CN1030149A - Heat treatment of workpieces " zero insulation " some microcomputer control device - Google Patents

Abstract

The present invention be a kind of be used for accurately determining workpiece quench before in heating furnace Microcomputer Detecting and the control device of required heat time heating time.It is characterized in that workpiece quench before in stove required heat time heating time be by thermal equilibrium state parameter in the indirect measurement stove, carry out calculation process by heat treatment of workpieces " zero insulation " mathematical model theoretical and that heat transfer theory derives out and real-time definite by microcomputer.Can be widely used in industrial and mining enterprises' heat treatment heating furnace transformation or, economize on electricity, improve distinguishing features such as surface of the work decarburization oxidation situation and raising workpiece mechanical property when control accuracy height, joint are arranged as its corollary apparatus.

Description

Heat treatment of workpieces " zero insulation " some microcomputer control device

The present invention be a kind of be used for determining workpiece quench before in heating furnace Microcomputer Detecting and the control device of required heat time heating time.

Known heating furnace Microcomputer Detecting and control device, t heat time heating time before its workpiece quenches ₀(a period of time till referring to when playing workpiece when furnace temperature arrives set point of temperature comes out of the stove) determine by following experimental formula, promptly

t ₀＝d·D·k ……（Ⅰ）

In the formula: d-represents heating coefficient, i.e. workpiece unit thickness required heat time heating time;

D-represents the workpiece net thickness;

K-represents workpiece shove charge correction factor.

By formula (I) as seen, t ₀Value size is equal to shove charge workpiece material, quantity, shape and have the pass, when these homoatomics change, and just correct artificially of the heating process parameter value in the control program (d, D and k).In addition, generally long by the heat time heating time that experimental formula (I) is calculated, the result causes energy dissipation, and surface of the work decarburization oxidative phenomena is serious, has influenced its mechanical property.How accurately to determine t heat time heating time ₀, " zero insulation " theory has provided rationale.So-called " zero insulation " theory is meant and is heated the theory that can finish phase transformation in a flash that workpiece has just become equal hot body.According to this theory, workpiece is in " zero insulation " point (be workpiece just heat penetration constantly) quenchings of can coming out of the stove immediately, and meaning is that the temperature retention time behind the workpiece heat penetration is zero.But because of still not finding a kind of measuring method to measure so far to be heated workpiece when to reach " zero insulation " point.Therefore, " zero insulation " is theoretical also can't realize in practical application.

Task of the present invention just provides a kind of Microcomputer Detecting and control device that workpiece reaches required heat time heating time in " zero is incubated " some moment of can determining accurately and real-time to be heated.

Microcomputer Detecting of the present invention and control device, be by indirect measurement heating furnace thermal equilibrium state parameter, theoretical and carry out calculation process by the mathematical model that heat transfer theory derives out and determine to be heated workpiece in real time and reach " zero insulation " point required heat time heating time by computing machine according to heat treatment of workpieces " zero insulation ".When workpiece is put into heating furnace (as the hot stove of electric heating) when being heated, computing machine on the one hand according to furnace temperature sampled value size control to be input to the electric power value of electric furnace constant to keep furnace temperature; On the other hand, one group of different power input value constantly that will sample are again brought corresponding mathematical model into and are carried out calculation process, obtain workpiece heat absorption heating-up time constant value T and workpiece and reach " zero insulation " some required time t ₀, and with actual heat time heating time t and t ₀Value is compared, as t 〉=t ₀The time, just send the alerting signal that arrives heat time heating time, at this moment, workpiece just can be come out of the stove immediately.

Because the present invention puts " zero insulation " theory into practice, so compared with prior art, it is about 1/3rd that the present invention can shorten workpiece insulation heat time heating time, and integrated power-saving 10～15% can improve surface of the work in addition and take off the char combustion situation, raising workpiece mechanical property.

Provided a specific embodiment of the present invention among the figure.

Fig. 1: be input electric power change curve in time;

Fig. 2: be Microcomputer Detecting of the present invention and hardware control system block diagram;

Fig. 3: be Microcomputer Detecting of the present invention and control system flow chart.

Below in conjunction with accompanying drawing, explain content of the present invention.

Can know by inference by heat transfer theory, when temperature in the heating-furnace keeps constant, input electric power p(t) be to change by exponential function curve shown in Figure 1, its function expression is:

In the formula: p ₀-be the body of heater heat radiation power;

p _c-be a fixed constant, and p _c=p _g-p ₀(p _gPerformance number during for the electric furnace full load);

Su J  when T-is workpiece heat absorption intensification

By (II) formula as can be known, as t=(4～5 heat time heating time) during T, the performance number that the workpiece heat absorption heats up and consumes $p_w\left(t\right)=P_C{e}^{-\frac{t}{T}}$ Level off to zero, meaning is that workpiece is in the heat penetration moment just at this moment, therefore, and desirable t ₀=5T reaches " zero insulation " point required heat time heating time of value as being heated workpiece.

Handle for the ease of control in real time, detection and computer data, we need (II) formula discretize.When the time interval of getting the mensuration input electric power is Δ t, then have:

t _n＝n·Δt （n＝1，2，……，N _o） ……（Ⅲ）

In the formula: n is the n time measurement point numerical sequence; N _oFor measuring total degree.

With (III) formula substitution (II) formula, can get

Can get thus, the index curve among the present invention backhauls the computing function f(p of the least square method of calculation ₀, expression formula T) is:

$f(\mathrm{po},T)=\underset{n=1}{\overset{N_o}{\mathrm{\Σ}}}{[p\left(t_n\right)-p_n]}^2\·\·\·\·\·\·\left(V\right)$

In the formula: p _nBe the n time measured input electric power value of measurement.

With (IV) formula substitution (V) formula, can get

F(p ₀, T) be a bivariate p ₀With the optimization problem of T, one group of discrete value (t that will record when us ₁, p ₁), (t ₂, p ₂) ... (t _No, p _No) substitution (VI) formula, after the machine calculation process, just can find out f(p at an easy rate as calculated ₀, minimal value T) corresponding to this minimizing variable T value, is exactly the workpiece heating-up time constant value that we will seek.This T value has been arranged, and then just can obtain being heated workpiece and reach " zero insulation " point required heat time heating time of t ₀Value, i.e. t ₀=5T.

Fig. 2 has shown Microcomputer Detecting of the present invention and hardware control system composition and has interconnected situation, as shown in Figure 2, control center is a Tp-801 single board computer (2), heating furnace input voltage signal and furnace temperature signal imitation amount pass through tension measuring circuit (8) respectively and the temperature change send element (9) to deliver to A/D transducer (7), send into Tp-801 single board computer (2) after being transformed into digital quantity, computing machine is on the one hand according to furnace temperature sampled value size, constantly send the signal that controllable silicon is opened and closed, this signal is through level conversion and isolator (3) conversion, send thyristor gating circuit (4) after the isolation, constant thereby the electric power of electric furnace (5) is sent in control to keep furnace temperature; On the other hand, will sample one group different input voltage value constantly of computing machine are brought mathematical model (VI) formula that the present invention sets up into and are carried out calculation process, obtain to be heated workpiece and reach " zero insulation " point constantly required heat time heating time of t ₀, and itself and workpiece actual heat time heating time of t compared, as t 〉=t ₀The time, just send the alerting signal that arrives heat time heating time to display alarm (6).In addition, computing machine also carries out the furnace temperature numeral by display alarm (6) and shows and fault alarm, by mini-printer (1) printout furnace temperature curve map.For the measurement that makes power input (being load power) becomes not only simply but also reliable, consider square being directly proportional of power input and input voltage, so determine the input electric power value that it is corresponding by measuring different input voltage values constantly here.

Fig. 3 has shown the computer program control procedure of Microcomputer Detecting of the present invention and control system.As shown in Figure 3, behind the programming start, after this first first Outside-skin-of-bamboo P-801 single card microcomputer programmable interface sheet PIO, CTC initialization carry out temperature detection and control, after furnace temperature arrives to fixed temperature, with regard to setting curve regressing calculation measure dot number N _oMeasure step delta t, the curvilinear regression computing amount of sign M(M=0 represents not carry out regressing calculation, and M=1 represents to carry out regressing calculation), simultaneously, set zero-time t=0, initial measuring point times N=0, after initial value is determined, interior controlling of sampling number of times B value during the setting measurement step delta t, enter temperature sampling, temperature data processing and temperature control, measurement of power and power data are handled.Subsequent control time numerical value B subtracts 1 computing and judges the B value, if the non-vanishing temperature sampling that then returns of B.Measurement of power and data processing; If B equals zero, then calculate temperature retention time t value.The judgement of the amount of sign M value then.If do not carry out regressing calculation (being M=0), then carry out measure dot number N value add-one operation, after the computing with setting N _oRelatively.If the control in then not turning back to during next measurement step delta t to regulation measuring point number; Count N if arrived the regulation measuring point _o, then find the solution the curvilinear regression computing of workpiece heating-up time constant value T, and set regressing calculation sign amount M and equal 1.After this, the control in turning back to during the Δ t again, Shang Ruoyi has carried out the curvilinear regression computing and has obtained T value, then transfers to judge whether temperature retention time t arrives.If temperature retention time is to (being t 〉=5T), then send the signalisation workpiece and come out of the stove, not coming out of the stove as if workpiece, then return thermostatic control again; If temperature retention time do not arrive, then do not signal and control in directly turning back to during the Δ t, up to temperature retention time till send signal and workpiece come out of the stove.

Observation on probation shows, adopt Microcomputer Detecting of the present invention and control device that RJX45-9 type resistance furnace is carried out control after, the 35C of ZQR-410 traction motor _rM _oThe heat tracing time of motor shaft reduced to present 144 minutes by 210 minutes that calculate by traditional experimental formula (I), and Jie Shida 30%.And, to compare with classic method, the workpiece metallographic structure is identical, and mechanical property slightly improves, and the surface is taken off the char combustion situation and is improved.

Claims (5)

1, a kind of microcomputer control quenching workpiece device of heat time heating time in heating furnace that uses, form by system for detecting temperature and control system thereof, it is characterized in that: before workpiece quenches among the present invention in stove required heat time heating time be by indirect measurement heating furnace thermal equilibrium state parameter, theoretical and carry out calculation process and determine in real time according to heat treatment of workpieces " zero insulation " by computing machine by the mathematical model that heat transfer theory derives out.

2, according to the described device of claim 1, it is characterized in that: before workpiece quenches in electric furnace required heat time heating time be by measure one group of different input electric power value constantly as calculated machine handle the back and determine in real time.

3, according to the described device of claim 2, it is characterized in that: determine the input electric power value that it is corresponding by measuring different input voltage values constantly or current value.

4, according to the described device of claim 1, it is characterized in that: with 4～5T(T is workpiece heat absorption heating-up time constant value) as the reference point of determining that workpiece quenches preceding required heat time heating time.

5, according to the described device of claim 1, it is characterized in that: when workpiece is put into electric furnace (5) when being heated, heating furnace input voltage signal and furnace temperature signal imitation amount are passed through tension measuring circuit (8) and temperature respectively and are become and send element (9) to deliver to A/D transducer (7), are transformed into to send into microcomputer (2) behind the digital quantity and handle.Computing machine is on the one hand according to furnace temperature sampled value size.Constantly send the signal that controllable silicon is opened and closed, this signal is through level conversion and isolator (3) conversion.Send thyristor gating circuit (4) after the isolation, constant thereby the electric power of electric furnace (5) is sent in control to keep furnace temperature; On the other hand, will sample one group different input voltage value constantly of computing machine are brought mathematical model (VI) formula into and are carried out calculation process.Obtain workpiece heat absorption heating-up time constant value T, and workpiece actual heat time heating time of t compared with 4～5T, when t 〉=4～5T, just send the alerting signal that arrives heat time heating time, utilize this signal can be by display alarm (6) notifying operation personnel or as the signal of coming out of the stove of workpiece in the robot control system(RCS).

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