Casting automotive parts

The history of automotive casting parts dates back to the early 20th century when the automobile industry began to take shape. In the beginning, most automobile parts were made by hand, which was a time-consuming and expensive process. Casting was seen as a more efficient and cost-effective way of producing complex parts in large quantities.

The first automobiles were made with cast iron parts, such as engine blocks and cylinder heads. The casting method used was sand casting, which allowed manufacturers to produce large, complex parts with greater accuracy and consistency.

In the 1920s, the die casting method was introduced, which allowed for the production of smaller, more intricate parts with greater precision.

In the 1930s, investment casting was introduced, which allowed for the production of even smaller and more intricate parts, such as carburetor components and fuel injectors. This method produced parts with excellent surface finish and dimensional accuracy.

Casting Transmission components

Automotive casting oil pump components

Automotive casting steering components

Automotive casting suspension components

Automotive casting braking components

Automotive casting spare parts

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Types of Automotive Parts Casting

Precision Casting-Investment Casting Automotive Parts

Precision Casting Steps involved

Create a wax pattern – a detailed and precise replica of the desired final product.
Create a ceramic shell by dipping the wax pattern into a slurry of ceramic material multiple times, allowing each coat to dry before adding the next.
Once the ceramic shell is thick enough, the entire structure is heated, causing the wax to melt and drain out of the shell.
The molten metal is then poured into the hollow ceramic shell.
After the metal cools and solidifies, the ceramic shell is broken away, leaving the final casting.

Advantages and disadvantages

Advantages
Disadvantages

High accuracy and precision casting in the final product.
Ability to cast complex shapes and thin walls.
Smooth surface finish and good surface detail.
Can be used for a wide range of metals and alloys.

High cost due to the complex process and materials involved.
Longer production time compared to other casting methods.
Limited size and weight of the final product.

Die casting Automotive Parts

- Steps involved
1. Create a metal mold, or die, that is the exact shape and size of the final product.
2. Inject molten metal under high pressure into the die.
3. Allow the metal to cool and solidify within the die.
4. Once the metal has solidified, the die is opened and the casting is removed.
5. Any excess material is trimmed away and the final product is finished.

Advantages
Disadvantages

High accuracy and precision in the final product.
Ability to cast complex shapes and thin walls.
Good surface finish and detail.
High production rate for large quantities.
Can be used for a wide range of metals and alloys.

High cost for tooling and equipment.
Not suitable for casting certain metals and alloys.
Limited size and weight of the final product.
Limited design flexibility.

Sand casting Automotive Parts

Steps involved

Create a pattern of the desired final product using wood, plastic or metal.
Place the pattern in sand and pack the sand around it to create a mold.
Remove the pattern from the mold.
Pour molten metal into the mold.
Allow the metal to cool and solidify within the mold.
Once the metal has solidified, the sand is removed from the casting and any excess material is trimmed away.

Advantages
Disadvantages

Low cost for tooling and equipment.
Suitable for casting large and heavy parts.
Can cast a wide range of metals and alloys.
Good design flexibility.
Can be used for low volume or high volume production.

Limited accuracy and precision in the final products.
surface finish and poor detail.
High material waste.
Limited ability to cast complex shapes and thin walls.

Some other casting methods in automotive parts production

Gravity die casting: Gravity casting offers several advantages, including good dimensional accuracy, excellent surface finish, and the ability to produce complex shapes. It is suitable for medium to high-volume production runs and is commonly used for automotive components like engine blocks, cylinder heads, transmission cases, and various brackets.
Permanent Mold Casting: In this method, a permanent metal mold is used to produce multiple castings. The mold is preheated and coated with a refractory material before the molten metal is poured. Permanent mold casting offers good dimensional stability and surface finish.
Squeeze Casting: Squeeze casting combines elements of casting and forging. Molten metal is poured into a preheated mold, and pressure is applied during solidification to reduce porosity and improve mechanical properties.
Centrifugal Casting: This method utilizes centrifugal force to distribute the molten metal within the mold. The mold is rotated rapidly, allowing for the formation of cylindrical shapes such as engine cylinders and pipes.
Materials Used in Automotive Parts Casting

Aluminum	This is one of the most commonly used materials in automotive casting due to its lightweight, excellent strength, and good corrosion resistance.
Iron	Cast iron is used for engine blocks, cylinder heads, and brake rotors due to its excellent wear resistance and thermal conductivity.
Steel	This material is used for parts that require high strength and durability, such as gears, drive shafts, and suspension components.
Magnesium	Magnesium is a lightweight material that is used for parts such as steering wheels and instrument panels.
Zinc	Zinc is commonly used for die-casting small parts such as door handles and trim pieces.
Copper	Copper is used for electrical components such as wiring harnesses and connectors due to its excellent conductivity.
Nickel	Nickel is used for parts that require high temperature and corrosion resistance, such as exhaust systems and turbocharger components.

Solution to Shrinkage Defects on Threaded Covers in Automotive Casting

In the production of investment casting automotive parts, shrinkage defects often occur on the castings. The occurrence of shrinkage defects is generally related to three aspects: casting structure, pouring system, and process design. In the analysis and resolution of shrinkage defects, it is important to follow the theory of temperature gradient, analyze the specific structural characteristics of the casting, and correctly implement thermal gating and continuous improvement.

The main difference of investment casting automotive parts compared to other casting methods is that it is poured under the condition of a ceramic shell (shell firing temperature around 1100℃). This allows for good filling capability, but it also presents challenges in terms of compensating for the shrinkage of the casting. In addition to using computer numerical simulation analysis, it is necessary to consider the temperature gradient during the cooling of the casting and adopt comprehensive strategies based on the structural characteristics of the casting. Continuous improvement is important. In this particular case, the focus is on addressing the shrinkage issues of isolated hot spots.

(1) Introduction of the investment casting automotive parts

Part name: Threaded cover, made of material 304. The dimensional accuracy and surface quality requirements are high. The weight of a single piece is 0.5kg. The schematic diagram of the casting can be seen in Figure left.

(2) First Pouring Process

Figure 6-50 shows the inner gate of the wax mold for the threaded cover, placed on a flat surface with a diameter of ø78mm and set symmetrically in two positions. Figure 6-51 shows the shape of the inner gate. There are two tree assembly schemes for the investment casting automotive parts: one with a horizontal mold head and the other with a vertical mold head. The shell is made using a mid-temperature wax, all-silica sol process, with a shell firing temperature of 1150℃ and insulation for 30 minutes. The pouring temperature is 1670℃. Prior to pouring, computer numerical simulation analysis was carried out, which did not reveal any shrinkage defects. However, serious shrinkage defects were observed during actual production using both the horizontal and vertical mold heads.

6-50 Internal gate position

6-51 The shape of the inner gate

6-51 Horizontal mold head group tree scheme

6-51 Vertical mold head group tree scheme

(3) The investment casting automotive parts Shrinkage analysis
Originally, it was believed that the complexity of the component was average. After the first pouring, a re analysis of the casting structure was conducted, and it was believed that the overall structure of the component was a thin-walled component. However, there is a flange shaped protrusion in the middle of the threaded cover, which has three stepped plane hierarchical structures.

The thickness of the first layer plane is 2.86mm, the thickness of the second layer plane is 4.98mm, and the thickness of the third layer plane is 9.26mm. The wall thickness difference is significant, Shrinkage occurs at the connection between the root of the threaded protrusion and the thread. The reason for this is that the area with the maximum wall thickness of the protrusion forms an isolated hot spot with the thread thin-wall.

During the solidification and cooling process, a positive temperature gradient cannot be achieved, and the thin-wall thread is not cooled first. The thick wall of the third stage of the protrusion is the thickest and must be cooled last to comply with the principle of sequential solidification, At the final solidification point, there must be sufficient steel liquid to supplement the body shrinkage during cooling. Otherwise, shrinkage defects will occur on the thread near the thickest part of the protrusion. At the same time, it should also be acknowledged that the advantages of the tree schemes in Figures 6-52 and 6-53, such as the absence of vortices during pouring, smooth flow of steel, smooth filling, and high process yield, must be retained.

At the same time, it is analyzed that the baking temperature of the investment casting automotive parts mold shell in the first pouring process is relatively low, the insulation time is still acceptable, and the pouring temperature of the steel liquid is too high, which violates the principle of “low-temperature steel liquid, red shell pouring”.

(4) Process improvement

Firstly, establish a feeding channel to supply the steel liquid to the flange shaped protrusion for feeding purposes. Therefore, an 8mm straight strip was added to the plane between the mold head and the protrusion, as shown in Figure on the right. And the calcination temperature of the mold shell was increased to 1180 ℃, kept for 30 minutes, and the pouring temperature was reduced to 1650 ℃.

Pouring result: Shrinkage has not been completely eliminated in the final investment casting automotive parts, but the range of shrinkage has significantly decreased and the depth of shrinkage has also become shallower. The analysis and judgment on the occurrence of shrinkage defects are correct, which further confirms that the added straight bars are too small and not in place. Ultimately, there is a lack of depth in understanding that different parts of the casting should have different cooling rates, and the adjustment of cooling rates is not well controlled by temperature gradients.

(5) Continuous improvement

A small plane of 9mmx9.5mm was found on the side of the third level of the flange shaped protrusion, which was selected as the location for the inner gate. The shape of the inner gate is shown in Figure below. The bottom size of the inner gate is 9mm long x 9.5mm wide x 12mm high, and it is made into a cone. Due to the small size of investment casting parts, the inner gate in the pouring system is generally not only the gate that connects the casting, but also serves as a riser, establishing a temperature gradient, allowing the investment casting automotive parts maximum wall thickness of the protrusion to be compensated, and sequentially solidifying and finally cooling.

Considering that thin-walled parts must be filled quickly, the other inner gate is still in its original position φ On a 78mm plane, connect with straps.
In order to improve production efficiency, the conventional bifurcated mold head is no longer used, and a dedicated mold head is redesigned. The setting of the internal gate is shown in Figure on the left.

After continuous improvement of the pouring system, the shrinkage holes on the threaded cover on the investment casting automotive parts were completely eliminated. From the cutting section of the internal pouring, the shrinkage effect was quite successful, and the yield rate reached 100%.

FAQ about automotive casting parts

Here are a few frequently asked questions related to steel casting services:

What materials are commonly used for casting automotive parts?

A: Aluminum, steel, and iron are commonly used for casting car parts.

2. What casting methods are commonly used for automotive parts?

A: Investment casting, die casting, and sand casting are commonly used for automotive parts.

3. What types of automotive parts can be cast?

A: Engine blocks, transmission housings, brake components, suspension components, and wheels are some examples of automotive parts that can be cast.

4. Can casting be used for high-performance automotive parts?

A: Yes, casting can be used for high-performance parts. Investment casting and die casting are particularly well-suited for producing high-performance parts with complex shapes and thin walls.

5. What are the benefits of casting automotive parts?

A: Casting allows for the production of large, complex parts with high accuracy and precision. It is also cost-effective for producing large quantities of parts.

6. What are the challenges of casting automotive parts?

A: The casting process can be time-consuming and expensive, particularly for smaller quantities. There may also be limitations in terms of the size and complexity of the parts that can be cast.

7. How do I choose the right casting method for my automotive parts?

A: The choice of casting method will depend on factors such as the size and complexity of the part, the materials being used, and the desired quantity of parts. Consulting with a casting expert can help you determine the best method for your specific needs.