I remember distinctly my first knowledge about constructing a die that was supposed to die casting china right into a deep, contoured shape. Not understanding much about aluminum, I assumed that it must be extremely formable-after all, they make beverage cans from it, don’t they?
My first thoughts were, “This will be a cake walk. I’ll bet this stuff stretches a mile. Yep, it needs to stretch a great deal because it’s really soft.”
This thought process was obviously a testimony to my ignorance regarding aluminum.
I believe I lost a sizable percentage of my hair trying to make that job work. I must have spent weeks fighting splits and wrinkles. It wasn’t prior to I got to the final outcome that drawing and stretching aluminum were not as easy as I needed thought.
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Since I am a bit wiser with regards to the formability of aluminum and aluminum alloys, I understand that my problem was really not the fault of the aluminum, but rather the truth that during the die tryout stages, I had been thinking like steel as an alternative to aluminum. Up until then, all of the things that I might have performed to correct the issue with a die that had been forming steel, I did so together with the aluminum. Obviously, I failed.
The reality is that aluminum is not steel. It doesn’t behave like steel, it doesn’t flow like steel, plus it certainly doesn’t stretch like steel. So performs this make aluminum tough to form? No, not if you feel like aluminum.
Aluminum is not a bad metal; it’s merely a different metal. Like all metal, they have advantages and disadvantages, and the bottom line is to understand the material’s behavior before designing a part or creating the procedure and die which can be to create it.
Should you be comparing aluminum to deep-drawing steel, generally you will recognize that aluminum lacks close to the elongation ability of steel. For instance, typical deep-drawing steel has elongation somewhere around 45 percent, while a 3003-O temper, meaning “dead soft,” aluminum will have elongation near 30 percent.
In most cases and dependant upon the alloy, aluminum has poor stretch distribution characteristics in comparison to deep-drawing steel. It is known as a material that strains locally, and therefore the majority of the stretch that happens when the metal is exposed to a stretching operation will occur in a small, localized area.
However, understand that the forming punch geometry features a greater affect on the way the metal stretches compared to metal itself. Stamped parts to become made from aluminum has to be designed so that the part shape forces the metal to distribute stretch more evenly.
Aluminum ironing process
Figure 2Generally speaking, aluminum is an excellent material when ironing can be used. During ironing, the metal is squeezed down a vertical wall to improve the outer lining area while decreasing the metal’s thickness. Ironing will be the basic process utilized to make beverage cans.
Parts requiring a lot of stretch in a small area with small male radii are doomed to fail if designed of aluminum, particularly if the final geometry will be made in a single forming operation. In contrast, large, liberal radii and flowing, gentle geometries are best-designed for aluminum.
First, don’t confuse drawability with stretchability. Drawability may be the metal’s capability to flow plastically when subjected to tension, while stretchability is definitely the increase of area as the result of tension.
Based on the type, aluminum can draw adequately (see Figure 1). It has a good strength-to-weight ratio and it is well-suitable for the deep-drawing process, in addition to multiple draw reductions. The reductions percentages are really corresponding to those often used when drawing deep-drawing steel.
Although aluminum is soft, it can nonetheless be abrasive. Although it is not going to rust conventionally, it forms a white powdery substance called aluminum oxide, which is often used to make 10dexppky wheels. Which means exactly the same abrasive which you have been using to grind your tool steel die sections may be present on the aluminum sheet surface.
It is possible to prevent this poor interface by using high-pressure barrier lubricants, which keep the aluminum from touching the tool steel sections during forming and cutting.
In most cases, aluminum is a great material when ironing can be utilized. During ironing, the metal is squeezed down a vertical wall to improve the top area while decreasing the metal’s thickness. It improves the metal sheet’s surface area by squeezing the metal as an alternative to exposing it to tension. Ironing is the basic process employed to make beverage cans (seeFigure 2).
When aluminum is ironed, it almost compressively flows similar to a hot liquid across the wall of the die cavity and punch, and it shines into a mirrorlike surface finish.
Aluminum has more springback than soft draw-quality steel. However, the level of springback that takes place can be controlled by designing the stamped product with regards to the springback value.