# US 10,870,905 B2 · Low-cost high-heat-conduction die-casting magnesium alloy and manufacturing method therefor

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- Number: US 10,870,905 B2
- Document ID: US10870905B2
- Status: Granted
- Kind: B2
- Application number: 15/780,161
- Filed: 2016-12-06
- Published: 2018-12-06
- Granted: 2020-12-22
- Earliest claimed: 2015-12-14
- Assignees: Baoshan Iron & Steel Co., Ltd.
- Applicants: Baoshan Iron & Steel Co., Ltd.
- Inventors: Shiwei Xu; Jichun Dai; Weineng Tang; Changlong Zhuo; Haomin Jiang; Pijun Zhang
- Web page: https://patentgrep.com/patent/US10870905B2

## CPC

- C22C 1/02: by melting {(C22C1/1036 takes precedence)}
- B22D 17/00: Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D 27/003: {by using inert gases}
- C22C 23/00: Alloys based on magnesium
- C22C 23/04: with zinc or cadmium as the next major constituent
- C22C 23/06: with a rare earth metal as the next major constituent
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- B22D: CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES (shaping of plastics or substances in a plastic state B29C; metallurgical processing, selection of substances to be added to metal C21, C22)

## Abstract

A die-casting magnesium alloy. The die-casting magnesium alloy comprises, by mass percent, 1% to 5% of La, 0.5% to 3% of Zn, 0.1% to 2% of Ca, 0.1% to 1% of Mn and the balance Mg and other inevitable impurities. The die-casting magnesium alloy manufacturing method comprises smelting, refinement and die-casting. The die-casting magnesium alloy has good mechanical performance, die-casting performance and heat conduction performance.

## Claims

### Claim 1

A heat-conduction die-casting magnesium alloy consisting of by mass,
La: 1 to 5%;
Zn: 2.5 to 3%;
Ca: 0.1 to 2%;
Mn: 0.1 to 1%; and
the balance is Mg and other inevitable impurities;
wherein the magnesium alloy has a microstructure comprising α-magnesium matrix and precipitation phases, and wherein the α-magnesium matrix comprises fine grains and a small amount of relatively larger grains, and the relatively larger grains have a volume ratio of 20% or less; and
wherein the fine grains have a size of 3-15 μm and the relatively larger grains have a size of 40-100 μm.

### Claim 2 (depends on 1)

The heat-conduction die-casting magnesium alloy of claim 1, wherein the precipitation phases comprises a Mg—Zn—La—Ca quaternary phase that is continuously distributed around grain boundaries and a Mg—Zn phase precipitated inside the grains.

### Claim 3 (depends on 2)

The heat-conduction die-casting magnesium alloy of claim 2, wherein the Mg—Zn phase has a width of 1-20 nm and a length of 10-1000 nm.

### Claim 4 (depends on 1)

The heat-conduction die-casting magnesium alloy of claim 1, wherein the magnesium alloy has a thermal conductivity of 110 W/m·K or more, a tensile strength of 200-270 MPa, a yield strength of 150-190 MPa, and an elongation of 2-10%.

### Claim 5

A manufacturing method for a heat-conduction die-casting magnesium alloy, comprising the following steps:
(1) melting pure Mg ingots and pure Zn ingots in a smelting furnace;
(2) adding Mg—Ca and Mg—Mn master alloys to the smelting furnace and melting them completely;
(3) adding Mg—La master alloy to the smelting furnace and melting it completely, and adding flux at the same time to cover the surface of a resulting melt;
(4) refining the melt;
(5) cooling the refined melt to 630-750° C.; and
(6) die-casting the melt to obtain a heat-conduction die-casting magnesium alloy consisting of by mass:
La: 1 to 5%;
Zn: 2.5 to 3%;
Ca: 0.1 to 2%;
Mn: 0.1 to 1%; and
the balance is Mg and other inevitable impurities;
wherein the magnesium alloy has a microstructure comprising α-magnesium matrix and precipitation phases, and wherein the α-magnesium matrix comprises fine grains and a small amount of relatively larger grains, and the relatively larger grains have a volume ratio of 20% or less; and
wherein the fine grains have a size of 3-15 μm and the relatively larger grains have a size of 40-100 μm.

### Claim 6 (depends on 5)

The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5, wherein in the step (1), temperature in the smelting furnace is controlled to 700-760° C., and the melting is performed under the protection of SF6 gas.

### Claim 7 (depends on 5)

The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5, wherein in the step (2), temperature in the smelting furnace is controlled to 700-760° C., and the melting is performed under the protection of SF6 gas.

### Claim 8 (depends on 5)

The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5, wherein in the step (3), temperature in the smelting furnace is controlled to 700-760° C., and the smelting is performed under the protection of SF6 gas.

### Claim 9 (depends on 5)

The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5, wherein in the step (4), temperature in the smelting furnace is controlled to 730-780° C., and Ar gas is introduced into the melt or the melt is manually stirred, while flux is simultaneously added for refining for 5-15 minutes to obtain a refined melt; and then the refined melt is kept standing at 730-760° C. for 80-120 minutes.

### Claim 10 (depends on 5)

The manufacturing method for the heat-conduction die-casting magnesium alloy of claim 5, wherein in the step (6), the die-casting is controlled such that an injection speed is 2-50 m/s, a die temperature is 220-400° C., and a casting pressure is 10-90 MPa.