JPH0445085B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method of measuring the thickness of a rolled steel plate using radiation, for example. [Prior art] One method of measuring the thickness of a rolled steel plate is the radiation transmission method, which involves transmitting radiation through the rolled steel plate, detecting the amount of transmission It, and substituting it into a preset calculation formula. Then, the plate thickness is calculated. Next, a general formula for determining the plate thickness t is shown. t=1/μm・ρ・lnIo/It …(1) where ρ: Density of the plate μm: Mass absorption number Io of the plate: Detected amount of radiation It when there is no plate between the radiation source and the detector: This is the amount of radiation detected. The mass absorption coefficient μm of the plate in the above equation (1) is determined by the following calculation equation (2). μm= 〓 ⁱ μmiAi/100 (2) where μmi: Mass absorption coefficient of constituent element i Ai: Constituent percentage (%) of constituent element i. Then, the density ρ of the plate is obtained by the following equation (3). However, ρs: density of pure iron (≒7.86 g/cm ³ ) ai: coefficient determined for Ai. In other words, the mass absorption coefficient μm and the density ρ are calculated in advance using the above equations (2) and (3) based on the analysis results of the component composition, and the calculated results and the detected amount of radiation are calculated in advance.
Substituting into equation (1), the plate thickness t is calculated. [Problem to be solved by the invention] By the way, the mass absorption coefficient μm should theoretically be a specific value for each constituent element regardless of the plate thickness, but apparently it is a property related to the plate thickness. , that is, it was known to exhibit plate thickness dependence. For this reason, for a plate composed of two types of elements A and B, for example, by using a sample plate with a plate thickness of t ₁ with element A and creating an apparent plate thickness dependence curve, It has been said that this thickness dependence curve can also represent the thickness dependence of element B. In other words, the plate thickness dependence curve determined by the ratio of μm values of elements A and B at plate thickness t ₁ , μmBt ₁ /μmAt ₁ , is the same even if the plate thickness is a value other than t ₁ . They assumed that it had a dependence curve. To explain specifically, when the approximate thickness of the plate to be measured is _t2 , the mass absorption coefficient μm of element A
Mass absorption coefficient μm in element B using At ₂
A method of calculating Bt ₂ is used, and μm
Bt ₂ has been determined as μmBt ₂ =μmAt ₂ ×μmBt ₁ /μmAt ₁ . However, in reality, the ratio of μm values, μmB/μmA
was found to be not constant but to vary depending on the plate thickness. In other words, the shape of the curve showing thickness dependence differs for each element, and the inventors have discovered that using the thickness dependence curve of one element as a representative to determine the mass absorption coefficient μm of other elements will result in an error. This was revealed through research. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radiation plate thickness measurement method that improves measurement accuracy by determining the mass absorption coefficient μm corresponding to the plate thickness dependence curve that differs for each element. shall be. [Means for Solving the Problems] The radiation plate thickness measurement method according to the present invention allows radiation to pass through the plate to be measured and detects the amount of radiation transmitted and the density of each element constituting the plate to be measured. In the radiation plate thickness measurement method, which calculates the plate thickness using the mass absorption coefficient and the mass absorption coefficient of the plate to be measured, the mass absorption coefficient specific to each element having thickness dependence is calculated individually for the approximate thickness of the plate to be measured. The method is characterized in that the mass absorption coefficient of the plate to be measured is determined using the calculation result. [Operation] The mass absorption coefficient of the plate to be measured is determined by using the mass absorption coefficient specific to each element, which is calculated individually for the approximate thickness of the plate to be measured, and this result is combined with the mass absorption coefficient of the plate to be measured. The thickness of the plate to be measured is calculated based on the density and the amount of radiation transmission. [Examples] The present invention will be explained below with reference to Examples. The present invention realizes highly accurate plate thickness measurement by accurately calculating the mass absorption coefficient μm of each element constituting the plate to be measured. There are two methods for calculating μm. In both cases, a curve showing the relationship between the μm value of each element and the plate thickness, that is, a curve showing the apparent dependence on the plate thickness, is created from actual measurement data, etc. Use. In calculating the μm value, the first method is to set the approximate thickness of the plate to be measured, that is, the manufacturing target thickness or nominal thickness of the rolling mill, etc.
As ts, each μmi(ts), which is the μm value corresponding to the set plate thickness ts of each element (i indicates the constituent element), is determined from the thickness dependence curve, and these μmi(ts) and From the component composition % value Ai, the following is shown (4)
Calculate μm using the formula. μm= 〓 ⁱ {μmi(ts)・Ai/100} …(4) In the second method, after creating a plate thickness dependence curve between μm value and plate thickness from actual measurement data, next βi(tj )=μmi(tj)/μmk(tj). βi (tj) is the ratio of μmi (tj), which is the μm value of other elements, to μm value of the basic element (for example, Fe), ie, μmk(tj), at each plate thickness tj. Then, βi (tj) is calculated in μm from βi (ts) obtained for the set plate thickness ts, which is the approximate plate thickness of the plate to be measured, and the component composition % value Ai of each element using the following equation (5). Calculate. μm= 〓 ⁱ {μmk(ts)・βi(ts)・Ai/100} …(5) Next, the conventional method shown in equation (2) and the method of the present invention
A numerical example will be explained using the method shown in equation (4).

【table】

〔effect〕

As described above, in the present invention, the mass absorption coefficient μm is calculated based on the individual thickness dependence of each element, taking into account that the thickness dependence curve is different for each element, so the accuracy of plate thickness measurement is improved. The present invention has excellent effects such as:

Claims (1)

[Claims] 1. The plate thickness is determined using the amount of radiation transmitted through the plate to be measured and detected, the density of each element constituting the plate to be measured, and the mass absorption coefficient of the plate to be measured. In the radiation plate thickness measurement method, the mass absorption coefficient specific to each element having thickness dependence is calculated individually for the approximate thickness of the plate to be measured, and this calculation result is used to calculate the thickness of the plate to be measured. A radiation plate thickness measurement method characterized by determining the mass absorption coefficient of.