Quantitative Study On Casting Surface Color

The surface consistency color is an important symbol of the external quality of castings. But, there do not exist a method to evaluate the castings surface color. This project studied the casting primary color and the color consistency of repaired casting.This project used the light color measurement instrument to quantitatively measure casting surface color, compiled casting surface color measurement standard, and used the CIE LAB colorimetric system to characterize quantitatively the casting surface color. The research analyzed the influences of instruments, surface roughness, organizations and modification treatments. The article selected the electric spark surfacing welding technique and adhesive patch technique to repair the casting defects, measured quantitatively the surface color of these repaired casting, and evaluated whether or not the color is in line with the casting surface color measurement standard.The main conclusions of this research are as follows:① The measuring instruments affected the casting surface color measurements, and the different instruments got different color data which would be of great difference. The roughness of the casting surface also influenced the practical measurement, and the main influence was the lightness parameter L*. The smoother the surface is, the lower roughness is, and the surface brightness and lightness parameter L* were higher. Due to the effects of the instruments and roughness on the color measurement, the conditions and status must stay the same while evaluating uniformity of the casting surface color.② The color of alloy element affect the color of the sample. The more black phase is, the lower bright is. The content of Si is only under Al element in Al alloy. Si exists in alloy of three phases: Si, Mg2 Si and Al Si Fe Mn, and all show the black color. The content of other element is so little that we did not discuss. Modification treatments influenced the surface color of A356, but the influence was so little that could not be observed. Thus we can use the same repairing conditions to repair these two alloys.③ The lightness became lower of the repaired HT200 and QT600, and surface color turned to be more darker. The color differences between the original and the repaired HT200 and QT600 were △E=1.78 NBS and △E=1.95 NBS separately, and the color differences stayed in 1.5~3.0NBS belonging to unrecognized range. Considering the surface color of HT200 and QT600, using the base materials as electrode materials to repair casting defect was appropriate and could meet the uniformity of color requirements.④ The color differences ΔE between the Al alloy sample and repair agent were 15-25 NBS belonging to the scope that we can distinguish clearly. The change of color difference ΔE followed the change of lightness difference ΔL. The large color difference between the sample and repair agent might be accounted for the smooth surface. The smooth surface increased the surface reflectance making the big lightness difference, and leaded to huge color difference ΔE consequently.