DE2637542A1 - PERFORATION PROCESS FOR THE MANUFACTURE OF DOLLARS - Google Patents

Description

Dipl.-Phys. Dr. W. Hassler Patent attorney in Lüdenscheid Dipl.-Chem. F. Schrumpf August 19, 1976 Patent attorney in Düren, Ά 7fi 197

Applicant: Nippon Steel Corporation
Tokyo / Japan

Hole punching process for the production of tubular blanks

The invention relates to a press-roll perforation method for production of tubular blanks, in which a polygonal billet is driven axially between a pair of one above the other arranged rollers each with a semicircular profile and against a perforated mandrel arranged between these rollers is pressed.

The conventional punching methods for seamless metal pipe (for example seamless steel rotation) include, for example, press punching and the skew roll piercing method. In recent times, a method is gaining interest, according to which cheap square billets with square or rectangular cross-section can be pressed and punched in one operation in a round hollow mold. According to the press-roll-punching process, a square billet is fed to a pair of rollers arranged one above the other, wherein force is applied in the axial direction. The tube billet is formed by piercing the billet core when it is rolled.

When designing and building the roller piercing press, the rolling force is an important factor in correctly determining the strength and Construction of the punch press, and the specification of the motor for the roller drive and the strength and construction To determine the power transmission system, you need precise knowledge of the roll torque, but so far there is none reliable calculation formula has been given.

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The factors that make the theoretical assumptions difficult are that the press roll piercing process has only recently come to this point has been investigated in order to at least bring it to practical use, and that the peculiarity of the deformation condition in Punch the square knot while pressing it into the circular one Ball profile and the simultaneous rolling of the outer surface could not be fully clarified so far. So far it is missing still on a secured process technology.

The object of the invention is to develop a press-roll perforation process, which makes it possible to build systems of suitable dimensions while keeping forces such as rolling force as low as possible To create rolling mill drive torque and to stabilize such forces.

The press-roll perforation process according to the invention not only solves this task, but also leads to an improved roll stitch effect and increased pipe quality while avoiding Rolling defects during punching, and enables deformation without unnecessary stress.

According to the invention, this object is achieved in that the Keeps the thrust at a predetermined value, that of the tension above the - .; flow rate of the billet at the beginning of the hole the actual stress occurring at the beginning of the piercing process possibly exceeding the yield stress can, by setting the «chuk speed and / or the Circumferential speed of the rollers the volume of billets to be pressed in per unit of time is approximately equal to the volume of the billets emerging from the rollers Holds tube blanks and causes the intended roll stitch of the billet.

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The invention is exemplified below with reference to the drawing explained.

Fig. 1 is a cross section through a press roll punching device for performing the method according to an embodiment of the invention

Fig. 2 shows in a graphical representation the relationship between the selected values of the shear stress and the occurrence of Missing stitches in%.

Fig. 3 shows in a graphical representation the relationship between the speed of thrust, the temperature at the forehead of the club and the reaction voltage.

Figure 4 is an electromagnetic oscillogram under control of the process with constant pushing speed.

Fig. 5 is an electromagnetic oscillogram when the process is controlled with constant rolling force.

Fig. 6 is an electromagnetic oscillogram under control • with constant roller torque.

Fig. 7 is a block diagram of the control system according to the embodiment the invention.

First of all, the press-roll perforation process is explained as follows:

As shown in Fig. T, a square billet 3-1 is made using a push rod 2 and a cylinder 1 between rollers 4,4 ' pressed, which are set in rotation by a drive 20. In front of and behind the rollers 4, 4 'are an inlet guide 5 and one Outlet guide 6 is provided so that the material 3, namely the square billet 3-1 and the tube billet 3-2, on the center line X-X

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the rolling device can be held. The aforementioned rollers 4, 4 ′ are provided with a circular ball profile, and the mandrel 7 is held by means of the mandrel bar 8 in the center of the passage between the two rollers 4, 4 '.

In the rolling frame, the square billet 3-1 becomes due to the pressing force of the cylinder 1 and the driving force of the rollers 4,4 'pushed forward. The core of the square billet is made by means of the mandrel 7 perforated and expanded tubular, and its outer surface is continuously rounded by the ball profile of the rollers. The deformation is almost complete at the center line Y-Y of the nip. The tubular blank 3-2 and the mandrel rod 8 are also included Help the guide rollers 10 held.

In the practical implementation of the above-described press-roll-punching method, according to the invention, two types & i of pressing possible,

One of these two methods works with constant pressure. The square billet is punched by keeping the thrust applied in its axial direction constant during the punching process, whereby the shear stress or ρ (shear force / material cross section) is set so that it is almost equal to the flow stress Ci m of the material (with a constant change in shape of 1 %) is.

The other method provides a constant (or specific) speed, the thrust F _n and the assumption £ "p><5" m being fixed. The thrust speed is chosen so that the volume of the billet to be advanced per unit of time and the volume of the tube billet to be withdrawn from the rollers per unit of time are practically the same.

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In concrete terms, the pushing speed Vp is determined by the formula

V _R (1)

where K _{1 is} a constant correction factor and depends on the material to be processed (for example, K ₁ for rolling billets is 1.0, while for continuous casting billets a value of
1.06 is to be applied). Even if the stick makes you special
has a large center space, K 'is no greater than 1.1. Accordingly is

*1 -
^L 2

the reciprocal of the constant elongation ratio.

K "is the ratio of the roller circumferential speed to
The exit speed of the material and the roller circumferential speed V "is obtained according to the following formula, in which the circumferential speed at the bottom of the roll barrel V _n and the smallest diameter of _{the roll barrel D .. T. T} as well as the profile

MIN

diameter d, while K ^ has a constant value from 0.95 to 1.20 has:

^D MIN ⁺ ° ' ^{2 d}

V-, can be determined at one point, for example at a ball area with the maximum diameter, where the calculation can be carried out easily, and the roller peripheral speed of the
Roll barrel with the selected diameter is then V ', while the K ₂ corresponding constant K' is calculated according to ₂

κ · ₂ = K ₂ v _R / v _R

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Since only the ratio between the roller circumferential speed and the feed speed is included in formula (1) when working with constant thrust speed, V_ and V _n can be changed if this ratio is observed, while K ₁ and K_, depending on the type of billet material and the rolling conditions are to be determined, are kept constant during the rolling process. In the press-roll punching method, however, unsatisfactory roll stitches often occur. This is because the push rod engages the rear face of the billet, and its front end is pressed against the mandrel held in the center of the rollers, and only when the front end has passed the rollers and leaves does the driving force of the rollers start the constant value to reach. The shear force required to complete the roll pass often exceeds the flow stress of the material. This tendency is aggravated by the fact that the temperature drop after the billet is removed from the heating furnace is greater at its front end than in the middle, the more time passes before the start of punching, and the difference is then made in the resistance to deformation noticeable .. The thrust required for the complete waltz engraving varies depending on the condition of the rollers, the dome and other parts of the punching device or the billet, but its value corresponds approximately to the flow stress of the material,

The relationship between the set value of the shear stress and the percentage occurrence of skipped stitches is shown in FIG.

When the ratio 6 * p> = 6 "m has been set and the roller pass due to some unfavorable conditions, both of them cause deformed front ends of the columnar billet initially a compression and take on a dog-bone-like shape, so that the contact surface with the rollers is increased. Then the compression in the middle part takes place at a lower speed. This condition continues until the Stitch is finished. However, if (Tp <6 * m, this tendency

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do not observe, there is a risk of a skipped stitch. If the shear stress Öp is set to a value that is sufficiently larger than 6 * m, as shown in FIG. 3, a reaction stress 6 * £ (= reaction force on the push rod / material cross section) acts on the push rod. Of course, the reaction stress [& £ ) cannot exceed the set value of the shear stress ((Tp). *

Curve A: The punching can be done because the pushing speed is too high do not continue. During the punching process, the billet sticks in front of the rollers, and so does the punching is unsatisfactory.

Curve B: The tendency for such a curve exists if the temperature drop is greater at the front end of the billet or depending on the condition of the rolls, the mandrel or other parts, ff-o ·. reaches a peak value of Pb that is above * m and drops below (Tm. If 6p is set to S & , i.e. to a value smaller than 6 "m, SK / can only rise to point Q, which is equal to 6 "> o, so that a skipped stitch occurs (in curve B, at the point in time where <rc> = 6" m, a bulge occurs in the transverse direction).

Curve C: If the temperature drop at the front end of the stick is small and the punching device has also been set to satisfactory values, the process proceeds according to curve C, even if one works with Ö'p> 6 ^/ m and even if the value at the highest point Pc is less than tfm. In this case ^ p = 6 * £ <6 "m is selected beforehand (provided that 6 ~ £ is above the point Pc); the roller pass can be carried out successfully and the curve becomes identical to curve C.

In practice, curves B and C appear in mixed forms, and if the thrust is not set to a value above the maximum (points Pa, Pb, Pc) / which for completion of the roller pass is necessary, the feed of the material ends at this point and the material is thrown off.

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When working with constant pressure, 0 ~ p and <5 "m are chosen almost equally, because at 6 ~ p C (Tm the roller stitch becomes quite difficult; the amount of the inner stitch reaches 16% at <Tp = 0.8 cm, and Since the thrust speed is not limited according to Gp>& m , the material is compressed during punching and accumulates in front of the rollers, so that ultimately punching is no longer possible. which is slightly smaller than 6 ~ m, but it is extremely difficult to take into account the fluctuation of (Tm due to the differences in temperature, composition or cross-sectional size for each individual billet, so that such a setting is not very suitable for technical practice.

When moving with constant pushing speed, rolling errors occur, which are unavoidable when working with constant thrust, significantly less, e.g. due to the bulging of the material when punching, and decrease when the inlet guide is designed as a sleeve to 4.5% and as a roller guide to 2.2%. At work with constant thrust speed, however - in comparison to the method with constant thrust with the correct setting, the Load fluctuation during the punching process is high, and the safety coefficient must therefore be used in the design and manufacture of the Investment with a higher value. For example, the rolling force is 1.2 to 1.6 times and the torque 1.1 to 1.6 times near the rear end with the punching process on the front part, and beyond that, differences occur in the deformation of the pipe, in particular it is disturbing that the excess material increases towards the end.

With the invention it is possible in the press-roll punching device Stabilize the load parameters at a low level by establishing the relationship between the feed rate or the peripheral speed of the rolls, the rolling force, the torque and the motor current is controlled. This leaves construct a system with the appropriate dimensions,

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Avoid rolling errors when punching and the quality of the produced Improve pipes because the deformation is done without unnecessary stress.

In the case of the constant pushing speed method During the event there are strong fluctuations in the load parameters the punching process from the fluctuation of the thrust force, the bulging of the material during the punching, resulting from fluctuations is accompanied in the contact area of the roller profile, the pressure distribution, the metal flow and, moreover, the difference in the deformation resistance due to temperature differences in the longitudinal direction of the material, and therefore the prediction is the overall influence on the above-mentioned load parameters is difficult.

In the following, the invention will now be described in more detail, the relationship between the thrust before the start of punching and the thrust speed or the roller rotation speed is set according to the method with constant thrust speed, thereby avoiding skipped stitches and initiating a smooth hole. The rolling force, the roller torque or the current of the roller drive motor are then measured, which confirms that the value has reached the level specified in the program Regulation.

In the method with constant pushing speed, the pushing force is therefore set to a value δ "p> eTm, because not only skipped stitches can be avoided, but the pushing speed and the peripheral speed of the roller are also independent allow each other to influence. The start of punching at a thrust speed according to formula (1) shows that The formula (1) comes extremely jialie to the desired value, and can can also be carried out with little control effort.

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The rolling force can be measured with a pressure transducer and dynamic tension meter, the roller torque with tension gauge, torque transmitter, torque transducer and dynamic tension meter and measure the current generally with an ammeter. It is possible, preferably not to apply the torque to the roller shaft, but between the roller and the reduction gear or

to measure between the reduction gear and the motor. if the desired value for the regulation is set, it can be checked with the usual devices at any time whether the constant value is reached or not. To simplify this, one chooses the non-constant section at the beginning of the Punch at 0.3 to 0.5 seconds at a push speed of 270 mm / sec, and can set the value to the time thereafter or to the value after one second, from the point in time when the Load parameters begin to fluctuate. Which of the various characteristics is to be selected as the control target can vary accordingly change from time to time, if For example, the strength of the rolling device or its rigidity turn out to be a problem, a certain rolling force becomes preferred, however, a certain torque or a certain current if the capacity of the roller drive motor or the strength of the driving force transmission are problematic, and if uniform deformation of the material is desired keeping the rolling force constant leads to high precision. The main load parameters apart from the rolling force: the roll torque and the power consumption of the roll drive motor (hereinafter referred to as rolling force, etc.) include the thrust, the thrust speed, the rolling pressure, the mandrel pressure, etc., but the relationship is with the rolling force etc. are not clear, and they cannot be used independently as a single factor. When punching with certain Pushing speed is initiated, the rolling force, etc., as shown in Fig. 4, is such that at the stitch time on one non-constant section is followed by a constant section, and then the slope turns into a slope.

* English: rolling load

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In practice, the thrust speed is reduced or the Roll circumferential speed increases as soon as the curve of the rolling force increases. The change in the roller peripheral speed is within + 20%, which is sufficient, and the change in the change in deformation due to the effect caused by the relationship between the roller circumference speed and the thrust speed exerted in the practical range is much lower. The acceleration during the punching process = however, should be kept to a minimum in order to keep the capacity of the plant as low as possible, and it will preferably associated with the decrease in the thrust speed. If the rolling force is in the falling branch of the curve, it is Countermeasure opposite to that for the incline, i.e. the roller circumferential speed is decreased, possibly together with an increase in the pushing speed. In this case the increase in the thrust speed only results in an increased load on the thruster, and therefore it should Increase can be made in an area where building space is available and it is not advisable to use the installation capacity for to interpret this purpose ». If the roller torque or the current for the roller drive motor (hereinafter referred to as torque, etc.) is attached special importance, the changes Situation something. If the torque, etc. increases, the pushing speed is reduced, or the pushing speed is reduced to a lesser extent together with the roller peripheral speed degraded. If the torque etc. decrease, the pushing speed will decrease increased, or the roller peripheral speed becomes lower Dimensions increased as the increased pushing speed.

The above measures are given as examples of the case described that the target values are fixed, but taking into account the fact that the temperature of the square billet decreases in the course of time and the deformation resistance to the rear becomes greater, and that in a similar way that to be machined Mass because of the bulging of the rollers or the dome

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becomes larger, and when emphasis is placed on the uniform deformation of the pipe, the control set point is preferable equal to the specific curve generated during the rolling process increases, and is encompassed by the invention / when the rolling force etc. is subjected to the regulation. However, this curve can Achieve the target sufficiently in the range of 0-v + 10%, based on the initial setpoint.

The practical embodiment of the invention will now be described. Table 1 shows the test conditions.

Tabel

Square billet dimensions (mm) Hole size (mm) Steel type

Heating temperature ( ⁰ C) roller profile dimension (mm) maximum barrel diameter (mm) mandrel diameter (mm) position of the mandrel tip

Reference roll diameter - peripheral speed (V) (mm / sec)

Initial pushing speed (V) (mm / sec)

set thrust (tons)

80 φ χ 1300

91 φ χ 22.7 χ 1700

low carbon steel (rolled)

1280
91.0 φ
452 φ
45.5 φ

40 mm in front of the inlet, measured from the roll center

300

270
38

Fig. 4 shows a recording of an electromagnetic oscilloscope the rolling force and the rolling torque in the event that the conditions of Table 1 are met from beginning to end will. Towards the back the load increases; the rolling force in the constant section is 2.2 times and the torque is 1.5 times. However, the set shear force is 38 tons, and when it is converted into the set shear stress,

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the result is a value of 6 kg / mm, about 3 times the yield stress of the material at the time. In fact, the reaction stress only slightly exceeds the yield stress. The cross section The square billet bulges out further during the punching process, on the lengths of all four sides by 2 - 5 mm.

5 shows the sequence / when the roller circumferential speed is kept constant, the rolling force a ^{1 is set} to the desired value and the thrust speed is influenced; the rolling force is within 1.4 times the nominal value and the rolling torque is within 1.2 times.

6 shows the sequence when the roller circumferential speed is kept constant, the roller torque b ″ to the desired one Value is set and the feed rate is changed; the rolling force is 1.2 times and the torque less than 1.1 times the target value, and clearly stabilizes at the low level / compared with the embodiment according to Fig. 4.

In the already mentioned Fig. 1, the system is for the above described regulation of the thrust speed and the roller circumferential speed shown.

The thrust applied to the stick and his The pushing speed is measured with the load cell (12) or the speed indicator 13 measured, and the measured signals are fed to the process computer via amplifiers 21 and 22. Further the rolling force and the rolling torque are measured by the load cell 14 and the torque meter 15, and the measured Signals are fed to the process computer via amplifiers 16 and 17.

The process computer 11 sends on the basis of the received Signals to the flow controller 18 and the motor control switch

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Control signals. The piston speed of the cylinder 1 and thus the thrust speed of the stick is determined by means of the flow rate Regulator 18 is controlled, and the motor 20 and. thus the roller peripheral speed through the * motor control switch 19.

FIG. 7 shows as a block diagram the control of the speed of the applied in the experimental arrangement described Cylinder for the material feed. The piston speed of the hydraulic cylinder is changed by the outflow of a variable axial piston pump with the help of a servo pump is changed, and the control is carried out so that the rolling force coincides with the target value.

As already stated, the rolling force is determined by the load cell 14 determined and amplified by the dynamic voltage amplifier 16. The signals from this amplifier are fed back and compared with the setpoints, and the control signals are led to the flow regulator 18. In the flow controller 18 is the Position of the lever mechanism 26 detected by a detector 23, and the signals returned by the detector 23 are compared with the control signals. The associated differential signal goes to the servo amplifier 24. The signal from the servo amplifier 24 is guided to the control cylinder 25, and lever mechanism 26 is operated in accordance with the actuation of the control cylinder adjusted. The flow rate of the pump 27 changes accordingly and thus also the piston speed of the hydraulic cylinder 1, so that the rolling force again with the target value is brought into agreement.

Of course, the thrust device does not have to be hydraulic system are formed. For example, the end of the square billet can be moved linearly by turning a motor is transmitted to a feed rod, or the rollers of the roller guide can be used to increase the thrust, etc. Further, the ratio of the thrust speed and roller peripheral speed relative, and a

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A similar effect can be achieved by using one or the other other of the two variables is influenced, as described above.

The invention can be applied not only to steel, but to any type of plastically deformable metal. Also is that Cross-sectional shape of the billet is not limited to a square or rectangle. After all, the cross-section of the tubular bobbin needs not to be circular, but can also consist of an oval or a polygon, such as an 80-corner, which is almost is circular.

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Claims (1)

August 19, 1976 A 76 127 Applicant in: Nippon Steefl Corporation Claims M .yPreß-roll perforation process for the production of tube blanks / in which a polygonal billet in the axial direction between a pair of driven rollers arranged one above the other each with a semicircular profile and is pressed against a piercer arranged between these rollers, thereby characterized in that the shear force is kept at a predetermined value, that of the stress above the yield stress of the billet at the start of punching, the actual value occurring at the start of punching Stress can possibly exceed the yield stress by adjusting the thrust speed and / or the circumferential speed of the rollers, the volume of billets to be pressed in per unit of time is approximately equal to the volume of the holds pipe blanks emerging from the rollers and causes the intended roller pass of the billet. 709808/0416 263754 2. The method according to claim 1, characterized in that the Pushing speed Vp according to the equation ^V p = ^K 1 ^K 2 ~ ^V R
2. it is determined in which K. is a correction constant that depends on the manufacturing process of the material and has a value of 1 "o - 1.1, K "is the ratio of the roller circumference speed V ₀ to £ R The exit speed of the material is and a value has from 0.95 - 1.20,
L _{1 is} the length of the material in front of and
L ^ the length of the material after punching is ₇ V is the peripheral speed of the roller and varies according to the formula "Τ? MIN + 0.2d. . ■ ^V r ^{= V} MIN * calculated, ^D MIN where ^ν _Μ γ _Ν ' roller circumferential speed at the bottom of the bale profile, D: roller diameter at the bottom of the ball profile d is the diameter of the ball profile. 3. The method according to claim 1, characterized in that the rolling is carried out with successive setting of the values will. 4. The method according to claim 3, characterized in that the rolling is carried out one after the other and the billet continuously from the beginning of the rolling to its completion with the thrust speed _. " 1 ■ ■ ■ r »~ 1 9 T P is moved forward, in which the individual sizes take up the have given meaning. 709808/0416 5o method according to claim 1, characterized in that the Rolling is carried out successively and the billet is rolled by adjusting the thrust speed and / or the roller peripheral speed is regulated. 6ο Method according to claim 5, characterized in that for control purposes the rollers are rotated at a predetermined speed, the rolling force of the rollers is measured and the pushing speed is selected in such a way " that the rolling force practically coincides with the nominal value" 7 = method according to claim 5, characterized in that for regulating the stick with the set thrust speed pressed between the rollers, the rolling force of the rollers is measured and the peripheral speed of the rollers is selected in such a way that that the rolling force practically coincides with the target value. 8. The method according to claim 5, characterized in that the rolling force of the rollers is measured and the thrust speed for regulation and / or the roller circumferential speed is selected such that the rolling force practically coincides with the target value. 9. The method according to claim 5, characterized in that for Regulation set the number of revolutions of the rollers to a certain value, measured the torque of the rollers and the pushing speed is chosen such that the torque practically coincides with the target value. 10. The method according to claim 5, characterized in that the number of revolutions of the rollers to a certain value for regulation set, the electric current of the roller drive motor measured and the thrust speed is selected such that the electric current practically coincides with the setpoint. 709808/0416 Λ, ¹ y 11. The method according to claim 5, characterized in that for Regulation of the stick with the certain speed pressed between the rollers, the torque of the rollers is measured and the Roll circumferential speed is chosen such that the torque practically coincides with the nominal value. 12. The method according to claim 5, characterized in that for Regulation of the stick with the certain thrust speed pressed between the rollers, the electric current of the roller drive motor measured and the roller circumferential speed is chosen such that the electric current practically with the Setpoint coincides. 13. The method according to claim 5, characterized in that the roller torque is measured and the thrust speed for regulation and / or the roller circumferential speed is selected in such a way that the torque practically coincides with the nominal value, 14. The method according to claim 5, characterized in that for Regulation of the electrical current of the roller drive motor and measured the thrust speed and / or the roller peripheral speed is chosen such that the electric current practically coincides with the setpoint value. 709 8 0 8/0416