Recent trends in surface metrology

A zinc alloy plated steel sheet, characterized in that it comprises a steel sheet and, applied thereon, a metal plating having a composition in mass %: Mg: 1 to 10 %, Al: 2 to 19 %, Si: 0001 to 2 %, the other elements except zinc: 05 % in total, and balance: Zn, and satisfies a Ra ≤ 10 μm, wherein Ra represents an average roughness on a center line, and a WCA ≤ 08 μm wherein WCA represents a filtered center line waveness; and the zinc alloy plated steel sheet which has a metal plating further comprising one or more of the following elements: Ca: 001 to 05 %, Be: 001 to 02 %, Ti: 00001 to 02 %, Cu: 01 to 10 %, Ni: 0001 to 02 %, Co: 001 to 03 %, Cr: 00001 to 02 %, and Mn: 001 to 05 % The zinc alloy plated steel sheet is excellent in the corrosion resistance after coating and the clarity of a coating applied thereon

Zinc-plated steel sheet excellent in corrosion resistance after coating and clarity of coating thereon

Multiscale characterizations of painted surface appearance by continuous wavelet transform

This study concerns the surface quality of coated and uncoated composite laminates intended for use as cosmetic, automotive body panels. A series of laminates were investigated ranging in fabric architecture, resin type and fabrication process. Laminate surface quality was assessed subjectively and used for contextual comparison with two quantitative methods; profilometry and reflectometry, which characterised the type and severity of the features on the laminate surface. Measurable changes in surface quality for varying fabric architecture, matrix contraction and tool surface roughness are used to infer the behaviour of composite laminates. We conclude that the arithmetic mean roughness parameter is suitable for relating bare laminate surface roughness to final paint quality with roughness thresholds being developed. Light reflectometry correlated well with subjective assessment for painted laminates with significant effects seen when varying laminate constituents and tool quality.

Characterisation of thermoset laminates for cosmetic automotive applications: Part I – Surface characterisation

The effect of material selection and manufacturing process on the surface finish of carbon fibre composites

Paint appearance is an important factor in the overall product quality of steel sheet, especially in the automotive industry. The present paper deals with the functional behaviour of the surface texture according to paint appearance. The main results on the improvement of paint appearance of outer car body panels, obtained with coated and uncoated cold rolled steel, textured with EBT-rolls, is reviewed. There are different methods to relate steel sheet surface texture to the appearance after painting. From the literature it is found that waviness has a detrimental effect on the surface appearance after painting. Different roughness and waviness parameters are compared in order to find a good relation with paint appearance. The following surface texture parameters are evaluated in this study: roughness parameters Ra, peak count Pc, waviness parameters Wca and amplitude between 0.5 – 5mm (Fourier analysis) and envelope parameters motif W and Ra-macro, measured with a spherical stylus of radius 1.5mm. Classical parameters such as Ra and Pc are only able to evaluate paint appearance for one single texturing process, and within very limited range. The ability to predict paint appearance by Ra-macro and Wca also seems to be limited, because of their dependency on the roll texturing technique. Based on extensive testing, it is suggested that Fourier analysis might be the best approach to predict the appearance after painting, and this independently of the texturing process. The results clearly show the improved appearance of Sibetex textured sheets compared to conventional textured sheets. This is due to the fact that, with Sibetex sheet, a reduction in waviness can be achieved.

Assessment of steel surface roughness and waviness in relation with paint appearance

Assessment of steel surface roughness and waviness in relation with paint appearance.

The paper describes some results of the analysis of Electron Beam Textured (EBT) steel sheet structures by means of the parameter set, proposed by the BCR-working group. Special attention is given to the correlation between the parameters and the functional behaviour. The frictional behaviour is compared with respect to the galling tendency, as it occurs in deep drawing applications. Some aspects related to painting are discussed as well. It is found that some of the proposed parameters are closely related to functional behaviour, but others will need further refinement. For the EBT-deterministic patterns presently used in steel sheet production, it is possible to characterise them fully by three parameters for the mill rolls and by four parameters for the steel sheet produced by these rolls.

3D-characterisation of EBT-steel sheet surfaces

The EBT texturing system introduces the full deterministic surface texture. The wide range of possible EBT textures makes it possible to combine deterministic EBT textures at the tandem and temper mill. The result is a new steel sheet surface with practically no waviness and a high bearing area.The surface effectively holds the lubricant before drawing. Change of the surface texture during drawing relubricates the contact spots between sheet and die. The absence of waviness enhances the hydrodynamic lubrication at lower Stribeck values than for other surfaces. The high initial bearing surface reduces galling. The absence of waviness results in an excellent paint appearance, even for high roughness.

C. De Mare

Papers

Assessment of steel surface roughness and waviness in relation with paint appearance

Assessment of steel surface roughness and waviness in relation with paint appearance.

3D-characterisation of EBT-steel sheet surfaces

Development of the SIBETEX sheet having excellent drawability and paint appearance