated pack put into the rolling mill has a thickness of 80 mm or more,
In the step of rolling the reheated pack, the rolling start temperature is 800 to 900°C, and the rolling end temperature is 700 to 800°C,
The thickness ratio of the core material to the total thickness of the pack is 0.3 or less, the method of manufacturing a titanium thin plate. The method of claim 1,
Covering both sides of the core material with a cover material and sealing the slopes in the thickness direction to manufacture a pack; In,
The thickness of the cover material is 30mm or more. Method of manufacturing a thin titanium plate. The method of claim 1,
Rolling the reheated pack; in,
A method of manufacturing a titanium thin plate that does not require reheating during the rolling process. The method of claim 1,
Covering both sides of the core material with a cover material and sealing the slopes in the thickness direction to manufacture a pack; In,
The inside of the pack is a method of manufacturing a titanium thin plate in a vacuum state. The method of claim 1,
Preparing the titanium core material; The
A method of manufacturing a titanium thin plate comprising the step of pickling a titanium plate. The method of claim 1,
Preparing the titanium core material; The
A method of manufacturing a titanium thin plate, further comprising the step of applying a release agent to the titanium plate. The method of claim 1,
Covering both sides of the core material with a cover material and sealing the slopes in the thickness direction to manufacture a pack; In
The core material is a method of manufacturing a titanium thin plate, which is a stack of two or more titanium plate materials. The method of claim 1,
Rolling the reheated pack; in
Rolling consists of two or more rolling passes, a method of manufacturing a titanium thin plate. The method of claim 8,
The two or more rolling passes have a reduction ratio of 10 to 20% per pass, a method of manufacturing a titanium thin plate. The method according to any one of claims 1 to 9,
The surface roughness (Ra) of the titanium thin plate manufactured by the method of manufacturing the titanium thin plate is 4 μm or less.

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