JP2006289487A - Crystal grain control method for obtaining high hardness and high strength non-ferrous metal, in particular, magnesium alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which mechanical strength of a product can be enhanced and increased for various kinds of non-ferrous metal cast molding, by fining metal structure crystal grain in a cast product or by controlling growth-enlargement thereof, and the mechanical tensile strength of, in particular, magnesium alloy is greatly increased by extremely fining the crystal grain. <P>SOLUTION: A part of fine pieces of raw magnesium alloy dipped and dried in water having anti-oxidant effect or clean water containing useful microbial group generating anti-oxidant material or distilled water, is added and mixed into a magnesium alloy (AZ91D) ingot and melted to obtain molten metal. The molten metal is cast by a die casting method to obtain a product in which metal structure crystal grain size is extremely fine. According to the extremely fined metal structure crystal grain size, the mechanical tensile strength of the product is greatly improved. This extremely fine metal structure is held unchanged and also the mechanical strength is kept even when rolling-treatment is applied to the cast product. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

Detailed Description of the Invention

The present invention relates to grain control for high strength casting of magnesium alloys, aluminum alloys, zinc alloys, copper alloys, and / or brass.

With regard to magnesium alloy casting technology, the present applicant has already invented and developed a casting method that does not require attraction by applying ultrasonic vibration to the casting core (patent pending). The crystal system of magnesium metal or magnesium alloy belongs to the HCP crystal system, and its axial ratio is close to the value of the ideal sphere HCP structure, c / a = 1.633, which means that the grain size of the metal structure crystal particles of the magnesium alloy is The smaller the value, the higher the mechanical strength.

In the research and development of ultrasonic vibration casting of magnesium alloy so far, it was found that the effect of ultrasonic vibration has the effect of aligning crystal grains in the structure of magnesium alloy product material. However, although the effect of applying ultrasonic waves from the inside becomes finer from the inside to the outside, the effect of controlling the size of the crystal grain size is only slightly seen as a whole. From the standpoint of enhancing the mechanical strength of magnesium alloy products, research is underway to control the grain size of the magnesium alloy structure in a smaller direction by applying pressure during solidification (Mie Prefectural Science and Technology Promotion Center, Industrial Research Department) (Business report, Yoichi Kanamori, Shuji Shibata, Metals Laboratory, Industrial Research Department, October 2003, Internet). According to the results, it has been reported that the mechanical strength of the cast product increases as the metal structure crystal grain size of magnesium metal and magnesium alloy decreases.

In the conventional technology, for the purpose of reducing the crystal grain size of the magnesium alloy solidified product, calcium cyanide (CCN ₂ ) is mixed with a refining flux, wax, calcium fluoride, carbon as a crystal refining treatment agent. It is considered that a crystal refining agent such as the above is mixed into the molten metal by electromagnetic induction stirring or the like, but their effects are not remarkable.

Therefore, regardless of any casting technology such as casting, pressing, extrusion, forging, precision mold forming, thixo mold method, semi-solid casting method, etc., all of the crystal refinement treatment is effectively applied to reduce the particle size. It is expected to produce molded products and produce magnesium alloy products with high mechanical strength.

Means for solving the problem

On the other hand, activated mineral water is produced by passing water through mineral deposits (Patent Publication No. Hei 4-74074), and the activated mineral water obtained is brought into contact with a solid object to exert the characteristics of the activated mineral water. A technique for this is disclosed (Japanese Patent Laid-Open No. 7-328418). The applied solid object that tries to exert its effect is left to future research and is still unclear.

The applicant for this patent has devised and studied the application of this activated mineral water contact technology to melt casting of magnesium alloys. As a result, water having antioxidative efficacy is effectively established in the grain refinement treatment, and therefore a magnesium alloy cast molded product having a very fine metal structure and a very high mechanical strength is obtained. A remarkable result was obtained. Although the action of the antioxidant effect water is not yet clear, it is assumed that the solid surface in contact with the antioxidant effect water has a strong antioxidant action.
The technology is described below.

A magnesium alloy strip (or a face) is infiltrated with antioxidant water and then dried.

The magnesium alloy ingot and the antioxidant water infiltrated magnesium alloy strip are mixed, and the mixture is put into a melting furnace crucible.

Finally, the molten metal is poured into a mold and cast according to a normal method. By the above method, a solidified structure having a very small crystal grain size can be obtained. Its mechanical strength is incomparably higher than magnesium alloy solidified products obtained by conventional solidification techniques. When the molten metal is injected, a faster die casting speed is effective in reducing the crystal grain size of the solidified structure.

In the present invention, instead of the crystal refining agent described in the section 0004, it may be considered that a magnesium alloy strip brought into contact with water having antioxidant effect is mixed with a magnesium alloy ingot.

If it is a molten molten metal mixture of magnesium alloy strips and magnesium alloy ingots that have been subjected to water infiltration treatment as described in paragraph 0009, not only die casting but also casting, press extrusion, forging, Any solidification molding method such as precision mold molding, thixomolding method, semi-solid casting method, etc. can provide the effect of refining the crystal grain of the solidified structure according to the present invention.

Not only magnesium alloy but also aluminum alloy, zinc alloy, copper alloy, and brass metal structure crystal particles are expected to have the effect of the antioxidant effect water infiltration treatment in the refinement or growth promotion of the present invention. .

Instead of antioxidant water, ceramics or activated carbon may be used to perform adsorption filtration treatment on tap water, and in particular, purified water from which chlorine has been removed, or distilled water obtained by desalting and purifying tap water by distillation, for example, may be used. . Further, the purified water containing the antioxidant substance produced by the “useful microorganism group” or the distilled water may be used. The purified water or distilled water containing the antioxidant substance produced by the useful microorganism group means a mixture of the purified water and the antioxidant substance produced by the useful microorganism group in the distilled water. Here, the useful microorganism group refers to a group of 80 or more microorganisms of 10 genera having different functions generally called “EM (Effective Micro Organism)”, and the main types of bacteria are a photosynthetic microorganism group, a lactic acid bacteria group, Yeast group and Actinomycete group.
The example and the result are described below.

Magnesium alloy ingot (AZ91D) 5kg and antioxidative effect produced by useful microorganisms 100g of magnesium alloy strips that have been infiltrated with water are put into a crucible in a melting furnace and melted, and the molten metal is die-cast. It is poured into a casting mold and normal high-speed die casting is performed. The metal structure of the obtained cast product is shown in FIG. A cast product made by die-casting only a magnesium alloy ingot without mixing purified water containing antioxidant effect water or antioxidants produced by useful microorganisms or magnesium flakes that have been infiltrated into the distilled water. The metal structures are compared and shown in FIG.

Magnesium that has been die cast under normal temperature and high speed conditions without adding purified water containing antioxidant water or antioxidants generated by useful microorganisms, or strips that have been infiltrated into distilled water In FIG. 2, which is a photograph of the metal structure of the alloy product, the grain boundaries in the structure are clearly photographed. The grain size of the crystal grains is about 30-50 μm.

Fig. 1 is a mixture of purified water containing antioxidant water and antioxidants produced by useful microorganisms, or magnesium alloy strips that have been infiltrated into the distilled water, mixed into a magnesium alloy ingot and dissolved. It is the metal structure photograph of the product which performed high-speed die-casting at the temperature of. Photographed at the same magnification as in FIG. 2, the metal structure is fine, and the crystal grain size is 4-5 μm.

In order to know the difference in mechanical strength between the products shown in FIG. 1 and FIG. 2, the Vickers hardness of both product samples was measured. FIG. 3 shows the sample position of the Vickers hardness measurement point.

The Vickers hardness measurement in the direction perpendicular to the bottom surface was performed at the center of the bottom surface of the U-shaped cast product. The measurement position is named measurement position A. On the other hand, a measurement position perpendicular to the side surface at the center of the side surface of the product is named measurement position B. The measurement was performed at several points from the surface after polishing the sample surface.

FIG. 4 shows the measurement results of Vickers hardness at the measurement position A. The circles indicate the measurement points of the products cast by adding the magnesium alloy strips that have been treated with water infiltration with the antioxidant effect to the magnesium alloy ingots, and the circles indicate the measurement results of the products with only the magnesium alloy ingots. From the figure, it can be clearly seen that the hardness of the product obtained by mixing and dissolving the magnesium alloy strips subjected to water infiltration treatment with antioxidant effect is very high.

Anti-oxidation effect Water-infiltrated magnesium alloy strip added effect is 14% hardness improvement by 11HV from 77HV to 88HV even at a depth distance of 0.8mm from the surface where the increase in hardness is minimal It becomes the effect. At a depth showing the maximum hardness increase, 0.4 mm from the surface, 42HV also increases (increases from 68HV to 110HV), which has a 62% hardness improvement effect. The average value shows a 30% improvement in hardness (from 76 HV to 99 HV).

The effect of adding anti-oxidation effect water, anti-oxidant added purified water produced by useful microorganisms, or infiltrated magnesium alloy strips to the distilled water is even more remarkable on the side of the product, that is, at the measurement position B. FIG. 5 shows the measurement results at the measurement position B. The meanings of ○ and ● are the same as those in FIG.

At the measurement position B, the hardness at a distance of 0.6 mm from the surface is 92 HV when the infiltrated strip is added, whereas it is 77 HV in the die-cast product with only the untreated magnesium alloy ingot, so the minimum increase in hardness is achieved. Even at depth, the hardness increases by 15 HV and has an effect of improving hardness by 19%, and at a depth of 0.2 mm from the surface where the maximum hardness improving effect is obtained, there is an increase of 36 HV by 43% (infiltration treatment) 119HV for added fine strips, 83HV for untreated magnesium alloy ingots). In terms of the average value, there is an effect of improving the hardness by 36% (treated strip added 103 HV, untreated 76 HV).

In FIGS. 4 and 5, the mechanical properties are examined using the Vickers hardness. However, it is necessary to more directly observe the effect of crystal grain refinement by the mechanical strength and tensile strength. Although it is about aluminum alloy as a reference, FIG. 6 shows a graph relating Vickers hardness and tensile strength. According to the figure, since both physical property values are in a proportional relationship, the percentage value of the hardness improvement effect described in the paragraphs 0024 and 0026 may be regarded as the improvement value of the mechanical tensile strength as it is. To directly refer to FIG. 6, the purified water containing the antioxidant effect water of FIG. 4 and FIG. 5 and the antioxidant substance produced by the useful microorganism group, or the infiltration treated strip into the distilled water was added and mixed. The 90 HV Vickers hardness commonly found in die cast magnesium materials corresponds to 30 kgf / mm ² (about 300 MPa). This value corresponds to about twice the strength of 5005Al-Mg alloy used as building materials and equipment.

Finally, another embodiment is shown. This embodiment relates to claim 6 and further adds a rolling process to the magnesium material die-casted by adding and mixing infiltration treatment pieces into purified water containing antioxidant water and useful microorganism group-generated antioxidant substances. The metallographic crystal grains of the finished product were examined.

FIG. 7 is a metallographic photograph (magnification 200 ×) of a magnesium alloy (AZ91D) obtained by ordinary die casting, infiltration treatment into purified water containing antioxidant water and useful microorganism group-generated antioxidants. It was obtained by die casting of raw materials that did not mix magnesium strips.

Compared to this, Fig. 8 is obtained by die casting from raw magnesium material mixed with magnesium ingot with magnesium strips that have been infiltrated into purified water containing antioxidant water and useful microbial group-generated antioxidants. 2 is a metallographic micrograph of a sample. In FIG. 7, crystal grains having a diameter of about 40 to 50 μm occupy the whole, whereas in FIG. 8, such crystal grains are not recognized at all. The effect of the grain refinement of the previous embodiment described in the paragraphs 0016 and 0017 is clearly recognized also in this embodiment.

The samples in FIGS. 7 and 8 are both samples that have not been subjected to rolling treatment yet. Several rolling processes (thickness 5 mmt → 2 mmt) were added to the solid sample, and the metal structure of the product was observed. FIG. 9 shows a metallographic photograph of the FIG. 7 sample after the rolling process. The giant crystal grains seen in FIG. 7 by rolling extend thinly in the lateral direction and exhibit unidirectional anisotropy, and a refinement effect is recognized by rolling.

FIG. 10 shows die casting from the raw magnesium material in which the magnesium ingot mixed with the magnesium ingot in the sample of FIG. 8, that is, the infiltrating treatment into the purified water containing antioxidant effect water and useful microorganism group-generated antioxidants. It is the metal structure photograph of the product which added the above-mentioned rolling process (thickness 5mmt-> 2mmt) to the solid sample obtained by (1). Compared to FIG. 8, the crystal grains are further refined in FIG. 10 by the rolling process.

Comparing Figure 10 with the other three photographs, magnesium strips that have been infiltrated into purified water or distilled water containing antioxidant water and useful microorganisms are mixed with magnesium ingots. In addition to subdividing the metallographic crystal grains of the die-cast product, it has also become clear that the metallographic crystal grain size of the rolled product can be reduced even if the product is subjected to a rolling treatment. . This effect is considered to be effective not only for rolling but also for various solid molding methods such as pressing, extrusion, forging, precision die molding, thixo molding method, semi-solid casting method and the like.

During die casting, when magnesium alloy strips are infiltrated into purified water containing distilled water with antioxidant effect water or useful microbial group-generated antioxidants, or a portion of this is mixed with the original magnesium alloy ingot and dissolved. The effect on the refinement of product crystal grains is remarkable. Antioxidant water that brings about crystal grain refinement and purified microorganisms containing useful microorganisms or the action of distilled water are still unknown, but raw metal materials with antioxidant effects and useful microorganisms are produced. The antioxidants contain a small amount of ash, including sodium atoms, and these components are precipitated as solidified crystal nuclei at the same time, resulting in ultrafine crystals as shown in FIGS. I think that grain structure may appear. In addition, when the sample temperature rises during die casting (when the die is cast, it is recognized that the temperature of the sample rises to 750 ° C. to 850 ° C.). It is also thought that it caused the grain refinement.

The invention's effect

As described above, at the time of die casting, a magnesium alloy strip (alloy name: AZ91D) is infiltrated into purified water containing antioxidant effect water, useful microorganism group-generated antioxidant substance, or distilled water, and a part thereof The effect of mixing and melting the raw magnesium alloy ingot makes the magnesium crystal grains of the solidified product very fine. Even in the experiment of applying pressure during solidification described in the previous section 0003, the minimum crystal grain size was about 30 μm to 60 μm (Mie Prefectural Science and Technology Promotion Center, Industrial Research Department Business Report). On the other hand, in the present invention, an average fine grain size of 4 to 5 μm is observed. This is immediately reflected in the mechanical tensile strength of the product. Magnesium strips are infiltrated with purified water or water containing antioxidants and useful microorganism-generated antioxidants. By mixing and melting and casting in an alloy ingot, the mechanical strength of the product was improved by 30% to 35% on average in tensile strength and increased by 43% to 62% at maximum.

In addition, it infiltrates into purified water containing distilled water with antioxidant effect water or useful microbial group-generated antioxidants, and a rolling treatment is applied to the magnesium alloy solid material that is partly mixed and dissolved in a magnesium alloy ingot and die-cast. And the metallographic crystal grains of the product show a tendency to be equal or further subdivided, indicating that the mechanical strength is improved and strengthened.

Using a molten metal in which a part of non-ferrous metal material is subjected to an infiltration treatment in purified water containing distilled water or an antioxidant effect water or a useful microbial group-forming antioxidant substance, and this is mixed and dissolved with the raw metal raw material. Reduce or increase crystal grain size in products by solid product manufacturing methods such as casting, pressing, extrusion, rolling, forging, precision mold forming, thixomol and method, semi-solid casting method, etc. It provides an effective way to control grain size in both directions. This provides an essentially effective way to increase and improve the mechanical strength of the manufactured product.

Metal structure photograph of high-speed die-casting magnesium alloy product of molten metal mixed and added with purified water containing antioxidant effect water and antioxidants produced by useful microorganisms or distilled water soaked in distilled water, × 200 Double. A metal structure photograph of a product obtained by casting only a magnesium alloy AZ91D by ordinary high-speed die casting, × 200 magnification. Vickers hardness measurement position of product, measurement position A: bottom of product, measurement position B: side of product Vickers hardness measurement results at various depths at measurement position A, ○: Mixed added sample of strips treated by immersion in purified water or distilled water containing antioxidant water or useful microorganism group-generated antioxidants, high-speed die casting ●: Antioxidation effect Water immersion treatment No mixing of strips, high speed die casting Vickers hardness measurement results at various depths at measurement position B, ○: Mixed addition sample of strips treated by immersion in purified water or distilled water containing antioxidant water or useful microorganism group-generated antioxidants, high-speed die casting . ●: Antioxidation effect Water immersion treatment No mixed addition of strips, high speed die casting. Relationship between Vickers hardness and mechanical tensile strength: Aluminum alloy. Metal structure photograph of magnesium alloy (AZ91D) ingot die-cast product, (200x magnification), mixed addition of strips treated by immersion in distilled water or purified water containing antioxidant water or useful microorganism group-generated antioxidants None. Metal structure photograph of a magnesium alloy (AZ91D) ingot die cast product in which strips subjected to immersion treatment of purified water or distilled water containing antioxidant water and useful microorganism group-generated antioxidants are added and mixed (magnification 200 × ). The metal structure photograph of the product which added the rolling process (5mmt-> 2mmt) to the die-casting product of the magnesium alloy (AZ91D) ingot (magnification 200x). Antioxidation effect to magnesium alloy (AZ91D) ingot No mixing addition of water soaked strips. The sample before the rolling process is the same as the sample in FIG. Rolling treatment (5mmt → 2mmt) to die-cast products of magnesium alloy (AZ91D) ingots, which are added and mixed with purified water containing antioxidant water and useful microorganism group-generated antioxidants, or distilled water-immersed strips The metal structure photograph of the added rolled product (magnification 200 ×).

Claims (9)

Add a water immersion treatment with antioxidant effect to the magnesium alloy strip, mix and melt it in the corresponding magnesium alloy ingot, die cast the molten metal, and make the metallographic crystal grains finer Crystal refinement method. Add a water immersion treatment with an antioxidant effect to a magnesium alloy strip, mix and melt it in a magnesium alloy ingot, die cast the molten metal, and refine the metallographic crystal grains A method for improving and enhancing the mechanical strength of the obtained magnesium alloy die-cast product. Add water immersion treatment with antioxidant effect to aluminum metal, aluminum alloy, zinc alloy, copper alloy, or titanium alloy strip, mix this with various metal ingots, melt and cast this molten metal, A method of controlling the crystal particle size, which controls the size of the metal structure crystal particle size. This metal melt is prepared by adding a water immersion treatment with an antioxidant effect to a strip of magnesium metal, magnesium alloy, aluminum alloy, zinc alloy, copper alloy, or titanium alloy, mixing it with the corresponding metal ingots, and melting it. And a method of controlling crystal grains in which the size of the crystal grain diameter of the metal structure of the product is controlled by pressing, extruding, and / or rolling. Add magnesium metal, magnesium alloy, aluminum alloy, zinc alloy, copper alloy, or titanium alloy strips with anti-oxidant water so that they can be mixed and melted in various metal ingots. A method of controlling crystal grains in which the size of the crystal grain diameter of the metal structure of the product is controlled by casting and forging. Add magnesium oxide, magnesium alloy, aluminum alloy, zinc alloy, copper alloy, or titanium alloy strips with an anti-oxidation effect, mix them with the corresponding metal ingots, melt and melt the molten metal. A method in which extrusion, rolling, and / or forging is added to a cast product and a molded product that have been cast to control the size of the metallographic crystal particle diameter of the product, thereby improving and enhancing its mechanical strength. A magnesium alloy, aluminum alloy, zinc alloy, copper alloy, or titanium alloy strip is subjected to water immersion treatment that has an antioxidant effect, mixed with the corresponding metal ingots, melted, A method for controlling crystal grains, in which mold casting is performed and the crystal grain diameter of the metallographic structure of the product is controlled. A method of controlling crystal grains in which a magnesium alloy strip is subjected to a water immersion treatment having an oxidizing effect, and is introduced from a hopper of a thixo mold machine to perform thixo molding to control the crystal grain size of the metallographic structure of the product. Add a water immersion treatment with antioxidant effect to a small piece of magnesium alloy or aluminum alloy, mix it with various metal incots to make billets, and perform semi-solid casting with a semi-solid casting machine. A crystal grain control method for controlling the crystal grain diameter of a metal structure.

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