JP5363792B2 - Design method of raw material in hot ring rolling process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for predicting the hot dimensions of a rough-shape material when hot-rolling a ring and making the application in hot to the design of the rough-shaped material possible. <P>SOLUTION: This method has: a stage where the specified cooling easiness of the rough-shaped material is determined from the surface area of the rough-shaped material, the volume of the same and the average thickness of the same; a stage where the end temperature of the rolling is determined from the starting temperature of the rolling and the specified cooling easiness of the rough-shaped material; a stage where the percentage of contraction is determined from the end temperature of the rolling and the coefficient of linear thermal expansion of the rough-shaped material and a stage where the design of the rough-shaped material or the design of the die is performed by using the determined percentage of contraction. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for designing a shape material in hot ring rolling, and in particular, a method for predicting the hot dimension of a shape material during hot ring rolling and applying it to hot shape material design. It is about.

  In hot ring rolling, various ring-shaped shapes such as bearing materials are manufactured.

  There is no conventional technique for predicting the hot dimension and shrinkage rate of the shaped material having this complicated shape. The hot dimension of the base material must be determined at the design stage of the mold, and for this purpose, information on the temperature at the end of processing (end temperature) and the shrinkage rate given from that temperature are required.

  Conventionally, the shrinkage ratio between hot and cold has been obtained from the standard classified by the outer diameter of the shape material and the steel type. However, this standard does not include the difference in temperature caused by the shape of the shape material, and in many cases does not match the actual situation.

As another technique, a technique for correcting the cutting length by measuring or predicting the temperature of a material when performing hot cutting in a bar wire manufacturing process can be found (for example, see Patent Document 1).
JP 2004-255472 A

  When manufacturing a shape material while hot, it is most important to design the shape material and mold by predicting the heat shrinkage from the processing end temperature (hereinafter referred to as the end temperature) to normal temperature. It is. The target dimensions for hot working are determined by “cold dimensions (delivery to customers) ÷ heat shrinkage ratio”, but if the heat shrinkage ratio is predicted incorrectly, a shape material with dimensions different from the target will be found. Will be obtained.

  On the other hand, the end temperature can vary depending on the shape of the shape material. This is because the heat balance during processing changes depending on the outer diameter, thickness, and surface area of the shaped material. In addition, among the items to be manufactured, as shown in the right figure, there is a shape material having an asymmetric shape. In this case, the end temperature at each part is not uniform because there is a difference in thickness depending on the part.

  From such a point, it is practically impossible to estimate the end temperature for each shape of each shape material. For this reason, the above-mentioned standard (the current standard) was used for comprehensive support, but the target hot dimension was sometimes incorrect. In order to solve this problem, a method for predicting the end temperature corresponding to the shape of the raw material is required, and the present invention is a method for solving the problem.

  The present invention has been made to solve such a conventional problem, and predicts the hot dimension of a raw material at the time of hot ring rolling and applies it to the hot material design. Is to provide a method that enables

  The method for designing a shape material in the hot ring rolling process of the present invention includes a step of determining the easiness of cooling of the shape material from the shape material surface area, the shape material volume, and the average shape material thickness, and starting rolling. Using the process of obtaining the rolling end temperature from the temperature and the easiness of cooling of the shape material, the step of obtaining the shrinkage rate from the rolling end temperature and the linear expansion coefficient of the shape material, and using the obtained heat shrinkage rate, And a step of performing a shape material design or a mold design.

  According to the present invention, by calculating the shrinkage rate according to the shape of the shape material, it is possible to accurately predict the hot dimension of the shape material without actually manufacturing the shape material. Then, by performing the shape material design and the mold design based on the prediction result of the hot dimension of the shape material, it is possible to improve the dimensional accuracy of the shape material in the cold state.

  Hereinafter, a method for designing a shape material in hot ring rolling processing, which is an embodiment of the present invention, will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of the shape of a shape material to which the method for designing a shape material in the hot ring rolling process of the present embodiment is applied. As shown in the figure, the shape material to which the design method of the shape material in the hot ring rolling process of the present embodiment is applied is a ring-shaped member having an inner diameter of D _in , and the outer diameter is D at one end. _L and large outer diameter portion a of the outer diameter is formed and a small outer diameter portion B of D _S at the other end.

(1) Quantify the ease of cooling of the shape material from the shape of the shape material As a result of investigating the shape of the shape material and the end temperature in hot ring rolling, there is a linear relationship between the two. There was found. That is, assuming that S is the shape material surface area, V is the shape material volume, and t is the shape material average thickness, the easiness of cooling α inherent to the shape material can be expressed by the following Equation 1.
(Formula 1)
α = (S ÷ V) ÷ t

Here, as shown in FIG. 1, the average shape material thickness t is defined as t _L = (D _L −D _in ) / 2, and the thickness of the small outer diameter portion B is defined as t _L = (D _L −D _in ) / 2. When the wall thickness is defined as t _s = (D _s −D _in ) / 2, it can be calculated by t = (t _L + t _s ) / 2.

  The value of α can be calculated from the raw material drawing. In this way, by using the “surface area, volume, and average wall thickness” of the shaped material, it becomes possible to predict heat removal (temperature decrease) during the rolling process, and predict the rolling end temperature. It becomes possible.

(2) Finding the rolling end temperature By substituting the value of α obtained above into Equation 2, the rolling end temperature T _end (° C.) is obtained. Note that the rolling end temperature T _end (° C.) obtained has a range of ± 30 ° C. from the viewpoint of prediction accuracy of this method.

(Formula 2)
T _end ± 30 ℃ ＝ T _ini -μ × α

Here, T _ini is the rolling start temperature (° C.), T _end is the rolling end temperature (° C.), μ is a coefficient obtained from the actual measurement result, and α is the characteristic cooling characteristic of the shape material. That's it.

  Formula 1 selects various shapes and various steel types for the rolling product that is actually manufactured, and investigates the relationship between the rolling end temperature and the shape of the shape material. As a result, the relationship between the end temperature and the shape of the shape material is determined. It is a relational expression found in between. In this embodiment, μ is 6640. This value “μ = 6640” is obtained from the result of actual measurement. In actual measurement, it is a result of measurement regardless of the steel type and shape, and the derivation method of Equation 1 is a result obtained by plotting data on a graph and obtaining a first-order approximation equation.

(3) Estimating the shrinkage rate according to the rolling end temperature The product of the rolling end temperature T _end obtained above and the linear expansion coefficient β of the steel is the shrinkage rate δ from the end temperature to room temperature.

(Formula 3)
δ = T _end × β

  Using this shrinkage rate δ, the hot shape material and the mold are designed. For example, in the design of a hot shape material, it is possible to calculate the hot size of each part by “cold shape material size ÷ shrinkage ratio δ”, and this hot size is the target for hot work. Value. Also, in the mold design, using the hot dimensions of each part calculated in the above hot shape material design, the rough land design before ring rolling (that is, the mold design of the rough land) and the mold during ring rolling Mold design can be performed. Further, once the shrinkage rate Δ is obtained, if it is the same processing, it is possible to continue processing using the numerical values obtained in advance thereafter.

(4) Correspondence to raw material having a thickness difference When there is a wall thickness difference for each part of the raw material as shown in FIG.

(Formula 4)
γ = (D _A -D _in ) / (D _B -D _in )

Here, D _A is the outer diameter of the large outer diameter portion A of industrial castings, D _B is the outer diameter of the small outer diameter portion B of industrial castings, D _in is the inner diameter of the formed and fabricated material.

  By substituting this thickness ratio γ into the following Equation 5, the temperature difference Δt (° C.) at each part can be obtained.

(Formula 5)
Δt ＝ a × γ- b

  Here, a and b are coefficients obtained from actual measurement results.

  Formula 5 selects various shapes and various steel types for the rolling products that are actually manufactured, and investigates the relationship between the temperature difference Δt and the wall thickness ratio γ at each part. As a result, the temperature at each part is determined. It is a relational expression found between the difference Δt and the thickness ratio γ. In this embodiment, a is 41.5 and b is 11.8. The values “41.5” and “11.8” are obtained from actual measurement results. In actual measurement, it is a result of measurement regardless of the steel type and shape, and the derivation method of Equation 5 is a result obtained by plotting data on a graph and obtaining a first-order approximation equation.

  By applying this temperature difference Δt (° C.) to Equation 1, it is possible to predict the difference in shrinkage rate δ that results from the temperature difference Δt (° C.) for each part.

Specifically, first, the rolling end temperature T _{A_end} of the large outer diameter portion A is predicted by Equation 2.

(Formula 6)
T _{A_end} ± 30 ℃ ＝ T _ini -μ × α

  Next, the temperature difference Δt is calculated by Equation 5 in the case of a shaped material having a thickness difference.

Then, it is possible to predict the rolling termination temperature T _{B_end} the small outer diameter portion B by subtracting the temperature difference Δt from the rolling termination temperature T _{A_end} the large outer diameter portion A obtained by Equation 6.

(Formula 7)
T _{B_end} = T _{A_end -Δt}

Thus, the shrinkage [delta] _A of the large outer diameter portion A, can be determined from the following equation 8.

(Formula 8)
δ _A = T _{A_end} × β

Further, shrinkage [delta] _B of the small outer diameter portion B may be determined from the following equation 9.

(Formula 9)
δ _B = T _{B_end} × β

As described above, according to the method for designing a shaped material in the hot ring rolling process of the present embodiment, by actually calculating the shrinkage rate δ _A and the shrinkage rate δ _B according to the shape of the shaped material, It is possible to accurately predict the hot dimension of the shaped material without producing the shaped material. Then, by performing the shape material design and the mold design based on the prediction result of the hot dimension of the shape material, it is possible to improve the dimensional accuracy of the shape material in the cold.

  In addition, by improving the accuracy of the hot target dimensions by predicting the rolling end temperature, the accuracy of the cold dimensions (customer delivery dimensions) will be improved, and the material allowance will be reduced. In addition, the labor for making prototype adjustments is reduced in the field operation.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

(1) from the formed and fabricated material shape, in the present embodiment for quantifying the cold ease of industrial castings, in industrial castings sectional shape shown in FIG. 1, formed and fabricated material surface area S is "114671Mm ^2", preformed A shape material having a material volume V of “691163 mm ³ ” and a shape material average thickness t of “18.125 mm” was used. Therefore, the easiness of cooling α inherent to the raw material is “0.0092” from Equation 1.

(2) Corresponding to the shape material having a thickness difference In this embodiment, the outer diameter D _A of the large outer diameter portion _A is “φ276.7 mm”, and the outer diameter DB of the small outer diameter portion _B is “ A shape material having a diameter of “φ256.2 mm” and an inner diameter D _in of “φ230.2 mm” was used. Therefore, the thickness ratio γ is “1.79” according to Equation 4.

  By substituting this thickness ratio γ into Equation 5, a temperature difference Δt “62.5” (° C.) between the large outer diameter portion A and the small outer diameter portion B was obtained. Note that “a” and “b” in Equation 5 are “41.5” and “11.8”, which are numerical values found for a rolling product that is actually manufactured.

  The values “41.5” and “11.8” in Equation 5 are obtained from the actual measurement results. As a result of measuring regardless of the steel type and the shape of the material, the actual measurement values are plotted, and a first-order approximation formula is used. It is the obtained numerical value. Specifically, the steel type is SUJ2, γ is 2.069, and Δt is 66 ° C.

  By applying this temperature difference Δt (° C.) to Equation 1, the difference in shrinkage rate δ resulting from the temperature difference Δt (° C.) for each part was predicted.

Specifically, first, when the rolling end temperature T _{A_end} of the large outer diameter portion A is obtained by Equation 6, “946 ° C.” is obtained.

  Note that μ in Expression 6 is “6640” which is a numerical value found for a rolling product actually manufactured.

  The value of “6640” in Equation 6 is obtained from the actual measurement result. As a result of the measurement regardless of the steel type and the shape of the material, the actual measurement value is plotted, and the numerical value obtained by the first order approximate expression. It is. Specifically, as shown in FIG. 3, the steel type is SUJ2, the end temperature is 907.8 ° C., and α is 0.0125.

Then, using a rolling termination temperature T _{A_end} "946 ° C." of the resulting large outer diameter portion A by Equation 6, when obtaining the rolling termination temperature T _{B_end} the small outer diameter portion B from Equation 7, "883.5 ° C." It becomes.

Accordingly, shrinkage [delta] _A of the large outer diameter portion A is "1.10" from the equation (8). The value of the coefficient of linear expansion β of steel is “11.6 × 10 ⁻⁶ ”.

Further, the shrinkage ratio δ _B of the small outer diameter portion B is “1.02” from Expression 9.

  Table 1 shows the results of predicting the end temperature and shrinkage rate by the above method and confirming with the actual machine.

Comparing the shrinkage rate at each part, the shrinkage rate derived by the conventional method (δ _A = 1.30%, δ _B = 1.30%) and the actual machine test results (δ _A = 1.16%, δ _B = 1.09%) Has a relatively large error. On the other hand, the shrinkage rate (δ _A = 1.10%, δ _B = 1.02%) derived by the prediction method of this example and the actual machine test results (δ _A = 1.16%, δ _B = 1.09%) agree well. I understand that.

Table 2 is a table showing the cold dimension result of the small outer diameter portion (dimension φD _s ) when the conventional design method is applied. Conventionally, it is designed without considering the temperature difference between the large outer diameter part (φD _L ) and the small outer diameter part (φD _S ), that is, the shrinkage rate of the small outer diameter part is Since they are the same, the target dimensions cannot be obtained. Specifically, the dimension is larger than the target value.

  On the other hand, in the case of the present embodiment, as can be seen from Table 2, the temperature difference between the large outer diameter portion and the small outer diameter portion is predicted in advance, and an appropriate shrinkage rate is applied to each part. It can be seen that the cold dimension is obtained.

  Thus, in the conventional design method, in the case of an asymmetric shaped material, the temperature difference for each part could not be predicted, and thus an error from the target dimension occurred. Then, the dimensions are almost as intended. Therefore, the validity of the method for designing the shape material in the hot ring rolling process of the present invention was proved.

It is sectional drawing which shows an example of the shape of the shaped material to which the design method of the shaped material in the hot ring rolling process of this embodiment is applied. It is a figure which shows the derivation method of Numerical formula 5 of this embodiment. It is a figure which shows the derivation method of Numerical formula 2 and Numerical formula 6 of this embodiment.

Claims (7)

A method of designing a shaped material that is hot ring rolled into a predetermined shape,
Determining the easiness of cooling of the shape material from the surface area, volume, and average thickness of the shape material; and
Determining the rolling end temperature from the rolling start temperature and the easiness of cooling inherent to the shape material;
Obtaining a shrinkage rate from the rolling end temperature and the linear expansion coefficient of the shaped material; and
Using the obtained heat shrinkage rate, and performing a shape material design or mold design;
A method for designing a shape material in hot ring rolling, characterized by comprising: In the case where the raw material has a large outer diameter portion and a small outer diameter portion having a thickness difference,
Obtaining a wall thickness ratio of the large outer diameter portion and the small outer diameter portion;
Obtaining a temperature difference between the large outer diameter portion and the small outer diameter portion from the thickness ratio;
Further including
In the step of determining the rolling end temperature,
Determine the rolling end temperature of the small outer diameter portion from the rolling end temperature and the temperature difference of the large outer diameter portion,
In the step of determining the shrinkage rate,
The shrinkage rate of the large outer diameter portion is determined from the rolling end temperature and the linear expansion coefficient of the large outer diameter portion, and the small outer diameter is determined from the rolling end temperature and the linear expansion coefficient of the small outer diameter portion. The shrinkage rate of a part is calculated | required, The shape material design method in the hot ring rolling process of Claim 1 characterized by the above-mentioned. 3. The element in the hot ring rolling process according to claim 1, wherein in the step of determining the easiness of cooling inherent to the shape material, the easiness of cooling inherent to the shape material is obtained by the following mathematical formula 1. How to design a shape.
(Formula 1)
α = (S ÷ V) ÷ t
Where α is the ease of cooling, S is the surface area of the shaped material, V is the volume of the shaped material, and t is the average thickness of the shaped material. The method for designing a shape material in hot ring rolling according to any one of claims 1 to 3, wherein in the step of obtaining the rolling end temperature, the rolling end temperature is obtained by the following mathematical formula 2.
(Formula 2)
T _end ± 30 ℃ ＝ T _ini -μ × α
Here, T _ini is the rolling start temperature (° C.), T _end is the rolling end temperature (° C.), μ is a coefficient obtained from the actual measurement result, and α is the characteristic cooling characteristic of the shape material. That's it. The method for designing a shape material in hot ring rolling according to any one of claims 1 to 4, wherein in the step of obtaining the shrinkage rate, the shrinkage rate is obtained by the following mathematical formula 3.
(Formula 3)
δ = T _end × β
Here, δ is a shrinkage rate, T _end is a rolling end temperature (° C.), and β is a linear expansion coefficient of the base material. 3. The method for designing a shape material in hot ring rolling according to claim 2 , wherein in the step of obtaining the thickness ratio, the thickness ratio is obtained by the following mathematical formula 4.
(Formula 4)
γ = (D _A -D _in ) / (D _B -D _in )
Where γ is the thickness ratio, D _A is the outer diameter of the large outer diameter portion of the shaped material, D _B is the outer diameter of the smaller outer diameter portion of the shaped material, and D _in is the original shape The inner diameter of the material. The method for designing a shaped member in hot ring rolling according to claim 2 , wherein in the step of obtaining the temperature difference, the temperature difference is obtained by the following mathematical formula 5.
(Formula 5)
Δt ＝ a × γ- b
Here, Δt is a temperature difference, γ is a thickness ratio, and a and b are coefficients obtained from actual measurement results.

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