JPS62124007A - Stretching length control method for stretch reducer - Google Patents

Abstract

PURPOSE:To obtain products having a high dimensional accuracy by measuring the wall thickness and length of a tube in a hot rolled condition, checking the sufficiency of the target stretching length, and correcting a predected weight of the tube end thickened part of the succeeding tube based on the difference between a calculated weight of a tube end thickened part and the predicted value. CONSTITUTION:When the weight WBM of a billet 20 before rolling is measured by a weighing scale 22, a controlling computer 32 subtracts the predicted weight of a tube end thickened part 10A from the WBM and calculates the target stretching length lT. A wall thickness and length of a tube 10 rolled by a stretch reducer 24 are measured by a wall thickness meter 28 and a length meter 30 in a hot rolled condition. The computer 32 calculates a measured weight of the part 10A based on the above wall thickness profile and checks the sufficiency of the stretch length lT. Then, the predicted weight of the part 10A of the succeeding tube 10 is corrected based on the difference between a measured value and a predicted value of the thickened part 10A. In this method, tubes having a dimensional high accuracy are obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for controlling the elongation length of a stretch reducer, and in particular, it is suitable for use in seamless vibrating reduction mills, stretch reducers, and forge welded tube mills to control exit wall thickness. The present invention relates to an improvement in a stretching length control method of a stretch reducer for controlling the stretching length of a duplex to a target value.

[Prior art 1] A method for controlling the elongation length of a tube rolled by a stretch reducer used as a final reduction mill for hot seamless pipe rolling to a target value is known, for example, in Japanese Patent Publication No. 51-43469 and Japanese Patent Application Publication No. 51-43469. These techniques are disclosed in Japanese Patent No. 60-21114, etc., but all of these techniques assume that the wall thickness of the tube 10 rolled by the stretch reducer is flat up to the tube end, as shown in FIG. standing in [Problems to be Solved by the Invention] However, as is well known, the tip and rear ends of a tube rolled with a stretch reducer are areas where tension is difficult to be applied, and it is difficult to apply tension to the tip and rear ends of a tube rolled with a stretch reducer. As shown in Fig. 4, the tube ends are increased in both cases when the tube ends are rolled, or when O-le rotational speed control is applied to apply more tension to both ends of the tube than in the center of the tube. A flesh portion 10Δ is generated. Nevertheless, conventionally, the target elongation length J2 is determined by the following formula.
T was calculated and used as it was to control the length of the elongation. AT-W8M(1-α) /(πγ tv (CIT-wo ding> )...(1)
Here, W8 is the actual value of billet weight, α is the scale loss of the heating furnace, π is pi, γ is the density at the time of tube rolling,
tT is the average wall thickness of the tube, and DT is the outer diameter of the tube. However, as is clear when considering the constant mass flow law, the above method (1) was performed without considering the presence of the thickened part at the pipe end.
It is clearly unreasonable to use the target stretch length J2T calculated by the formula as it is, and an accurate target stretch length cannot be obtained. Furthermore, there is a problem in that no method has been proposed for feeding back the difference between the length and the exact target length.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned conventional problems, and is a stretch reducer that can determine the target stretch length with extremely high accuracy and, therefore, can obtain a tube with good wall thickness dimensional accuracy. The purpose of the present invention is to provide a stretching length control method.

[Means to solve the problem]

The present invention is a stretch reducer stretch length control method for controlling the stretch length of a dupe rolled by a stretch reducer to a target value, as shown in FIG. The target elongation length of the tube is determined from 1Iifil, which is obtained by subtracting the predicted weight of the thickened portion at the end of the tube, and the wall thickness and length of the tube rolled with the stretch reducer are measured hot. Calculate the actual weight of the thickened part of the pipe end from the thickness profile, check whether the target elongation length is 18 from the measured length, and adjust according to the difference between the measured weight of the thickened part of the pipe end and the predicted weight. The above objective was achieved by correcting the predicted weight of the thickened portion of the pipe end of the next duplex.

[Effect]

In the present invention, when controlling the elongation length of the tube rolled by the stretch reducer to a target value, the first piece at the start of rolling is determined based on, for example, an empirically proven double-end profile model. The predicted weight circumference is determined, and the target elongation length of the tube is determined from the billet weight ω before rolling minus the predicted weight ω. In addition, the wall thickness and length of the tube rolled by the stretch reducer are measured hot using, for example, a hot thickness meter and a hot length meter, and the thickened portion at the tube end is determined from the measured wall thickness profile. In addition to calculating the actual weight of the measured weight, it is confirmed whether the target elongation length has been obtained from the measured length. Furthermore, depending on the difference between the actually measured flit of the thickened part of the pipe end and the predicted I■ gate, we can predict the thickened part of the pipe end after the second piece. I am trying to modify Il[ffi. Therefore, the target elongated length can be determined with extremely high accuracy, and a tube with good wall thickness dimensional accuracy can be obtained. To explain in more detail, for the first piece of the rolling lot, the billet weight Ifkw is measured, and from the rolling tip wall thickness profile model tvop (i) and the rolling trailing edge wall thickness profile model teor (i), The weight of the thickened part of the tube end is 1uwvop (tip type ta > + Weor < rear end type I
Find f ). Here, since it has been empirically known that the wall thickness profile model (i) varies depending on the rolling conditions, an independent model is determined using actual measurement data from past rolling results. These models can be expressed, for example, by the following equations. trap (i)− a(p−i) 3+ b(p
-i) 2+c(P-i)+d・・・・・・・・・
・(2) t 8 0 (i) − a”
(P − i) '+ b− (
P-i)2+c-(P-i)+d-・・・・
...(3) Here, i is sampling "It"? L, P are quantization lengths or pitches, a, a=, b, b-1c, c=
, 'd1 (M is a coefficient. This model is applied from the tube end until the target wall thickness tT is reached. If the above model is used, the tube end weight 1, that is, the tip type fi) WTop and the rear end weight w90T are respectively expressed by the following equations. WTop-ffi7r7 jvop (i) i oligo I X (DT - trap (i))
tsoy (i)) XP-Σπγ tr (Dr- d) As shown in the formula, from the actual billet weight W day H, the tip weight W7OF and the rear end mf
It can be obtained by subtracting Rwe o t. WBM--WBM-WTOP-WBov...(6
) Therefore, the accurate stretchability A with the stretch reducer
T is finally expressed by the following equation. p-nee WaM-(1-α)/(πγ ty (DT-tv))...(7) Next, calculate the wall thickness and length after this one piece is rolled with a stretch reducer, for example, by hot rolling. Measure with a wall thickness gauge and hot length gauge. The wall thickness measured with a hot wall thickness gauge is measured in quantized length units P, so the weight of the rolled tube JnWv
is expressed by the following formula. XpXi (8) Here, N is the total number of samples of wall thickness measured over the entire length of the tube. Normally, the scaled quality P is 100n pitch, so in order to absorb this scaling error, take the ratio of the actual elongation length βτH measured by the hot length meter and NXP, as shown in the following equation, The tube weight W T calculated by the equation (8) above is corrected to obtain the actually measured tube weight lit W TM. WTM-W×(λ×M/ (NXP>)・= (9)
Next, as shown in the following equation, the difference ΔW between the actually measured tube ff1ffiW calculated using equation (9) and the billet weight excluding the scale loss due to the heating furnace is determined. Δw-WTM WBM(1-α)...(10)
The difference ΔW obtained by this equation (10) is used as a model error, for example, in the form of the following equation, and the prediction weight for the thickened portion at the end of the next tube is corrected. WTOP (j+1>+ WBOT (j+1>
= (1-λ) 6w(j) +λ(WTOP(j)+WBOT(j))・
(11) Here, j is the rolling piece number and λ is the weighting coefficient. Thereafter, by repeating the above steps, the accuracy can be increased.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a stretching length control device for a stretch reducer to which the present invention is applied will be described in detail with reference to the drawings. As shown in FIG. 2, this embodiment includes a weighing machine 22 for measuring the weight of a steel slab 20 before rolling, a stretch reducer 24 used as a final reduction rolling machine for hot seamless pipe rolling, and a stretch reducer 24 used as a final reduction rolling machine for hot seamless pipe rolling. A motor control device 26 for controlling the motor driving the roll of the reducer 24, and a hot wall thickness gauge 28 for hot measuring the wall thickness of the tube at the exit side of the stretch reducer 24. Based on the outputs of the hot length meter 30 for hot measuring the length of the duplex on the outlet side of the stretch reducer 24, the pillar hIIi 122, the hot wall thickness meter 28, and the hot length length meter 30. to control the motor control device 26 tl11'
! ! and a control computer 32. As the hot wall thickness gauge 28, for example, the present applicant and others have already disclosed Japanese Patent Application Laid-Open No. 58-158510 and Japanese Patent Application Laid-Open No. 60-13331.
The radiographic thickness measuring device proposed in 0 can be used. In this case, the wall thickness can be measured online with high precision, which is effective. The effects of the embodiment will be explained below. First, as shown in FIG. 2, the weight W of the steel billet 20, which is the material of the seamless tube, is measured for each piece and transmitted to and stored in the control computer 32.The control computer 32 , the above-mentioned formulas (2) to (a) are calculated, and when the piece is conveyed to the stretch reso user 24, the motor control device The roll rotation speed is set to 26. The tube 10 rolled by the stretch reducer 24 has its wall thickness and length determined by the hot wall thickness gauge 28 and the hot length gauge 3.
In particular, the hot wall thickness gage 28 measures the wall thickness profile of the tube 10 and transmits the results to the control computer 32 for storage. The control computer 32 calculates the above-mentioned equations (8) to (11) based on the measurement results, predicts the ml of the thickened portion of the pipe end of the next piece, and determines the target elongation length of the next piece. Accurately calculate t1 for 4 pieces. From now on, repeat the above calculation. In this example, the applicant, etc. has already
Since the radiographic thickness measuring device proposed in No. 58510 and JP-A-60-13310 is used, the wall thickness can be measured online with high accuracy. Note that the type of hot wall thickness gauge is not limited to this. Furthermore, in this embodiment, the control computer 32
In controlling the motor control device 26, the method already proposed by the applicant in Japanese Patent Application No. 60-21114 is adopted, so that the roll rotation speed can be set accurately. Note that the method for setting the roll rotation speed is not limited to this.

【Effect of the invention】

As explained above, according to the present invention, the target elongation length can be determined with extremely high accuracy, and therefore, a tube with good wall thickness dimensional accuracy can be obtained, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of a method for controlling the length of stretching of a stretch reducer according to the present invention, and FIG. 2 is a block diagram showing the configuration of an embodiment of a stretch length control device for a stretch reducer to which the present invention is adopted. 3 is a cross-sectional view showing the cross-sectional shape of the tube assumed in the conventional elongation length control method, and FIG. 4 is a cross-sectional view showing an example of the actual cross-sectional shape of the tube. 10...Tube, 10A...Tube end thickening part, 4 tubes...Target elongation length, W e M...Actual billet weight, tvop(i)
, teov(i)... Thickness profile model, WT Op... Tip weight, W day OT... Rear end weight, 47M... Actual extension length, WTM... Actual tube weight, ΔW ...difference, 2o... steel billet, 22... weigher, 24... stretch reducer, 28... hot wall thickness gauge, 30... hot length meter, 32...・Control computer.

Claims (1)

[Claims] (1) In the stretch reducer stretch length control method for controlling the stretch length of the tube rolled by the stretch reducer to a target value, the predicted weight of the thickened portion at the tube end is calculated from the billet weight before rolling. Determine the target elongated length of the tube from the subtracted weight, hotly measure the wall thickness and length of the tube rolled with the stretch reducer, and calculate the actual weight of the thickened portion at the end of the tube from the measured wall thickness profile. At the same time as calculating, check whether the target elongated length has been obtained from the measured length, and predict the increased thickness at the end of the next tube according to the difference between the actual weight of the increased thickness at the end of the tube and the predicted weight. A method for controlling the length of stretch of a stretch reducer, characterized by modifying the weight.