Advantages of magnesium processing in Semi-solid Magnesium Alloys

Magnesium has very good processability, that is to say, it has good casting properties. Compared with other materials, its manufacturing cost is very low. It is worth noting that although the price per kilogram of magnesium ingot is more expensive than that of aluminum and iron, the unit volume of finished product is almost the same price.

The physical and chemical characteristics of magnesium make it more suitable for die-casting large parts than aluminum. The melting latent heat per unit volume of magnesium is only 2/3 of aluminium, the specific heat is only 3/4 of aluminium, and has very low solubility of iron. These characteristics allow magnesium die castings to achieve almost the same production cost as aluminum per kg. The production costs of Mg die castings are much lower than that of aluminum if they are to be applied to the highly productive HOT RUNNER technologies (such as the latest THIXOMAT results).

1. advantages of magnesium processing
Ordinal advantage
1 the cost of melting is only 2 / 3 of aluminum
2 die-casting production efficiency is higher than aluminum 25%, metal mold casting higher than aluminum 300 - 500K, lost foam casting 200% higher than aluminum
3, the surface quality and appearance of magnesium castings are obviously better than aluminum (because the thermal load of the die is reduced and the inspection frequency can be reduced)
4 the life of the die is 2 times (or more) of aluminum, depending on the shape of the cavity
5, the magnesium removal angle is small (which can be cancelled by subsequent machining) and the surface is well formed (because of the low viscosity of magnesium)

2. defects in magnesium processing performance
Of course, compared with other materials, magnesium processing also has some characteristics of increasing costs. As follows, the defects of magnesium processing performance are discussed as follows
Ordinal advantage
2-1: aluminum and metal casting, magnesium die casting a higher residual waste rate (compared with the output rate of scrap aluminum)
2-2: magnesium die-casting or THIXOMOLD production equipment investment is very high. Compared with the aluminum gravity / low pressure / nitrate mold, the magnesium die casting machine is very expensive (because it needs higher clamping force and filling speed), of course, its productivity is 4 times as much as that of the former
2-3: magnesium die casting requires higher trial cost and longer trial production time, while steel parts (manufacture using simple welding technology by drawing) or plastic parts (using low-cost prototype tooling) is much simpler
2-4: and aluminum die or die casting ratio, magnesium die casting needs higher mold cost. Because die casting large and complex, but also to withstand Gao Suomo force (of course, high productivity can also reduce the cost of a single product)
2-5: compared with magnesium die casting and aluminum die-casting, the burning rate is higher than 2% 50K, which is 4% (because of a higher surface active magnesium)
2-6: magnesium die chip recycling costs higher than aluminum, dry magnesium chip is not easy to recover, the moisture is even more difficult, and must be very careful to prevent fire

3: comparison of properties between magnesium alloy and several materials
Performance parameters; specific gravity; g/cm3 tensile strength; Mpa ratio; strength; yield strength; Mpa elongation;% modulus of elasticity; Gpa ratio; stiffness; thermal conductivity; w/mk; coefficient of shock absorption
AZ91D  1.81  250  138  160  745  25.86  54  50
A380  2.70  315  116  160  371  25.9  100  5
Carbon steel  7.86  517  80  400  22  200  24.3  42  15
ABS 1.039693   60      0.9

4: application of magnesium
In China and abroad, the application of magnesium is mainly concentrated in the three fields of aluminum alloy production, die casting production and steelmaking desulfurization, and also used in rare earth alloys, metal reduction and other fields.
Magnesium is an important alloy element because of its small density, high specific strength, and high strength alloy with metals such as aluminum, copper and zinc. The world's largest consumption of magnesium is to add elements to aluminum alloys. In 2002, 145 thousand and 600 mg of magnesium was used in the consumption of the original magnesium in the major regions of the world, accounting for 40% of the total magnesium consumption. In 2003, 21 thousand tons of magnesium were added to aluminum alloy, accounting for 41% of the total consumption. In general, the consumption ratio of magnesium to aluminium is about 0.4%.
In 2002, die casting accounted for 35% of the total magnesium consumption in major parts of the world. In the magnesium die casting industry, North America, Latin America and Western Europe use the most, because the automotive manufacturing industry to promote the market demand for magnesium growth. Statistics show that in the past 10 years, the use of magnesium alloy die castings in automobiles has risen by about 15%, and this trend will continue.
Many steel mills in Europe, America, Russia and other regions and countries use magnesium desulphurization. In 2002, 57 thousand and 300 of the total magnesium consumption in major regions of the world was spent on steel desulphurization, accounting for 15.70% of the total. In 2003, 8000 tons of magnesium were used for desulphurization of iron and steel, accounting for 15.62% of the total consumption. The use of magnesium particles than the desulfurization effect of calcium carbide is good, although the price of magnesium calcium carbide than high, but its amount is only 1/6 1/7 of calcium carbide, calcium carbide is the total cost of desulphurization economy. In general, consumption of magnesium powder 0.4 - 0.5 kg, after desulfurization, sulfur of 0.001 - 0.005%.
The use of magnesium sacrificial anode cathodic protection, is an effective method of preventing corrosion of metals, magnesium sacrificial anode has the following characteristics: good corrosion resistance, without external DC power supply, after the installation of automatic operation, no maintenance, small occupation area, low cost, and the external environment without any interference. Magnesium sacrificial anodes are widely used in petroleum, natural gas pipelines, gas pipelines and storage tanks; ports, ships, pipelines, drilling platform; airport, parking lot, bridges, power plants, municipal construction, water treatment plants, petrochemical plants, refineries, gas station corrosion protection and water heater, heat exchanger, evaporator, boiler equipment.
In human cells, magnesium is the second most important cations, it can activate a variety of enzymes in vivo inhibition of abnormal nervous excitability, maintaining the stability of the structure of nucleic acids, proteins involved in the synthesis, muscle contraction and thermoregulation. Recent studies have shown that atherosclerosis, cardiovascular and cerebrovascular diseases, hypertension, diabetes, cataracts, dysmenorrhea, osteoporosis and depression are all related to the lack of magnesium. More and more attention has been paid to the application of magnesium in the field of medicine.

5: application fields of magnesium alloys
As one of the metal structure of magnesium alloy materials with minimal current density, widely used in aerospace industry, military field, traffic areas (including the automotive industry, aircraft industry, motorcycle industry, bicycle industry), 3C etc..
The characteristics of magnesium alloy can meet the requirements of noise absorption, shock absorption and radiation protection of light materials in aerospace and other high-tech fields. It can greatly improve the aerodynamic performance of aircraft and reduce the structural weight obviously. Beginning in 1940s, magnesium alloys were first given priority in the aerospace sector.
In foreign countries, B-36 heavy bombers per frame for 4086kg magnesium alloy sheet; jet fighter with magnesium plate machine "Lockheed F-80" wing, make the number of parts is reduced from 47758 to 16050; "Derelainai" spacecraft starting rocket "Hercules" used in magnesium alloy 600kg; "deformation the use of 675kg magnesium alloy Weilieer Oscar season satellite; about 1 meters in diameter" Vigel "rocket shell is made of magnesium alloy extruded tube.
Our fighters, bombers, helicopters, transport aircraft, civil aircraft, airborne radar, surface to air missiles, rockets, satellites, spacecraft are made of magnesium alloy component: a type of aircraft up to selected 300-400 magnesium alloy component; a part of the weight of the heaviest near the maximum size of a 300kg; the component is more than 2m.
In military affairs, magnesium alloy plate is needed to improve the strength of structural parts, reduce the weight of equipment, and improve the hit rate of weapons. At present, domestic plates and strips have to be imported from abroad.
In the past twenty years, the world automobile output has been increasing continuously, with an average annual growth rate of 2.5%. The development degree of automobile industry is one of the important signs of the developed level of a country, and the metal material is the important foundation of the development of the automobile industry. For energy conservation and environmental protection, car design experts are trying to reduce the weight of the car to reduce gasoline consumption and exhaust emissions double effect. As the lightest structural material, magnesium alloy can meet the requirements of increasingly strict energy-saving exhaust gas emission. It can produce light weight, low fuel consumption and environmental friendly new type of automobile. The benefits of magnesium alloy automotive parts can easily be summed up as:

• small density, can reduce the weight of the vehicle, indirectly reduce fuel consumption;
• the specific strength of magnesium is higher than that of aluminum alloy and steel. It is closer to the alloy and steel than that of the alloy and can bear a certain load;
• magnesium has good casting and dimensional stability, easy to process, low reject rate;
• magnesium has good damping coefficient, vibration reduction is greater than aluminum alloy and cast iron. It can be used to reduce noise in the shell. The seat and rim can reduce vibration and improve the safety and comfort of the car.

Magnesium alloys have been used for parts of automobiles for about 70 years. As early as 1930, it was used in the piston of a racing car and the gasoline pump box in Opel, and the amount and application area gradually increased. In 60s, in some types of vehicles, the amount reached 23 kg, mainly used as valve shell, air cleaning box, brake, clutch, pedal frame, etc.. At the beginning of 80s, due to the adoption of new technology, strictly limit the content of iron, copper, nickel and other impurities, the corrosion resistance of magnesium alloy has been solved, at the same time, cost reduction and greatly promoted the application of magnesium alloys in automobiles. Since 90s, auto makers in Europe, America, Japan and South Korea have gradually begun to apply magnesium alloys to many automotive parts.
The application of magnesium alloy die castings in automobiles has shown a long-term growth trend. Over the past ten years, its annual growth rate has exceeded 15%. In Europe, 300 different magnesium components have been used to assemble cars, with an average of 2.5kg mg per European car. Optimistic estimates suggest that demand for magnesium per vehicle will rise to 70 - 120kg for the need for weight loss.
At present, the application of Mg alloy die casting products on automotive instruments, seats, steering systems, engines, transmissions, intake manifolds, hubs, engines and safety components.