Aluminum Die Casting Company(aluminumalloydiecasting)

CNMFRS.com: Trusted Quality Manufacturers in China

Sat, 26 Oct 2024 09:00:46 +0000

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China’s Leading B2B Marketplaces for Manufacturers & Suppliers: An Overview

China’s rapid e-commerce expansion has fundamentally transformed how businesses conduct transactions, particularly in the B2B sector. As one of the world's largest e-commerce markets, China has seen a surge in specialized B2B marketplaces that connect manufacturers, suppliers, and exporters with global buyers. Platforms like CNMFRS.com are at the forefront of this shift, facilitating trade across various industries, including agriculture, electronics, and machinery. By addressing the inherent fragmentation in B2B industries, these marketplaces streamline procurement processes and foster business growth.

What is CNMFRS?

CNMFRS.com serves as a premier B2B platform designed to simplify the procurement process for businesses worldwide. This platform features a comprehensive directory of China's top manufacturers, effectively bridging the gap between global buyers and local suppliers. Industries such as textiles, electronics, and machinery benefit from the connectivity provided by CNMFRS. With an intuitive interface and advanced search functionalities, CNMFRS makes it easy for buyers to find the products they need while providing suppliers with an effective channel to showcase their offerings. The platform not only streamlines transactions but also fosters long-lasting partnerships between manufacturers and buyers, ensuring that both parties benefit from their interactions.

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B2B marketplaces play a crucial role in connecting sellers and buyers, creating a centralized environment for transactions that enhances efficiency for both parties. For buyers, platforms like CNMFRS offer a one-stop-shop experience where they can compare products, prices, and suppliers in real-time. This centralization empowers buyers to make informed purchasing decisions while accessing a global marketplace from the comfort of their offices.

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Conclusion

In summary, China’s emergence as a leader in online B2B marketplaces, exemplified by platforms like CNMFRS, highlights the country’s robust adaptation to digital commerce trends. These platforms not only streamline procurement processes for global buyers but also empower Chinese manufacturers and suppliers across diverse sectors. By leveraging advanced technology and tailored services, CNMFRS facilitates efficient trade interactions, fosters international partnerships, and enhances the competitive edge of domestic enterprises in the global market. As more businesses embrace these platforms, the landscape of international trade continues to evolve toward greater efficiency and accessibility, paving the way for future growth and innovation in the B2B sector.

Quality Improvement of Aluminum Alloy Cylinder Block Die Casts

Sun, 11 Feb 2018 01:52:54 +0000

At present, people's requirement of automobiles tend to be high performance, low energy consumption and low pollution based on energy and environmental protection. There are two ways to realized that. One is to improve the power system; the other is to reduce the weight of the car, that is, the lightweight car. Aluminum alloy is the most widely used light metal in automobile engines, because aluminum alloy has excellent properties such as light weight and good corrosion resistance, which make aluminum alloy meet the requirement of engine pistons, cylinder blocks and cylinder heads working in the harsh environment. Let's take the example of a new engine. The new engine is 14.7kg lighter than the old engine. The fuel consumption is reduced by 1L per 100km and the emission of CO2 is reduced by about 10g per kilometer.

Automotive engine die casting parts such as cylinder blocks, cylinder heads, sprocket shells and oil pans are die casts with complex shapes, changeable structures, precision sizes and good compactness. The requirements of high standards and high rates of finished products have challenged techniques and quality assurance of aluminum alloy die casts.

In order to obtain die casting parts with high quality, the key process parameters such as temperature, speed, pressure and time must meet the requirements of die casting production.

Temperature control
Pouring temperature should be controlled at 640 to 680 ℃. When pouring temperature is too high, shrinkage is great, which will make the crack and big grain easily appear on the die casting part and the die cast stick to the mold; when the pouring temperature is too low, defects such as cold shuts and metal shortages will occur. Make sure that oxide layers on surfaces of aluminum alloy liquid in the holding furnace are cleaned timely; otherwise, the oxide layer may lead to oxide inclusions.

The die casting mold should be preheated to a certain temperature before it is used. In continuous production, temperature of the die tends to increase. Too high temperature can lead to slow cooling of the die cast besides the molten metal being stick to the mold, making the grain big and deform.

Speed and pressure control
Changes of the injection process parameters can greatly influence quality of the cylinder block die cast. High speed easily leads to increased gas in the die casting part, while too low speed will easily cause poor filling. When injection pressure is too low, defects such as blow holes and shrinkage cavities will increase; when the injection pressure is too high, defects like the joint flash will increase, which will cause damage to the mold. Adopting appropriate injection speed or pressure, determining the location of a reasonable speed conversion and rapidly increasing pressure on the die casting part before the solidification process can reduce defects on the die cast.

A die casting machine with 28000kN should be adopted due to large sizes, complex structures and great difference in wall thickness of cylinder blocks. Set the slow injection speed at about 0.2m/s, the slow injection stroke 400mm, the fast injection speed about 5.5m/s and pressure at about 45MPa.

What Kinds of Surface Treatments Do Aluminum Alloy Die Casts Have? (Part One)

Fri, 22 Dec 2017 02:42:21 +0000

Surface treatment of aluminum alloy die casts can be classified into pre-treatment and post-treatment. Pre-treatment is used for removing oxide skins and oil so as to improve adhesion force of post-treatment and make the die casting part's appearance better. There are three commonly used pre-treatments for aluminum alloy die casts, that is shot blasting, sand blasting and phosphating. Post-treatment generally can be divided into spraying, oxidation, electroplating and electrophoresis four kinds, and other surface treatments are only applied to the die casting part with special requirements due to the cost.

If we take costs into account, the following steps are for pre-treatment of the die casting part:
Shot blasting → sand blasting → phosphating → polishing and then spraying → electrophoresis → oxidation → electroplating
Please noted that the workpiece can only have spraying or electrophoresis treatment and can't have oxidation or electroplating treatment after the phosphating process.

If we take decoration and anti-corrosion into account, the following steps are for post-treatment of the die casting part:
Polishing → phosphating → sand blasting → shot blasting and then oxidation → electroplating → spraying → electrophoresis
Car engine shells generally adopt shot blasting and then spraying treatment.

Methods of surface pretreatment
1. Manual treatment
Scrapers, steel brushes and grinding wheels can be used for manually removing rust and oxide skins on surfaces of the workpiece. However, manual treatment has high labor intensity, low productivity, poor quality and incomplete cleaning.

2. Chemical treatment
Chemical treatment mainly adopts acid-base or alkaline solutions to react with oxide skins and oil on surfaces of workpieces so that oxide skins and oil can be dissolved in acidic or alkaline solutions and oxide skins and oil can be removed. Chemical treatment is suitable for cleaning the thin workpiece, but there is a disadvantage. If the time is not controlled properly, over etchings will happen on steel even if inhibiter is added. For more complex structural parts and parts with holes, residual acid which is immersed in the gap or the hole is difficult to be removed completely after the part is put into the pickling acid solution. If we don't deal with the problem well, it will become a hidden danger of corrosion of the workpiece later. Chemicals are easy to volatilize and have a high cost. It is very difficult to handle the chemical discharge after the treatment. If the chemical discharge is handled improperly, it will cause serious pollution to the environment. With the improvement of people's environmental protection awareness, chemical treatment is replaced by mechanical treatment.

The Common Defects of Aluminum Die Casting Parts (Part Three)

Thu, 16 Nov 2017 09:04:22 +0000

7. Segregation
Features: The chemical composition at the bottom and top of the crucible is uneven during the smelting process. The die casting part which solidifies first and the die casting part that solidifies later have uneven chemical composition.

Analysis of causes: The precipitated phase and the liquid phase contain different solute concentration during the solidification of alloy. In most cases solute of the liquid phase gathers and there is no enough time for it to spread, which will lead to the die casting part which solidifies first and the die casting part that solidifies later have uneven chemical composition. The chemical composition at the bottom part of the crucible is uneven in a certain temperature range during the smelting process, because compounds which are formed by some element have different density from mother liquor.

Prevention methods: 1. Stir the metal liquid more and put it aside appropriately during the smelting process. 2. Appropriately increase speeds of solidification and cooling.

8. Tumor forms of segregation
Features: The bump on the surface of the die cast has the shape of tumors.

Analysis of causes: When the central part of the die cast has not solidified, the liquid phase which doesn't solidify in the shrinkage center of the die cast's surface penetrates and forms tumor forms of segregation.

Prevention methods: 1. Properly lower the pouring temperature. 2. Appropriately improve the cooling ability of the mold. 3. Extend the opening time.

9. Super poor compositions
Features: Chemical elements are higher than the maximum number or lower than the lower limit, and impurity elements exceed the allowable upper limit.

Analysis of causes: 1. Compositions of intermediate alloy or prealloy are not uniform or errors of composition analysis are too great. 2. Calculations of furnace burdens or weights of burdens are wrong. 3. The smelting operation is improper, and elements which are easily oxidized burn too much. 4. Stirs of smelting are uneven, and easily segregated elements distribute evenly.

Prevention methods: 1. Properly adjust the composition when compositions of alloy are unqualified. 2. Consult with the design department when the final test is unqualified.

10. Cold shuts
Features: The molten metal is separated by the oxide skin, which causes the metal not completely fuse, resulting in forming cold shuts. If the situation is serious, metal shortages will happen. Cold shuts often appear on top walls of die casts, thin horizontal and vertical surfaces as well as parts between thin and thick parts, and they appear to be lines.

Analysis of causes: 1. Improper running gate systems make flow paths of alloy liquids too long or alloy liquids converge at very thin parts. 2. The discharge of the mold is poor, which makes alloy liquids blocked, oxidize and not fuse well. 3. The pouring temperature is too low. 4. Structures of die casts are improper. For example, outer corners are too small, which will lead to poor flows of alloys.

Prevention methods: 1. Improve designs of running gate systems; avoid flow paths of alloy liquids being too long and prevent alloy liquids converging at very thin parts. 2.Tilt the pouring to make the liquid flow smoothly. 3. Improve the discharge capability of the mold and strictly control the moisture of the molding sand. 4. Appropriately increase the pouring temperature and pouring speed. 5. Improve the structural design of die casts.

The Common Defects of Aluminum Die Casting Parts (Part Two)

Thu, 16 Nov 2017 00:37:30 +0000

4. Inclusions
Features: Inclusions are particles, whose composition is different from that of the casting, formed on the surfaces of the die casting part or inside the casting due to the coating materials, molding materials and refractory materials getting into the alloy melt.

Analysis of causes: First, other materials is mixed with alloy melt and are poured into the casting mold. Second, the refining effect is bad. Third, the exotic items or molding materials from the cavity surface of casting mold peel off.

Prevention methods: First, carefully refine and slag off. Second, the coating layer of the smelting tool should be firmly adhered. Third, the casting system and the cavity should be cleaned. Fourth, the furnace burden should be kept clean. Fifth, the surface inclusions can be removed by grinding, and welding repairing treatment can be used when necessary.

5. Slag Inclusions
Features: First, the flocculent oxide inclusions exist inside the casting, and the fracture surfaces are yellow or off-white. Second, the flux inclusions are dun dots, and they become holes with smooth surfaces after slag inclusions are removed. Sometimes the corrosion characteristics appear after the oxide inclusions are exposed to air for a period of time.

Analysis of causes: First, the slags are not completely removed after refining modification. Second, there is not enough time for standing after refining modification. Third, the casting system is not reasonable, and the secondary oxide skin is mixed into alloy melt. Fourth, the alloy melt is stirred or polluted after refining.

Prevention methods: First, strictly follow the process requirement of refining modification casting. Second, the metal liquid should be steadily poured into the casting mold in the pouring process. Third, the furnace burden should be kept clean, and the foundry returns treatment as well as application amount should strictly follow the technological procedure specification.

6. Cracks
Features: First, cracks are straight lines or irregular curves. Second, the fracture surfaces of cracks have oxidation characteristics without metallic luster, which often occur inside the sharp corner of hot spots, the intersection of thick and thin fracture surfaces together with lose structure. Third, the fractured metal surfaces are clean.

Analysis of causes: First, each part of castings is not evenly cooled. Second, the castings can not freely shrink due to the external obstruction during the process of solidification and cooling, and cracks appear since the internal stress exceeds the alloy's intensity.

Prevention methods: First, try to maintain the sequence or solidify the alloy melt simultaneously to reduce internal stress. Second, refine the alloy structure. Third, choose the proper pouring temperature. Fourth, increase the deformability of molds.

The Common Defects of Aluminum Die Casting Parts (Part One)

Thu, 12 Oct 2017 09:46:23 +0000

1. Blowholes
Features: First, the surfaces of the hole wall are relatively smooth with metallic luster. Second, blowholes are existing under the surfaces of the die casting parts individually or in groups. Third, the blowholes of lampblack are oil color.

Analysis of causes: First, the gas brought in will exist in the castings in the form of blowholes after the solidification of alloy melt when the liquid metal is casting. Second, there will be blowholes that are generated under the surface of the die casting part after the reaction of metal and the casting mold. Third, the slag inclusion of alloy melt or the gas attached to the oxide skin gets into alloy melt, which forms blowholes.

Prevention methods: First, avoid getting into air in the die casting process. Second, alloy melt should be filtered by the filter screen so that the slag inclusions, oxide skin and bubbles can be removed before entering the mold cavity. Third, change die casting materials or add some coating layers to avoid the reaction of alloy melt and the die casting mold. Fourth, clean up the parts allowing the repair welding and have the repair welding for the parts.

2. Pinholes
Features: First, they are evenly distributed across the whole fracture surfaces of the casting and they have the diameter less than 1mm. Second, the parts with the fast solidifying rate usually have small holes in a small quantity, while the parts with slow solidifying rate usually have big holes in a large quantity. Third, pinholes become circular holes in eutectic alloy and the pinholes become long-shaped holes during the solidifying interval. Fourth, they are black dots on the X-ray film, while they become discontinuous small milky pits on the fracture surfaces.

Analysis of causes: Hydrogen is the main gas which forms in the molten alloys, and it precipitates from the alloys during solidification, resulting in holes evenly distributing on fracture surfaces of die casts.

Prevention methods: First, thoroughly make alloy refine to degas when the alloy is in the liquid state. Second, accelerate the solidifying rate during solidification to prevent the fusible gases precipitating from alloy. Third, the die casting parts will solidify under the pressure, which will prevent the fusible gases precipitating from alloy. Fourth, the furnace burden, auxiliary materials and tools should be dried.

3. Porosity
Features: First, the spongy loose structure will become, and the shrinkage cavity will happen when being in severe cases. Second, the surfaces of holes become coarse pits with large grains. Third, the fracture surfaces are gray or light yellow and they will become off-white, light yellow or black after heat treatment. Fourth, porosity usually happens on parts which solidify finally. Fifth, they are nebulous on the X-ray film, while they become dense little bright dots during the fluorescent inspection.

Analysis of causes: First, porosity forms because the alloy melt is not degassed completely. Second, there is not enough feeding for the last solidifying part. Third, the overheating, excessive moisture and poor discharge of the partial die casting mold can also cause porosity.

Prevention methods: First, keep the rational solidification sequence and feeding. Second, keep the furnace burden clean. Third, put the chill on the parts which have porosity. Fourth, clean up the parts allowing the repair welding and have the repair welding for the parts.

Technical Analyses of Automobile Aluminum Alloy Lower Cylinder Blocks (Part Three)

Sat, 23 Sep 2017 03:59:56 +0000

We have X-ray inspections for die casts, and find some inner defects such as shrinkage cavities, blow holes and shrinkage porosity existing in die casts after die casts are manufactured. We put forward the following corresponding countermeasures in order to improve defects and quality of die casts.

1. Improving the structure of the overflow box
The overflow box has the effects of eliminating the gas in the cavity, storing the mixed gas and transferring the shrinkage cavity and the shrinkage porosity. We find that we can improve defects such as shrinkage cavities and blow holes by extending and adding overflow boxes after repeated experiments. Usually, vertical overflow gates should be chosen because of much shrinkage porosity in the middle of die casts so as to avoid filling pressure being affected.

2. Optimizing the cooling system of the mold
Shrinkage cavities of die casts often occur in positions where partial temperatures of die casts are too high or walls of die casts are too thick. After the research, we find that temperatures at two sides of die casts' thick walls are high, which will easily cause shrinkage cavities. We select the smallest die cooling pipe with the diameter of 12mm at the beginning, and it can't cool the temperature of the above positions. Therefore, we adopt the high-pressure cooling equipment and the stainless steel die cooling pipe with a diameter of 4mm to improve the structure of the die cooling pipe. We cool temperatures of mold cores of die cast's two sides to 180℃, which can greatly reduce shrinkage cavities and improve quality of die casts.

3. Improving the separation of the insert
We can take the following measures to solve the separation problem between the insert and the aluminum alloy die cast. Firstly, use the diluent to clean the insert so as to improve the wettability of the insert; secondly, inspect the insert by the location hole, and inspect the appearance of the insert; use the steel wire to remove the partial spot on the insert; thirdly, preheat the insert; we find that when the temperature is over 120℃, the separation problem of the insert can be solved effectively after a research.

In conclusion, this article analyzes the difficulties of the aluminum alloy lower cylinder block's die casting technology, and puts forward the scientific design of the cylinder block die cast's running gate system. The tooth-shaped chilled exhaust block vacuum die casting technology and conducting an experiment of preheating the insert are recommended for aluminum alloy lower cylinder blocks. In addition, this article also summarizes aluminum alloy lower cylinder blocks' die casting defects such as shrinkage cavities, blow holes and shrinkage porosity and puts forward the corresponding countermeasures, which provide theories for your reference concerning aluminum alloy lower cylinder blocks' die casting processes of automobile engines.

Technical Analyses of Automobile Aluminum Alloy Lower Cylinder Blocks (Part Two)

Sat, 09 Sep 2017 01:45:33 +0000

We believe that technical key points of lower cylinder blocks are mainly as the following according to experimental analyses.

1. Scientifically design gating systems of cylinder block die casts; inserts which are placed in the middle of lower cylinder blocks have thin walls; the upper and the lower parts of the lower cylinder block are the thick parts; therefore, we choose the unilateral pouring; by doing this, the aluminum liquid will flow from the bottom side of the cavity to the middle of the insert and then to the top of the cavity.

2. We use the tooth-shaped chilled exhaust block vacuum die casting; tooth-shaped chilled exhaust blocks and vacuum machines can improve bad mobility caused by thin walls of the two sides and ensure good quality of die casts.

3. We preheat inserts in order to improve wetness of aluminum alloy liquids and cast iron inserts, which not only ensures that cast iron parts are not separated from aluminum alloy after molding processes, but also improves mobility of aluminum liquids.

We can obtain the lower cylinder block with the compact structure and good appearance after the test. Scientific and reasonable technological parameters are guarantees of obtaining lower cylinder blocks with high quality in die casting processes. We believe that the following technological parameters are the key factors affecting the moldings of the die casts.

1. Die casting temperatures
Temperatures of aluminum liquids should be well controlled in die casting processes, because too high or too low temperatures can not achieve good die casting effects; too high temperatures will easily cause the shrinkage cavity and the shrinkage porosity; too low temperatures will easily cause poor fillings. Generally speaking, the reasonable temperature of the aluminum liquid should be from 650 to 665℃ and the temperature of the mold after being sprayed should be between 150 and 200℃.

2. Inserts' temperatures
When the temperature of the insert reaches from 120 to 140℃, the aluminum liquid will overflow one side of the overflow launder, which can improve the internal quality.

3. Fast injection speed, slow injection speed and pressure of die casting
Fast injection speed and slow injection speed should be controlled at about 4 m/s and 0.22 m/s and the pressure under about 70MPa.

4. Aluminum liquid's quality
As the basic material for the die cast, the quality of the aluminum liquid determines the quality of the die cast; therefore we need to ensure the quality of the aluminum alloy liquid; every bag of aluminum alloy liquids must have refining treatments to degas aluminum alloy liquids and to avoid pollution.

Technical Analyses of Automobile Aluminum Alloy Lower Cylinder Blocks (Part One)

Sat, 09 Sep 2017 02:09:05 +0000

In recent years, energy saving and emission reduction has become the trend of the time and lightweight of automobile is also general trends. Under the background of the two trends, aluminum alloy materials are more widely used in automobiles; more and more automobile parts are made by die casting processes. As core components of automobiles, engine blocks mainly adopt aluminum alloy and cast iron as the materials; among these two materials, aluminum alloy cylinder blocks gain more and more recognition; car corporations from Japan, South Korea, Europe and the United States mostly use die casting aluminum alloy cylinder blocks.

In production fields of cylinder blocks, ordinary sand mould cast iron cylinder blocks have advantages of simple processes, low costs, good rigidity and heat resistance, but they also have a disadvantage; that is, sand mould cast iron cylinder blocks are overweight. If we divide the cylinder block into lower crankshafts and upper cylinder jackets two parts, we will adopt aluminum alloy for the lower part and cast iron for the upper part; by doing this, we can not only reduce weights of cylinder blocks, but also keep advantages of cast iron cylinder blocks.

Lower cylinder blocks refer to the lower crankshafts of the engines after we divide cylinder blocks into two parts. Lower cylinder blocks are parts with thick wall and their wall thickness have great differences; therefore, lower cylinder blocks are very difficult to be made by die casting processes. Learning from the related experience at home and abroad, we design and develop die casting technology for lower cylinder blocks based on an engine with 1.5 tons and the experiment is very successful.

Difficulties of die casting aluminum alloy cylinder blocks
The weight of the aluminum alloy cylinder block die cast is 8.4 kilograms; the overall dimension is 382 mm X 258 mm X 67 mm; the weight of the die cast is 11.1 kilograms; the material is A380 and the average wall thickness is 7.2 mm. Lower cylinder blocks and crankshafts are connected; therefore, we should place cast iron inserts at bottoms of cylinder blocks.
Lower cylinder blocks die casting processes are complex and the main difficulties of the processes are as the following.
1. Five pieces of cast iron inserts should be placed on die casts and they should be perfectly inlaid into aluminum alloy die casts.
2. The thinnest lower cylinder block's wall thickness is 2 mm; the thickest thickness is 24 mm; the wall thickness has great differences.
3. Because wall thickness of inserts on both sides has great differences, this not only brings difficulties to filling processes of aluminum alloy liquid, but also tests die casts' feeding capacities.
4. Aluminum alloy die casts can easily have blowholes, shrinkage, cracks, shrinkage porosity and other defects; thus, it is difficult to control their quality.

Five Surface Treatments for Aluminum Alloy Die Casts

Mon, 14 Aug 2017 06:48:17 +0000

1. Aluminum phosphating
Guanidine nitrate has features of good water solubility, small amount and rapid film forming, which is an effective accelerator for aluminum phosphating. Fluoride can accelerate the forming of the film, increase film's weights and refine grains; Mn2+ and Ni2+ can obviously refine grains and make phosphating film even and compact as well as improve appearance of phosphating film; when concentration of Zn2 + is low, the film can not be formed or the film is poor; with the increase of Zn2 + concentration, film's weight also increases; the PO4 content has a great influence on weight of phosphating film and increasing the PO4 content can add more weight to phosphating film.

2. Alkaline electropolishing of aluminum
Adding appropriate additives to NaOH solutions can have good effects of polishing. After NaOH solutions of glucose being electropolished by dc constant voltage under some condition, reflectivity of aluminum surfaces can reach 90%. Using the pulse-electropolishing process can have the effect of leveling, but the leveling speed is relatively slow.

3. Environmental chemical polishing of aluminum and aluminum alloy
The main role of nitric acid in aluminum chemical polishing is to restrain pitting corrosion and to improve brightness of polishing. Adding special substances in nitric acid should be able to restrain pitting corrosion and to slow down overall corrosion; meanwhile, good leveling and brightness can be obtained.

4. Electrochemical surface strengthening treatment of aluminum and its alloy
The technical research result shows that in the Na_2WO_4 neutral mixed system, concentration of film forming accelerator is from 2.5 to 3.0g/l; concentration of complexing film former is from 1.5 to 3.0g/l; concentration of Na_2WO_4 is from 0.5 to 0.8g/l; the density of the peak point current is from 6 to 12A/dm2; slightly stirring the solutions can obtain complete, uniform and glossy gray series of inorganic non-metallic film. The thickness of the film is from 5 to 10μm and the microhardness is from 300 to 540HV; the film has good corrosion resistance. The neutral system can well adapt itself to aluminum alloy and film can be formed well on various kinds of aluminum alloys such as rust-proof aluminum and forging aluminum.

5. Surface treatment technology of YL112 aluminum alloy
YL112 aluminum alloys are widely used for structural parts of automobiles and motorcycles. There should be surface treatment for YL112 aluminum alloy so as to improve its corrosion resistance and to form surface layers that easily bond with organic coatings.