DE3500011C2 - Process for the controlled demagnetization of rod-shaped, ferromagnetic and tempered semi-finished or finished products in the ongoing production process - Google Patents

Abstract

Steel products in the form of long stainless steel rods leave the manufacturing, finishing and testing lines of the manufacturing plants with very different remanent induction values. In order to deliver these products as remanence-free as possible and to ensure their further processing by electric welding, cutting or non-cutting deformation using ferromagnetic tools in partially or fully automated machine tools and production lines without disruption and loss of quality, a method and an arrangement for the controlled demagnetization of these workpieces by means of digital control of DC-fed demagnetization coils is required proposed, which can be arranged after the last processing step of the workpiece, does not place any condition on the transport speed of the workpiece and does not affect the ongoing production process in any way.

Description

The invention relates to a method for demagnetizing workpieces according to the preamble of the patent claim 1.

Steel products in the form of long stainless steel rods leave the production, finishing and testing lines of Manufacturing plants with very different remanent induction values. These are used in quality control mostly determined at the ends of the staff and are distributed purely statistically within the same federation. It Efforts are therefore made to deliver these products as remanence-free as possible in order to achieve their - Further processing by electric welding, cutting or non-cutting deformation by means of ferromagnetic Tools in partially or fully automated machine tools and production lines without interference and to ensure a loss of quality.

In the case of the metal-cutting shaping, those that arise during the machining of the remanent material remain Chips stick to the workpiece and thus prevent sufficient dimensional accuracy and surface quality. When transporting magnetism-afflicted materials, the reliability with inductive scanners or Hall probes working controls are reduced and in extreme cases can even lead to the failure of a production line to lead. The advantages of demagnetization also result from the reduction in abrasion in gears and axle bearings and through peduction the deflection error in electron beam welding.

The demagnetting systems are required to take the impressed magnetism of the material Eliminate to a tolerable minimum without the

is to change other material properties. About that In addition, they should cover a wide range of different rod dimensions and material compositions be usable and finally it must not hinder the flow of material in ongoing production in any way.

If one examines long, magnetism-afflicted stainless steel rods more closely, one finds that this task is made more difficult by the following findings:

- The stationary magnetization curves are almost rectangular and thus indicate a magnetically hard material with high romance values.
- The remanent magnetism can constantly change its intensity and its polarity several times along the rod axis. There are therefore also cases of remanent stainless steel rods where both ends are polarized in the same way.

A number of degaussing methods and arrangements are known from the prior art, which differ in terms of the given task and the intended area of application in

Shape, quality and quantity of the workpieces to be demagnetized

Type of field generation, such as via permanent magnets, alternating, direct current or mixed-supply Degaussing coils with voltage regulators, frequency converters or pulse generators as Ballasts

Type and design of the demagnetizing coil, such as air-core coils, arnished coils, open and closed pole yokes, overflow coils, tunnel, gate or flat coils, Deutro coils, and permanent magnets such as plates, rollers or gyroscopes
Method of demagnetization, such as changing the field excitation by varying the current value or moving permanent magnets with the workpiece at rest or moving the workpiece with a constant field.

From US-PS 41 58 873 a method of the type mentioned is known. For the function of this known method, however, a third and fourth ^ coil is required, which is connected to the first and second coil in Is connected in series and are located at a certain distance from them. As rectifier elements c controllable silicon rectifiers are used. The voltage resp. Current half-waves are switched in phase control via the rectifier valves, an oscillator circuit

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sends the control impulses. The rectifier circuit is designed for one pair of coils connected in series. A regulation of the demagnetizing field is not provided, only the phase position of the two rectifier circuits can be adjusted via adjustable resistors be matched.

In DE-AS 14 89 988 is a Verfarhen with a Circuit arrangement described, which a continuous demagnetization of ferromagnetic Materials without presence: magnetic interference fields permitted. The halftime of the demagnetizing The alternating field is amplified or increased in opposite directions by an amount corresponding to the interference field. weakened so that the interference field is compensated for during demagnetization. According to the circuit arrangement will be on the one hand parallel to the dining room. Transformer and the degaussing coil an adjustable resistor and a rectifier connected in series and on the other hand between the feeding transformer and the degaussing coil, connected in series with this, a resistor or a controlled rectifier, that of a series circuit consisting of a rectifier and a controllable resistor is bridged. In the demagnetization coil are the amplitudes of the current half-waves once through adjustable resistors or through the controlled Adjustable rectifier.

DE-AS 15 89 889 describes the design of the control loop specified in DE-AS 14 89 988. Thereafter the remaining remanence of the material after passing through the degaussing device continuously measured and the opposite "amplification or weakening of the half-waves of the demagnetizing current regulated as a function of the measured remanence values. In addition, a The previously set demagnetizing current was saved. For practical implementation an electromechanical control circuit is provided for the device.

In the PE-OS 32 38 609 there is another facility for the demagnetization of rod-shaped workpieces while passing through the magnetic field of a demagnetization coil described in which switching devices are attached in front of and behind the coil, the processable Display signals when the workpiece is entering and exiting.

The invention is therefore based on the object of providing a method according to the preamble of claim 1 indicate which one is structurally easy to set up and operationally reliable arrangement enables it to be carried out.

This object is achieved according to the invention by the im characterizing part of claim 1 specified features solved.

Special modes of execution of the invention are the subject matter of the subclaims.

The advantages achieved with the invention are, in particular, that a controlled demagnetization of rod-shaped, ferromagnetic and tempered semi-finished and finished products in the ongoing production process, independent of their! other environment related to the influence of magnetic fields / and irrespective of their diagrammatic design will. The control parameters are freely available for optimizing the magnetization results. The changing conditions during demagnetization are also due to their variation alone different materials and diameters are taken into account. The procedure works independently of the transport speed of the workpieces to be demagnetized. For controlled demagnetization only two demagnetizing coils, arranged at a short distance from each other, are required. There as Power supply is provided for the method according to the invention direct current, on the one hand, the use is omitted expensive frequency converter or AC power controller and on the other hand problems arise because of the necessary Penetration depth of the magnetic field in the workpiece to be demagnetized does not increase.

Further details and advantages of the subject matter of the invention emerge from the following description of the accompanying drawings, in which an embodiment of a device for carrying out the method according to the invention has been shown schematically
In the drawings shows

F i g. 1 a block diagram of the regulated GSC currents magnetization;

F i g. 2 a signal flow pian de '-. Control circuit of the same:

F i g. 3 is a block diagram of the digital controller;
4 shows a block diagram of the measuring method used;

F i - 5 shows a diagram of the relationship between the function profiles of magnetic induction B _n and flux Φ via the location χ on a steel rod;

F i g. 6 examples of the distribution of magnetic polarities on a long steel rod;

7 shows a flow chart for the use of a demagnesizing device in production;

8 shows the block diagram of an overall arrangement in the production process.

In this case, the workpiece 1 to be demagnetized is usually supported and guided a roller table 2, consisting of continuously arranged, elevated and mounted double cone rollers as support and guide rollers that are mounted on a metal frame. Along this roller table 2 two hollow cylindrical degaussing coils 3 and 4 are in a short distance behind one another in such a way centered that. In relation to their diameter, workpieces of different thicknesses their inner bore can happen. The degaussing coil 4 also carries in its plane of symmetry perpendicular to Transport direction one measuring winding 5.

While the coil 3, which is arranged for the purpose of magnetization, is connected to a constant voltage source 6 via a controllable on / off switch 10, the voltage to the oppositely polarized winding of the coil 4 is supplied via a voltage source 7 controlled by a control device 8 The scanning switches 9 are used to detect the position of a workpiece before it enters the demagnetization device and after it has run out, as well as the setting of defined initial and final states of the control device. The electrical signal of the measuring effect 5 is fed to the control device 8 and processed according to a predetermined algorithm. The controller 8 generates a digital ^, fiSignal.zum; On / Off Switch del 'Konstantsjiannungs - "(6 qüeiie for the ^■: SpüIe 3 and an analog signal for?

controllable voltage source 7 of the coil 4.
The control device 8 consists, as shown in FIG. 2 show, from a preamplifier 14, an analog / digital converter 15, an integrator 16, a digital controller 11, a digital / analog converter 12 and a buffer converter

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stronger 13. The preamplifier 14 is used to prepare the voltage induced in the measuring winding 5 for sufficient control of the digital / analog converter 15. The buffer amplifier 13 serves to protect and isolate the digital / analog converter 12. The controllable voltage source 7 applies a DC voltage with the correct sign as specified by the control device 8 to the degaussing coil 4. The control algorithms of the digital controller 11 are through a program realized and saved. The integrator 16 is also implemented as a computer program. the The arrangement is thus divided into a part with digital and a part with analog measured value processing.

The digital Reg.er 11 includes, see FIG. F i g. 3, the central unit 19 with control unit and arithmetic, the static memory 17, in particular required for storage the read in induction distributions, the read-only memory 18 for receiving the monitor and of the user program, the serial input / output unit 20 for connecting the operating peripherals and for keeping records, as well as the parallel input / output unit 21 in connection with the control assembly 22 for the purpose of determining the status of the sampling switches 9, control of the alarm display and execution of switching functions for the power supply units, the ΛνΎ recorder and the analog tape recorder.

The operation of the device is explained in more detail below. If a transported on a roller table 2, magnetism-affected workpiece 1 the degaussing device, then by triggering of the sampling switch 9a (Fig. 1) via the control device 8 the switch 10 is actuated and the circuit of the coil 3 via the constant voltage source 6 is closed. The constant current Λ flows, which causes the workpiece 1 to be magnetized via the coil 3. When the switch 9a was actuated, the controllable voltage source 7 was also set to a fixed value Initial value set, a current / 2 flows through the marked wound coil 4 and causes demagnetization of the steel rod 1. Passes through the workpiece 1 the measuring winding 5 of the coil 4, a voltage is induced in it. This is the control device 8 supplied, which regulates the current / 2 according to amplitude and direction via the controllable voltage source 7 so that that the existing remanence is canceled at every point on the workpiece 1. Leaves the workpiece 1 the sampling switch 96. the currents of both coils switched off.

The remanent magnetic flux Φϋαη of a steel rod 1, F i g passing through the coils 3 and 4. 2, can be viewed as a disturbance variable in the control loop. It induces a voltage U _m d in the measuring winding 5. which at constant transport speed ν of the workpiece 1 according to Eq. (1) the normal component of the induction B _n on the workpiece surface is proportional environmental B _n.

ILt = N-

German

■ »■ kU

B άΑ

eo

(D

= M-- II B "rd (pdx dt J ■ · 0 0

= 2πτΝΒ _π ν.

65 The digital regulator 11 reads in the voltage Um via the analog / digital converter 15 and integrates it, FIG. 4. The integral is according to GL. (2) proportional to the magnetic flux Φ and therefore independent of the transport speed v. It is referred to below as the actual flow value <Pi _st .

B UA

χ 2t

.-YY

χ 2

= JJ B "raq>

« 0

= 2 η r NB _n x.

dx

(2)

A comparison with the stored nominal flux value ί? £ =. '.' ^he gives the control difference as a starting point for the measures of the regulation. F i g. 5 shows an example of the courses of the induction B _n and the magnetic flux Φ over the location χ on a steel rod and F i g. b Examples of the distribution of magnetic polarities on a long steel rod of length /.

The flux setpoint Φς _ο ιι is initially set to zero, setpoint 1. The aim of the control is to also check the flux actual value Φι ,, to Nuil and to counter any change in flux on '! Em rod immediately by means of a current change / 2. A negligible change in the flux over the rod length also means a disappearance of the induction and a complete demagnetization of the workpiece after it has passed through the arrangement. However, it is not possible to measure the induction of the workpiece in isolation. On the one hand, the changes in current in the coil 4 also induce voltages in the measuring winding 5; on the other hand, the inductive coupling between the windings of the degaussing coil 4 and the Nießwieklüng 5 changes greatly when a workpiece enters or leaves the arrangement.

As a solution to this indicated problem, the setpoint specification is changed during the transport of the workpiece through the arrangement. As already mentioned, the regulation begins with a nominal flux value of zero, the nominal value 1. This initially causes an increase in the current / 2 when the rod magnetized in coil 3 approaches coil 4. ^. If it reaches approximately its middle, the current h begins to decrease because the coupling between the winding of the coil 4 and the measuring winding 5, which is now strengthening, simulates an excessively high current or an insufficiently magnetism. Therefore the control process is now interrupted. The instantaneous current h is retained, but the induced voltage is further integrated until a previously stored value is reached. This value, the setpoint 2, serves as the starting point for the control that is now starting again. At this point in time the steel rod has moved approx. 20 cm into the coil 4 and the degree of inductive coupling has stabilized at its maximum value. If the rod end approaches the measuring winding 5, the coupling becomes weaker again and a current that is too low or a magnetism that is too high is simulated, so that the regulation would increase the current inappropriately. This is countered in that the regulation is now ended and the current strength / 2 is maintained until the switch 96 is switched off.

It is also possible to refer to the sampling switch 9έ

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7th 5 oil 8th Amperage angle induced Setpoint on the transport direction, in front of the degaussing / Steel bar length, workpiece length Magnetic river actual value coil 4 to be arranged, so that the shutdown of the currents / Number of turns Normal component / i and h takes place before the workpiece ends the arrangement N radius indexing Rem remanence In addition 6 sheets of drawings voltage leaves. r Time Intended to The parameters of the control are in addition to the ampl 10 t tension ind kung v, which both hardware-wise in the course of the Vorver U Speed - gain is gain ν /, of amplifier 14, F i g. 2, as well as soft V Coordinate, location η ware.Tiäßig saved as gain factor v _s , be X can be influenced, the current start value / 2.1 and the Greek letters Setpoint 2 of the magnetic flux <Ps 2 15th The invention does not require any additional Trarisport- φ systems in production. The demagnetization unit Φ direction can be changed after the last processing of the Workpiece, the z. B. the crack test by means of magne table procedures or ultrasound, di 20th right in the area of the processing or testing machine to be ordered. The transport speed of the Workpiece is arbitrary and is determined by the type of before The processing or examination that has been started is determined. Further tasks such as a measured value 25th detection before demagnetization, a success factor troll after demagnetization or a protocol for documentation and alarm output
during the demagnetization, see Fig. 7, can
• * · t> t ti * 1 * T ^ * 1 t I * * »t without additional effort in the field of digital Regulator are implemented and only require 3C the arrangement of additional sampling switches 9 and Measuring coils 5 by one workpiece length each / in front of or behind the degaussing device and the In ■ ir installation of appropriate logging devices according to JD dc * n in FIG. 8 shown block diagram of a poss overall arrangement in the production process. List of reference symbols 1 workpiece 40 2 roller table 3 first degaussing coil 4 second degaussing coil 5 measuring winding 6 constant voltage source 45 7 Controllable voltage source 8 control device 9 sampling switches 10 controllable switch 11 Digital controller 50 12 digital / analog converters 13 buffer amplifiers 14 preamplifiers 15 analog / digital converter 16 integrator 55 17 Static Storage 18 read-only memory 19 central unit 20 Serial input / output unit 60 21 Parallel input / output unit 22 Control assembly Direction of winding of the coil 65 - Direction of transport List of sizes used and formula symbols Latin letters A area B Magnetic induction, flux density

Claims (3)

35 OO Oil patent claims: 1. Process for demagnetizing workpieces in the form of rod-shaped, ferromagnetic and remunerated semi-finished or finished products such. B. bar steel, bright steel, hollow profiles in the flow due to the magnetic field of DC-powered degaussing coils during the ongoing production process, regardless of their other, related to the influence of magnetic fields Environment, where the magnetic field of a first coil (3) fed with constant direct current the workpiece (1) is magnetized to a certain level and a second is fed with direct current Coil (4), which is located in the immediate vicinity of the first coil (3) and polarizes in opposite directions is, the impressed magnetism by generating a negative coercive field strength just again cancels, characterized in that one in the plane of symmetry of the second coil (4) Measuring winding (5) arranged perpendicular to the transport direction generates signals that are converted and processed a control device (8) are fed to the feeding according to a predetermined algorithm The direct current of the second coil (4) is regulated with the aid of a controllable voltage source (7). 2. The method according to claim 1, characterized in that. Relative to the transport direction, in front of and behind the arrangement of the first and second coils (3 and 4), switching devices (9) generate signals which process the entry of the workpiece (1) into the arrangement and the exit of the same from the arrangement display and the control device (8) for E ^: position defined initial and final states. 3. The method according to claim 1, characterized in that. based on the direction of transport in front of the arrangement of the first and second coil (3 or 4) and between the two coils of the arrangement attached switching devices (9) generate signals that the entry of the workpiece (1) into the Display the arrangement and the outlet of the same processable from the arrangement and the control device (8) to set defined initial and final states.