Preheat flash butt welding method

Abstract

The present invention discloses a preheat flash butt welding method including fixture clamping, flash flattening stage, preheating stage, continuous flashing stage, upset stage and reset stage, and controls the advance and retreat of the moving fixture in the flash flattening stage, preheating stage and continuous flashing stage according to the relationship between the welding current and the threshold current, and determines the flash flattening starting point according to the distance between the moving fixture and the stationary fixture when the welding current is larger than the threshold current for the first time in this stage, and similarly determines the starting point of continuous flashing in the continuous flashing stage. The present invention can automatically determine the flash flattening starting point, more accurately realize the flash flattening, and avoid material waste, and controls the advance and retreat of the moving fixture and the amount of further preheat compression according to the relationship between the welding current and the threshold current in the preheating stage, so that the preheating is stable, the material consumption is small, the advance speed of the continuous flashing stage is proportional to the flashing distance, and the effect of accelerating the flashing is generated, and the energy accumulation is fast, the flashing is not easily interrupted, and the material consumption is small, and ensures that the optimal flashing speed is reached at the end of the flashing.

Description

[Technical field]

[0001] The present invention relates to machining techniques, and in particular to a preheat flash butt welding method. [Background technology]

[0002] Marine anchor chains and mooring anchor chains are chains that connect anchors to ship hulls or marine engineering equipment. With the increase in the demand for marine resources in countries around the world, and the destruction of marine resource exploration and oil production facilities and mooring units due to poor sea conditions and natural weather such as tsunamis, hurricanes, and frequent earthquakes in the sea area in recent years, the demand for high-level mooring chains for marine engineering is constantly increasing. With the progress of marine development, the operation of mooring units such as new marine platforms and related marine engineering structures has begun, and the demand for high-level mooring chains as an essential safety assurance part for marine oil production and mining equipment fixing devices will become increasingly large.

[0003] Chinese Patent 201080048430.0 discloses a method for flash butt welding rail steel, which controls the heat-affected width of the head of the welded joint to 27 mm or less by regulating the time of current flow in the preheating process, so as not to significantly affect the structural performance of the rail after this. Chinese Patent 201910407841.7 discloses a flash butt welding method for hard alloy blades, which contacts and separates the workpiece ports multiple times during preheating before welding until all of the ports are heated to the rated temperature, and limits the current flow time each time. During intermittent flash butt welding, the initial speed and acceleration of the moving clamp are set to perform an accelerated forward movement, and the upset speed is adopted after a predetermined flash remaining amount is reached. However, the preheating step is not adjusted according to the actual working conditions. For example, the preheating step cannot control the change in threshold current, etc., so that when performing the flashing step, the flashing step is interrupted due to insufficient temperature, and the subsequent flashing step and preheating are alternated, which further leads to an uncontrollable melting length. The flash acceleration stage is not adjusted to the actual melting situation, which is likely to affect the quality of the welded joint. Summary of the Invention [Problem to be solved by the invention]

[0004] Object of the invention: The object of the present invention is to provide a preheat flash butt welding method which adjusts according to actual working conditions. [Means for solving the problem]

[0005] Technical solution: the preheating flash butt welding method described in the present invention includes a fixture clamping, a flash flattening stage, a preheating stage, a continuous flashing stage, an upset stage and a reset stage, in which the advancement and retreat of the moving fixture is controlled based on the relationship between the welding current i and the threshold current I in the flash flattening stage, the welding current is greater than the threshold current for the first time in this stage, and the flash flattening starting point is determined based on the distance between the moving fixture and the stationary fixture, and similarly the starting point of continuous flash in the continuous flashing stage is determined.

[0006] Further, the flash planarization step further comprises: A step (2.1) of applying a current to the electrodes; a step (2.2) of determining a flash flattening starting point, in which the moving jig advances at a speed of ν0, and when the welding current i becomes >I for the first time, the moving jig stops, and the flash flattening starting point is determined, and at this time, the distance i0 between the moving jig and the stationary jig at the start of flash flattening is set to =l; If i>I, the moving jig retreats at a speed of -ν0 until i≦I, and if i≦I, the moving jig advances at a speed of ν0 until i>I, thereby performing flush flattening (2.3); Determine the flush flattening distance and check if the current distance l between the moving jig and the stationary jig is > i0-L a (L a is the flash flattening length), return to step (2.3) and conversely, step (2.4) where the flash flattening phase ends.

[0007] Furthermore, the preheating step comprises: Step (3.1) of setting n = 0, The moving jig advances at a speed of ν1, and when i > I, it continues to advance by a preheating compression amount Δp at a speed of ν1 so that the end faces of the two workpieces to be welded are brought into closer contact. Step (3.2), Step (3.3) where the moving jig stops for a time t1, Step (3.4) where the moving jig retracts at a speed of -ν1 until i ≤ I, The moving jig is at time t s Step (3.5) of stopping, n := n + 1, and when n < N (N is the rated number of preheating times), it returns to (3.2), and conversely, step (3.6) of ending the preheating stage.

[0008] The continuous flash stage includes: Step (4.1) of determining the starting point of the continuous flash. The moving jig advances at a speed of ν3, and when i ≤ I, the moving jig stops, determines the starting point of the continuous flash, and at this time, sets the distance i1 between the moving jig and the stationary jig at the start of the continuous flash to = l. Step (4.1), When i > I, until i ≤ I, the moving jig

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[0009] The upsetting step includes: Set t to 0, and the initial distance between the moving jig and the stationary jig at the start of the upset

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[0010] The reset step comprises: A step (6.1) of releasing the moving fixture and the stationary fixture; The moving fixture returns to the initial position and the welding process ends (6.2). Effect of the Invention

[0011] The beneficial effects are as follows: Compared with the prior art, the notable advantages of the present invention are: 1. In the flash flattening stage, the present invention automatically judges the flash flattening starting point based on the electrode position where the welding current is greater than the threshold current for the first time, so as to more accurately realize the flash flattening and avoid material waste; 2. In the preheating stage, the advance and retreat of the moving jig and the amount of further preheating compression are controlled based on the relationship between the welding current i and the threshold current I, so as to have the advantages of stable preheating and low material consumption; 3. The forward speed of the successive flashing stages is proportional to the flashing distance, so as to have the effect of accelerating the flashing, and has the advantages of fast energy accumulation, less interruption of the flashing, and small material consumption, so as to ensure that the optimal flashing speed is reached at the end of the flashing; 4. The present invention automatically identifies the welding start position and ensures the consistency of the length after welding; 5. In the flash flattening stage, the present invention avoids the problems of uneven heating and flash discontinuity caused by the unevenness and inconsistency of the end surface of the workpiece to be welded; 6. The preheating stage, which can be controlled in number, improves the consistency of the input energy, reduces the loss of material, and ensures the continuous progress of the subsequent successive flashing. [Brief description of the drawings]

[0012] [Figure 1] 2 is a flowchart of the present invention. [Diagram 2] FIG. 2 is a typical electrode position signal diagram during preheat flash butt welding. [Diagram 3] FIG. 2 is a typical current signal diagram during preheat flash butt welding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be further described below with reference to the drawings.

[0014] The welding parameters related to the preheat flash butt welding method described in the present invention are the welding current i, the current distance l between the moving jig and the stationary jig, and the initial distance l between the moving jig and the stationary jig at the start of flash flattening.

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[0015] The specific steps are as follows:

[0016] (1) Jig clamping: A pair of workpieces to be welded are clamped within a moving jig and a stationary jig that are separated by a distance l0 (80 mm), and the current distance l between the moving jig and the stationary jig and the welding current i during welding are monitored in real time.

[0017] (2) Flash flattening stage: (2.1) Pass a current through the electrodes.

[0018] (2.2) Determine the flash flattening starting point: The moving jig advances at a speed of ν0 (1 mm / s). When the welding current i becomes > (450 A) for the first time, the moving jig stops and the flash flattening starting point is determined. At this time, the distance between the moving jig and the stationary jig at the start of flash flattening is

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[0019] (2.3) If i>I(450A), the moving jig retreats at a speed of -ν0 (-1 mm / s) until i≦I(450A), and if i≦I(450A), the moving jig advances at a speed of ν0 (1 mm / s) until i>I(450A), beginning flush flattening.

[0020] (2.4) Determine the flush flattening distance, and determine the current distance l between the moving fixture and the stationary fixture.

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[0021] (3) Preheating stage: (3.1) Set n = 0.

[0022] (3.2) The moving jig moves forward at a speed of ν1 (10 mm / s), and when i>I (450 A), it continues to move forward by Δp (0.5 mm) at a speed of ν1 (10 mm / s) to bring the end faces of the two workpieces to be welded into closer contact, as shown by s1 in Figure 2.

[0023] (3.3) The moving jig stops at time t1 (2 s), as shown by s2 in FIG.

[0024] Until (3.4) i ≤ I (450 A), the moving jig retreats at a speed of -ν1 (-10 mm / s), as shown by s3 in Figure 2.

[0025] (3.5) The moving jig stops for a time t2 (1 s), as shown by s4 in Figure 2.

[0026] (3.6) n := n + 1. When n < N (9), it returns to (3.2), and conversely, the preheating stage ends.

[0027] (4) Continuous flash stage: (4.1) Determine the starting point of continuous flashing: The moving jig moves forward at a speed of ν3 (2 mm / s). When i > I (450 A), the moving jig stops, determining the starting point of continuous flashing. At this time, the initial distance between the moving jig and the stationary jig at the start of continuous flashing

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[0028] (4.2) When i > I (450 A), until i ≤ I (450 A), the moving jig

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[0029] (4.3) Judge the distance of continuous flashing,

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[0030] (5) Upset Phase: (5.1) Set t = 0, and set the initial distance between the moving jig and the stationary jig at the start of the upset.

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[0031] (5.2) The moving jig advances at an upset speed of ν4 (35 mm / s) and performs the charge upset. At this time, t ≥ t u The currently elapsed time t continues to be recorded until it reaches (0.2 s), which is shown as s5 in FIG.

[0032] (5.3) The welding current is switched off.

[0033] (5.4) The moving jig is upset at a speed of ν4 (35 mm / s).

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[0034] (5.5) Moving fixture

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[0035] (6) Reset phase: (6.1) Release the moving fixture and the stationary fixture.

[0036] (6.2) The moving jig returns to l0 (80 mm) from the initial distance, and the welding process ends. [Explanation of symbols]

[0037] In the figure, s1-forward, s2-heat, s3-reverse, s4-balance, s5-powered upset, s6-powered upset

Claims

1. 1. A preheat flash butt welding method comprising the steps of:

1. A preheating flash butt welding method comprising: a jig clamping step, a flash flattening step, a preheating step, a continuous flashing step, an upset step and a reset step, wherein the advancement and retreat of the moving jig is controlled based on the relationship between the welding current i and a threshold current I in each of the flash flattening step, the preheating step and the continuous flashing step, and a flash flattening starting point is determined based on the distance between the moving jig and the stationary jig when the welding current is greater than the threshold current for the first time in this step in the flash flattening step, and a starting point of continuous flash in the continuous flashing step is similarly determined.

2. The flash planarization step includes: A step (2.1) of energizing the electrodes; In the step (2.2) of determining the flush flattening starting point, the moving jig is moved to v 0 When the welding current i becomes >I for the first time, the moving jig stops and the flash flattening start point is determined. At this time, the distance between the moving jig and the stationary jig at the start of flash flattening is [0025] Step (2.2) of setting = l; When i>I, the moving jig moves to −ν 0 When i≦I, the moving jig moves back at a speed of v 0 a step (2.3) of flash flattening by advancing at a speed of Determine the flush flattening distance, and the current distance l between the moving jig and the stationary jig is [0026] (L a and (2.4) if x = 0, y = 1, y = 1, and y = 2, then returning to step (2.3) and conversely the flash flattening phase is terminated.

3. The preheating step comprises: A step (3.1) of setting n to 0; The moving jig is ν 1 When i>I, the speed of the workpiece is increased to bring the end faces of the two workpieces into closer contact with each other. 1 Step (3.2) of continuing to advance by the preheat compression amount Δp at a speed of The moving jig moves at time t 1 A stopping step (3.3); Until i≦I, the moving jig moves to −ν 1 a step (3.4) of moving backward at a speed of The moving jig moves at time t 2 A stopping step (3.5); and a step (3.6) of returning to (3.2) and terminating the preheating step if n:=n+1 and n<N (N being the rated number of preheats).

4. The successive flash steps include: A step (4.1) of determining the starting point of successive flashes, 3 When the speed of the moving jig reaches i>I, the moving jig stops and determines the starting point of the continuous flash. At this time, the distance between the moving jig and the stationary jig at the start of the continuous flash is [0027] Step (4.1) of setting = l; If i>I, the moving jig moves until i≦I. [0028] When i≦I, the moving jig moves backward at a speed of [0029] (4.2) continuously flashing forward at a speed of Determine the distance of successive flashes, [0030] In the case of , return to (4.2) [0031] In the case of , the moving jig is ν 3 Move forward at a uniform speed of [0032] Step (4.3) in which the moving jig is stopped and the continuous flash phase is ended when L b is the melting length, [Equation 33] 2. The method of claim 1, further comprising the step (4.3) of: wherein: a is the length of the shortest continuous flash.

5. The upsetting step includes: Set t to 0, and set the initial distance between the moving jig and the stationary jig at the start of upset. [0034] Step (5.1) of setting = 1; The moving jig is ν 4 The charge upset is performed at a speed of t ≧ t u (t u (5.2) continuing to record the currently elapsed time t until (t=t+t+t=t+t+t) (where t=t+t+t is the charge upset time); A step (5.3) of switching off the welding current; The moving jig is ν 4 At a speed of [Equation 35] (L c (5.4) moving forward to the upset length ( The moving jig moves at time t m (t m is the upset sustain time) [0036] 2. The method of claim 1, further comprising the step of: remaining stationary at said first contact with said first metal.

6. The reset step comprises: A step (6.1) of releasing the moving jig and the stationary jig; 2. The method of claim 1, further comprising the step (6.2) of returning the moving fixture to its initial position and completing the welding process.

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