JP2011509833A - Rolling process method for creating reverse temperature field of highly plastic magnesium alloy sheet - Google Patents

Abstract

  This is a rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet. Magnesium and magnesium alloys are poorly plastic and difficult to machine, making them a major technical bottleneck for the development of the magnesium industry. As a rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet, the rolling roller of a heated steel plate rolling machine is rolled in the reverse temperature field, and the temperature of the rolling roller and the rolled sheet material are compared to the heating described in this document. The initial temperature field of is applicable. The reverse temperature field referred to in this book is that the surface temperature of the semi-finished product of the plate material to be rolled is higher than the temperature at the center of the semi-finished product, and the amount of heat in the rolling and deformation process is transferred from the outside to the inside. The method of the present invention is used to produce a highly plastic magnesium alloy sheet.

Description

Detailed Description of the Invention

  The present invention relates to a method of rolling magnesium and a magnesium alloy sheet in a state where a semi-finished product of a rolled steel sheet is in a reverse temperature field.

[Background Technology]
Magnesium and magnesium alloys are praised as the most promising lightweight structural metal materials in the 21st century, and are environmentally friendly materials with excellent energy saving, recyclable resources, electromagnetic shielding performance, aerospace, space, weapons, automobiles, High potential for practical value in fields such as motorcycles, bicycles, trains, metro trains, 3C products, electronic communications, home appliances, sports equipment, medical equipment, medical intervention materials, buildings, and submarine cables.

Magnesium and magnesium alloys are poorly plastic and difficult to machine, making them a major technical bottleneck for the development of the magnesium industry. For any metallic material application, the market for production products based on casting technology only occupies 10-15%, whereas plastic processed products occupy more than 80% market share. The difficulty of plastic working of magnesium and magnesium alloys has been a common perception in the world. Magnesium and magnesium alloys are not only difficult to perform primary plastic processing, but secondary plastic processing is more difficult than primary. The main contents of primary plastic working technology are as follows:
Extrusion technology: extruded bar, tube, mold.

  Drawing technology: drawn yarn material, wire material, pipe material.

  Rolling technology: rolled plate, wire, rod, mold.

  Forging technology: Molded parts made of magnesium alloy ingots.

  Among primary plastic working techniques, the rolling technique of magnesium and magnesium alloy sheets is the most difficult. Magnesium alloy sheet (0.3-2 mm thickness) sawing rate is as low as 30-40%, rolling speed is slow, there are many rolling processes, and many heating steps are required. The manufacturing cost is high and the price is very expensive. Sheet material accounts for 60% of primary plastic processed products, and magnesium alloy sheet rolling technology is the main technology that hinders the industrial development of magnesium and magnesium alloys.

  Since the plasticity of the magnesium plate produced by rolling by primary plastic working is poor, secondary plastic working is required. For example, in the case of a hot-extrusion molded part, unlike a mild steel sheet and an aluminum sheet, a molded part cannot be formed by cooling extrusion and cooling extrusion at room temperature, so the productivity is low. The surface quality of thermoformed parts is poor, the cost is high, and it is very expensive. In warm extrusion or heat extrusion, cracks are easily generated, leading to difficulty in the production process.

  Increasing the plasticity, finish rate, and productivity of magnesium and magnesium alloys to reduce costs is the goal of long-term efforts by scientists and engineers around the world, but has not yet achieved breakthroughs.

  The application and spread of plate materials that cannot be solved by plastic processing technology, particularly plate material rolling technology, is a limiting factor in the application of mold materials, yarn materials, pipe materials and the like. As a result, the magnesium and magnesium alloy industry is not as fast as the aluminum and aluminum alloy industry.

  Magnesium's crystal structure belongs to six solid sets, and the poor plasticity at room temperature is “naturally weak”, so it is impossible to change the crystal structure. If you change the composition of the six solid sets, it will no longer be magnesium and magnesium alloy. Increasing the purity of magnesium and a magnesium alloy can improve the anticorrosion performance and plasticity, but is not suitable for mass production because it requires expensive costs. Currently, the whole world is in a state of gathering with the goal of how to subdivide the crystal grains of magnesium alloy. This is because the finely divided crystal particles can greatly improve the plasticity of magnesium and a magnesium alloy. In this way, finally, it is useful for secondary plastic working parts of magnesium alloy.

  According to research, it is necessary to subdivide the crystal grains into 10 um in order to greatly improve the plasticity of magnesium alloys, which is a necessary condition. It is a sufficient condition not only to subdivide to 10 um but also to keep the crystal grains uniform in size.

  Such a technique can effectively increase the plasticity of magnesium and a magnesium alloy.

  Based on conventional magnesium alloy hot rolling and cold rolling technology, it is very difficult to subdivide the crystal grain of magnesium alloy sheet to 10 um or less and keep the crystal grain size uniform, and it is absolutely necessary for mass production Not suitable.

Currently, new technologies and methods for subdividing domestic and foreign magnesium alloy crystal particles are as follows:
Fast powder solidification set extrusion re-hot rolling technology, extrusion method (ECAE) by the same diameter path, etc. are mentioned. These techniques can greatly improve the plasticity if the size of the magnesium alloy crystal particles is subdivided into submicrons, but they are suitable for mass production due to lower productivity and higher cost. Therefore, it cannot respond to the production of plate materials.

  Currently, the double-roller process for magnesium alloy sheet, which is popular in Japan and overseas, can subdivide crystal grains into 10 um or less, but because of the cast structure, it can be used for hot rolling and cold rolling. Implementation is necessary. If the double roller plate material is used as it is, it is suitable only for pure magnesium and low strength magnesium alloy, and the plasticity index of the plate material is unstable and the quality is the most difficult to control. I can't. In individual developed countries, liquid magnesium alloy double-roller casting technology is only suitable for semi-finished products, reducing the amount of work in the subsequent hot rolling process and increasing productivity, thus reducing costs. However, it is already recognized that the plasticity of the board needs to be significantly improved, is not feasible at the moment and must be considered further.

  Therefore, only the Australian National Science and Technology and Industrial Research Center has produced small-scale production using double roller casting technology, and other countries such as the United States, Germany, and China are still in the testing stage. Currently.

  Other than the present invention, at present, there has not been an essential breakthrough in the rolling technology of magnesium and magnesium alloy sheet, the market price of magnesium and magnesium alloy sheet is still very expensive, and it can be easily applied and popularized. Can not.

[Summary of the Invention]
[Problems to be Solved by the Invention]
The present invention solves a series of problems such as reduction in yield, reduction in productivity, high cost, high cost in magnesium and magnesium alloy sheet material using one kind of reverse temperature field rolling technology, and the plasticity of magnesium alloy sheet material. The purpose is to solve the problem of badness.

  A foundation will be laid for secondary plastic processing of magnesium alloy sheets, that is, extrusion and extrusion of sheets in a room temperature environment.

[Means for solving the problems]
To achieve the above objectives, the following technical solution should be used:
This is a rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet. The rolling roller of the heated steel plate rolling machine is rolled out of the reverse temperature field, and the temperature of the rolling roller and the initial temperature field of the non-rolled sheet material correspond to the heating described in this document. The rolling process method for creating the reverse temperature field of the highly plastic magnesium alloy sheet material referred to in this book. The reverse temperature field indicates that the surface temperature of the semi-finished product at the start of rolling of the rolled sheet material is higher than the center of the semi-finished product In other words, the amount of heat is transferred from the outside to the inside during the rolling deformation process. In the rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet as described in this document, the surface temperature of the semi-finished product is 450-250 ° C and the temperature in the center is 20-150 ° C during the rolling process described in this document. The amount of rolling downward is 20% to 70% of the relative value and the rolling speed is 5 to 10 meters / minute. In the rolling process method for creating the reverse temperature field of the highly plastic magnesium alloy sheet material described in this document, the surface temperature of the semi-finished product is 450 ℃, 400 ℃, 300 ℃ in the rolling process described in this document, The temperature is at 20 ° C.

  In the rolling process method for creating the reverse temperature field of the highly plastic magnesium alloy sheet material described in this document, the surface temperature of the semi-finished product can be selected as 450 ° C during the rolling process described in this document, and the temperature at the center is 100 ° C.

  In the rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet as stated in this book, when rolling the ingot that makes the original semi-finished product a number of times, the first to the second round The amount of rolling shall be 20-30% of the relative deformation, 30-40% for the 3rd to 6th times, 40-50% for the 6th to 10th times, and 50-70% for the 10th time and above.

  In the rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet as described in this book, when rolling the ingot with the original semi-finished product as a component, the first to the second round The rolling amount is 20-30% of the relative deformation amount, the third to fifth times are 30-40%, and when rolling after that, depending on the thickness of the final plate, the downward rolling amount of each time is 30-30% of the relative deformation amount. 60% is the range.

〔The invention's effect〕
1. The current hot rolling technology for magnesium alloy sheet materials in Japan and overseas has an initial temperature of 420 ° C to 50 ° C, a final temperature of about 300 ° C, and a downward rolling amount of about 20% each time. In order to roll an ingot with a wall thickness of 120 mm to a l-2 mm plate, it is necessary to heat 3-5 times. The required number of rolling operations is 26 to 28, and the yield is 30 to 40%. Unlike the existing domestic and overseas rolling technology, the magnesium and magnesium alloy sheet rolling technology in the present invention adopts the reverse temperature field rolling technology. For thin sheets rolled from 120 mm to l mm in thickness, the number of times of heating is one time for a semi-finished product, the initial temperature is 420 ° C., and the amount of downward rolling can be increased to 30-60% each time. About 13 to 14 times, the number of times of heating can be reduced 2 to 4 times, and the total number of times can be about 1/2 of the general rolling technology. Furthermore, the utilization rate of materials is 60-70%. In addition to this, since the crystal particles of the magnesium alloy plate material proposed in the present invention are small and averaged, the size of the crystal particles of the plate material is suppressed to 10 μm or less, and in normal cases, 2 to 6 μm. Since it can be subdivided within the range and the plasticity of the plate material can be greatly improved, the extension rate of the plate material can be stably achieved at 21% or more regardless of the horizontal or vertical, and the majority is 25 It can reach ˜28% and eventually 34%. In addition, the discrepancy between the longitudinal and lateral performances of the plate is very small and can be kept to a small range of 10-15%.

  2.The present invention solves the problem of the manufacturing cost of the magnesium alloy sheet, thereby enabling to achieve or approximate the manufacturing cost of the aluminum alloy sheet, and solving the problem of poor plasticity of the sheet. Therefore, the plasticity index of the plate material was achieved at the level of the rust-proof aluminum alloy, and the plastic index of the mild steel plate material was approached. In essence, the present invention solves the problem of plastic processing technology of magnesium and magnesium alloy.

  3. The present invention has changed the conventional idea that the magnesium alloy has poor plasticity and difficulty in plastic working, and breaks through the penalty area where magnesium alloy can not be cooled plastically processed at room temperature. is doing. It can be said that there has already been a significant breakthrough in the plastic processing technology field of magnesium and magnesium alloys. As a result, a new technological path was created for the application and diffusion of magnesium and magnesium alloys.

  4.In the reverse temperature field rolling of the present invention, the temperature field resulting from the fact that the surface temperature of the semi-finished product of the plate material to be rolled is higher than the temperature at the center of the semi-finished product is called reverse temperature field rolling. It is just opposite to the temperature gap of the temperature field in the rolling process. In all common rolling techniques, whether hot rolling or cold rolling at room temperature, the temperature of the center of the semi-finished product is higher than the surface temperature, and the amount of heat goes from the semi-finished product to the outside and the rolling roller. Heat dissipation, that is, a temperature field in the positive direction in which the temperature at the center of the plate is higher than the surface temperature of the plate is formed.

  Since the room temperature plasticity of the magnesium and magnesium alloy chambers is poor, plastic processing cannot be easily performed. The present invention has begun to repair plasticity of plastic processing technology of magnesium and magnesium alloy, and solves all the problems of non-adaptation to plastic processing of magnesium and magnesium alloy in all conventional plastic processing technology methods, Currently, all plastic working processes belong to the positive temperature field, and the so-called positive temperature field is plasticity in the deformation process because the temperature inside the deformed body of all plastic working is higher than the surface temperature. The amount of heat generated in the deformation is dissipated in the direction of the mold, so that the temperature difference in the center of the deformable body is higher than the surface temperature of the deformable body. In the present invention, since the surface of the deformed body has a higher disparity than the temperature at the center, it is opposite to the temperature field in the positive direction. Just as was opposite to the positive direction of the temperature field, the present invention is defined that it is "plastic working of the reverse temperature field". The reverse temperature field rolling technique is one of the reverse temperature field plastic working methods during the reverse temperature field plastic working.

  Since a new technical method called reverse temperature plastic working is proposed for the process of forward temperature field in conventional plastic working from the technical principle, reverse temperature field is a betrayal to conventional forward temperature field. It is. In the temperature field of conventional plastic processing that has been artificially changed, whether it is hot rolling plastic processing or cold rolling plastic processing, the temperature field of the deforming body under deformation based on all methods Rules have been established, and it can be said that this is a process of heat dissipation and heat conduction in the direction of the mold. Therefore, the deformation process in the thermoplastic working in the reverse direction is a process in which heat is transferred from the surface of the deformed body to the inside of the deformed body, and the present invention is proposed for magnesium and magnesium alloys, It has a universal significance in terms of technical theory, applied to the process of plastic processing of metallic materials. Therefore, the reverse temperature field rolling process method of magnesium and magnesium alloy of the present invention has a solid technical theory basis.

  From the technical point of view, since this method corresponds to the plastic working of magnesium and magnesium alloy, the rolling work of magnesium and magnesium alloy sheet is the most difficult. It is submitted corresponding to the rolling process method for the alloy sheet.

[Mode for Carrying Out the Invention]
〔Example〕
[Example 1]
This is a rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet. The rolling roller of a heated steel plate rolling machine is rolled out of the reverse temperature field, and the temperature of the rolling roller and the initial temperature field of the non-rolled sheet material correspond to the heating mentioned in this document.

  The reverse temperature field referred to in this document refers to the initial temperature field of the semi-finished product at the start of rolling, the temperature at which the surface temperature of the semi-finished product is higher than the center of the semi-finished product, and the amount of heat in the rolling deformation process. Is to communicate from outside to inside.

[Example 2]
In the rolling method of Example I, the surface temperature of the semi-finished product is 450 to 250 ° C., the temperature of the central part is in the range of 20 to 150 ° C., and the downward rolling amount is 20% to 70% of the relative value every time, the rolling speed Is in the range of 5-10 meters / minute.

Example 3
In the rolling method of Example 1, the surface temperature of the semi-finished product is 450 ° C, and the temperature in the center is 100 ° C.

Example 4
In the rolling process method for creating the reverse temperature field of the highly plastic magnesium alloy sheet material described in this book, when rolling the ingot that makes the original semi-finished product a number of times, the first or second time The rolling amount is 20 to 30% of the relative deformation amount, 30 to 40% for the 3rd to 6th times, 40 to 50% for the 6th to 10th times, and 50 to 60% for the 10th time or more.

Example 5
Of the high plasticity magnesium and magnesium alloy sheet rolling methods described in Examples 1, 2 and 3 above, when rolling the ingot with the original semi-finished product as a constituent part many times, the first and second times The rolling amount is 20-30% of the relative deformation, and the third to fifth rounds are 30-40%. Thereafter, when performing the rolling operation, the downward rolling amount of each time can be selected from 30 to 60% of the relative deformation amount based on the thickness of the final plate material.

Example 6
1. Raw material: 100mm thick flat ingot is adopted. The width is determined by the length of the roller of the steel plate rolling machine. In this embodiment, the width is 400 mm and the length is 600 mm.

  The alloy is AZ31 magnesium alloy (components conform to US standards).

2. Heating of the raw material ingot: The temperature of the heated ingot surface and the surface and the central part at the start of work is about 400 ℃ ~ 20 ℃
3, rolling speed: 5-10m / min.

  4, Lubricant: Adopt the surface of rolling roller and semi-finished product based on spray coating of silicon oil, vegetable oil.

5, the amount of downward rolling and the total number of rolling times:
The amount of downward rolling each time is controlled to 30 to 60% of the relative deformation, and the thickness is rolled from 100 mm to 1 mm. The total number of rolling operations is 13 to 14 times.

  6. After rolling, cutting edge and processing to head / trailer plate.

  7, material utilization: 65-66%.

8, after rolling, mechanical performance of lmm thin plate:
Longitudinal performance of the board:
Bending strength: l56Mpa, tensile strength 26lMpa, extension rate 26%.

Lateral performance of the board:
Bending strength: 165 MPa, tensile strength 255 MPa, elongation rate 24%.

Example 7
1, raw material: zK61 magnesium alloy (components conform to US standards) ingot.

  Ingot dimensions: Thickness 20mm X400mm (width) X400mm (length).

  2, the heating of the ingot semi-finished product: the surface of the heating ingot, the temperature of the surface and the central part at the start of work is about 400 ℃ ~ 20 ℃ 450 ℃ ~ 100 ℃.

  3, rolling speed: 5-10m / min.

  4 、 Lubricant: Adopt the surface of rolling roller and semi-finished product based on spray coating of silicon oil and vegetable oil.

5, the amount of downward rolling and the total number of rolling times:
Rolling an ingot with a thickness of 20mm to a thickness of 0.5mm to 0.4mm;
The first rolling downward amount is 20%.
2nd downward rolling amount is 30%;
The third to sixth rounds of downward rolling are 40%;
The seventh to eighth rounds of downward rolling are 50%;
The total number of times is 8.

  6. After rolling, cutting edge and processing to head / trailer plate.

  7, material utilization: 65-66%.

8 、 Mechanical performance of 1mm thick sheet after rolling:
Longitudinal performance of the board:
Bending strength: 230Mpa, tensile strength 340Mpa, extension rate 34%.

Lateral performance of the board:
Bending strength: 250 MPa, tensile strength 336 MPa, elongation rate 28%.
The core technical specifications in Example 1 and Example 2 of the present invention are the initial reverse temperature field control of the semi-finished product and the control of the downward rolling amount each time.

  The reverse temperature field control refers to the temperature difference between the surface and the center of the semi-finished product, that is, the temperature difference. This can even control the temperature field during initial rolling, i.e., the initial temperature field. In order to gradually match the temperature of the surface and the center of the plate by receiving heat energy generated in heat conduction and plastic deformation during the rolling deformation process. For this reason, since the temperature field is changing, it takes time to achieve the coincidence of temperature with respect to the thick plate by eliminating the temperature difference when the instantaneous temperature of the thin plate is deformed. In the examples, only one kind of parameters of the implementation method is proposed, and in fact, the temperature difference in the initial reverse temperature field can be adjusted by the downward rolling amount and the alloy composition each time depending on the plate thickness. it can. For example, the temperature disparity range: the surface temperature of the semi-finished product can be adjusted in the range of 250 ° C. to 450 ° C., and the temperature of the central part can be adjusted in the range of 20 ° C. to 150 ° C.

  In selecting the downward rolling amount each time, it is determined according to the alloy composition of the ingot and the ingot configuration. In normal cases, the downward rolling amount at the beginning of rolling can be set a little smaller, and as the number of times increases, the downward rolling amount can be gradually added, so the downward rolling amount should be selected in the range of 20 to 70%. Can do.

Claims (7)

  This is a rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet. The rolling roller of the heated steel plate rolling machine is rolled outside the reverse temperature field, and the temperature of the rolling roller and the initial temperature field of the non-rolled sheet material correspond to the heating described in this document.   As described in claim 1, in the rolling process method for producing a reverse temperature field of a highly plastic magnesium alloy sheet, the reverse temperature field referred to in this document is the initial temperature field of the semi-finished product at the start of rolling, The surface temperature of the semi-finished product at the start of rolling of the rolled plate material indicates a temperature higher than the central portion of the semi-finished product, and heat is transferred from the outside to the inside in the rolling deformation process.   As described in claims 1 and 2, in the rolling process method for producing a reverse temperature field of a highly plastic magnesium alloy sheet material described in this document, the surface temperature of the semi-finished product is 450 to 250 in the rolling process described in this document. The temperature of the central part is in the range of 20 to 150 ° C., the downward rolling amount is 20% to 70% of the relative value every time, and the rolling speed is in the range of 5 to 10 meters / minute.   As described in claims 1 and 2, in the rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet material described in this document, the surface temperature of the semi-finished product is 450 ° C. during the rolling process described in this document. 400 ° C. and 300 ° C., and the central temperature is room temperature.   As described in claims 1 and 2, in the rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet material described in this document, the surface temperature of the semi-finished product is 450 ° C. during the rolling process described in this document. The temperature at the center is 100 ° C.   As described in claims 3 and 4, the rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet as described in this document is the number of times for an ingot that is composed of the original semi-finished product. When rolling, the amount of rolling for the first and second rounds is 20 to 30% of the relative deformation, the third to sixth rounds are 30 to 40%, the sixth to tenth rounds are 40 to 50%, the tenth round The above is characterized by 50 to 60%.   As described in claims 3, 4 and 5, in the rolling process method for creating a reverse temperature field of a highly plastic magnesium alloy sheet as described in this document, the number of times for the ingot which makes the original semi-finished product a constituent part. When rolling one or two times, the rolling amount for the first and second rounds is 20 to 30% of the relative deformation, the third to fifth rounds is 30 to 40%, and when rolling after that, depending on the thickness of the final plate, The amount of downward rolling each time is in the range of 30 to 60% of the relative deformation amount.