Choi steel application is becoming more and more widely, and its rich color, be in all walks of life, the beautiful scenery of all kinds of buildings. This landscape is formed, caigang industry is how to test for color, in the process and the matters needing attention, this article, the author do some basic introduction.

     Basic knowledge of the color

  The three elements of color

    1. The brightness (L)

   The L value, the greater the said material is white; Such as: L = 100 said the white; L = 50 said gray; L = 0 value indicates black;、；

   2. The hue (also known as tone, usually expressed in A, B)

   Hue refers to the color of light color category; + A indicates the degree of partial red; - A, indicates the degree of partial green. + B indicates the degree of the yellow; - B said the extent of the blue;

   3. (also known as the saturation, chroma is refers to the degree of color depth)

•     L -- -- -- -- > delta L: the deviation between actual luminance brightness and standard;

•     A -- -- -- -- > delta A: material the partial red, green, extent and the gap between standard quality inspection;

•     B -- -- -- -- > delta B: material in the actual yellow blue degree and the gap between standard quality inspection;

•    Delta E: actual value and standard value in the L/A/B on the overall difference.

     Light and color

     1. The visible light (see below) : light is a substance in the form of electromagnetic waves, the human eye can see light is visible light, the average person can sense the electromagnetic wave wavelength of 400 nm to 700 nm, others can sense the electromagnetic waves between 380 nm to 780 nm;

    2. There are two kinds of color originating body:

         ① The color of light shows;；

         ②Not light presented by the light color, the color of the light shows and illuminate its light source；

     The principle of the three primary colors (R - red; G - green; B - blue)

         1. Most of the colors in nature, can use three primary colors mixed according to certain proportion, on the other hand, the nature of the color can be broken down into three primary colors;

         2. The three primary colors were independent of each other color, no a primary colors can be generated by two other primary colors;

         3. Between the three primary colors mixed proportion, determines the mixture color hue and saturation;

         4. The chromaticity triangle

     The definition of color difference

         Refers to the differences of two color color, brightness, hue and saturation composite differences of these three. At present the most practical and universal model is used to measure the color of the object space L * A * B * color space, it is the CIE (international lighting space commission) hue of the definition of space.

     Color - chromatic meter measurement

     The classification of the chromatic meter

         According to the performance parameters, precision of range and use requirement can be divided into handheld color difference meter, portable color difference meter and three types of desktop chromatic meter.

         1. Handheld chromatic meter: also known as color color difference meter, can directly read data, don't have to connect the computer, not matching software, easy to use, cheap, but the precision is low, widely used in the field of color management, the general, such as OU4600;

         2. Portable chromatic meter: also called portable light color measurement instrument, its besides can directly read data, also can connect computer, equipped with software, small volume, easy to carry, high precision, price moderate, as lubricious li SP series, etc.;

      3. Desktop chromatic meter: also known as table light colour matching instrument, its reading window, need to use for connection to the computer Color measurement, Color matching software, has a high accuracy of Color measuring and matching function, large size, stable performance, high prices, such as Hunter Lab, Date Color, etc.

     The working principle of chromatic meter

      Chromatic meter is to simulate human eyes of red, green, and blue light induction measuring instrument, the object to be measured can be multi-angle analysis.

     Chromatic meter can be according to the principle of CIE chromaticity space Lab, Lch, show sample and same sample off color Δ E and Δ L, a and b Δ Δ values. Δ E is defined as the total sample color difference, the bigger Δ E value said the color difference, but can't reflect the sample bias color, the sample color to use Δ L, a and b Δ Δ.

      Different brand and different types of chromatic meter, test results vary, one of the main factors is the measurement of optical/different geometric structure, the current common has the following three：

      1. The polygonal effect color measurement instrument, can measure angles off color;

  2. The light measuring learning institutions for 45/0, ° ring illumination, 0 ° Angle observation, annular illumination system, eliminating the way dependence, whether to change the position of the sample, sample or turning instrument can achieve higher precision and repeatability, would reduce the impact of the grain. In grinding, texture and structured materials on the surface of the measuring brings great advantage;

   3. Measurement geometry / 8 D, integral ball diffuse lighting, 8 ° Angle observation, is currently the international general observation condition;

     The light source

        1. Llluminant A (A light source) : represented by incandescent CIE standard illuminant, yellow - orange, associated with the color temperature of 2856 ° K;

        2. Llluminant C source (C) : simulation of the tungsten filament lamp as a representative of the average sun CIE standard illuminant, such as blue, the related color temperature is 6774 ° K;

         3. Llluminant D (D light source) : represented by fluorescent lamp of CIE standard illuminant, based on real measurement spectrum of the sun, the related color temperature of 6504 ° K, D65 and D75 etc. The most commonly used several kinds of color temperature, color paint and steel industry commonly used D65 light source;

         4. Llluminant F light source (F) : represented by fluorescent CIE standard illuminant, F2 on behalf of the cool white fluorescent lamp (4200 ° K), F7 represent broad daylight fluorescent lamp (6500 ° K), F11 on behalf of the narrowband white fluorescent lamp (4200 ° K).

      Specular reflection and diffuse reflection

         1. SCI (Specular Component Include: acceptable Specular reflection and diffuse reflection light (including gloss), commonly used in the study and don't care about color color attribute attached samples of the surface gloss of enterprises or institutions;

         2. SCE (Specular Component Exclude) : do not accept mirror reflected light (does not include the luster), generally applies to those who were directly observed, measurement results and the visual is very close to the sample of enterprises or institutions;

         3. Llluminant D (D light source) : represented by fluorescent lamp of CIE standard illuminant, based on real measurement spectrum of the sun, the related color temperature of 6504 ° K, D65 and D75 etc. The most commonly used several kinds of color temperature, color paint and steel industry commonly used D65 light source;

      The color difference range (tolerance)

         1. 0 ~ 0.25 Δ E very little or no ideal match, can be ignored, the naked eye is hard to distinguish;

         2. 0.25 ~ 0.5 Δ E small and acceptable match, can be ignored, the naked eye is hard to distinguish;

         3. 0.5 1.0 Δ E small to medium; Acceptable in some applications, long-term professional trained people can distinguish;

         4. 1.0 2.0 Δ E medium, acceptable in the specific application, is easy to distinguish;

         5. 2.0 4.0 Δ E have difference, in a specific application can be accepted, easy to distinguish

        6. 4.0 above Δ E very big, is not acceptable in most applications.

      Shandong huijin, according to the specific requirements of different products, generally acceptable Δ E 0 ~ 1.5 off color range.

      Using chromatic meter measuring color difference general considerations

         1. Before the use should check the equipment status is normal;

         2. The calibration qualified rear can use, calibration board or other standards board should be properly kept, so as to avoid dust fall or discoloration;

         3. Choose the correct light source (D65);

         4. If you need to choose the way to measure, then choose SCI.

         5. If you want to replace the measuring aperture, after changing the aperture should be calibrated again;

        6. Choose the international general and universal space model: L * A * B * color space;

         7. In the strong magnetic field, and other special environment using high heat and humidity;

         8. More than 10 ℃ environment temperature changes should be calibrated again;

      The color difference problem analyses

         1.The same model, multiple detection appear off color, possible reasons are:：

              ① Chromatic meter in different brands and models;

              ②One or more parties detection equipment abnormal state;

              ③There are differences between the adopted standards；

              ④ Detection of improper operation;

         2.Choi steel production process color difference problem, a common cause:

              ①Testing equipment abnormal state;

              ② Without the right standard;

              ③ Detection of improper operation;

              ④ Improper coating film thickness;

              ⑤ Improper plate temperature;

              ⑥Paint color difference problem;