JPH0478362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling a tube in a tube reducing mill (stretch reducer) so that the length of a tube after rolling becomes a predetermined value.

[Prior Art] Conventionally, for example, Japanese Patent Publication No. 51-43469 or Japanese Unexamined Patent Application Publication No. 1983-1982 has been used as a method for controlling the length of a rolled tube in a stretch reducer to a predetermined value.
There is a method described in the -21114 publication. That is,
In either method, first see Figure 3 or 4.
As shown in the figure, the relationship between the roll rotation speed of each stand and the control amount (hereinafter referred to as "taper amount") that determines its distribution is determined in advance. Next, as shown in FIG. 5 or 6, the relationship between the taper amount and the elongation rate of the tube is experimentally determined in advance. After preparing the above,
Depending on the measured length of the tube before rolling, the relationship between the elongation rate of the tube and the amount of taper, and the amount of taper and the number of roll rotations of each stand are determined so that the tube after rolling has a predetermined length. The roll rotation speed of each stand is adjusted according to the following relationship.

[Problems to be Solved by the Invention] However, the relationship between the elongation rate and taper amount of the tube is determined by the tube's deformation resistance, which is determined by the tube's outer diameter, wall thickness, material and temperature before and after rolling, and by the roll. It changes in various ways depending on influencing factors such as the state of the pipe and the pipe, and its quantitative analysis is extremely difficult.

In the prior art, the variation in the length of the rolled tube due to the above-mentioned influencing factors can be somewhat reduced by learning control, but sufficient control accuracy cannot be obtained.

The disadvantage of the conventional technology is that when determining the roll rotation speed of each stand, an intermediate parameter called taper amount, which is independent of the rolling characteristics, is used, so the relationship between the elongation rate of the pipe and the taper amount varies, and the The length of the tube varies.

Therefore, the present invention is capable of controlling the length of the rolled tube to a predetermined value by determining the roll rotation speed of each stand using a method based on rolling characteristics without using the parameter of taper amount. With the goal.

[Means for Solving the Problems] The present invention provides a rolling control method for a tube reducing mill comprising a plurality of roll stands, which includes: (a) setting in advance the cross-sectional area of the tube for each stand determined by the rolling schedule; (b) Measure the material weight of the succeeding pipe and the length of the main pipe before reduction rolling, and based on the reference material weight and reference main pipe length in the same lot and their measured weight and length, calculate the Find the pipe cross-sectional area ratio, (c) Compare the pipe cross-sectional area for each stand in (a) above to find the cross-sectional area correction ratio for each stand from the entry side, (d) Restrict the leading pipe. The length of the pipe after rolling is actually measured, and the cross-sectional area ratio of the pipe on the exit side of the reducing rolling machine is determined based on the length of the pipe after reduction rolling determined from the rolling schedule and the measured length, and (e) the above ( Compare the cross-sectional area of the pipe for each stand in a) to find the cross-sectional area correction ratio for each stand from the outlet side, and (f) calculate the cross-sectional area correction ratio for each stand from (c) and (e) above. (g) Convert the cross-sectional area correction ratio for each stand in (f) above to the roll rotation correction ratio for each stand, find the roll rotation speed for each stand, (h) Each of the above (g) By adjusting the roll rotation speed for each stand, the length of the subsequent tube after rolling is controlled to a predetermined value.

In the present invention, the "reference material weight" is the billet weight preset to obtain a reduced-rolled tube of a predetermined size (outer diameter, wall thickness, length), and the "reference main pipe length" is This is the theoretical length of the tube before reduction rolling obtained using the above material. Therefore, during actual rolling, the billet weight and main tube length (the length of the tube before reduction rolling) change, so the actual measurements of these are called "actual weight" and "actual length." shall be taken as a thing.

[Operation] The operation of the present invention will be explained with reference to FIG. 2.

2 is a weight scale for measuring the billet 1, 4 is a main tube rolled by the mandrel mill 3, 5 is a length measuring meter for measuring the length of the main tube 4, 6 is a stretch reducer, and 8 is a stretch tube. A steel pipe rolled by a reducer, 7 a length measuring meter for measuring the length of the steel pipe 8, 9
receives the signals from weight scale 2 and length measuring scales 5 and 7,
This is a computing unit that controls the roll rotation speed of each stand of the stretch reducer 6.

First, a rolling schedule is set for each product type and size. For example, as shown in FIGS. 1a and 1b, the cross-sectional area of the pipe is set in advance for each stand number, and this is used as the reference pattern. When the weight of the billet is measured by the weighing scale 2, it is determined from the rolling schedule that each standard value (circumferential speed for each stand, roll rotation speed for each stand, stretch reducer input, exit tube length) is set.

Next, on the entry side of the stretch reducer 6, by actually measuring the length of the main pipe 4, which is the pipe to be controlled (following pipe), before rolling with the length measuring meter 5, the reference value Loe on the entry side and the actual measurement value are determined. Find the ratio of Le. That is, length ratio (inlet side) = Le / Loe ... (1) Next, on the outlet side of the stretch reducer 6, the length of the pre-rolled tube 8 (the rolled tube that has been previously reduced-rolled) after rolling. By actually measuring the length with a length measuring meter 7, the ratio between the reference value Lod and the actual measurement value Ld on the exit side is determined. That is, length ratio (output side) = Ld/Lod (2) On the other hand, since the mass flow of each stand during rolling is constant, the following relational expression (3) holds true.

Ae・Ve=AiVi(1+Fi)=Ad・Vd=Mf ……(3) where Ae: Cross-sectional area of the pipe before rolling, Ai: Cross-sectional area of the exit side pipe from #i stand, Ad: Cross-sectional area of the pipe after rolling. , Ve: Stretch reducer inlet pipe speed, Vi: #i stand roll circumferential speed, Vd: Stretch reducer outlet pipe speed, Fi: #i stand advance rate, Mf: Mass flow, i = 1 ~ n ( n: final stand) When the variation rate for each quantity (reference value) determined from the rolling schedule in equation (3) is linearly approximated, the following equation (4) is obtained.

△Ae/Aoe+△Ve/Voe=△Ai/Aoi+△Vi/Voi+△(1
+Fi)/1+Foi=△Ad/Aod+△Vd/Vod=△Mf/Mof…
...(4) However, △: amount of variation with respect to the standard value, o: represents the standard value.

Here, in order to control the length of the subsequent rolled tube (the rolled tube that is reduced and rolled after the preceding rolled tube 8 and becomes the controlled tube), the number of roll rotations of each stand is adjusted. Strictly speaking, if the tension between each stand is varied by changing the tension between each stand, the advancement rate will change, resulting in equation (4), but in a stretch reducer, this rate of change is practically negligible. Therefore, the following formula (5) holds true.

△Aa／Aoe＋△Ve／Voe＝△Ai／Aoi＋△Vi／Voi＝△Ad／
Aod＋△Vd／Vod＝△Mf／Mof……(5) Now, in equation (5), △Ae／Aoe, △Ai／Aoi, △Ad／Aod
Explain how to find.

First, as shown in Figure 1a, the length of the tube before rolling: Le is shorter (or longer) than its standard value: Loe, that is, the cross-sectional area: Ae is larger (or smaller) than its standard value: Aoe. ) Consider the case. In this case, according to equations (6) and (7) below, so that △AD/Aod=0, the correction ratio of the cross-sectional area of the pipe of #i stand due to the change in the length of the pipe before rolling: (△Ai/ Aoi) Find e.

△Ae/Aoe=Ae−Aoe/Aoe=Ae/Aoe−1=Loe/Le−1 …(6) (△Ai/Aoi)e=△Ae/Aoe Aoi−Aod/Aoe−Aod……(
7) Furthermore, according to the law of constant volume, Equation (6) above is based on Ae・Le
= Aoe・Loe, therefore, Ae/Aoe=Loe/Le
It is derived based on the fact that

In addition, the above equation (7) is a problem of setting how the deviation rate of the cross-sectional area of the pipe to be rolled from the standard value is corrected in each stand. In other words, equation (7) shows that, as shown in Figure 1a, the difference between the reference cross-sectional area of each stand and the reference cross-sectional area of the pipe after rolling is the difference between the reference cross-sectional area of the pipe before rolling and the reference cross-sectional area of the pipe after rolling. This method calculates the ratio to the difference in cross-sectional area and distributes the deviation rate of the cross-sectional area of the pipe to be rolled from the standard value to each stand according to that ratio. .

On the other hand, as shown in Figure 1b, the length of the tube after rolling: Ld is shorter (or longer) than its standard value: Lod, that is, the cross-sectional area: Ad is larger than its standard value: Aod (or Consider learning control in the case of (small). In this case, use the following equations (8) and (9) to find the correction ratio of the cross-sectional area of the pipe of #i stand due to the change in the length of the pipe after rolling: (ΔAi/Aoi) d.

△Ad/Aod=Lod/Ld−1 ……(8) (△Ai/Aoi) d=△Ad/Aod Aoe−Aoi/Aoe−Aod……(
9) Furthermore, according to the law of constant volume, Equation (8) above has Ad・Ld
＝Aod・Lod, therefore, Ad／Aod＝Lod／
It is derived based on the fact that Ld.

Furthermore, the purpose of the above equation (9) is to learn the amount (deviation rate) in which the cross-sectional area of the pipe that has already been rolled does not conform to the standard value, and to use this information in setting it from the next time. In other words, equation (9) is
As shown in , find out what ratio the difference between the standard cross-sectional area of the pipe before rolling and the standard cross-sectional area of each stand is to the difference between the standard cross-sectional area of the pipe before and after rolling, and according to that ratio, This represents the distribution of learned values of the cross-sectional area deviation rate of the pipe after rolling.

Further, ΔAi/Aoi is expressed by the following equation (10).

△Ai/Aoi=(△Ai/Aoi)e−(△Ai/Aoi)d……(10
) The above equation (10) takes into account the cross-sectional area deviation rate of the pipe to be rolled, expressed by equation (7), and the cross-sectional area deviation rate of the pipe that has already been rolled, expressed by equation (9). , is a formula for determining the correction rate of the cross-sectional area of each stand. For example, if (△Ai/Aoi) _d = 0 for the pipe that has already been rolled, only the (△Ai/Aoi) _e of the pipe to be rolled needs to be considered; conversely, if (△Ai/Aoi) _e = 0, learning As a result, −(△Ai/Aoi) _d can be considered.

On the other hand, if the roll circumferential speed: Vk of any one stand, for example stand #k, is fixed, ΔVk/Vok=0, so the following equations (11) and (12) hold true.

△Ni/Noi=△Vi/Voi=△Ak/Aok−△Ai/Aoi……(11
) Ni=Noi(1+△Ni/Noi)...(12) However, Ni: #i Roll rotation speed of the stand Note that the above equations (11) and (12) are derived as follows. That is, Voi=・DRi・Noi Here, DRi: #i Since the roll diameter DRi of the stand is constant, linear approximation of the fluctuation rate with respect to the reference value in the above equation is △Vi/Voi=△Ni/Noi Furthermore, arbitrary If we fix the roll peripheral speed of the stand and call it stand #k, then from equation (5) △Ai/Aoi+△Vi/Voi=△Ak/Aok+△Vk/Vok, and △Vk/Vok=0. From △Vi/Voi=△Ak/Aok−△Ai/Aoi From the above, equation (11) holds true.

Furthermore, since equation (12) is defined as △Ni/Noi=Ni-Noi/Noi, equation (12) can be obtained by transforming this equation.

Note that the #k stand for calculating △Ak/Aok, which must be taken into account in the above equation (11), is:
Any stand is fine as long as the circumferential speed is fixed.
Therefore, for example, when using a 24-stand rolling mill, if you want to use the final stand #5 to #24 depending on the rolling size, for example, set k = 4 and use the #4 stand. The circumferential speed can be fixed.

The present invention adjusts the roll rotation speed of each stand as described above.

[Example] Examples of the present invention will be described below.

First, billet weight: Wb was measured and shown below (13)
Determine the standard length of the pipe before and after rolling: Loe and Lod using the formula and formula (14).

Loe=Wb(1-μe)/FeAoe...(13) Lod=Wb(1-μd)/FdAod...(14) Where, μe: Inlet scale loss rate, ρe: Inlet density, μe: Outlet Scale loss rate, ρd: outlet density, and then the length of the pipe before rolling: Le, was actually measured, and formula (6) was obtained.
Using equation (7), find the cross-sectional area modification ratio of the pipe of #i stand due to the change in the length of the pipe before rolling: (△Ai/Aoi) _e . Next, find the actual measured length Ld of the pipe after rolling before the billet, and from this and Lod of equation (14), equation (8) is obtained.
Using formula (9), find the cross-sectional area correction ratio of the pipe of #i stand due to the change in the length of the pipe after rolling: (△Ai/Aoi) _d , smooth the value if necessary, and obtain the formula (10). The cross-sectional area correction ratio of the pipe of #i stand: △Ai/Aoi is determined by the formula.

Next, the roll rotation speed: Ni of the #i stand is determined by equations (11) and (12), and the roll rotation speed is adjusted to control the length of the rolled tube to a predetermined value.

FIG. 7 shows the variation in length of the tube after rolling by the method of the present invention. Incidentally, for comparison, the variation in length of the tube after rolling by the conventional method described in the above-mentioned Japanese Patent Application Laid-open No. 60-21114 is also shown. As a result, it is recognized that according to the present invention, the deviation in length of the tube after rolling is reduced by about 1/3.

In addition, if you want to control Lod constant, calculate the target wall thickness (ted) of the rolled pipe according to the measured billet weight (Wb) from equation (15), and use this ted to determine the standard cross-sectional area of the rolled pipe. (Aod) and the standard cross-sectional area (Aoi) of each stand.

Wb=Pdπted(Dod−tad)Lod...(15) However, Dod: Standard outer diameter of the pipe after rolling [Effects of the Invention] As described above, according to the present invention, the diameter of each stand determined by the rolling schedule is By setting the cross-sectional area of the pipe in advance and actually measuring the length and billet weight of the subsequent pipe as the controlled pipe before rolling, as well as actually measuring the length of the leading pipe after rolling,
By determining the cross-sectional area correction ratio of the pipe for each stand and adjusting the roll rotation speed based on the fact that the mass flow change rate of each stand is constant, the length of the pipe to be controlled after rolling can be determined. control to a predetermined value,
It becomes possible to improve the control accuracy of the length after rolling.

[Brief explanation of the drawing]

Figures 1a and b are diagrams for determining the cross-sectional area correction ratio of the present invention, Figure 2 is a control system diagram showing the control method of the present invention, and Figure 3 is the roll rotation speed and taper amount of conventional technology 1. Figure 4 is a diagram showing the relationship between roll rotation speed and taper amount in Conventional Technology 2, Figure 5 is a diagram showing the relationship between taper amount and tube elongation rate in Conventional Technology 1. FIG. 6 is a diagram showing the relationship between roll rotation speed and taper amount in Prior Art 2, and FIGS. 7a and 7b are diagrams showing the effects of the present invention. 1... Billet, 2... Weight scale, 4... Main pipe,
5, 7... Length meter, 6... Stretch reducer, 8... Steel pipe, 9... Arithmetic unit.

Claims (1)

[Claims] 1. A rolling control method for a tube reducing mill consisting of a plurality of roll stands, which includes: (a) setting in advance the cross-sectional area of the tube for each stand determined by the rolling schedule; and (b) controlling the material of the subsequent tube. Measure the weight and the length of the main pipe before reduction rolling, and calculate the pipe cross-sectional area ratio on the entry side of the reduction rolling machine based on the reference material weight and reference main pipe length in the same lot and the measured weight and length. (c) Calculate the cross-sectional area correction ratio for each stand from the entry side by comparing the cross-sectional area of the pipe for each stand in (a) above, and (d) Find the length of the pipe after reduction rolling of the leading pipe. Based on the length of the pipe after reduction rolling determined from the rolling schedule and the measured length, find the cross-sectional area ratio of the pipe on the exit side of the reduction rolling mill, Calculate the cross-sectional area correction ratio for each stand from the outlet side by comparing with the cross-sectional area of the pipe, (f) Calculate the cross-sectional area correction ratio for each stand from (c) and (e) above, and (g) Convert the cross-sectional area correction ratio for each stand in (f) to the roll rotation correction ratio for each stand, calculate the number of roll rotations for each stand, and (h) calculate the number of roll rotations for each stand in (g) above. A rolling control method for a tube reducing mill, characterized in that the length of a subsequent tube after rolling is controlled to a predetermined value by adjustment. 2. The rolling control method for a tube reducing mill according to claim 1, characterized in that the roll rotation speed in (g) is determined by the following formula. Ni = Noi (1 + △Ak / Aok - △Ai / Aoi) Ni; Roll rotation speed for each stand Noi; Reference rotation speed for each stand △Ak / Aok; For any one stand with constant circumferential speed Pipe cross-sectional area correction ratio △Ai／Aoi; Pipe cross-sectional area correction ratio for each stand