Patent Application
20200269297
The present disclosure relates to a metal or metal alloy and a method for manufacturing the same, particularly to a metal or metal alloy having good formability and a method for manufacturing the same.
Magnesium, accounting for 2.7% of the earth crust, is a metal material widely available in our daily life. It may be extracted from ores or sea water. After refining, its purity may be up to 99.8%. In addition, magnesium is the lightest metallic structural material that has been found to date. Its density is only 1.74 g/cm3, which is two thirds of the density of aluminum, and one fourth of the density of steel. This characteristic allows magnesium to be used as a metal in place of aluminum and steel for wide applications in the fields of automobiles, aircrafts and rail vehicles. The use of magnesium alloy may save energy, thereby reducing operational cost. For example, if the weight of an automobile is reduced by 100 kg, its fuel consumption will decrease by 0.38 liter per hundred kilometers, and its emission of CO2 will decrease by 8.7 gram per kilometer. However, the room-temperature formability of section products and flat products of magnesium and magnesium alloy is not high. Due to this limitation, magnesium alloy plates have so far not gained wide industrial applications.
The hard workability of magnesium at room temperature is decided by its nature. The main deformation modes of magnesium include basal slip, prismatic slip, pyramidal slip and crystal twinning. Except for basal slip, the other slip systems are difficult to be activated at room temperature. In processing, gradual formation of a strong basal texture in magnesium makes activation of basal slip increasingly difficult. Activation of crystal twinning depends on whether the grain orientation of magnesium before processing is suitable for the activation of crystal twinning. Even if crystal twinning is activated, the bearable strain is not large, wherein the largest strain is only 8% of the total strain. In contrast, aluminum and aluminum alloy have high room-temperature formability. They can be processed into pop-top cans from aluminum plates at room temperature. In comparison, magnesium and magnesium alloy break at a reduction rate of 30% when rolled at room temperature.
Up to now, addition of appropriate alloy elements has been a main measure for improving the room-temperature formability of magnesium. The reason for this is that the addition of some alloy elements can weaken the texture, or can make activation of the slip systems other than basal slip easier at room temperature. Even so, the room-temperature formability of magnesium is still poor. Despite that grain boundary slip as an additional deformation mode may be activated at room temperature after magnesium is deformed greatly by processing (e.g. equal channel angular pressing), the maximum reduction rate in the compression at room temperature is only 20%. Besides, magnesium alloy samples processed by great deformation generally have small sizes, insufficient for industrial applications.
One of the objects of the present disclosure is to provide a magnesium having ultra-high room-temperature formability, i.e. ultra-high formability at room temperature, wherein, in view of the problem of poor room-temperature formability of magnesium in the prior art, simple processing means are employed to prepare the magnesium having ultra-high room-temperature formability, so that magnesium which is intrinsically difficult to be deformed achieves good room-temperature formability and can be shaped easily.
To achieve the above object, there is proposed herein a magnesium having ultra-high room-temperature formability, wherein its grain size is ≤2 microns, i.e. having a grain size of 2 microns or less.
After extensive experimental research, the present inventors have discovered that, when the grain size of magnesium is ≤2 microns, magnesium or magnesium alloy traditionally having poor formability obtains ultra-high room-temperature formability, and can be shaped easily. The reason for such an achievement is that the deformation modes of magnesium having coarse grains (grain size being far greater than 2 microns) are intragrain deformations, including dislocation slip and crystal twinning. Due to the influence of the hexagonal structure of magnesium, the intragrain deformation modes are limited, and are not sufficient to endure large plastic deformation. Hence, the coarse grain magnesium has poor room-temperature formability. In the magnesium or magnesium alloy having ultra-high room-temperature formability according to the present disclosure, when the magnesium grain size is ≤2 microns, the main deformation modes of magnesium change from intragrain deformations to grain boundary deformations, for example, grain boundary slip and bodily rotation of grains. In the plastic deformation of magnesium having ultrafine grains (grain size ≤2 microns), these grain boundary deformations provide additional deformation modes. At the same time, as the grain size of magnesium decreases and the grain boundary area increases, dynamic recrystallization in the plastic deformation at room temperature occurs more easily, and the degree of intragrain strain decreases. The large-scale activation of grain boundary deformation modes and dynamic recrystallization at room temperature prevent accumulation of the intragrain strain of the ultrafine grain magnesium to such a degree that breakage occurs. As a result, ultra-high room-temperature formability is obtained.
Further, in the magnesium having ultra-high room-temperature formability according to the present disclosure, its grain size is ≤1 micron.
In addition, another object of the present disclosure is to provide a magnesium alloy having ultra-high room-temperature formability, wherein the magnesium alloy having ultra-high room-temperature formability has good room-temperature formability.
To achieve the above object, there is proposed herein a magnesium alloy having ultra-high room-temperature formability, wherein its grain size is ≤2 microns.
Further, in the magnesium alloy having ultra-high room-temperature formability according to the present disclosure, its grain size is ≤1 micron.
Further, in the magnesium alloy having ultra-high room-temperature formability according to the present disclosure, the magnesium alloy having ultra-high room-temperature formability comprises at least one of aluminum, zinc, calcium, tin, silver, strontium, zirconium and rare earth elements, wherein a total mass percentage of the at least one of aluminum, zinc, calcium, tin, silver, strontium, zirconium and rare earth elements is ≤1.5%.
Accordingly, yet another object of the present disclosure is to provide a method for manufacturing the magnesium having ultra-high room-temperature formability as described above, wherein a magnesium section product made from the magnesium having ultra-high room-temperature formability obtained by this manufacturing method has good ultra-high room-temperature formability.
To achieve the above object, there is proposed herein a method for manufacturing the magnesium having ultra-high room-temperature formability as described above, wherein the magnesium having ultra-high room-temperature formability is processed into a magnesium section product, and wherein the method comprises a step of extruding a raw material at a temperature of 20-150° C. and an extrusion ratio of 10:1-100:1 to obtain the magnesium section product.
After extensive research, the present inventors have discovered that magnesium recrystallizes dynamically in an extrusion process at various temperatures. In this process, a coarse cast structure transforms into a recrystallized structure, and extrusion temperature is a major factor that influences recrystallized grain size. In a conventional extrusion process (wherein a conventional extrusion temperature is generally higher than 300° C.), magnesium grain boundaries migrate readily. After nucleation, dynamically recrystallized grains of magnesium rapidly grow to about 10-100 microns. In the technical solution of the present disclosure, to obtain a structure having grains of 2 microns or less, the extrusion temperature needs to be controlled to induce substantial dynamic recrystallization, but the moving speed of grain boundaries is relatively slow, so as to control the recrystallized grain size.
Hence, in the technical solution of the present disclosure, to obtain a structure having grains of 2 microns or less in the magnesium having ultra-high room-temperature formability, the extrusion temperature is controlled at 20-150° C., and the extrusion ratio is controlled at 10:1-100:1, so as to obtain the magnesium section product having the desired microstructure.
In the above technical solution, the reason why the extrusion ratio is controlled at 10:1-100:1 is that an unduly high extrusion ratio requires an excessive high resistance to the extrusion force which is difficult to be provided by an equipment, while an unduly low extrusion ratio results in insufficient deformation of the extruded material, such that recrystallized grains are not refined sufficiently and cannot obtain a desired grain size.
It's noted that an extrusion ratio represents a ratio of a cross sectional area of a material before extrusion (e.g. a circular cross sectional area of a cylindrical cast bar) to a cross sectional area of the material after the extrusion.
In some embodiments, the extrusion temperature is controlled at 20-80° C. for the reason that the present inventors have discovered after extensive research that the grain size of pure magnesium is about 1.2 microns when the extrusion temperature is decreased to 80° C. When the extrusion temperature is further decreased, or a small amount of an alloy element(s) is added (e.g., at least one of aluminum, zinc, calcium, tin, silver, strontium, zirconium and rare elements, wherein a total mass percentage of the at least one of aluminum, zinc, calcium, tin, silver, strontium, zirconium and rare earth elements is ≤1.5%), the moving speed of the recrystallized grain boundaries will be further slowed, so as to refine the recrystallized structure to 1 micron or less.
Further, in the method for manufacturing the magnesium having ultra-high room-temperature formability according to the present disclosure, the method has an extrusion push rod speed of 0.05 mm/s-50 mm/s.
It's noted that a speed of an extrusion push rod refers to the speed of the extrusion rod moving toward a die during an extrusion process.
Accordingly, still another object of the present disclosure is to provide a method for manufacturing the magnesium having ultra-high room-temperature formability as described above, wherein a magnesium flat product made from the magnesium having ultra-high room-temperature formability obtained by this manufacturing method has good ultra-high room-temperature formability.
To achieve the above object, there is proposed herein a method for manufacturing the magnesium having ultra-high room-temperature formability as described above, wherein the magnesium having ultra-high room-temperature formability is processed into a magnesium flat product, wherein the method comprises the following steps:
(1) extruding a raw material at a temperature of 20-150° C. and an extrusion ratio of 10:1-100:1; and
(2) rolling at 20-100° C. to form the magnesium flat product.
In the present disclosure, the submicron structure of the magnesium or magnesium alloy having a grain size of ≤2 microns does not change in a cold rolling process. Hence, it can be rolled into flat products of various specifications/dimensions. However, to prevent growth of grains at high temperatures, the rolling temperature is controlled at 20-100° C.
Further, in the method for manufacturing the magnesium having ultra-high room-temperature formability according to the present disclosure, the method comprises an extrusion push rod speed of 0.05 mm/s-50 mm/s in Step (1).
Further, in the method for manufacturing the magnesium having ultra-high room-temperature formability according to the present disclosure, the magnesium flat product has a thickness of 0.3-4 mm or 0.04-0.3 mm.
In view of the required dimensions of products in practical applications, the thickness of the magnesium flat product in the present disclosure is 0.3-4 mm or 0.04-0.3 mm.
In addition, yet still another object of the present disclosure is to provide a method for manufacturing the magnesium alloy having ultra-high room-temperature formability as described above, wherein a magnesium alloy section product made from the magnesium alloy having ultra-high room-temperature formability obtained by this manufacturing method has good ultra-high room-temperature formability.
To achieve the above object, there is proposed herein a method for manufacturing the magnesium alloy having ultra-high room-temperature formability as described above, wherein the magnesium alloy having ultra-high room-temperature formability is processed into a magnesium alloy section product, and wherein the method comprises a step of extruding a raw material at a temperature of 20-150° C. and an extrusion ratio of 10:1-100:1 to obtain the magnesium alloy section product.
In the above technical solution, the extrusion ratio is controlled at 10:1-100:1 accordingly for the reason that an unduly high extrusion ratio requires an excessive high resistance to the extrusion force which is difficult to be provided by an equipment, while an unduly low extrusion ratio results in insufficient deformation of the extruded material, such that recrystallized grains are not refined sufficiently and cannot obtain a desired grain size.
Further, in the method for manufacturing the magnesium alloy having ultra-high room-temperature formability according to the present disclosure, an extrusion push rod has a speed of 0.05 mm/s-50 mm/s.
In addition, yet still another object of the present disclosure is to provide a method for manufacturing the magnesium alloy having ultra-high room-temperature formability as described above, wherein a magnesium alloy flat product made from the magnesium alloy having ultra-high room-temperature formability obtained by this manufacturing method has good ultra-high room-temperature formability.
To achieve the above object, there is proposed herein a method for manufacturing the magnesium alloy having ultra-high room-temperature formability as described above, wherein the magnesium alloy having ultra-high room-temperature formability is processed into a magnesium alloy flat product, wherein the method comprises the following steps:
(1) extruding a raw material at a temperature of 20-150° C. and an extrusion ratio of 10:1-100:1;
and
(2) rolling at 20-100° C. to form the magnesium alloy flat product.
Further, in the method for manufacturing the magnesium alloy having ultra-high room-temperature formability according to the present disclosure, the method comprises an extrusion push rod speed of 0.05 mm/s-50 mm/s in Step (1).
Further, in the method for manufacturing the magnesium alloy having ultra-high room-temperature formability according to the present disclosure, the magnesium alloy flat product has a thickness of 0.3-4 mm or 0.04-0.3 mm.
In the above stated manufacturing methods, the “raw material” used for manufacturing magnesium having ultra-high room-temperature formability refers to a “magnesium raw material” which is an elemental magnesium metal that has neither a grain size of ≤2 microns nor excellent ultra-high formability as desired; and the “raw material” used for manufacturing magnesium alloy having ultra-high room-temperature formability refers to a “magnesium alloy raw material”, wherein the magnesium alloy raw material is an alloy formed from metallic magnesium and the alloy element(s) (at least one of aluminum, zinc, calcium, tin, silver, strontium, zirconium and rare earth elements, wherein a total mass percentage of the at least one of aluminum, zinc, calcium, tin, silver, strontium, zirconium and rare earth elements is ≤1.5%), and the magnesium alloy raw material has neither a grain size of ≤2 microns nor excellent ultra-high formability as desired. Depending on the specific die and the shape of the finished product, the magnesium raw material or the magnesium alloy raw material may have any desirable shape, such as a cylindrical, cubic or cuboid ingot.
After the above indicated “raw material” is extruded at a temperature of 20-150° C. and an extrusion ratio of 10:1-100:1, a magnesium section product or a magnesium alloy section product is obtained. As described above, after the extrusion process, the magnesium section product or magnesium alloy section product has the desired ultra-high room-temperature formability. The processing means decides that the resulting magnesium or magnesium alloy having ultra-high room-temperature formability is in a form of section product. Therefore, the terms “section product”, “magnesium section product” and “magnesium alloy section product” used herein refer to a magnesium having ultra-high room-temperature formability or a magnesium alloy having ultra-high room-temperature formability that has the desired ultra-high room-temperature formability and is in a form of section product after extrusion processing.
The extrusion operation in the present disclosure is performed using a conventional extrusion apparatus, wherein the improvement made by the present disclosure lies in the elaborate design of the temperature and extrusion ratio in the extrusion operation. The extrusion apparatus may be selected and modified as desired, with the proviso that the temperature and extrusion required by the present disclosure can be fulfilled. In the present disclosure, the temperature of “20-150° C.” is the temperature of the magnesium/magnesium alloy being processed by extrusion, and the temperature is achieved by heating the magnesium/magnesium alloy, or heating the magnesium alloy and the extrusion barrel, die and push rod of the surrounding extrusion apparatus all together. In one embodiment of the present disclosure, the push rod, extrusion barrel and die are all made from die steel. A die cavity, which may be determined in light of the specific requirements of a product, comprises a chamber and a through hole extending through the die, wherein the chamber is used to contain a magnesium raw material or a magnesium alloy raw material, and the through hole may have a tapering or constant cross section size. The extrusion ratio defined specifically by the present disclosure may be obtained by adjusting the cross section size of the through hole and the cross section size of the magnesium raw material or the magnesium alloy raw material. The push rod has an end portion that matches the extrusion barrel, the chamber of the die and the size and shape of the magnesium raw material or magnesium alloy raw material, and is used to push and squeeze the magnesium raw material or magnesium alloy raw material through the extrusion barrel, the chamber of the die and the through hole in the extrusion process, so as to obtain the desired ultra-high room-temperature formability while a section product is formed.
After the magnesium section product or magnesium alloy section product having ultra-high room-temperature formability is obtained using the above extrusion operation, it may be optionally further rolled at 20-100° C. to form a magnesium flat product.
The magnesium or magnesium alloy having ultra-high room-temperature formability according to the present disclosure fundamentally solves the problem of the magnesium being difficult to be molded at room temperature. In addition, the method for manufacturing the magnesium or magnesium alloy having ultra-high room-temperature formability has the advantages of low cost and high production efficiency, and may be put into industrial manufacture directly.
The magnesium or magnesium alloy having ultra-high room-temperature formability and the manufacture method thereof according to the present disclosure will be further explained and illustrated with reference to the specific examples and the accompanying drawings. Nonetheless, the explanation and illustration are not intended to unduly limit the technical solution of the disclosure.
A section product of magnesium or magnesium alloy having ultra-high room-temperature formability was manufactured by a process comprising the following step: extruding a raw material at a temperature of 20-150° C., an extrusion ratio of 10:1-100:1 and an extrusion push rod speed of 0.05 mm/s-50 mm/s to obtain the magnesium section product.
A flat product of magnesium or magnesium alloy having ultra-high room-temperature formability was manufactured by a process comprising the following steps:
(1) extruding a raw material at a temperature of 20-150° C., an extrusion ratio of 10:1-100:1 and an extrusion push rod speed of 0.05 mm/s-50 mm/s; and
(2) rolling at 20-100° C. to form the magnesium flat product.
The thickness of the magnesium flat product was 0.3 mm-4 mm or 0.04 mm-0.3 mm.
Table 1 lists the specific process parameters for the method for manufacturing the magnesium or magnesium alloy having ultra-high room-temperature formability in Examples 1-12.
Table 2 lists the grain sizes of the magnesium or magnesium alloy having ultra-high room-temperature formability in Examples 1-20.
In order to verify the properties of the magnesium or magnesium alloy having ultra-high room-temperature formability according to the present application, it was extruded at an extrusion ratio of 19:1 at different temperatures, wherein the extrusion temperature was room temperature (25° C.) for Examples 1-2, 65° C. for Examples 3-6, 80° C. for Examples 7-12, 160° C. for Comparative Example 1, 200° C. for Comparative Example 2, 250° C. for Comparative Example 3, 300° C. for Comparative Example 4, and 400° C. for Comparative Example 5. Before extrusion, a graphite coating was sprayed on the ingot for Examples 1-12 and Comparative Examples 1-5 and the die to reduce friction force during the extrusion process. After extrusion, Examples 1-4, 7 and Comparative Examples 1-5 were cooled with water rapidly, followed by room-temperature compression testing and cold rolling. In the compression testing, the compressing rate was 0.6 mm/min; in the cold rolling process, the reduction per pass was 0.1 mm, and the roll speed was 15 m/min.
It was observed from the testing that, after the pure magnesium cast ingot in Examples 1-4, 7 and 8 according to the present disclosure was extruded, the polycrystalline magnesium section products obtained ultra-high room-temperature formability. In comparison, when the pure magnesium cast ingot in Comparative Examples 1-5 was extruded and processed into section products, the section products exhibits poor room-temperature formability. When Comparative Examples 1-5 were subjected to compression tests at room temperature, the maximum reduction rate was 20-30%, and the phenomenon of work hardening was obvious. In addition, when processed into magnesium section products, the magnesium having ultra-high room-temperature formability in the various Examples according to the present disclosure didn't break in compression at room temperature, and work hardening didn't occur. The test samples softened as the strain increased gradually. This softening suggests that slip and crystal twinning are not the major deformation modes in the compression at room temperature. This softening is generally related with grain boundary slip and/or dynamic recrystallization. In magnesium alloy, grain boundary slip and dynamic recrystallization generally occur at high temperatures instead of room temperature.
As shown by
As can thus be seen, the room-temperature formability of the magnesium having ultra-high room-temperature formability in Example 7 according to the present disclosure is notably superior over the conventional magnesium in Comparative Example 5.
The magnesium having ultra-high room-temperature formability in Example 8 was extruded into a magnesium square bar, and rolled from an extruded state having a thickness of 3 mm into a magnesium flat product having a thickness of 1 mm. The resulting magnesium flat product having ultra-high room-temperature formability didn't crack at any edge. This magnesium flat product was further rolled into a magnesium flat product having a thickness of 0.12 mm. At this time, the rolling of the magnesium flat product from 3 mm to 0.12 mm led to a reduction rate of 96% and a true strain of 3.2, much greater than the maximum cold rolling reduction rate (30%) and the corresponding true strain of 0.4 of the conventional magnesium. The magnesium flat product having a thickness of 0.12 mm was cut into two sections which were bent into “m” and “g” shapes. As can thus be seen, when processed into a section or flat product, the magnesium having ultra-high room-temperature formability in Example 8 according to the present disclosure exhibited excellent room-temperature formability, and surface cracking didn't occur easily.
As can be seen from the comparison of
To further verify the ultra-high room-temperature formability of the Examples in the present disclosure, the magnesium having ultra-high room-temperature formability in Example 8 was processed into a 1 mm thick magnesium flat product and bent. No breaking occurred after a 180° bend.
See
In addition, after the magnesium having ultra-high room-temperature formability in Example 8 was processed into a 0.12 mm thick magnesium flat product, the magnesium flat product could be bent twice without cracks visible to the naked eye after unfolded.
See
As compared with the Examples according to the present disclosure, when the conventional magnesium in Comparative Example 5 was processed into a 1 mm thick magnesium flat product and bent, cracking occurred when it was bent to 95°; when the conventional magnesium in Comparative Example 5 was processed into a 0.12 mm thick magnesium flat product, obvious cracking was observed when it was bent only once and then unfolded.
See
As can be seen from
In order to reveal the reason why the magnesium has ultra-high formability at room temperature, the inventors characterized the microstructures of the extruded samples of the magnesium in Comparative Example 5 and the magnesium having ultra-high room-temperature formability in Example 7. These two samples consist of equiaxed crystals, and both had strong textures. The average grain diameters of Comparative Example 5 and Example 7 were 82 μm and 1.3 μm respectively. After Comparative Example 5 extruded at 400° C. was compressed or rolled by 20% at room temperature, the average grain diameter of Comparative Example 5 was reduced to 56-61 μm due to the generation of twin crystals. Completely differently, after Example 7 according to the present disclosure was compressed or rolled by 50% at room temperature, neither the size nor the shape of the grains had any obvious change. Even if the microstructure of the sample was characterized from different angles, the average grain diameter of the Example according to the present disclosure was 1.1-1.2 μm in all cases. After the cold deformation, the texture of Example 7 got slightly stronger.
In addition, even if the sample of Example 7 was cold rolled to a thickness of 0.12 mm, the size and distribution of the grains were still very similar to those in the extruded state. Besides, the deformation amount of the extruded sample of Example 7 was 50%, far greater than the deformation amount of 20% of the extruded sample of Comparative Example 5, but the intragrain misorientation of the extruded sample of Example 7 after deformed by 50% was far less than the intragrain misorientation of the extruded sample of Comparative Example 5 after deformed by 20%. These phenomena indicate that the intragrain deformation of Example 7 according to the present disclosure was very small in the deformation at room temperature.
See
As shown by
As shown by
As shown by
As shown by
As can be seen from
In order to study the deformation modes of the extruded samples of Comparative Example 5 and Example 7 in the shaping process at room temperature, the present inventors polished the side surfaces of these samples (i.e. the faces parallel to the extrusion direction) respectively, and subjected the above samples to compression testing at room temperature respectively. The present inventors discovered that when the extruded sample of Comparative Example 5 was compressed by 20%, a good number of signs indicating the activation of crystal twinning and slip appeared on its side surfaces (see a and b in
In order to explore the deformation mechanism at room temperature of the extruded sample of Example 7, the present inventors characterized the microstructures of the extruded sample of Example 7 before and after compression at room temperature using a quasi-in-situ EBSD method. The present inventors discovered that when the sample was compressed by 6%, a “new” grain appeared (see c and d in
In addition,
To further investigate the deformation mechanism of Example 7, two new grains showing up in the high strain zone of the deformed grains were compared with said “new” grain (i.e. the grain at the locations labeled with the cross signs in d and fin
The microstructure and texture of said two grains are shown in
As shown by
As such, the present inventors discovered that the major deformation mechanisms of Comparative Example 5 were intragrain slip and crystal twinning due to the coarse grains of Comparative Example 5; whereas the major deformation mechanisms of Example 7 were crystal boundary mechanisms, including grain boundary slip, grain rotation and dynamic recrystallization, because of the fine grains in Example 7 according to the present disclosure.
As shown by
In
As shown by
In
It should be noted that in the above figures, P1 is a legend for crystal orientation; P2 is a legend for grain orientation spread; P3 is a graphical representation for a pole figure of texture; ED represents extrusion direction; CD represents compression direction; RD represents rolling direction; ND represents normal direction; and TD represents traverse direction.
In addition, it's to be further noted that in the above solutions, “20%” in “compressed by 20% at room temperature” involved means that the height of a sample after being compressed is reduced by 20% in the compression direction as compared with the sample before being compressed. Likely, “50%” in “compressed by 50% at room temperature” involved means that the height of a sample after being compressed is reduced by 50% in the compression direction as compared with the sample before being compressed. “20%” in “cold rolled by 20%” means that the height of a sample after cold rolled is reduced by 20% in the reduction direction as compared with the sample before being cold rolled. Likely, “50%” in “cold rolled by 50%” means that the height of a sample after cold rolled is reduced by 50% in the reduction direction as compared with the sample before being cold rolled.
To sum up, as can be seen from the Examples according to the present disclosure and
Examples 13-20 illustrate a number of magnesium alloys having various compositions, prepared using the corresponding process parameters listed in Table 1, and resulting in the characteristic average grain sizes and structures listed in Table 2. The corresponding product samples all exhibit good ultra-high room-temperature formability.
It's to be noted that the prior art portions in the protection scope of the present disclosure are not limited to the examples set forth in the present application file. All the prior art contents not contradictory to the technical solution of the present disclosure, including but not limited to prior patent literature, prior publications, prior public uses and the like, may all be incorporated into the protection scope of the present disclosure.
In addition, the ways in which the various technical features of the present disclosure are combined are not limited to the ways recited in the claims of the present disclosure or the ways described in the specific examples. All the technical features recited in the present disclosure may be combined or integrated freely in any manner, unless contradictions are resulted.
It's also to be noted that only some specific examples of the present disclosure are listed above. Obviously, the present disclosure is not limited to the above examples to which many similar variations can be made. All modifications directly derived or contemplated from the present disclosure by those skilled in the art fall in the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201710875802.0 | Sep 2017 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2018/106867 | 9/21/2018 | WO | 00 |
