Magnesium Alloy Die Castings

In recent years, the magnesium alloy automobile die casting industry has achieved great development: when developing the automobile industry, Magnesium alloy die castings are the focus of investment promotion. Steering wheels, wheels, doors and other projects emerge in an endless stream. The Machine Parts Co., Ltd. has also invested in the automotive steering column project before. The company currently has more than 10 cold chamber die casting machines of 200T-1250T models, and a total of 3 hot chamber die casting machines of 88T-168T models. Excellent quality has created The reputation of gold quality makes the other shore products quickly famous at home and abroad. More than 70% of the products are exported to the United Kingdom, Germany, Japan, the United States, Taiwan and other countries and regions.

Product Dsecription

1. Implementation standards: the company strictly implements ISO9001, ISO14001, IATF16949 certification

The products have passed the certification of ROHS, FDA EU, etc.

2. Product material standards: ISO, GB, ASTM, SAE, ISO, EN, DIN, JIS, BS

3. Main processes: die casting process, investment casting, shell casting, deburring, sand blasting, machining, heat treatment, leak testing, surface treatment, etc.

4. Casting available materials:

Magnesium alloy, aluminum alloy, zinc alloy, tin bronze, silicon bronze, aluminum bronze, brass, red copper, titanium alloy, high manganese steel, high chromium steel, high nickel steel, carbon steel, alloy steel, stainless steel, gray iron, , cast iron, cast steel, cast aluminum, etc. are customized according to customer requirements.

Available materials for die casting:

Magnesium alloy die castings mainly include Mg-Al-Zn-Mn, Mg-Al-Mn, Mg-Al-Si-Mn alloys.

Process flow

1. Main process flow chart of Magnesium alloy die castings

2. Magnesium alloy die casting

2.1 Magnesium alloy melting process

2.1.1 Selection of magnesium alloy grades

Magnesium alloy ingots are AZ91D, which has high elongation and strength and good fluidity.

2.1.2 Magnesium alloy melting furnace

Due to the flammable characteristics of magnesium alloys, the magnesium alloy melting furnace needs to have both melting and heat preservation functions, and inert gas is used to isolate the air. The pouring adopts quantitative pouring, and the magnesium liquid is pumped into the melting cup through the clinker tube, and the clinker tube is heated and kept warm. The smelting of magnesium alloys generally adopts a double-chamber furnace.

2.1.3 Magnesium alloy holding furnace

The holding furnace for smelting and holding magnesium alloy needs to use a holding double-chamber furnace, that is, the melting furnace and the holding furnace are separated (as shown in Figure 2 below):

1) Protective gases need to be added during smelting and pouring: nitrogen and sulfur fluoride;

2) No. 2 solvent is used during smelting: magnesium chloride, particle size (80-150);

3) Do not use the return furnace;

4) The holding furnace adopts quantitative furnace;

2.2 Magnesium alloy die-casting process

2.2.1 Process parameters of magnesium alloy die casting

Compared with aluminum alloy, magnesium alloy die-casting process has more advantages than aluminum alloy. The specific parameters of magnesium alloy are shown in the following table

2.2.2 Magnesium alloy die-casting process

With Bühler's die-casting vacuum technology, the pressure chamber, pusher and cavity can all be evacuated, as shown in Figure 3 below:

2.2.3 Fire and explosion-proof of die-casting workshop

Due to the flammable and explosive characteristics of magnesium alloys, the die-casting workshop needs to be treated with fire and explosion protection. The following measures are taken:

1) The cooling method of the parts after die casting can use water cooling or air cooling;

2) Equipped with magnesium alloy special fire extinguisher: dry sand, covering agent, D-level fire extinguisher;

3) When the magnesium alloy is heated to 350 degrees, the mixed gas of nitrogen and sulfur fluoride is introduced into the sealed melting furnace, and the melting of magnesium alloys generally does not exceed 700 degrees;

4) It is forbidden to bring water into the workshop;

5) Tools in contact with magnesium alloys need to be preheated to more than 150 degrees;

6) The tools with rust should be polished and preheated before they come into contact with the magnesium alloy liquid.

2.2.4 On-site requirements for die-casting cleaning

Compared with other alloy materials (such as aluminum alloy), the die-cast magnesium alloy has a brighter appearance after cleaning and grinding, but the deformation of the magnesium alloy after die-casting is larger. At 0.7mm, due to its hardness, it is difficult to correct, as shown in Figure 4 below. Shown (left picture is aluminum alloy, right picture is magnesium alloy):

Magnesium alloys have many safety factors in the cleaning process. The main factors include: electrical circuit sparks, friction sparks during cleaning, and dust encountering open flames. The following safety measures are required:

1) The grinding dust must pass through the exhaust system in time to draw the magnesium chips into the coolant;

2) The grinding workshop must be an open working environment;

3) Class D fire extinguishers are used, and the fire extinguisher material usually uses sodium chloride-based powder or a passivation-treated graphite-based powder, the principle of which is to smother the flame by excluding oxygen;

4) Use covering agent or dry sand, which can be used to cover the flame when a small area is on fire. The principle is also to smother the fire by removing oxygen.

5) Clean up the fire protection of the line body;

6) Clean magnesium chips in time (every 2 hours), store them in a fixed area, and recover them by the manufacturer after a period of time;

7) Ventilation to the outside, absorbed through the rain shower system.

Post Casting Process

1. Heat treatment: annealing, carbonization, tempering, quenching, normalizing, surface tempering

2. Processing equipment: CNC, WEDM, lathe, milling machine, drilling machine, grinder, etc.;

3. Surface treatment: powder spraying, chrome plating, painting, sandblasting, nickel plating, galvanizing, blackening, polishing, bluing, etc.

Moulds and Inspection Fixtures

1. Mold service life: usually semi-permanent. (except for lost foam)

2. Mold delivery time: 10-25 days, (according to product structure and product size).

3. Tooling and mold maintenance: Zhongwei is responsible for precision parts.

Quality Control

1. Quality control: the defective rate is less than 0.1%.

2. Samples and trial run will be 100% inspected during production and before shipment, sample inspection for mass production according to ISDO standards or customer requirements

3. Testing equipment: flaw detection, spectrum analyzer, golden image analyzer, three-coordinate measuring machine, hardness testing equipment, tensile testing machine;

4. Provide after-sales service.

5. The quality can be traced back.

Application

Magnesium alloy die castings have good light weight, machinability, corrosion resistance, shock absorption, dimensional stability and impact resistance, which are far superior to other materials. These characteristics make magnesium alloys used in a wide range of fields, such as transportation, electronics, medical, military, etc. This trend will only increase. Especially in the fields of 3C products (Computer, Consumer Electronic Product, Communication), high-speed rail, automobile, bicycle, aerospace, architectural decoration, hand-held tools, medical rehabilitation equipment and other fields, the application prospect is good and the potential is great. It will become one of the development directions of new materials in the future. Among the more than 400 new material catalogues supported by the Ministry of Industry and Information Technology during the designated "Twelfth Five-Year Plan" period, 12 are related to magnesium.

Certicifation