An intelligent preheating flash butt welding method considering the change of the temperature field of the welded joint

Abstract

The present invention discloses an intelligent preheating flash butt welding method considering the change of the temperature field of the welded joint, including clamping, flashing flat stage, preheating stage, continuous flashing stage, upsetting stage and reset stage. In the flashing flat stage, according to the welding current I t and the threshold current I 门限 relationship and the temperature field of the welded joint, control the time and number of flashes for a single flashing flat to ensure that the flashing flat is completed under the conditions of the shortest time, the least material and energy consumption. In the preheating stage, according to the welding current I t and the threshold current I 门限 relationship and the temperature field of the welded joint, control the single preheating cooling time and the number of preheating times to improve the heating efficiency and quality and shorten the consumption in the preheating stage. In the continuous flashing stage, determine the starting point of continuous flashing according to the distance between the moving and static fixtures when the welding current is greater than the threshold current for the first time in this stage. In the upsetting stage, control the time of non-electric upsetting according to the temperature field of the welded joint, and shorten the upsetting holding time on the premise of ensuring the weld strength, which has the advantage of improving the welding efficiency.

Description

Technical Field

[0001] The present invention relates to machining technology, and in particular to a method for controlling preheating flash butt welding according to the change of the temperature field of the weld joint. Background Art

[0002] With the development of science and technology, the application of flash butt welding technology is becoming increasingly widespread, and the requirements for the strength, welding efficiency and energy consumption of welds are also getting higher and higher. The key to obtaining high-quality welds is to establish a consistent temperature field near the weld joint during the continuous flashing process before upsetting. However, due to the influence of random factors such as the initial temperature of the workpiece, the fluctuation of the power grid voltage, and the deviation of the alignment angle of the workpiece, it becomes extremely difficult or requires a long time, a large amount of materials and energy to establish a stable and consistent temperature field near the weld joint.

[0003] Chinese Patent No. 202111432144.0 discloses a flash welding method with short-circuit preheating. During the flash flattening stage, the cross-section to be welded of the rail is flattened and cleaned through flash blasting; during the short-circuit preheating stage, the end face of the rail is heated to a sufficient temperature by setting parameters such as the predetermined number of times of cyclic contact and separation, contact time, separation time, and applied voltage. This method is prone to cause material consumption and energy consumption for workpieces with different flatness degrees and inclination angles during the flash flattening stage through flash blasting; the preheating stage does not consider the actual working conditions, such as the welding quality fluctuations caused by different initial temperatures of the workpieces and the change of welding voltage, and the problem of unstable welding process, which is prone to cause overheating and material burning.

[0004] Chinese Patent No. 202110450016.2 discloses a flash welding method. During the pressure holding and cooling step after upsetting, the phase change process of the hot plastic metal in the joint area is completed by maintaining the upsetting force to obtain a solid-state welded joint. This method cannot accurately control the upsetting holding time according to the actual cooling process of the workpiece during the upsetting stage, which is prone to problems such as time waste and low welding efficiency. Summary of the Invention

[0005] Object of the Invention: The present invention aims to provide a method for dynamically adjusting and controlling preheating flash butt welding according to the change of the temperature field of the weld joint.

[0006] Technical Solution: The intelligent preheating flash butt welding method considering the change of the temperature field of the weld joint according to the present invention includes clamping, flash flattening stage, preheating stage, continuous flashing stage, upsetting stage and resetting stage. Among them, during the flash flattening stage, the time and number of flash flattening times for a single time are controlled according to the relationship between the welding current I t and the threshold current I 门限 and the temperature field of the weld joint; during the preheating stage, according to the welding current I t and the threshold current I 门限Control the single preheating and cooling time and the number of preheating times according to the relationship and the weld temperature field; in the continuous flashing stage, determine the starting point of continuous flashing according to the distance between the moving and static jigs when the welding current is greater than the threshold current for the first time in this stage; in the upsetting stage, control the non-electric upsetting time according to the weld temperature field.

[0007] Further, the flashing and flattening stage includes the following steps:

[0008] (2.1) Electrode energization;

[0009] (2.2) The moving jig advances at a speed of v1 for flashing and flattening until I t >I 门限 , the moving jig stops and the flashing and flattening stops;

[0010] (2.3) Measure and extract the weld temperature field data to form a matrix Traverse the matrix T0 to extract the highest temperature t ij , this highest temperature t ij is located in the i-th row and j-th column of T0, and count the number of elements N1 in the j-th column vector of T0 whose values are greater than the flashing and flattening minimum temperature T c1 ;

[0011] (2.4) If control the moving jig to retreat at a speed of -v1 until I t <I 门限 stop and return to (2.2);

[0012] If traverse the j-th column vector {t 0j ,…,t mj} of T0, and extract the vector {t aj ,t (a+1)j …t (b-1)j ,t bj}, this vector is the measured temperature data of the end face where the highest temperature point on the weldment is located, where W is the width of the temperature field; D is the width of the weldment, η1 is the flashing and flattening coefficient, t aj is the first element greater than or equal to the flashing and flattening minimum temperature T c1 , t bj is the last element greater than or equal to T c1 , and a and b are constants, 0≤a≤b≤m;

[0013] (2.5) The flashing and flattening stage ends.

[0014] Further, the preheating stage includes the following steps:

[0015] (3.1) Start heating: The moving jig advances at a speed of v2 until I t >I 门限, continue to move forward at a speed of v2, stop after preheating and compressing by Δp, and the end faces of the welded parts are in close contact for heating;

[0016] (3.2) Measure and extract the temperature field data of the weld to form a matrix T1, and construct a vector {t' aj , t ( ' a+1)j … t' (b-1)j , t' bj};

[0017] (3.3) If Maintain heating and return to (3.2); if Stop heating, the moving fixture retreats at a speed of -v2 until t I < I 门限 The moving fixture stops and the welded parts cool down; where T c2 is the maximum heating temperature;

[0018] (3.4) Measure and extract the temperature field data of the weld to form a matrix T2, and construct a vector {t' a ' j , t ( ” a+1)j … t' ( ' b-1)j , t' b ' j};

[0019] (3.5) If Increment j by one and return to (3.4);

[0020] If Then the vector {t' a ' j , t ( ” a+1)j … t' ( ' b-1)j , t' b ' j} is the vector with the lowest average measured temperature on the welded parts; where T c3 is the lowest temperature of the welded parts;

[0021] (3.6) Measure and extract the temperature field data of the weld to form a matrix T3, and construct a vector

[0022] (3.7) If Return to (3.6); if This cooling ends; where T c4 is the lowest cooling temperature;

[0023] (3.8) Measure and extract the temperature field data of the weld to form a matrix T4, and construct a vector Where, L a is the melting length, L b is the upsetting length; if and then the preheating is completed; otherwise, return to (3.1).

[0024] Further, the continuous flashing stage includes the following steps:

[0025] (4.1) Determine the starting point of continuous flashing: The moving fixture advances at a speed of v4 until I t > I 门限 At this time, the moving fixture stops, and the starting point of continuous flashing is determined. At this time, let the distance between the moving and static fixtures at the start of continuous flashing be l1 = l, where l is the current distance between the moving and static fixtures;

[0026] (4.2) Measure the welding current I again t , when I t > I 门限 , the moving fixture retreats at a speed of until I t ≤ I 门限 ; when I t ≤ I 门限 , the moving fixture advances at a speed of for continuous flashing until I t > I 门限 ; where, L a is the melting length, η2 is the dynamic continuous flashing length coefficient, and v3 is a fixed value, which is the minimum speed of the defined flashing stage;

[0027] (4.3) Judge the continuous flashing distance. If l > l1 - η2L a , then return to (4.2);

[0028] If l ≤ l1 - η2L a , the moving fixture makes a uniform feeding motion at a speed of v4 until l ≤ l1 - L a , the moving fixture stops, and the continuous flashing stage ends.

[0029] Further, the upsetting stage includes the following steps:

[0030] (5.1) Let t = 0. The initial distance l2 between the moving and static fixtures at the start of upsetting is l, where l is the current distance between the moving and static fixtures;

[0031] (5.2) The moving fixture advances at a speed of v5 for energized upsetting until the energized upsetting time requirement is met: t ≥ t0; where t0 is the energized upsetting time;

[0032] (5.3) Cut off the welding machine current and start non-energized upsetting;

[0033] (5.4) The moving fixture advances at upsetting speed v5 to l2 - L b and then stops. The moving fixture remains stationary at l2 - L b and measures and extracts the temperature field data of the weld to form matrix T5, and extracts the maximum temperature where L b is the upsetting length;

[0034] (5.5) If the upsetting is completed, otherwise return to (5.4); where T c6 is the lowest temperature during cooling in the upsetting stage.

[0035] Furthermore, the reset stage includes the following steps:

[0036] (6.1) The moving fixture and the static fixture are loosened;

[0037] (6.2) The moving fixture retracts to the initial position and the welding process ends.

[0038] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are as follows: 1. In the flashing and flattening stage, the true flashing and flattening process of the weld can be obtained in real time. For workpieces with different flatness and inclination angles, flashing and flattening can be completed under the conditions of the shortest time, the least material and energy consumption; 2. In the preheating stage, by obtaining the temperature distribution near the weld in real time and dynamically adjusting the heating and cooling time each time, the heating efficiency is effectively improved, and material burning caused by overheating is avoided; and the number of heating times during each welding is dynamically adjusted according to the change of the temperature distribution on both sides of the weld to obtain a weld with an ideal temperature distribution, thereby providing a good foundation for the continuous flashing stage and avoiding problems such as welding quality fluctuations and unstable welding process caused by different initial temperatures of the workpiece and changes in welding voltage, and can also further shorten the time and energy consumed in the preheating stage; 3. In the upsetting stage, the temperature change near the weld can be obtained in real time, so as to shorten the upsetting holding time on the premise of ensuring the weld strength, and has the advantage of improving welding efficiency. Description of the Drawings

[0039] Figure 1 is the flow chart of the flashing and flattening stage of the present invention;

[0040] Figure 2 is the flow chart of the preheating stage of the present invention;

[0041] Figure 3 is the flow chart of the continuous flashing and upsetting stages of the present invention;

[0042] Figure 4 is the working principle diagram of the flash butt welder. Detailed Embodiments

[0043] The present invention will be further described below with reference to the accompanying drawings.

[0044] The intelligent preheating flash butt welding method considering the change of the temperature field of the welded joint according to the present invention includes clamping, flashing flat stage, preheating stage, continuous flashing stage, upsetting stage and resetting stage. Among them, in the flashing flat stage, according to the welding current I t and the threshold current I 门限 relationship and the temperature field of the welded joint to control the time and number of flashes for single flashing flat; in the preheating stage, according to the welding current I t and the threshold current I 门限 relationship and the temperature field of the welded joint to control the single preheating and cooling time and the number of preheating times; in the continuous flashing stage, determine the starting point of continuous flashing according to the distance between the moving and static fixtures when the welding current is greater than the threshold current for the first time in this stage; in the upsetting stage, control the time of non-electric upsetting according to the temperature field of the welded joint.

[0045] Parameter setting: the temperature field T near the welded joint; the length of the temperature field L = 300 mm; the width of the temperature field W = 200 mm; the width of the welded part D = 80 mm.

[0046] Step 1, clamping: Clamp the paired welded parts in the moving fixture and the static fixture with a distance of l0 = 85 mm between them, and monitor the current distance l between the moving and static fixtures and the welding current I t in real time during the welding process.

[0047] Step 2, flashing flat:

[0048] Flashing flat parameter setting: flashing flat speed v1 = 1 mm / s; threshold current I 门限 = 450 A; flashing flat minimum temperature T c1 = 1300 °C; flashing flat coefficient η1 = 0.9.

[0049] (2.1) The electrodes are energized;

[0050] (2.2) The moving fixture advances and flashes flat at a speed of v1 (1 mm / s) until I t > I 门限 (450 A), and the moving fixture stops and the flashing flat stops;

[0051] (2.3) Measure and extract the temperature field data near the welded joint to form an (m + 1)*(n + 1) matrix Traverse the matrix T0 to extract the highest temperature t ij , this highest temperature is located in the i-th row and j-th column of T0, and count the number of elements N1 in the j-th column vector of T0 whose values are greater than the flashing flat minimum temperature T c1 (1300 °C);

[0052] (2.4) If Control the moving fixture to retract at a speed of -v1 (-1 mm / s) to I t <I 门限 (450 A) Stop and return to (2.2);

[0053] If Traverse the j-th column vector {t 0j ,…,t mj} of T0, and extract the vector {t aj ,t (a+1)j …t (b-1)j ,t bj}, which is the temperature measurement data at the end face where the highest temperature point on the welded part is located. Among them, t aj is the first element greater than or equal to the lowest temperature T c1 of flash flattening, and t bj is the last element greater than or equal to T c1 . a and b are constants, where 0 ≤ a ≤ b ≤ m;

[0054] (2.5) The flash flattening stage ends.

[0055] Step three, preheating:

[0056] Set preheating parameters: preheating speed v2 = 6 mm / s; preheating compression Δp = 0.2 mm; maximum heating temperature T c2 = 1500 °C; minimum temperature of the welded part T c3 = 1200 °C; minimum cooling temperature T c4 = 1450 °C; minimum temperature after preheating completion T c5 = 1400 °C; burning length L a = 10 mm; upsetting length L b = 15 mm.

[0057] (3.1) Start heating: The moving fixture makes a feeding motion at a speed of v2 (6 mm / s) until I t >I 门限 (450 A), continue to move forward by Δp (0.2 mm) at a speed of v2 (6 mm / s) and then stop, and the end face of the welded part is in close contact for heating;

[0058] (3.2) Measure and extract the temperature field data near the weld to form a matrix T1, and construct a vector {t' aj ,t′ (a+1)j …t' (b-1)j ,t' bj};

[0059] (3.3) If Maintain heating and return to (3.2);

[0060] If Stop heating, the moving fixture retracts at a speed of -v2 (-6 mm / s) until I t <I 门限 (450 A) The moving fixture stops and the welded part cools down;

[0061] (3.4) Measure and extract the temperature field data near the weld to form matrix T2, and construct the vector {t″ aj , t″ (a+1)j … t″ (b-1)j , t″ bj};

[0062] (3.5) If Let j increment by one and return to (3.4);

[0063] If Then the vector {t″ aj , t″ (a+1)j … t″ (b-1)j , t″ bj} is the vector with the lowest average measured temperature on the welded part;

[0064] (3.6) Measure and extract the temperature field data near the weld to form matrix T3, and construct the vector

[0065] (3.7) If Return to (3.6);

[0066] If This cooling is completed;

[0067] (3.8) Measure and extract the temperature field data near the weld to form matrix T4, and construct the vector Among them, If And The preheating is completed, otherwise return to (3.1).

[0068] Step Four, continuous flashing:

[0069] Flashing parameter setting: Dynamic continuous flashing length coefficient η2 = 0.8; The initial distance l1 between the moving and static fixtures at the start of flashing; Flashing initial speed v3 = 0.6 mm / s; Flashing final speed v4 = 2 mm / s.

[0070] (4.1) Determine the starting point of continuous flashing: The moving fixture makes a feeding movement at a speed of v4 (2 mm / s) until I t >I 门限 (450 A), the moving fixture stops, determine the starting point of flashing, and at this time let the distance l1 between the moving and static fixtures at the start of continuous flashing be l;

[0071] (4.2) Measure the welding current I again t , when It >I 门限 (450 A), the moving fixture retracts at a speed until I t ≤I 门限 (450 A); when I t ≤I 门限 (450 A), the moving fixture advances at a speed for continuous flashing until I t >I 门限 (450 A);

[0072] (4.3) Judge the continuous flashing distance. If l > (l1 - 8) mm, return to (4.2);

[0073] If l ≤ (l1 - 8) mm, the moving fixture makes a uniform feeding motion at a speed of v4 (2 mm / s) until l ≤ l1 - 10 mm, then the moving fixture stops and the continuous flashing stage ends.

[0074] Step Five, upsetting:

[0075] Upsetting parameter setting: the initial distance l2 between the moving and static fixtures at the start of upsetting; the energized upsetting time t0 = 0.1 s; the upsetting speed v5 = 40 mm / s; the lowest temperature T c6 = 600 °C.

[0076] (5.1) Let t = 0, and the initial distance l2 between the moving and static fixtures at the start of upsetting is l;

[0077] (5.2) The moving fixture advances at an upsetting speed of v5 (40 mm / s) for energized upsetting until the energized upsetting time requirement is met: t ≥ t0 (0.1 s);

[0078] (5.3) Cut off the welding machine current and start non-energized upsetting;

[0079] (5.4) The moving fixture advances to (l2 - 15) mm at an upsetting speed of v5 (40 mm / s) and then stops. The moving fixture remains stationary at (l2 - 15) mm, measure and extract the weld joint temperature field data to form a matrix T5, and extract the highest temperature t ij ;

[0080] (5.5) If the upsetting ends, otherwise return to (5.4).

[0081] Step Six: Reset:

[0082] (6.1) Release the moving and static fixtures;

[0083] (6.2) The moving fixture retracts to the initial distance l0 (85 mm), and the welding process ends.

Claims

1. An intelligent preheating flash butt welding method considering the change of the temperature field of the welded joint, characterized in that, It includes a clamping stage, a flashing flat stage, a preheating stage, a continuous flashing stage, a upsetting stage and a resetting stage. Among them, in the flashing flat stage, the time and number of flashing flats for a single time are controlled according to the relationship between the welding current I t and the threshold current I 门限 and the weld joint temperature field; in the preheating stage, the time and number of preheating and cooling for a single time are controlled according to the relationship between the welding current I t and the threshold current I 门限 and the weld joint temperature field; in the continuous flashing stage, the starting point of continuous flashing is determined according to the distance between the moving and static jigs when the welding current is greater than the threshold current for the first time in this stage; in the upsetting stage, the non-electric upsetting time is controlled according to the weld joint temperature field.

2. The intelligent preheating flash butt welding method considering the change of the weld temperature field according to claim 1, characterized in that, The flashing and flattening stage includes the following steps: (2.1) Energize the electrodes; (2.2) The moving fixture advances and flashes flat at a speed of v1 until I t > I 门限 , the moving fixture stops and the flashing flat stops; (2.3) Measure and extract the temperature field data of the welded joint to form a matrix Traverse the matrix T0 to extract the highest temperature t ij , this highest temperature t ij is located in the i-th row and j-th column of T0. Count the number of elements N1 in the j-th column vector of T0 whose values are greater than the lowest temperature T of the flash butt welding c1 ; (2.4) If Control the moving fixture to retract to I at a speed of -v1 t <I 门限 Stop and return to (2.2); If traverse the j-th column vector {t 0j , …, t mj} of T0, and extract the vector {t aj , t (a+1)j … t (b-1)j , t bj}, where W is the width of the temperature field; D is the width of the welded part, η1 is the flashing flat coefficient, t aj is the first element greater than or equal to the flashing flat minimum temperature T c1 , t bj is the last element greater than or equal to T c1 , a and b are constants, 0 ≤ a ≤ b ≤ m; (2.5) The flashing and flattening stage ends.

3. The intelligent preheating flash butt welding method considering the change of the weld temperature field according to claim 2, characterized in that, The preheating stage includes the following steps: (3.1) Start heating: The moving fixture advances at a speed of v2 until I t >I 门限 , continue to advance at a speed of v2, stop after preheating the compression amount Δp, and the end faces of the welded parts are in close contact for heating; (3.2) Measure and extract the temperature field data of the welded joint to form a matrix T1, and construct a vector {t' aj , t′ (a+1)j … t' (b-1)j , t' bj}; (3.3) If where T c2 is the maximum heating temperature; maintain heating and return to (3.2); if stop heating, the moving fixture retracts at a speed of -v2 until I t < I 门限 the moving fixture stops and the welded part cools down; (3.4) Measure and extract the temperature field data of the welded joint to form a matrix T2, and construct a vector {t″ aj , t″ (a+1)j … t″ (b-1)j , t″ bj}; (3.5) If increment j by one and return to (3.4); If then the vector {t″ aj , t″ (a+1)j … t″ (b-1)j , t″ bj} is the vector with the lowest average measured temperature on the welded part; where T c3 is the lowest temperature of the welded part; (3.6) Measure and extract the temperature field data of the welded joint to form matrix T3 and construct a vector (3.7) If return (3.6); If this cooling ends; where T c4 is the lowest cooling temperature; (3.8) Measure and extract the temperature field data of the welded joint to form matrix T4, and construct a vector where L a is the melting length, L b is the upsetting length, and L is the length of the temperature field; if and then the preheating is completed; otherwise, return to (3.1).

4. The intelligent preheating flash butt welding method considering the change of the weld temperature field according to claim 1, characterized in that, The continuous flashing stage includes the following steps: (4.1) Determine the starting point of continuous flashing: The moving fixture advances at a speed of v4 until I t > I 门限 When this occurs, the moving fixture stops, and the starting point of continuous flashing is determined. At this time, let the distance between the moving and static fixtures at the start of continuous flashing be l1 = l, where l is the current distance between the moving and static fixtures; (4.2) Measure the welding current I again t , when I t > I 门限 , the moving fixture retreats at a speed of until I t ≤I 门限 ; when I t ≤I 门限 , the moving fixture advances and flashes continuously at a speed of until I t > I 门限 ; where L a is the melting length, η2 is the dynamic continuous flash length coefficient, and v3 is the minimum speed in the custom flash stage, which is a fixed value; (4.3) Determine the continuous flash distance. If l > l1 - η2L a , then return to (4.2); If \(l\leq l_1-\eta^2L\) a , the moving fixture makes a uniform feeding motion at a speed of \(v_4\) until \(l\leq l_1 - L\) a , the moving fixture stops and the continuous flashing stage ends.

5. The intelligent preheating flash butt welding method considering the change of the weld temperature field according to claim 1, characterized in that, The upsetting stage includes the following steps: (5.1) Let t = 0. At the start of upsetting, the initial distance l2 between the moving and stationary jigs is l, where l is the current distance between the moving and stationary jigs; (5.2) The moving jig advances at a speed of v5 for energized upsetting until the energized upsetting time requirement is met: t ≥ t0; where t0 is the energized upsetting time; (5.3) Cut off the welding machine current and start non-energized upsetting; (5.4) The moving fixture advances at upsetting speed v5 to l2 - L b and stops. The moving fixture remains stationary at l2 - L b and measures and extracts the weld temperature field data to form matrix T5, and extracts the highest temperature where L b is the upsetting length; (5.5) If upset forging is completed, otherwise return to (5.4); where T c6 is the lowest temperature for cooling during the upset forging stage.

6. The intelligent preheating flash butt welding method considering the change of the weld temperature field according to claim 1, characterized in that, The resetting stage includes the following steps: (6.1) Release the moving and stationary jigs; (6.2) The moving jig retracts to the initial position and the welding process ends.

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