JPH07227603A - Cutting method for pipe stock for cold working - Google Patents

Abstract

PURPOSE:To perform the sampling of a pipe of arbitrary weight by finding a cutting position to cut a short sized pipe stock of desired weight from a simplex equivalent value and the pipe axial direction position of a long sized pipe stock. CONSTITUTION:The long sized pipe stock for cold working is cut to a short sized pipe stock of weight suitable for cold working. At this time, the major diameter and thickness of the long sized pipe stock are measured. A cutting mode decision value J is found by equation I based on a measured value. When the value J is smaller than a prescribed value, a major diameter value is assumed as the simplex equivalent value. The long sized pipe stock is cut by finding the cutting position by which the short sized pipe stock of desired weight can be obtained from either simplex equivalent value and pipe axial direction position. In equation I, a major diameter mean value at every long sized pipe stock is assumed as XOD, a major diameter reference deviation at every long sized pipe stock by frequency distribution calculation formula as sigmaOD, and a thickness mean value at every long sized pipe stock as XWT. In this way, it is possible to improve efficiency and yield in the cold working.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a cold working cold rolled pipe used for cold pipe rolling with a cold pilger mill.

[0002]

2. Description of the Related Art In cold pipe rolling with a cold pilger mill, a so-called extruded pipe manufactured by a hot extrusion method is used as a raw pipe. This extruded pipe is manufactured as a long pipe longer than the length of the raw pipe in terms of efficiency and the like, and is cut into a short pipe having a length convenient for rolling before being subjected to cold pipe rolling.

An important point in this cutting is that it is necessary to control the cutting position not by the length but by the weight. That is, in the long raw tube used for cold tube rolling, that is, the extruded tube, the unit weight distribution in the tube axis direction is not constant due to dimensional variation, uneven thickness, and the like.
Therefore, when the cutting position is controlled by the length, the weight of the short tube to be subjected to the cold tube rolling becomes excessive or insufficient. Insufficient weight leads to a short product length, and excessive weight leads to a reduction in rolling efficiency due to excessive rolling, and a reduction in yield due to removal of unnecessary portions after rolling.

As a technique for controlling the cutting position of a long raw pipe to be subjected to cold pipe rolling by weight, a weighing scale is provided before and after the cutting position in the cutting line, and the raw pipe is weighed by two weighing scales. Japanese Patent Laid-Open No. 58-17121
No. 5 publication.

[0005]

However, this method can only divide the long tube into two. Recently, complicated multi-strips such as 5 divisions, 6 divisions, and 7 divisions have been adopted for the purpose of efficient collection of raw tubes, and a method that can only perform 2 divisions cannot be put to practical use.

[0006] Further, it is not practical to measure the weight of the raw pipe in the line from the viewpoint of efficiency and facility, which is very limited.

An object of the present invention is to provide a method for cutting a cold-working raw pipe which can divide an elongated raw pipe into an arbitrary number of isobaric pieces and is easy to carry out.

[0008]

[Means for Solving the Problems] In order to control the cutting position of a long tube for cold-rolling by weight, it is conceivable to measure the outer diameter and wall thickness of the long tube. That is, the cross-sectional area is obtained by measuring the outer diameter and the wall thickness of the long element pipe, and by correlating this with the position in the tube axis direction, the unit weight distribution in the tube axis direction of the long element tube is obtained. However, even if the outer diameter of the long tube can be accurately measured by a laser or the like, it is difficult to accurately measure the wall thickness, so that the cross-sectional area cannot be accurately measured over the entire length of the tube.

The present inventors have paid attention to the fact that the outer diameter of a long tube can be relatively easily and accurately measured.
When the relationship between the outer diameter and the unit weight was investigated, a high correlation was established between the square value of the outer diameter and the unit weight, and the long element pipe was cut based on the square value of the outer diameter. For example, it has been found that not only an arbitrary number of equal-divided unit tubes but also a short unit tube having a desired weight can be easily obtained.

When cutting the long raw pipe manufactured for cold working into a short raw pipe having a weight suitable for cold working, the outer diameter of the long raw pipe corresponds to the axial position. Measured continuously or intermittently and squared the measured value (outer diameter 2
Multiply value) is regarded as a unit weight equivalent value, and from the unit weight equivalent value and the axial position of the long tube, a cutting position at which a short tube of a desired weight is obtained is obtained, and at that position We have previously proposed a method for cutting a cold-working raw pipe that cuts a long raw pipe (Japanese Patent Application No. 4-
280540). This method will be briefly described below.

A long raw tube used for cold working, typically a hot extruded tube, has an almost perfect circle because its inner and outer surfaces are defined by a die and a mandrel, and is caused by misalignment of both. Mainly causes uneven thickness. Then, dimensional changes occur in the tube axis direction due to dimensional changes due to tool heat during processing, changes in shrinkage due to changes in material processing heat, and the like. However, in the dimensional variation, the outer diameter variation has a larger effect on the unit weight than the wall thickness variation.

Now, assuming that the outer diameter D and the wall thickness of the long raw pipe to be cut are t, the pipe cross-sectional area S is S = π · (D / 2) ² −π (D / 2−t) ² = Π (D · t−t ² ). Here, if t / D is 10%, t ²
The term has a small influence, and the pipe cross-sectional area S is approximated by S≈π · D · t. Further, t = D · t / D, and t / D can be considered to be constant because the inner and outer diameters are determined by the dimensions of the die and the mandrel. Therefore, after all, the pipe cross-sectional area S is S ≈ π (constant ) ・ D ・ D ・ t / D (constant) S∝D ² . That is, the unit weight can be obtained from the squared value of the outer diameter.

Further, in the dimension measurement of the pipe, the outer diameter can be directly measured with high accuracy by a laser or the like, but the thickness measurement is an indirect measurement using ultrasonic waves or the like, so that the measurement error is large. Therefore, even if the wall thickness is measured to obtain a theoretically correct unit weight, the actual accuracy is low, and the unit weight approximated from the outer diameter squared value is actually higher in accuracy.

In the previously proposed method for cutting a cold working pipe, the outer diameter squared value is regarded as equivalent to the unit weight and the cutting position is determined. Therefore, simple and highly accurate cutting position management based on weight is possible. It will be possible.

However, subsequent investigations by the inventors of the present invention have revealed that the cut short tube has a considerable variation in weight depending on the dimensions, the number of divisions, etc. of the hot extruded tube.

For the purpose of further reducing this weight variation, the present inventors first investigated the influence of the method of determining the equivalent weight value on the weight variation for a large number of samples. The results are shown in FIGS. 6 and 7.

FIG. 6 shows a nominal outer diameter of 40 mm and a nominal wall thickness of 6.
When cutting a 3 mm hot extruded pipe by equal weight cutting based on the estimated unit weight, if the outer diameter itself is regarded as the equivalent weight value (A in the figure), the outer diameter squared value is the unit weight. When it is regarded as an equivalent value (FIG. B), the wall thickness is also measured at the outer diameter measurement position, and the cross-sectional area calculated from the measured outer diameter and wall thickness is regarded as a unit weight equivalent value (FIG. C). 3) shows variations in the weight of cut short tubes for three types.

Further, FIG. 7 shows the results of an examination when a hot extruded tube having a nominal outer diameter of 54 mm and a nominal wall thickness of 8.5 mm was similarly cut by the same weight.

As can be seen from FIGS. 6 and 7, in the case of any hot extruded pipe, the outer diameter itself is equivalent to the unit weight rather than the equal weight cutting in which the outer diameter squared value is regarded as the unit weight equivalent value. With equal weight cutting, the variation in weight is smaller. Further, in any case, the equal weight cutting in which the cross-sectional area is regarded as the unit weight equivalent value has a larger weight variation than the equal weight cutting in which the outer diameter itself is the unit weight equivalent value. In equal weight cutting where the cross-sectional area is regarded as a unit weight equivalent value, the weight variation of this cutting becomes large even though the weight variation is minimal in principle. It is thought to be due to the following reasons.

The wall thickness is generally measured by using an ultrasonic wall thickness measuring device and capturing the reflection of the ultrasonic wave incident from the outer surface of the tube from the inner surface of the tube. It is a hot extruded tube, and its inner and outer surfaces are rough due to blasting etc. to remove the glass lubricant. Therefore, the incident efficiency when the ultrasonic waves are incident from the outer surface and the reflection efficiency when the ultrasonic waves are reflected from the inner surface are reduced, and the values largely vary depending on the measurement position.

Since the hot extruded pipe has a large thickness deviation,
The measured value differs depending on which position in the pipe circumferential direction is measured.

When the wall thickness of the long tube is continuously or intermittently measured in correspondence with the position in the tube axis direction, the long tube is usually conveyed in the tube axis direction and arranged in this conveying path. The measurement is performed by the ultrasonic wall thickness measuring instrument described above. However, a misalignment occurs in the long tube to be conveyed, and the misalignment also reduces the measurement accuracy.

By the way, judging from the results of FIGS. 6 and 7, if the outer diameter is used as the equivalent value of the unit weight, the variation in the weight of the cut single-sized blank tube becomes small. However, to regard the outer diameter as a value equivalent to the unit weight is to ignore the thickness variation. Recently, it is expected that the hot extruded tube will become longer, and the variation in wall thickness in the axial direction of the hot extruded tube due to the thermal expansion and wear of the die and the mandrel will be larger than in the past. Therefore, if it is assumed that the wall thickness variation does not exist for all the hot extruded pipes and the outer diameter is regarded as the unit weight equivalent value, there is a risk that the weight variation may become large in some cases.

That is, it is important to consider the outer diameter as a value equivalent to the unit weight, but depending on the hot extruded pipe, there is a problem in the measurement accuracy of the wall thickness, but it was calculated from the outer diameter and the wall thickness. It is predicted that the cross-sectional area cannot be ignored.

Then, the present inventors next considered the influence of the dimensional variation of the hot extruded tube on the weight variation of the cut short tube as the equivalent diameter of the outer diameter, and performed equal weight cutting. And the case where equal weight cutting was performed by regarding the cross-sectional area calculated from the outer diameter and the wall thickness as the equivalent value of unit weight.
The survey results are shown in FIG.

In the investigation, the outer diameter and the wall thickness of the hot-extruded pipes of various lots having different sizes and materials were intermittently measured at the same position in the pipe axial direction, and the outer diameter was regarded as a unit weight equivalent value. An equal weight of each hot extruded tube was cut into the number of divisions. Moreover, the cutting data was analyzed, and the results were estimated assuming that the cross-sectional area was regarded as a unit weight equivalent value and that equal weight cutting was performed.

The chart on the left side is based on the actual cutting result in which the "outer diameter" is regarded as the equivalent value of the unit weight, and the chart on the right side considers the "cross-sectional area" as the equivalent value of the unit weight. This shows the result when it is assumed that the cutting is performed. And on both sides, the first chart shows the relationship between the "outer diameter variation rate" of each hot extruded tube and the weight variation rate of the cut short tube when the extruded tube is cut by equal weight. The second chart shows the relationship between the "wall thickness variation rate" of each hot extruded tube and the weight variation rate of a cut short tube when each extruded tube is cut by equal weight. The chart shows the relationship between the "cross-sectional area variation rate" (outer diameter variation rate x wall thickness variation rate) of each hot extruded tube and the weight variation rate of a cut short tube when each extruded tube is cut by equal weight. It is organized.

Here, the weight variation rate, the outer diameter variation rate, and the wall thickness variation rate are calculated by the following equations. Weight fluctuation rate = σ _W / X _W × 100 (%) X _W : Weight average value of short cut tubes for each hot extruded tube σ _W : Short cut for each hot extruded tube by frequency distribution calculation formula Tube weight standard deviation Outer diameter fluctuation rate = σ _OD / X _OD × 100 (%) X _OD : Average outer diameter for each hot extruded tube σ _OD : For each hot extruded tube by frequency distribution calculation formula Outside diameter standard deviation of wall thickness fluctuation rate = σ _WT / X _WT × 100 (%) X _WT : Average wall thickness for each hot extruded tube σ _WT : For each hot extruded tube by frequency distribution calculation formula Average wall thickness of

According to FIG. 8, between the weight variation of the cut short tube and the outer diameter variation rate of the hot extruded tube, and between the weight variation of the short cut tube and the wall thickness variation rate of the hot extruded tube. Indicates that there is no clear correlation whether the outer diameter is used as the equivalent weight value or the cross-sectional area is used (the two-sided charts in the first and second rows).

However, paying attention to the third side charts showing the relationship between the variation in the weight of the cut short tube and the variation rate of the cross-sectional area of the hot extruded tube (outer diameter variation rate × wall thickness variation rate), the outer diameter When the value is equivalent to the unit weight (third step on the left side), the cross-sectional area variation rate is 0.25 or less, and the variation in weight of the cut short pipe is very small, but the cross-sectional area variation rate exceeds 0.25. On the contrary, the weight variation of the cut short tube becomes large. On the other hand, when the cross-sectional area is set to a value equivalent to the unit weight (the third step on the right side), the cross-sectional area variation rate is 0.25 or less, and the weight variation of the cut short pipe is large, and the cross-sectional area variation rate is When it exceeds 0.25, the variation in weight of the short tube in cross section becomes considerably small.

Therefore, in the case of this example, the cross-sectional area variation rate is 0.
When it is 25 or less, the outer diameter is regarded as a unit weight equivalent value, and when the cross-sectional area variation exceeds 0.25, the cross-sectional area is regarded as a unit weight equivalent value and equal weight cutting is performed. Variations in the weight of the short pipe can be reduced.

The present invention is based on such knowledge, and when cutting a long raw pipe manufactured for cold working into a short raw pipe having a weight suitable for cold working, the outer diameter of the long raw pipe is And the wall thickness are continuously or intermittently measured corresponding to the position in the axial direction of the pipe, and the cutting mode judgment value J is obtained by the following formula based on the measured value, and the cutting mode judgment value J is equal to or less than a predetermined value. In the case of, the measured outer diameter value is regarded as a unit weight equivalent value, and when the cutting mode determination value J exceeds a predetermined value, it is calculated from the measured outer diameter value and wall thickness value. The cross-sectional area is regarded as a unit weight equivalent value, and from any of the unit weight equivalent values and the axial position of the long tube, the cutting position at which a short tube of a desired weight is obtained is obtained and obtained. The gist is a method for cutting a cold-working raw pipe, which is characterized in that a long raw pipe is cut at a position. J = (σ _OD / X _OD × 100) × (σ _WT / X _WT × 100) …… X _OD : Average outside diameter of each long tube σ _OD : Long tube based on frequency distribution calculation formula Outer diameter standard deviation for each tube X _WT : Average wall thickness for each long tube σ _OD : Wall thickness standard deviation for each tube using the frequency distribution calculation formula

[0033]

The cutting mode judgment value J represented by the above equation
Is the cross-sectional area variation rate (outer diameter variation rate x wall thickness variation rate)
Is. As described above, the cross-sectional area variation rate indicates the magnitude of the variation in the weight of the cut short pipe when the outer diameter is regarded as the unit weight equivalent value and when the cross-sectional area is regarded as the unit weight equivalent value. When there is the same boundary value to divide and the outer diameter is regarded as the equivalent value of unit weight, the weight variation of the cut short pipe becomes small below this boundary value and the cross-sectional area is regarded as the equivalent value of unit weight. When the boundary value is exceeded, the variation in weight of the cut short pipe becomes small.

In the method for cutting a cold working tube of the present invention,
The boundary value is obtained in advance from the cutting results of the long tube, the cutting mode determination value J is obtained at the time of cutting, and the cutting value is compared with the boundary value. Based on the comparison result, the outer diameter is equivalent to the unit weight value. It is possible to reduce the weight variation of the cut short tube by using the mode that determines the cutting position by considering it as a mode and the mode that determines the cutting position by considering the cross-sectional area as the unit weight equivalent value. .

The reference value for comparing the cutting mode judgment values J, that is, the boundary value, differs depending on the type of the long tube to be cut, and therefore, a value corresponding to the type is obtained in advance. If the long tube is a hot extruded tube, dimensions,
It is about 0.25 without being affected by the material.

[0036]

Embodiments of the present invention will be described below with reference to the drawings.

In the cutting method of the present invention, determining the cutting position is an important process. In the present embodiment, this consists of four processes of data acquisition, mode determination, calculation and correction.

FIG. 1 is a block diagram of an apparatus used for data capture, FIG. 2 is a flow chart showing a data capture procedure, FIG. 3 is a flow chart showing a mode determination procedure, FIG. 4 is a flow chart showing a calculation procedure, and FIG. Is a flowchart showing a procedure of correction.

Device used for data acquisition (Fig. 1)
Has a measuring unit 2 for measuring the outer diameter of the long tube 1. The measuring unit 2 measures the outer diameter of the long tube 1 with a laser or the like in two directions orthogonal to each other, and measures the wall thickness in four directions with ultrasonic waves. The outer diameter measurement data is an outer diameter value OD obtained by averaging the outer diameters in two directions by the OD meter 3. The wall thickness measurement data is the wall thickness value WT obtained by averaging the wall thickness in four directions with the wall thickness meter 6.
It is said that Then, these are input to the arithmetic unit 5 together with the pitch data in the tube axis direction of the long raw tube 1 measured by the pulse generator 4. The calculation unit 5 uses the input data to execute data capture, mode determination, calculation and correction processes.

In the data acquisition (FIG. 2), after the initial setting (S1), the presence or absence of the material is judged (S2). When there is a material, the outer diameter value OD _n and the wall thickness value WT _{n for} each pitch are taken in, and the product of OD _n and the measured pitch (equivalent weight value) and its total integrated value are calculated, Area S _n [= π (OD _n WT _n −WT _n ² )] and measurement pi
The product of tch (equivalent value of unit weight) and the total integrated value thereof are calculated (S3 to S8). When the material is used up, the total length L _Z of the material is calculated using the immediately preceding n (S9).

In the mode determination (FIG. 3), the taken-in outer diameter value OD _n and wall thickness value WT _n are used to measure the outer diameter average value X _OD , the outer diameter standard deviation σ _OD , and the wall thickness in the axial direction of the material. The thickness average value X _WT and the wall thickness standard value σ _WT are sequentially obtained, and then the cutting mode measurement value J is calculated using these (S1 ′ to S).
5 '). The calculated cutting mode judgment value J is compared with a predetermined reference value α (the boundary value), and when J ≦ α, the outer diameter calculation mode is selected, and when J> α, the cross-sectional area calculation mode is selected. (S6'-S8 ').

In the calculation (FIG. 4), from the unit weight equivalent value W _n stored in the data approach, , W _n total integrated value (W _total ), and target pipe weight W _p (= W _total / N)
Is calculated. As the unit weight equivalent value W _n , the product of OD _n and pitch is used when the outer diameter calculation mode is selected in the mode determination, and S is used when the cross-sectional area calculation mode is selected.
_Use the product of _n and pitch.

As a procedure, after the initial setting (S10), the unit weight equivalent value W _n is integrated every pitch, and the integrated value W is compared with the target pipe weight W _p (S11 to S13). W = W
_When it becomes _p , the position of the pitch number is set as the cutting position, and the process proceeds to the calculation of the next cutting position (S14 to S17).

When the integrated value W exceeds the target pipe weight W _p , first, the ratio of the exceeded portion to W _n (W _p -W) / W _n
Is obtained and multiplied by pitch to obtain the length Δl ′ of the exceeded portion. From pitch, this length Δl ′
Is subtracted to obtain the proportional distribution length Δl to the cutting position at the n-th pitch. Then, Δl is added to the cumulative length up to the n-1 pitch to obtain the cutting position LQ (S18). Further, the initial set value Ws is set to (W _p − to add the length Δl ′ of the exceeded portion to the calculation of the next cutting position.
W) (S19).

By repeating this, the cutting position LQ (= N-1) for N lines is obtained. Also, the length of the last one is calculated (S20).

In the correction (FIG. 5), first, the total length of the long tube is actually measured by other means. Next, using the total length L _z of the long tube obtained by data acquisition, the measured total length L with respect to L _z
The ratio α of meas is obtained (S21, S22). Then, the cutting position LQ obtained by the above calculation is multiplied by α as a correction coefficient, this correction is performed for all cutting positions LQ, and each corrected cutting position LQ ′ is output (S23 to S26).

Based on the cutting mode judgment value J, a mode in which the outer diameter is regarded as a unit weight equivalent value for performing equal weight cutting, and a mode in which the cross-sectional area is regarded as a unit weight equivalent value for performing equal weight cutting By selectively using and, it is possible to suppress the weight variation of the cut short tube as shown in FIG.

In the above embodiment, the long tube is cut at the equal weight position, but a short tube of arbitrary weight can be collected from the long tube. For example, in the case where the entire material is cut at a weight ratio of 3: 2, this cutting can be performed by setting the number of cuts in the above-mentioned embodiment to 5 and setting 3 cutting positions from the tip.

[0049]

As is clear from the above description, in the method for cutting a cold working tube of the present invention, the cutting position is determined by using the unit weight of the tube, so that an equal number of equal-weight divisions can be performed. Moreover, it is possible to collect tubes of arbitrary weight. Moreover, since the mode for estimating the unit weight from the outer diameter and the mode for estimating the cross section based on the cutting mode determination value, which is the cross-sectional area variation rate of the long tube, are used separately, the accuracy is high and the implementation is easy. is there. Therefore, it becomes possible to perform simple and highly accurate cutting based on the weight, and it is possible to obtain a great effect in improving efficiency in cold working, improving yield, and the like.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus used for data acquisition.

FIG. 2 is a flowchart showing a procedure of data acquisition.

FIG. 3 is a flowchart showing a procedure of mode determination.

FIG. 4 is a flowchart showing a calculation procedure.

FIG. 5 is a flowchart showing a correction procedure.

FIG. 6 is a frequency distribution diagram showing the weight variation of the cut short tube.

FIG. 7 is a frequency distribution chart showing variation in weight of the cut short tube.

FIG. 8 is a chart showing the relationship between the dimensional variation of the long tube and the weight variation of the cut short tube.

FIG. 9 is a chart showing the relationship between the dimensional variation of the long tube and the weight variation of the cut short tube.

[Explanation of symbols]

 1 Long tube to be cut 2 Outer diameter measuring part 4 Pulse generator 5 Calculation part 6 Thickness gauge

Claims (1)

[Claims] 1. When cutting a long raw pipe manufactured for cold working into a short raw pipe having a weight suitable for cold working, the outer diameter and the wall thickness of the long raw pipe are set in the axial direction of the pipe. The cutting mode judgment value J is obtained by the following formula based on the measured value continuously or intermittently, and when the cutting mode judgment value J is a predetermined value or less, The diameter value is regarded as a unit weight equivalent value, and the cutting mode judgment value J
When exceeds a predetermined value, the cross-sectional area calculated from the measured outer diameter value and wall thickness value is regarded as a unit weight equivalent value,
From any one of the unit weight equivalent values and the tube axial direction position of the long tube, a cutting position at which a short tube of a desired weight is obtained is obtained, and the long tube is cut at the obtained position. Method for cutting cold working tube. J = (σ _OD / X _OD × 100) × (σ _WT / X _WT × 100) …… X _OD : Average outside diameter of each long tube σ _OD : Long tube based on frequency distribution calculation formula Outer diameter standard deviation for each tube X _WT : Average wall thickness for each long tube σ _OD : Wall thickness standard deviation for each tube using the frequency distribution calculation formula