SU979050A1 - Method of determining penetration time constant - Google Patents

Description

The invention relates to the field of automation of welding processes and can be used in the calculations and design of automatic penetration control systems.

A known method for determining the penetration time constant, in which the seam of predetermined geometric parameters is preliminarily formed by an arc of installed power, after which during the welding process the arc power is abruptly changed and a seam with other parameters are formed, and the penetration time constant is determined by changing the corresponding weld size (seam width, penetration width) during a stepwise change of one of the welding parameters - arc current Zd, arc voltage U _A or their ratio. Moreover, the values of the time constant 20 are determined by the time corresponding to the change in the penetration to a value equal to 0.63; the established value of £ 1].

The disadvantage of this method is that careful preparation of the samples is required to increase the size of the transient boundary by an epidemioscope, in addition, when the jump voltage changes on the arc, the arc spot distorts the boundaries of the transient process. Hence the low accuracy of determining the constant penetration, unsatisfactory repeatability of the experiment.

The aim of the invention is to improve the accuracy of determining the constant penetration time.

This goal is achieved by the fact that in the known method for determining the penetration time constant, in which the seam of predetermined geometric parameters is preliminarily formed by an arc of installed power, after which during the welding process the arc power is abruptly changed and a seam with other parameters is formed, and the penetration time constant is determined by the change in geo3 979050 metric parameters on the time interval from the transition from one welding mode to the establishment of another, as a parameter * * change geometric dimensions *, measures the seam use a temperature measured continuously at a distance from the axis of the electrode equal to half the width of the seam.

In FIG. 1 shows a location diagram of a temperature sensor; in FIG. 2 distribution of temperature in the plate along the axis of the OS; in FIG. 3 - determination of the penetration time constant from the oscillogram of the temperature change.

The temperature field in the plate according to the diagram of a linear heat source can be represented by the expression Vx 2d by the following principle: ^T ~ 4 AcA • e

J 4α la t o o

G - X where

V SL i For

- heat source power, W;

- the velocity of the heat source, m / s;

- coefficient of thermal diffusivity · m ^ / s;

- coefficient of thermal conductivity, W-m-grad;

- plate thickness, m;

- time, s. quasistadione state

Wow . ¹ Ίΐίλό ^{1 е} * 0 where К _о is the Bessel function.

When the sudden arc power на changes (by changing the arc voltage of the welding current), the temperature field changes to a new quasistanionary state, respectively. The penetration width changes from B to B ¹ (see Figs. 1 and 2).

Temperature changes at points A ^ and A2 (em. Fig. 1) in a coordinate system moving with speed occur almost simultaneously, since the points are at a slight distance from one another.

It is known that the width of the seam is proportional to the arc power; therefore, when passing from one quasi-stationary state to another, the isotherms occupy the positions shown in FIG. 2.

Thus, there is a one-to-one correspondence between the temperature change and the change in the penetration width.

The method for determining the penetration time constant is that it records an oscillogram of the transient process of temperature change by a sensor located at a distance from the electrode equal to the seam half width, after which the time constant is determined from the oscillogram.

Note er As a temperature sensor, an almost inertialess thermocouple is chosen, which is located at a distance of R = 3 mm; In _shte = .6 mm; d ¹ - 2.5 mm; welding current □ = 90 A; arc voltage U _A = 9.5 V; welding speed V _CB = 0.3 cm / s.

The tertiopair is mixed with the welding speed simultaneously with the torch, which is achieved by attaching the thermocouple to the bracket rigidly connected to the torch. A current jump of + 10-15% is carried out by changing the resistance of the ballast rheostat included in the welding circuit.

The resulting waveform of temperature changes over time is recorded using an oscilloscope. Further, by the value of 0.63 yT \ _ST , the value of the penetration time constant is determined (see Fig. 3).

The use of the invention improves the accuracy of determining the time constant, which, when calculating and setting up systems for automatic control of penetration, will improve the quality of products.

Claims (2)

(54) METHOD FOR DETERMINING PERMANENT TIME The invention relates to the field of automation of welding processes and can be used in calculations and design of systems for automatic control of the size of melting. There is a known method for determining the constant penetration time, in which a seam of specified geometrical parameters is preliminarily formed by an arc of fixed power, after which, during the welding process, the arc power is changed abruptly and the grooves are formed with other parameters, and the constant penetration time is determined by a change in the corresponding weld size (weld width, penetration width) with a stepwise change in one of the welding parameters — the current of foolishness, arc voltage U, or their correlation. In this case, the values of the time constant are determined by the time corresponding to the change in the value of penetration to a value of 0.63 & nor the established value of 11}. QUESTIONS 1. A disadvantage of the known method is that careful preparation of samples is required to increase the size of the transition boundary of the epididium scanner, moreover, when the voltage changes across an arc, the spot arc distorts the transition boundary. Hence, the accuracy of determination of the constant penetration is low, the repetition of the experiment is unsatisfactory. The aim of the invention is to improve the accuracy of determining the constant melting time. The goal is achieved by the fact that in the known method of determining the constant time of penetration, in which a seam of predetermined geometrical parameters is preliminarily formed by an arc of set power, then the arc process changes the arc power abruptly and forms a seam with other parameters, and the time of melting is determined according to the change in geometrical parameters in the interval of transition from one welding mode to the establishment of another, as a parameter to change the geometric dimensions of the gap The temperature measured continuously at a distance from the axis of the electrode equal to half the joint width is used. FIG. 1 shows the layout of the temperature sensor; in fig. 2 the temperature distribution in the plate along the axis of the shelter; in fig. 3 - determination of the constant penetration time using the oscillogram of temperature change. The temperature field in the plate according to the scheme of the linear heat source can be represented by the expression Vx t V C, dt. t r where 1, is the heat source power, W; V is the speed of movement of the heat source, m / s; a is the thermal conductivity coefficient, and A is the thermal conductivity coefficient Wm – ha; SL - plate thickness, m; i - time, s. For the quasistationary state, iTixd oVZci where KQ is the Bessel function. When the arc power changes by ucj (by changing the arc voltage of the welding current), the temperature field changes to a new quasi-decay state, respectively. The penetration width changes from B to B (see Fig. 1 and 2). The temperature changes at points A and AZ (i.e., Fig. 1) in the two-coordinate system of coordinates with syrosity occur almost simultaneously, since the point is located at a small distance from one another. It is known that w: Irina of the seam is proportional to the power of the arc, therefore, when going from one quasistated state to another, the isotherms occupy successive positions shown in fig. 2. Thus, there is a one-to-one correspondence between a change in temperature and a change in the width of penetration. The method of determining the constant penetration time is that it records an oscillogram of the transition process of changing the temperature by a sensor located at a distance from the electrode equal to the seam half width, after which the time constant is determined from the oscillogram. Approx. The temperature sensor is a practically inertia-free thermocouple, which is located at a distance of R 3 mm; .6 mm; from 2.5 mm; welding current J 90 A; voltage across the arc Yd 9.5 V; welding speed Vjjg 0.3 cm / s. TefMonapy is moved at a speed of welding simultaneously with the burner, which is achieved by mounting the thermocouple on a bracket rigidly connected to the burner. The current jump by + 10-15% is carried out by changing the resistance of the ballast rheostat included in the welding circuit. The resulting oscillogram of temperature change over time is recorded using an oscilloscope. Further, the value of the constant penetration time is determined by the value of 0.63 (see Fig. 3). The use of the invention makes it possible to increase the accuracy of determining the constant time, which, when calculating and setting up systems for the automatic adjustment of the melting, will improve the quality of products. The method of determining the constant penetration time, in which a seam is preliminarily formed with specified geometrical parameters by an arc of a fixed power & geometrical parameters on the time interval for the transition from one welding mode to the establishment of another, characterized in that, in order to improve accuracy, as a parameter for changing the geometry eskih suture sizes use the temperature as measured by continuously at a distance from the electrode axis, equal to half the width of the joint. Sources of information taken into account in the examination 1. N. Ilyenko. On the dynamics of regulation during argonodut welding on the weight of sheet steel. -Welding production, 1967, No. 4, p. 13-14 (prototype) ./ AT I QSJa Tycm 0