SU1426720A1 - Method of producing guaranteed penetration of edges in automatic argon arc welding with nonconsumable electrode - Google Patents

Abstract

The invention relates to welding production and can be used in the manufacture of edektro welded pipes. The goal is to increase the productivity and quality of the weld surface by eliminating weld undercuts. The increase in welding speed and the corresponding increase in current is carried out under the criterion parameter d,., Where d is the thermal spot diameter, dc is the diameter of the power spot arc. During the welding process, the current values of the welding current, welding speed, voltage are measured. arc, thickness of the material being welded, width and length of the weld pool, followed by using the result of the calculation to control the current and the welding speed. Compensation is also uncontrollable; technological disturbances. The method is used in pipe welding control systems on automatic arc welding units. 3 il. ; 55 (L

Description

4 GO

is smiling

1HE

The invention relates to welding production and can be used, for example, in the manufacture of welded pipes.

The aim of the invention is to achieve maximum productivity with guaranteed absence of defects in the form of undercuts,

The method is based on the known assumptions that the size and shape of the welding pool are determined by the thermal characteristics of the arc, and the movement of the molten metal nJDTOKOB along the melting and crystallization front is caused by the force effect of the arc on the melt. During the welding process, the dimensions are exposed to uncontrolled disturbances associated with changes in gas consumption, with erosion of electrophores, as well as with changes in thermal diffusivity and thermal conductivity of the material, which occurs due to changes in the chemical composition of the material, and the appearance of undercuts due to the size of the weld pool, and hydrodynamic processes in c. her.

Thus, to compensate for the effect on the weld formation process of the whole gamut of thermal and power disturbances, having control of the outside of the weld pool, it is necessary to have information on the parameters of the thermal floor and the force effect of the arc.

It is known that the effective thermal effect of an arc discharge is kakterizatsii with a diameter of thermal spot d, which is almost equal to the bath shaft B. The force effect of the arc on the metal is characterized by the diameter of the force spot d. It is well known that, if it is a generalized criterion, to accept the diameter ratio of 5, this qualitative formation is provided when the condition K (d./df,) is fulfilled. seam. To exclude undercuts, the quality criterion 1 is accepted.

Fig. 1 shows the influence of arc pressure on the melt of the weld pool a for the case when the diameter of the heat spot dr exceeds the diameter of the power spot dc, i.e. dr dcj 6 for the case when); in fig. 2 - kr0

five

0

five

0

d, - and dj changes. depending on the welding speed v when the penetration depth H is constant (the welding current increases simultaneously); in fig. 3 - automatic control system agreed with the invention.

To achieve the goal, take the condition that during welding d: 0.9 d-, and during the welding process; control the width of the weld pool B „, thereby controlling the diameter of the thermal spot of the arc, additionally control the length of the weld pool N.

With increasing welding speed, it is necessary to increase the welding current dp to ensure constant penetration depth. It was established that the diameters of both thermal and force spots of the arc grow, and the diameter of the power spot grows exponentially and at some moment begins to exceed the diameter of the heat spot. A further increase in speed leads to the appearance of undercuts along the edges of the welding rod. For the working speed Tr It is assumed that at which the current I бот corresponding to it creates a heat spot equal to the measured width of the seam В „and the force spot d,:, 0,9 d, ..:

It is known that the diameter of the power spot d.

five

d.

H L-.

- | kg

determined from the expression A. .rj; 2i

In

(one)

michi

0

0

five

. Where P

MCJKC

m "and

five

maximum pressure along the arc axis, Pa; minimum pressure defining the diameter of the power spot. Pa; K {- coefficient of concentration of the distributed pressure of the arc, see As the welding speed V increases, the welding current I increases synchronously and, consequently, the pressure of the R. lax ARC increases. Here, the pressure does not depend on the bath area, since we are dealing with a local value of the arc phenomenon. The minimum pressure P „,„, which determines the diameter, of the force spot, depends on the density of the material and the surface tension force, and also depends on the current I, as well as the maximal change of the current I, changes the position of the PMIM relative to the arc axis, but the value P min post n 14

but (for a given material), and the value Rddacs is variable and always on the arc axis.

Experimentally determined as follows.

During welding, the welding speed is gradually increased until the appearance of undercuts, while the values of the welding current and arc length remain constant. After welding, the width of the seam is measured. Then, an arc is ignited on a non-consumable anode with a gating hole (the current values and arc length are constant, as in welding), and the arc pressure is measured at a distance equal to half the width of the arc axis using a micromanometer. This is the value, c for steel 12X18UT determined experimentally and is 250 - 280 Pa. It was also experimentally established that

Rma ".75 -.1. K. 188 - 27.2- Inl

The quality of the seam formation corresponds to 1 or vice versa. To ensure the technological reserve for inaccuracies in the adjustment process, d 0.9V d 0.9 V is taken.

NIN, KC, RMIM

tion (1), get 2

-

,

-.1188 - 27.2 -Inl

 0.9 V

Hence, express the welding current

- e

152.3., E

4+ ag. at

Mwie

It is known that

  4S 2

  T t; g

0.724

-L- t

 -, fW

P

B, L - width R length welding

baths, cm;

a - coefficient of thermal diffusivity, cm / s; D is the coefficient of thermal conductivity, j / cm C; q — arc power, J / s; D is the material thickness, cm;

Тг ,, - melting point TepHanaj C, Expression (l) leads to

In t.

L TP

Taking into account that the penetration should be ensured throughout the entire thickness of the material, take the calculated penetration depth equal to the thickness of the material, i.e. Hp D. From the expression (5)

razhaet hp through get

B and L, as a result

H

R

I and dt,

four

mj

(6)

This equation is used in the method for adjusting the depth of the melt-down. The working speed VP is determined from

expressions

(five)

R

V. P

U

1 (vg, bb 5.b 4 gg. About 6

F

(7)

35

40

Equation (8) is used in the method for adjusting the welding speed to eliminate the appearance of defects in the form of undercut.

For the implementation of the method, the nominal values of the welding current Tj are specified, the welding voltages v, the arc voltage and the thickness of the product to be welded b. During the welding process, the values of the indicated parameters are measured at 1 c, Hz, U, DM, and their deviations are calculated & I

 1 "- 1", UV

- V,

n

li and „45

four)

50

- UH, & D В „- DH, the nominal penetration depth H is also set, provided that H, CH, Additionally, measure the length L, and the width B, of the weld pool, and determine the current penetration depth H p by calculation using the expression (b )

R

:: I

and

2-v,

D.

one

g I)

(-C 1

Sha l -C-)

(eight)

where 1 „, and„, UE, B

h

L "current

values of the parameters, and dp to achieve guaranteed penetration adjust the welding current in accordance with the expression

U-i to, - & v + Kj- & D - K, .D.and "

-t- KjH - Hp)

(9)

TO

where K ,, Kj, k, K, are adjustable coefficients,

a; then forcibly increase the welding speed to the working value determined by the expression (7), and for welding the weld without undercuts, the speed of the sights is changed in accordance with the extrusion

V .. (10)

142672П6

KM-8, the signal of which is converted by filtering and delaying unit 10, with a speed sensor 1I of speed of type g VEZ 1B, the signal of which is converted

UV VP p

block 12 frequency. Voltage and welding current signals are removed from measuring shunt 13 and converted by filter blocks 14 and 15, Parameters

10 of the welding bath is measured by an optoelectronic system created on the basis of the optical sensor 16 with a special filter that separates the image of the welding bath of the type ОКС-3, v- - m.

and

2052.3-b -US, 5). , 0 V

R

Uh

) c, B „- current values

 and 5 Si parameters,

; The use of the first three terms of equation (9), which determine the reciprocal of the directly measured disturbances, is necessary for the stabilization of the heat input per unit thickness of the material being welded and the coefficients K, K, Kj are approximated by the ratio

.(-one-)..

The last member of equation (9) determines the negative feedback on the deviation of the depth of melting, the use of which provides compensation for uncontrolled disturbances of heat and heat. The exact values of the coefficients K, Kj5 K.

9

K4 generally depends on the current values of the welding process parameters, therefore, to improve the quality of regulation, their values should be adjusted during the welding process in accordance with the required identification algorithm, and equation (S) can compensate for uncontrolled hydrodynamic disturbances.

The method is implemented in welding of welded pipes.

The weldable belt 1 is driven by the forming rolls 2 by means of the drive 3 at a speed v. The welding arc 4 is excited between the fire (gl och 5 and tube billet 6 fed from the controlled welding spot 7, melts the edges of the pipe, forming the weld pool 8 and forms the weld. The welding process is controlled by a contact thickness gauge 9 type

KM-8, the signal of which is converted by filtering and delaying unit 10, with a speed sensor 1I of speed of type g VEZ 1B, the signal of which is converted

block 12 frequency. Voltage and welding current signals are removed from measuring shunt 13 and converted by filter blocks 14 and 15, Parameters

The welding bath is measured by an optoelectronic system created on the basis of an optical sensor 16 with a special filter that separates the image of the welding bath type OX-3, the KT-2 television camera 17 and the PTU-50 television installation 18. Measured values VP, Б „, Uf ,, Б„, Ln are fed to the input of an analog computing device - controller

0 19, performed on operational amplifiers K140UD7, which has inputs. settings of settings U ,, DO and coefficients K, Kj, K., K4. The controller manages the control action.

5 over the current ul according to formula (9), which is summed with the manually settable operator manually set the current I ..

H

and is worked out by a tracking system of a controlled welding power source 7 0 created on the basis of the VKSM-1000 microfilters with a thyristor control unit, as well as on the speed of the remote controller according to the formula (S), which is summed up with the speed setting v and reflected on control system of the drive 3 of the mill, the Measured signals 1 ", and", D ,, B ,, L, -, are fed to the input 20 of the system for collecting and transmitting data to the microcomputer 21. by means of the device 22 interface with the object

ACSKS-1024-00G (USO) with a common bus 23. The computer 21 performs the calculation and control of the coefficient controller K, K, K, K through 5 interface unit 24 USO 22. In the developed system for the control of welding of pipes on ADS mills The microprocessor DZ-28 microcomputer used in its structure consists of a magnetic tape drive 25 required for storing software, an alphanumeric display 26, and a thermal printing device 27.

Using this system, a method was implemented to control the depth of penetration and welding speed in automatic argon-arc welding with a non-consumable electrode for welding stainless steel pipes 12X18H10T

0

five

with a diameter of 3.8 cm with a wall thickness of 0.2 cm on an ADS 10-60 mill,

For the base speed - 2 m / min (3.33 cm / s) - the geometrical dimensions of the weld pool were calculated using the expression (1) ki

-X 0.33 J / cmC. C, H 0.5, T „, I 400 A, and 20 V. The weld pool is 0.91 cm wide and 1.87 cm long, the current geometrical values were measured process welded with characteristics: a 0.07 cm / s

In addition, they control the welding bath parameters, which indirectly characterize the penetration depth, determine the current value of the penetration depth by calculation and compare it with the measured value, and the algebraic sum of all the error signals is used to tune the welding current under new conditions, characterized in that , in order to achieve maximum performance with guaranteed absence of defects in the form of undercuts by maintaining the heat spot diameter throughout the entire welding process d arc greater than the diameter of the power arc spot d, «during the welding current value and the width B of the weld puddle length Lq additionally measured, proschittvayut maximum allowable welding current value IMOKC wherein d is equal to

15

20

AT

h

25

 e

d 0.9 d

157.3-6. &

44 ggo;

1 "ax

And the maximum amount was 0.9 cm, and the length was 1.9 cm (they coincide with the calculated values). For a weld pool width of 0.9 cm, the permissible welding current is calculated by the formula (G), it is approximately 580 A, and by the formula (7) the working speed Vp is 6.65 cm / s, i.e. about 4 m / min. This suggests that the welding speed can be increased by 2 times without the loss of quality. Welding was carried out at a speed of 4 m / min, a current of 580 A, arc voltage of 20 V. The system ensured the uninterrupted operation of welding equipment during one shift (8 hours) with a break of 45 minutes associated with overproduction of electrode sharpening . In the process of welding, customizable coefficients were adapted in accordance with a one-step identification algorithm.

The use of the proposed welding method provides compensation for the effects on the process of measurable and uncontrolled technological disturbances, which allows, without loss of quality where K, - K4 are the control coefficients, increase the productivity of the continuous welding speed Vp, which ensures at a given current full prop7 and

R

m

Move

after

what the welding speed is forced to increase to the value of Vp according to the law and carry out substuv

P 35

recurrence of current in accordance with the expression

UI K, & v + KjAD - Kj & n - - K (H - Hp),

vani approximated from the relation d () О and substraitsess 2 times.

Claims (1)

Invention Formula The method of obtaining guaranteed penetration in automatic argon-arc welding with a non-consumable electrode, mainly when welding longitudinal pipe joints, at which the nominal parameters of the mode are set: welding current 1c, arc voltage U |, welding speed Vp and nominal edge thickness DH, control them in the process welds and calculate deviations from the nominal value; in addition, they set the penetration depth HH corresponding to the nominal thickness of the edges being welded. additionally control the parameters of the weld pool, which indirectly characterize the depth of penetration, determine the current value of the depth of penetration by calculation and compare it with the measured value, and the algebraic sum of all the error signals is used to adjust the welding current for new conditions, characterized in that in order to achieve maximum performance with guaranteed absence of defects in the form of undercuts by maintaining the heat spot diameter throughout the entire welding process arc d greater than the diameter of the power spot arc d, "during the welding process, the current widths and lengths of the weld pool length are additionally measured, the maximum allowable value of the welding current IMOKC at which d is equal AT h  e d 0.9 d 157.3-6. & 44 ggo; 1 "ax And extreme addition welding speed Vp, given this current full prop7 and R m Move after ZO tinkering dd where K, - K4 - the coefficients of the what the welding speed is forced to increase to the value of Vp according to the law and carry out substuv P 35 recurrence of current in accordance with the expression  K, - K4 - coefficients re UI K, & v + KjAD - Kj & n - - K (H - Hp), where K, - K4 - coefficients vani, approximately determined from the relation d () O and p45 identified during the process in accordance with the required algorithm, identification; and, the Hp is determined from the expression H 0  Jn un / mi - bh ). Iih Where -P and and § Vn, BP - current (measured) parameter values .but, 0.348 LP 2 PA GO, 0.724 4a Z. TT ;, temperature coefficient of 1426720 water content coefficient of thermal conductivity, J / cm-s. WITH; thermal efficiency of the arc, ten I p and " thermal power of the arc, j / s; TeNmepaTypa melting material, C. (s, s / t, H dr tfc Thebes. one I / Phage. 2 Fig.d