CN103544403A - Method for quantitative description of surface color and luster degree of galvanized plate - Google Patents

Abstract

The invention provides a method for quantitative description of the surface color and luster degree of galvanized plates. The method comprises the steps of (1) establishing a functional relation formula of the surface roughness Ra and a diffusion parameter sigma; (2) selecting at least 5 galvanized plates different in color intensity, respectively measuring the surface roughness Ra and the diffusion parameter sigma of each plate to obtain a formula determined by undetermined coefficients; (3) selecting the galvanized plates with normal surfaces, measuring the surface roughness Ra0, calculating the diffusion parameter sigma0 through the formula and using the diffusion parameter sigma0 as a reference; (4) measuring the surface roughness Ran of the galvanized plates having chromatic aberration and calculating the diffusion parameter sigman through the formula; (5) comparing the sigman with the sigma0, wherein the plates are brighter if a sigman-sigma0 numerical value is a positive number, the color and luster degree is higher if the value is larger, the plates are dimmer if the sigman-sigma0 numerical value is a negative number, and the color and luster degree is lower if the value is larger. The method utilizes online quantification of the surface color and luster degree of the galvanized plates to determine the chromatic aberration level of the surfaces of galvanized steel plates and is simple in operation, practical and high in working efficiency.

Description

The quantitative description of galvanized sheet surface color degree

Technical field

The present invention relates to galvanized sheet surface quality evaluation method, refer to particularly a kind of quantitative description of galvanized sheet surface color degree.

Background technology

Because thickness of coating is uneven, the height of coating rises and falls, thickness of oxidation film is different, make galvanized sheet without zinc flower obtain the outward appearance of uniformity very difficult.Anaclasis forms shade deviation to surface, has greatly affected presentation quality and the corrosion stability of galvanized sheet, thereby has affected the market competitiveness of galvanized sheet.The galvanized sheet that is applied to automobile exterior panel requires very high to color and luster, otherwise can have a strong impact on the postorder quality of spraying paint, thereby vehicle body outward appearance is caused to serious impact.

Want to solve the color and luster problem of galvanized sheet, just must know the quantitative of color and luster.Color and luster refers to color and gloss, is generally applied to describe food, clothes, and the apparent mass of ornaments etc., is an important indicator of quality evaluation.Aberration is evaluated existing longer applicating history in the related industries fields such as textile printing and dyeing, pulping and paper-making, paint film coating, clothes, food, but seldom data display application is in the color evaluation method of steel industry.

At present, Chinese most of iron and steel enterprises adopt artificial visual sampling observation and dodge the methods such as light detection frequently and carry out surface color check, and report by probability statistics and testing staff's experience formation overall quality.But sensory evaluation is had relatively high expectations to detection person, the factor that impact is evaluated also has a lot, and the possibility of result of different regions, different manufacturers has larger difference.

The factor that affects galvanized sheet surface color difference is a lot, is wherein apparent that the most surfaceness.Due to microcosmic out-of-flatness, it is different by force that illumination is mapped to surface reflection, and the part roughness of projection greatly just obtains grey dark face, and therefore the little wet look that just forms of sunk part roughness has formed surface chromatic aberration.

There is no at present the method for galvanized sheet surface color being carried out to on-the-spot Fast Evaluation.

Summary of the invention

Object of the present invention will overcome the existing deficiency of prior art exactly, a kind of quantitative description of galvanized sheet surface color degree is provided, utilize surfaceness to provide the quantitative description of surface color degree, to meet the requirement of on-the-spot Fast Evaluation hot galvanizing surface color and luster.

For achieving the above object, the invention provides a kind of quantitative description of galvanized sheet surface color degree, comprise the following steps:

1) set up the relational expression between surface roughness Ra and diffusion parameter σ, as shown in Equation (1), a wherein, b, c, d, e are five undetermined coefficients:

${\mathrm{\σ}}^2=\frac{{{\mathrm{aR}}_a}^2+{\mathrm{bR}}_a+c}{{(R_a+d)}^2{(R_a+e)}^2}$ Formula (1);

2) choose again at least 5 galvanized sheets that bright-dark degree is different, and measure respectively its surface roughness Ra and diffusion parameter σ, by the Ra in formula (1), it is independent variable, σ is dependent variable, by matlab software, by self-defining function, carry out matching, to determine the value of a, b, c, d, five undetermined coefficients of e, obtain formula as follows (2)

${\mathrm{\σ}}^2=\frac{{{1629R}_a}^2-{4262R}_a+3770}{{(R_a-0.7373)}^2{(R_a+27.84)}^2}$ Formula (2);

3) then choose the galvanized sheet of a normal surface, measure its surface roughness Ra ₀, by formula (2), calculate its diffusion parameter σ ₀, and using this as the benchmark of evaluating surface color degree;

4), for the galvanized sheet that has aberration, first measure its surface roughness Ra _n, then calculate diffusion parameter σ by formula (2) _n,

5) then by the σ calculating _nthe benchmark σ calculating with normal surface ₀compare:

Work as σ _n-σ ₀numerical value while being positive number, bigger than normal, illustrate that surface color degree is bright, it is brighter that positive departs from larger explanation surface color degree;

Work as σ _n-σ ₀numerical value while being negative, less than normal, illustrate that surface color degree is dark, it is darker that negative value departs from larger explanation surface color degree.

In the present invention, the derivation of formula (1) is as follows:

When light beam is irradiated to after body surface at a certain angle, because surface is imperfect smooth, can there is scattering phenomenon.Surfaceness and scattered light intensity are distributed with certain relation.For the less surface of surface roughness value, reflection luminous energy stronger, scattering luminous energy a little less than; Otherwise, the surface that surface roughness value is larger, reflection luminous energy a little less than, scattering luminous energy is stronger.A bit the image that obtains in the distribution of spatial light intensity, according to point source diffusion function (PSF), determine, the distribution of some light intensity in space is to describe by the Gaussian distribution that obedience variance is diffusion parameter σ:

$h(x,y)\frac{1}{{2\mathrm{\π\σ}}^2}{e}^{\frac{x^2+y^2}{{2\mathrm{\σ}}^2}}---\left(i\right)$

Diffusion parameter σ is mean square deviation, and the larger expression light distribution of σ is overstepping the bounds of propriety loose, otherwise more concentrated.

In a theoretic unaberrated system, imaging point (image point) has minimum dimension, but size is not infinitesimal.Due to the identification power of human eye, in fact have aberration to exist, so smallest spot cannot form above-mentioned ideal image, but present a kind of irregular shape and energy distribution.Along optical axis direction, move forward and backward pointolite, as the picture becoming in plane, will become the circle that has certain diameter, circular size depends on aperture diaphragm diameter D and pointolite departure degree (object distance) u, with diffusion parameter σ, characterizes circular size,

σ＝Du （ii）

According to convex lens formula, have:

v is image distance, be here camera lens to the distance between measured point, on the normal section of measured surface, the arithmetic mean of profile offset distance absolute value is Ra, i.e. u=R _a+ s, s is that camera lens arrives the distance between tested plane, therefore

$u=\frac{f\·s+f\·R_a}{s-f+R_a}---\left(\mathrm{iii}\right)$

(iii) formula is gone in bringing into (ii), has

$\mathrm{\σ}=D\frac{f\·s+f\·R_a}{s-f+R_a}---\left(\mathrm{iv}\right)$

Because Ra unit is micron order, fR _a< < fs, will (iv) be reduced to

$\mathrm{\&sigma;}=D\frac{f\&CenterDot;s}{s-f+R_a}---\left(v\right)$

White light is the light of multi-wavelength, and white light is comprised of the monochromatic light of many colors (red, orange, yellow, green, blue, indigo, purple).Every kind of monochromatic wavelength and focal length are different.Therefore,, due to the effect defocusing, two kinds of monochromatic fuzzy differences are ${\mathrm{\&sigma;}}_i^2-{\mathrm{\&sigma;}}_j^2,i,j\&Element;\{R,O,Y,G,B,C,P\},$

In order to embody the relation between diffusion parameter and surfaceness, the polynomial expression of surfaceness will (vi) be write as,

${\mathrm{\&sigma;}}_i^2-{\mathrm{\&sigma;}}_j^2=\frac{{{\mathrm{aR}}_a}^2+{\mathrm{bR}}_a+c}{{(R_a+d)}^2{(R_a+e)}^2}---\left(\mathrm{vii}\right)$

Order

obtain formula (1):

${\mathrm{\&sigma;}}^2=\frac{{{\mathrm{aR}}_a}^2+{\mathrm{bR}}_a+c}{{(R_a+d)}^2{(R_a+e)}^2}$ Formula (1)

Formula (1) has been set up the relation between diffusion parameter and surfaceness, and a, b, c, d, e are five undetermined coefficients, only relevant with measuring system.Therefore, by formula (1), just can provide the quantitative description of color and luster.

Beneficial effect of the present invention is: the present invention utilizes galvanized sheet surface properties, and surfaceness, evaluates color and luster quality, can quantitatively determine galvanized steel sheet surface aberration grade.The present invention can improve surface color by improving surfaceness, thereby can instruct producer to formulate production technology, more corresponds to actual needs.The present invention's practicality simple to operate, work efficiency is high, can realize online detection.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in further detail.

The quantitative description of galvanized sheet surface color degree of the present invention, comprises the following steps:

1) set up the relational expression between surface roughness Ra and diffusion parameter σ, as shown in Equation (1), a wherein, b, c, d, e are five undetermined coefficients:

${\mathrm{\&sigma;}}^2=\frac{{{\mathrm{aR}}_a}^2+{\mathrm{bR}}_a+c}{{(R_a+d)}^2{(R_a+e)}^2}$ Formula (1);

2) choose again the different galvanized sheet of 15Kuai bright-dark degree, and with surface profiler, measure its surface roughness Ra respectively and CCD extracts the diffusion parameter σ of surperficial light distribution, as shown in table 1;

The measurement result on table 1 galvanized sheet surface

By the Ra in formula (1), be independent variable, σ is dependent variable, according to the data in table 1, by matlab software, by self-defining function, carries out matching, to determine the value of a, b, c, d, five undetermined coefficients of e, obtains formula as follows (2),

${\mathrm{\&sigma;}}^2=\frac{{{1629R}_a}^2-{4262R}_a+3770}{{(R_a-0.7373)}^2{(R_a+27.84)}^2}$ Formula (2);

3) then choose the galvanized sheet of a normal surface, measure its surface roughness Ra ₀, by formula (2), calculate its diffusion parameter σ ₀, to evaluate surface color degree, and using this as benchmark;

4), for the galvanized sheet that has aberration, first measure its surface roughness Ra _n, then calculate diffusion parameter σ by formula (2) _n,

5) then by the σ calculating _nthe σ calculating with normal surface ₀compare,

Work as σ _n-σ ₀numerical value while being positive number, bigger than normal, illustrate that surface color degree is bright, it is brighter that positive departs from larger explanation surface color degree;

Work as σ _n-σ ₀numerical value while being negative, less than normal, illustrate that surface color degree is dark, it is darker that negative value departs from larger explanation surface color degree.

Can facilitate like this producer to judge fast the order of severity of surface chromatic aberration, to propose improvement measure.

Claims (1)

1. a quantitative description for galvanized sheet surface color degree, is characterized in that, comprises the following steps:

1) set up the relational expression between surface roughness Ra and diffusion parameter σ, as shown in Equation (1), a wherein, b, c, d, e are five undetermined coefficients:

${\mathrm{\&sigma;}}^2=\frac{{{\mathrm{aR}}_a}^2+{\mathrm{bR}}_a+c}{{(R_a+d)}^2{(R_a+e)}^2}$ Formula (1);

2) choose again at least 5 galvanized sheets that bright-dark degree is different, and measure respectively its surface roughness Ra and diffusion parameter σ, by the Ra in formula (1), it is independent variable, σ is dependent variable, by matlab software, by self-defining function, carry out matching, to determine the value of a, b, c, d, five undetermined coefficients of e, obtain formula as follows (2)

${\mathrm{\&sigma;}}^2=\frac{{{1629R}_a}^2-{4262R}_a+3770}{{(R_a-0.7373)}^2{(R_a+27.84)}^2}$ Formula (2);

3) then choose the galvanized sheet of a normal surface, measure its surface roughness Ra ₀, by formula (2), calculate its diffusion parameter σ ₀, and using this as the benchmark of evaluating surface color degree;

4), for the galvanized sheet that has aberration, first measure its surface roughness Ra _n, then calculate diffusion parameter σ by formula (2) _n,

5) then by the σ calculating _nthe benchmark σ calculating with normal surface ₀compare:

Work as σ _n-σ ₀numerical value while being positive number, bigger than normal, illustrate that surface color degree is bright, it is brighter that positive departs from larger explanation surface color degree;

Work as σ _n-σ ₀numerical value while being negative, less than normal, illustrate that surface color degree is dark, it is darker that negative value departs from larger explanation surface color degree.