Meta Description: Stainless steel casting is a tough job. It requires skills and experience. In this article, we will talk about the investment casting method.
Stainless Steel Investment Casting: The Best Casting Method
Stainless steel – We see it everywhere now, from our glasses to smartphones, to complex machinery. Stainless steel is everywhere around us. The reason for it is its corrosion resistance.
Corrosion weakens steel and therefore makes it lose its functionality. That is why we use stainless steel instead. But everything has its price. For stainless steel, that price is money.
Stainless steel is expensive, to begin with. Then there is the cost of casting. The casting cost of stainless steel is higher than other steels.
In this article, we will be looking at the investment method of stainless steel casting.
What Kind Of Stainless Steel Is Best For Casting?
Stainless steel has its classifications and grading. Stainless steel contains iron, carbon, chromium, and other materials.
Chromium is the main element that makes stainless steel corrosion-resistant, making up not more than 10.5% on each unit. Based on the availability and percentage of other materials, stainless steel can be of different grades.
For casting purposes, we would say that the 304 and 316-grade stainless steel are the best ones. They are both above the 300 level and contain nickel.
So, make sure that the stainless steel foundry you are hiring has stainless steel 304 and 316 available.
Stainless Steel Investment Casting Method
Stainless steel investment casting is a very popular method of casting stainless steel. It is a simple method, but you can achieve great feats with it. The steel can be shaped in any way and you can make thin parts (up to 0.15 inches).
Let’s have a look at the procedure:
1. Prepare the pattern with wax
Right at the beginning, you need to prepare a replica of the final product with wax. You can use other materials such as foam, or plastic. But wax seems to be the best choice because it can be easily melted away, which will pay off in later casting stages.
2. Make a tree with the wax patterns
If you are casting one part multiple times, then you need to make the shape with wax (or whatever you choose in the previous step). Then put all of those wax parts together and form a tree-like structure that can be dipped together.
3. Dip the wax tree
Now you need to dip the tree structure in a substance to create the mold. That substance could be ceramic slurry, or it could be white industrial latex, also known as silicon dissolved pulp.
The reason why you need to use these materials for preparing the mold is that you need to break down the mold later to take the steel out. Also, these materials can be reused, which reduces the cost by a little.
While dipping the wax structure in the mold, you may need to dip it multiple times. This will ensure that there are no leaks and the mold will be thick. The thicker the mold is, the stronger it will be for handling the hot melted stainless steel.
4. Melt the wax
After dipping the shape in the substance multiple times and achieving the desired thickness, put the mold in an oven to heat it.
Heating the mold will achieve two things. First, it will melt away the wax, or plastic inside of it to make the mold hollow. Second, the structure of the mold will become stronger and less fragile.
If you have used wax, the temperature of this oven should be between 900C to 1800C. This is enough to melt away all the mold. The melted wax will get out through the sprue gate. The sprue gate is also the gate in which you need to pour the melted stainless steel.
5. Preparing the stainless steel
As discussed earlier, you should pick stainless steel 304 or 316 for casting. It is better to pour it into the mold when the mold itself is hot. To do that, you should start heating the steel and prepare the mold simultaneously.
6. Pour the heated alloy
After the mold is prepared and the steel is melted, pour the steel into the mold. But before that, heat the mold to 550 ⁰C – 1100 ⁰C. Pour the melted alloy when the mold is near that temperature.
There are two reasons why you should keep the mold heated. One, the melted alloy will be able to flow through the mold smoothly. Second, the smooth flow will let the alloy fit in the thin spaces, which will ensure a perfect dimensional fit.
7. Solidify and break the mold
After pouring the steel, now let the steel cool down and solidify. It does not take much time.
After totally solidifying, break the mold. Stainless steel foundry has different ways of breaking the mold. Don’t stress about this part. Besides, the steel inside will be tougher than the old. So, hitting it with a hammer won’t do much damage.
8. Cut off the components from the tree
Now, all you need to do is cut off the components from the tree. You may need to polish the components before use. But the casting process is finished.
Is Investment Casting the Best Method?
The investment casting method is one of the simplest methods of casting stainless steel. You can create any kind of shape with this process, but it’s best to keep the mass under 75 lb. Otherwise, the mold may break down.
But keep in mind that this procedure is relatively more expensive than other methods of stainless steel casting. Moreover, this method is more about skills, less about labor.
Stainless steel is one of the best choices for preparing components that will go under continuous stress and will be exposed to the open environment. Their corrosion-resistant properties make them unique.
But it requires a lot of skills to cast them and bring them to the desired shape. Don’t worry about that part, though. Just prepare your design and bring it to the Stainless Steel Foundry. They will handle the rest. Just be sure to pick the right alloy: Stainless Steel 304 and 316.