JPH0252108A - Method for deciding changing time of mandrel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining when to replace a mandrel in a tube rolling mill that reduces the wall thickness of a tube material by using grooved rolls while passing the mandrel through the tube material.

Conventionally, the method of manufacturing tubes by rolling involves rolling a blank tube pierced with a piercer or the like to a predetermined outer diameter and wall thickness using a mandrel mill, plug mill, etc., and there are various rolling methods.

In recent years, mandrel mills have been adopted from the viewpoint of productivity, such as rolling efficiency, yield advantages, and ease of automation, as well as from the viewpoint of quality, such as the quality of the inner surface of the tube material, the accuracy of wall thickness distribution, and the occurrence of scratches. It's starting to look like this.

This rolling method using a mandrel mill also uses PFM (Pulle
l Float 1andrel m1ll), SFX
(Sea lRe5trained Ploatl
ng 5andrel m1ll), RRM(
Fully e Re5tralned & Retr
Methods such as ``acted Iandrc'1a+1li)'' have been implemented. The above-mentioned mandrel mill methods are classified mainly based on the difference in the operation of the mandrel, but the method still involves rolling the raw pipe passed through the mandrel between a grooved roll and a mandrel.

FIGS. 1 and 2 are schematic diagrams before and during rolling with a mandrel mill. The figure shows a configuration based on RRM.

In FIGS. 1 and 2, 1 is a mandrel propulsion block to which a mandrel bar 2 is connected, and a mandrel 3 is further connected to this mandrel bar 2.

4 is a propulsion device for the mandrel propulsion block 1, and 5 is a drive motor for the propulsion device W4. The mandrel propulsion block 1 slides on a track, but the track is not shown in the figure. 6 is the mandrel drive control beam, as shown in Figure 2.
During rolling, the mandrel propulsion block 17 is connected to the solenoid 1.

The mandrel drive control beam 6 is controlled by a mandrel drive control device 7 and a mandrel drive motor 8 which is a drive source.
, controlled. A gear mechanism or a hydraulic mechanism is generally used for the mandrel drive control device 7. The drive rod 9 is drive-controlled by the mandrel drive control device 7, and the mandrel drive control beam 6 connected to the drive rod 9 is connected to the mandrel propulsion block 1 and the mandrel propulsion block connected to the mandrel drive control beam 6. The mandrel 3, which is integral with the mandrel 1, is driven and controlled.

When the raw pipe 10 pierced by a piercer etc. comes onto the entrance table, the mandrel propulsion block 1 advances and the mandrel 3
passes through the gaps between the raw pipe 10 and the grooved rolls rl, rz...'n-1r incorporated in the rolling stand, and at the same time, the mandrel propulsion block 1 and the mandrel drive control beam 6 are connected.

While the raw pipe 10 is being rolled by the grooved rolls r1 to ro, the movement and speed of the mandrel 3 are controlled by the mandrel drive control device 7.

14- (1,) , 14- (2) ,...1
4-(nl) and 14-(n) are motors for driving the grooved roll r112n-1''n, respectively.

In Fig. 1 and Fig. 2, the grooved roll “1゜2
n-1"n is drawn in a line as shown in the figure for convenience, but in reality, it is common for the roll axis of each stand to be arranged at an intersection angle of 906 with the adjacent stabilizer.Actual work It is extremely important to control the tension or compression force acting on the tube material passed through the six stands to an appropriate value in accordance with the rolling conditions.

The tension acting on the tube material between the stands or the improper tension within the f-line will not only change the diameter and wall thickness of the tube material, resulting in uneven dimensions in the rolled product, but also cause bulges, scratches, etc. This will result in serious defects. Furthermore, if the mandrel is not replaced at an appropriate time, there is a problem that the internal columnar shape of the product pipe material will not be good.

However, in tube rolling mills such as mandrel mills that are equipped with a mandrel and grooved rolls, and rolling is performed between the mandrels and grooved rolls, the mandrels are not replaced at an appropriate time. is the current situation.

The present invention provides a mandrel that can quantitatively determine the coefficient of friction between the inner surface of the pipe material and the surface of a mandrel such as a mandrel, making it possible to obtain a product with good inner surface properties without making a mistake when replacing the mandrel. This provides a method for determining when to replace the

First, we will discuss the basic model when a tube material is rolled between a mandrel and a grooved roll. FIG. 3 is a schematic diagram showing a tube 11 being rolled between a grooved roll r and a mandrel 3. Ll: The pipe before rolling (O is called the raw pipe 10, but during compression, it is all called the pipe material 1).

In Figure 3, there is a rear tension T! on mandrel 3! Lt is working and the mandrel bar T, -0 or the rear tension of the tube material T, and B, ++
1 ra, 1 and the forward tension T of the tube material are both T, -m, ++!
Suppose that it is in the m, +T, -00 state. Above front and back 4/ζm, +
+1 The force may be a compressive force.

Such a state corresponds to RRM or SFM of the above-mentioned mandrel mill rolling methods, and corresponds to the case where rolling is performed only on the first stand or the last stand.

In Fig. 3, the rolling weight is P. , the rolling torque is G,. Further, the friction coefficient of the inner surface of the mandrel 3a tube material 11 is assumed to be μ. Rolling torque G. is (1).

It is expressed by the formula.

G 1,0 −T,,' R1+ 28!
``P+,o''' (1) In the formula (1), R is the average roll radius determined by the shape and dimensions of the grooved roll, the dimensions and shape of the tube material before and after rolling, and the diameter of the mandrel; In rolling plate materials or long steel,
Generally, it corresponds to the physical quantities expressed as 2aI=Gl, 0''i, 0.

Since the mandrel 3 and the tube material 11 always have a relative velocity, μ,
is the kinetic friction coefficient, and the following equation (2) is expressed as ! There is a relationship.

TB, I-μ, -p,,, ------・
(2) From equations (1) and (2), calculate the following equation (I7).

G − (μ R, + 2 a,) P *, o−
...(3) l, b 1 1 1
That is, equation (3) is the relational equation between the rolling load and the rolling torque when there is no tension when rolling a tube material using a mandrel. However, in a continuous rolling mill, tension or compression forces act on the rolled material on the front and rear surfaces of the stand.

FIG. 4 is a schematic diagram during continuous rolling on three stands.

As mentioned above, adjacent stands have their roll axes 90 degrees apart from each other.
Although they are arranged at an intersection angle of 0.06, they are shown as shown in the figure for convenience. In FIG. 4, the rolling torque G of the l stand is expressed by the following equation (4).

G, -T -R-T -R+
B, J I B, i+l
II! +2a P +ΔG, -ΔG, , -(
4) 1 1 +, b Here, from the balance of the force in the rolling direction, there is a relationship expressed by the following equation (5).

TB, i″″μm °PI T −μ · P B, ++l ++1. II+ Therefore, equation (4) becomes the following equation.

)...(5) G, -(μ, ・R4・P.

I l11 1'' country゛R country -P, ・1) + 2 a + -P + +ΔGi, b - ΔGj, r
In equation (4) and equation (6), ΔGi and b are stone materials 11
This is the change in torque from the time of no tension (hereinafter referred to as rear torque) due to the generation of rear tension Tm, i when viewed from one stand.
m, I+1 due to the occurrence of torque change from the state of no tension (hereinafter referred to as forward torque)
It is. From equation (6), ΔG, , r becomes equation (7).

ΔGi, r= (μI ``'i − Pi − μ country ° R country”
1ll) +2a, P, -G, +△Gi, b... (7) In order to make the front tension of the l stand zero, the correction amount of the roll rotation speed of the l stand is proportional to the front tension torque of the l stand. The integral control gain g is multiplied by the following equation.

ΔN −g ・Δ system, f ・・ (8)
I Ni indicates the motor revolution number of the l stand. Furthermore, when controlling the tension applied to the front attachment of the l stand to T, m,++1, 4ΔN becomes the following equation.

ΔN-g(ΔG1.f-ΔGi, T)...(9)!
I In equation (9), b'', ΔGi, T is the target tension T,
The front target tension torque corresponding to ta, ++1 is expressed by the following equation (10).

ΔG, −・R1・Tm, I. 1 +, T (1+f) ・ (10)η, is
The reduction ratio (gear ratio) of the l stand, fl is the advance rate of the l stand. At this time, the rear tension torque ΔG acting on the 1+1 stand is the same as +l, b. Since the rolling force required for rolling the mill can be regarded as constant, the following (
1) Equations 2 to (11) are the basic models for tension control when pipe material is continuously rolled using a mandrel and grooved rolls. They introduce the tension acting on the mandrel and the friction coefficient between the mandrel and the pipe material, and This is an analytical model that takes into account the tension applied to the tube itself and the torque arm of tube rolling.

FIG. 5 shows a conceptual diagram in which, for example, a load detector 12 is installed in order to know the tension TB acting on the mandrel. In Figure 5 (
Figures a) and (b) show examples in which a load detector 12 is installed on the mandrel propulsion block 1 to detect the tension To applied to the mantle lever 2 connected to the mandrel.

In addition, in FIG. 3C, the mandrel drive control beam 6 and the drive ring 9 are connected via a load detector 12 to detect the tension T8 applied to the mandrel bar 2.

It is also easy to modify an existing mandrel mill and install a load detector to detect the tension in the mandrel.

Alternatively, if the mandrel drive torque GB of the mandrel drive motor 8 shown in FIGS. 1 and 2 is known, the tension Tn applied to the mandrel 3 can be determined by the following equation (2).

GBωB=TB VB+αB...(12)ω
B is the angular velocity of the mandrel drive motor 8, ■ is the motion speed of the mandrel, and αB is the mandrel drive control device 7.
is a constant determined by the use of .

The mandrel motion speed VB is a rigid body that does not undergo plastic deformation, and can be easily determined from ωI3 and the reduction ratio of the mandrel drive control device.

The rolling load P can be detected by a load cell installed in the rolling mill, and the rolling torque G can generally be calculated using the following equation (14) when a torque converter is not installed.

... (14) In equation (14), V is the motor voltage, ■ is the motor current, R is the armature resistance, N1 is the motor rotation speed, β, γ, and δ are constants, and the first term on the right side is the motor torque , the second term is acceleration/deceleration torque, and the third term is loss torque.

Thus, the tension, rolling load, and
If the rolling torque is known, the friction coefficient between the inner bend of the tube and the mandrel during rolling can be determined, and it is possible to determine when to replace the mandrel based on the change in the determined friction coefficient over time.

Hereinafter, a case of tensionless control (zero tension acting on the pipe H) of pipe material rolling will be specifically described as an example. FIG. 6 is a conceptual diagram showing a state in which rolling is performed only in the first star in an n-stand mandrel mill, and the mandrel 3 penetrates through the n-stands, and the direction of movement is backward (upstream). It is. This corresponds to the RRM described above.

The tube material 11 is in a state where no tension (compressive force) is acting on it, the rolling load is P, the rolling torque is 1, OG, and the tension of the mandrel is TB, I. Rolling 1
．． The suffix 1 for 0 load and rolling torque means the first stand, and 0 means no tension.

If there is tension, 1. as in P and G.
1 1.1 Show. Further, the suffix 1 for the mandrel tensions To and t indicates that rolling is performed only on the first stand. T.B.
, i indicates the mandrel tension when rolling is performed from the first stand to the first stand. The same applies to the suffixes of the symbols below.

In Figure 6, the relationships (15) and (16) are shown.

G −μ・P IR+2a1・Pi,.

1.0 1 1,0 1...(ko 5) TB, 1 - μm ・P, ro
... (16) From equations (15) and (16), ul and a
r is 4'f'Wed. Next, FIG. 7 is a conceptual diagram in which the pipe material 11 is rolled by the first stand and the second stand, and tension Tm, l is generated in the pipe H between the first stand and the second stand. . The rolling l・lux G1 of the first stand is G − (μm・Pl−R2・R2)R1+ 28
t P i -ΔG1.1' Therefore, ΔG - (μm · Pl - R2 · R2) R.

1, r +2a P −G = (17) 1 1
l Also, TB, 2-μl -P1+μ2 ・R2...(
18) R2 is calculated from equation (18), and ΔG1. r is calculated.

The speed correction amount of the first stand is ΔN −g ・ΔGI, f ... (1
9) At this time, the rear tension torque ΔG2 of the second stand. b
Therefore, G2,0''=62+Δa21.-(20)
If the control is completed before the pipe material 11 is caught in the third stand, the second stand will also be in a tension-free state, and the detected rolling load P2 and rolling torque G2 at this time will naturally be in the relationship of equation (21). be.

P-PG-G
... (21) 2.0 2 ゝ 2,0
2 At this time, since the following equation (22) holds, (22
) Calculate G2 using the formula.

G = μP R+ 2 a 2 P 2. o
...(22)2.0222 FIG. 8 shows a conceptual diagram when the tube material 11 is caught up to the third stand. With the start of rolling on the third stand, some tensions T 1 , T 2 , m,! Ill,2 is generated and a corresponding tension torque is generated.

First stand forward tension torque ΔG1. r is 6″G1.
1''''(I P1 ''2 °P2)R.

12a −P −G =・(23)II Second stand rear tension torque ΔG2. b is therefore,
Front tension torque ΔG2 of the second stand. .

is aG, r-(“2'P2-3' P 3) R2+ 2
22 P 2 G 2 + ΔG2. b(25) in formula μ3
is calculated using the following formula.

TB, 3-μm ・Pt+μ2 ・P2+μ3 ・R3
... (26) ΔG22 expressed by equation (25). can be calculated, and therefore the speed correction amount ΔN2 of the second stand is ΔN2""2'Δ
G2. r ''' (27) At this time, the speed correction amount ΔN1 of the first stand is: Rear tension torque ΔG3.b of the third stand Therefore, the non-tension torque G3.0 of the third stand is 63.0 = 63+ΔG3.b
-('3 (1) If the control is completed before the pipe material 11 is caught in the fourth stand, the third stand is also in a tensionless state, and the detected rolling load at this time is R3 and the rolling torque is G3. Then, P -P G -G
・-(3]) 3.0 3' 3.0
363.0 ""3 R3,OR3+2a3 R3,0
... (32). G3 is calculated using equation (32).

It is possible to calculate the friction coefficient μm for all stands by performing the same calculation below. When the tension of the tube material rolled between the mandrel and the grooved roll is controlled to be constant, the friction coefficient μ can be determined in the same manner using a basic model based on equation (9).

According to the present invention, the friction coefficient μI between the mandrel surface and the inner surface of the tube can be determined by direct calculation from the mandrel tension value, rolling load, and rolling torque. The mandrel wears out under harsh rolling conditions and the surface t
n also increases. If this wear on the mandrel surface or increase in surface roughness exceeds a limit, it will have a great negative effect on the inner surface properties of the tube material. Therefore, the mandrel is empirically replaced at a certain time, for example, based on the number of rolled pipes or the number of rolled tonnages.

According to the present invention, it is possible to quantitatively understand the change over time in the coefficient of friction between the mandrel and the inner surface of the pipe material, and for example, as shown in Fig. 9, it is possible to know when to replace the mandrel by setting the upper limit of the coefficient of friction μm. . In Fig. 9, the horizontal axis is time, the vertical axis, which explains changes and mandrel replacement timing, is the friction coefficient, and the shaded area is a diagram of the mandrel.

This is the upper limit of the friction coefficient μ, which indicates when to replace the drill. Quantitative knowledge of changes in the coefficient of friction over time will enable concrete improvements to be made to mandrel lubrication systems and lubricants.

As described above, according to the present invention, the friction coefficient between the inner surface of the pipe material and the surface of the mandrel such as a mandrel can be quantitatively determined, and products with good inner surface properties of the pipe material can be obtained without erroneously knowing when to replace the mandrel. Obtainable.

Claims (1)

[Claims] A tube material rolling mill comprising a mandrel and a rolling stand having a plurality of pairs of grooved rolls into which the rolled tube material penetrated by the mandrel is inserted, and rolling the tube material by the grooved rolls and the mandrel, A method of determining the coefficient of friction between the inner surface of the pipe material being rolled and the surface of the mandrel from the tension applied to the mandrel and the output of the mandrel drive motor, and determining when to replace the mandrel based on changes in this coefficient of friction over time.