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The Traditional Method Of Steelmaking Si-Al Alloy

Steelmaking Si-Al Alloy has the characteristics of light weight, high strength / weight ratio, good corrosion resistance, excellent processing performance and reasonable cost. The steelmaking Si-Al alloy can improve its strength by alloying, cold hardening and aging precipitation strengthening. Cast aluminum and deformed aluminum alloys have been widely used in production. This article TECH-NOTES describes the preparation of samples for casting Al-Si alloys.

We selected Al-Si alloys of three components, and their Si contents were 7.15, 11.82 and 19.85%, respectively, with a small amount of Cu, Fe, Mg, Ti and Zn (Al-7.15% Si alloy containing 0.32% Mg, the rest is an impurity element). The steelmaking Si-Al alloy samples are taken from thin-walled castings with a thickness of no more than 12 mm (0.5 inch). The Al-Si alloys of the three components were studied by sub-eutectic (7.15% Si), eutectic (11.82% Si) and hypereutectic (19.85% Si) alloy samples, respectively. Al-7.15% Si alloy castings have a certain number of obvious shrinkage, the other two alloy samples only contains a small number of negligible shrinkage. In the hypereutectic alloy samples can be seen due to cutting and grinding caused by the larger block of primary silicon broken for the study of how to control the embossing problem.

The traditional method of steelmaking Si-Al alloy

Thirty years ago, when I first attended the work, the method of preparing the steelmaking Si-Al alloy was shown in Table 1. The steelmaking Si-Al alloy was usually ground with different thickness of SiC sandpaper and then treated with one or two Step of the diamond polishing agent for polishing, the last step with MgO

Polished finish for final polishing. These steps are done by hand.

Place the sample (six diameters of 30 mm) on the sample holder and rinse from 120 to 600 grit (ANSI / CAMI) with five-step SiC sandpaper using water as the lubricant. Then a two-step diamond polishing paste, and finally a very viscous 1um MgO polishing paste applied to the RAYVEL® polishing cloth for final polishing. "Kitten Ear" polishing cloth is no longer used, but thirty years ago in the Al alloy sample preparation is very common.

Since the wet MgO is easily formed by the formation of magnesium carbonate on the sample, it is necessary to thoroughly clean the polishing cloth after use, use (1: 1) diluted HCL aqueous solution to clean the polishing cloth, and the solution remaining on the polishing cloth Can prevent the formation of magnesium carbonate. Once the formation of magnesium carbonate on the polishing cloth, will lead to scratches on the sample. For most metals, it is perfectly possible to use 0.3 μm of alpha alumina and 0.05 μm of gamma alumina for final polishing, but this method is not suitable for Al alloys, and vibration polishing is often used for the final polishing of Al alloys. Samuels recommends the addition of some disodium hydrogen phosphate-citrate slow release solution or propylene glycol (2 parts) + water (1 part) to prevent the formation of magnesium carbonate when using a vibratory polishing machine. It has been shown that these additives have a good effect in preventing carbonate formation. Cu and Cu alloys, such as bronze, are not suitable for use as polishing discs for polishing machines because the annoying electroplating reaction will cause the sample surface to be plated with copper, so usually use Al alloy or stainless steel as the polishing disc.