CN102514193A - Electrofusion welding process for preventing generation of cold welding and over welding defects and electrofusion welder - Google Patents
Electrofusion welding process for preventing generation of cold welding and over welding defects and electrofusion welder Download PDFInfo
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- CN102514193A CN102514193A CN2011104283472A CN201110428347A CN102514193A CN 102514193 A CN102514193 A CN 102514193A CN 2011104283472 A CN2011104283472 A CN 2011104283472A CN 201110428347 A CN201110428347 A CN 201110428347A CN 102514193 A CN102514193 A CN 102514193A
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Abstract
The invention which relates to an electrofusion welder technology aims to provide an electrofusion welding process for preventing the generation of cold welding and over welding defects and an electrofusion welder. The process comprises the following steps: 1, measuring the current and the voltage of a welding circuit in real time in the welding process to obtain the resistance value change case of a resistance wire, controlling the voltage of the welding circuit to realize the control on the resistance value of the resistance wire and the welding power, and simultaneously controlling the temperature of a polyethylene material around the resistance wire in the welding process; and 2, recording the real-time welding power of the resistance wire in the welding process, carrying out accumulating calculation to obtain welding input heat, and ending the welding when the welding input heat reaches the value of total heat Q needed by the welding completion through an electrofusion sleeve. According to the invention, the electrofusion welder can automatically determine a reasonable welding technology only through giving the needed welding input heat. A present digital welder which can be conveniently added with the control forms the novel electrofusion welder with the cold welding and over welding prevention functions.
Description
Technical field
The present invention relates to the electro-fusion welding machine technology, particularly can prevent to produce cold welding and weld the electric smelting welding method and the electro-fusion welding machine of defective excessively.
Background technology
In recent years, the further enforcement of important energy source strategic plans such as the adjustment of China's energy resource structure and policy and transfering natural gas from the west to the east has brought huge development space for the gas pipeline industry of China.Plastic conduit and thermoplasticity reinforced plastics multiple tube are developed fast in every profession and trade with its excellent comprehensive mechanical properties and are used.The electric smelting welding is one of plastic tube and the topmost connected mode of multiple tube, the compound pipeline complex pipeline that especially uses down in some complicated adverse circumstances (like high pressure, mud etc.), and the electric smelting welding almost is unique suitable connected mode.
Rational welding is the key that ensures the electric fusion joint quality.Existing electric fusion joint is in the welding procedure development phase; All adopt the method for testing to confirm the reasonability of technology; Promptly, prepare the electric fusion joint of weldering system under the different technology conditions, then through the stretch release test through constantly changing weld interval; Satisfy 33% the brittle break of stipulating among the GB15558.2 of being no more than if peel off the back sample, just think qualified welding procedure.
The major defect of this method is; Construction cycle is long; Disbonded test fluctuation as a result is bigger, and can only whether cold welding arranged or cross the weldering generation through the destructive testing analyzing adapter, and can not monitor in real time in the joint welding process, to avoid taking place cold welding or to cross weldering welding process.The detection of the polyethylene pipe cold welding joint of propositions such as Shi Jianfeng and evaluation method can only be applicable to that the joint to accomplishing welding detects, and can not when implementing welding, just avoid cold welding or cross the generation of welding.(Shi Jianfeng, the detection of polyethylene pipe electric fusion joint cold welding defective, evaluation and the research of formation mechanism thereof, Zhejiang University's doctorate paper, 2011)
Cold welding with cross that to weld defective be common by the unreasonable defective that causes of welding procedure in the engineering.If the weld interface temperature is crossed low or not long enough more than melt temperature, can produce the cold welding defective, the electric fusion joint that contains the cold welding defective may take place to lose efficacy along the expansion of fusion face generation through-wall crack in the process under arms.If welding heat input is too much, may make the inner polyethylene Yin Wendu of electric fusion joint too high and cracking takes place, produced the weldering defective.
The main constant voltage welding manner that adopts 39.5V of existing electric smelting welding, unique control parameter is weld interval.But the temperature value of weld interval and electric smelting weld interface does not have direct incidence relation; And in fact, because different producer's resistance wire technology has nothing in common with each other, even therefore identical weldingvoltage; The welding input power is different, thereby required weld interval is also inequality.
Summary of the invention
The technical problem that the present invention will solve is, overcomes deficiency of the prior art, provides a kind of preventing to produce cold welding in the electro-fusion welding termination process and cross the method for welding defective.
The technical scheme that the present invention adopts is:
Provide a kind of and can prevent to produce cold welding and cross the electric smelting welding method of welding defective, comprising:
(1) in welding process, measures the electric current and the voltage of welding circuit in real time, to obtain the resistance change situation of resistance wire in the electric smelting sleeve; Through the voltage of control welding circuit, to realize control to resistance wire resistance value and bonding power; Simultaneously, the temperature T of polythene material around the resistance wire in the control welding process
PEAll the time satisfy:
T
m＜T
PE＜T
d
Wherein, T
mBe the temperature of the complete fusion of polyethylene, ℃; T
dBe the temperature of polyethylene cracking, ℃;
To T
PEControl be according to following formula, the resistance value through resistance wire in the control electric smelting sleeve realizes:
In the formula, α
tBe the resistance wire temperature coefficient, ℃
-1R is the resistance value of measuring in real time, Ω; R
0Be the initial resistivity value of electric fusion joint, Ω; T
0Be original ambient temperature, ℃; Δ T is polythene material and the temperature difference between the resistance wire around the resistance wire, and its value can be taken as 20～60 ℃, depends on resistance wire and poly applying degree.
(2) the real-time bonding power of resistance wire in the record welding process, and accumulation calculating welding heat input, when welding heat input reached the numerical value of the required total input heat Q of electric smelting sleeve completion welding, welding finished.
As a kind of improvement, before beginning welding, input electric smelting sleeve is accomplished the numerical value of the required total input heat Q of welding in the controller of bonding machine; When welding heat input reaches the numerical value of total input heat Q, cut off the power supply of welding circuit automatically.
Further; The present invention also provides a kind of electro-fusion welding machine that is used for preceding method; Comprise precision (or current measurement is with little) resistance and current measurement circuit in its welding circuit; Comprise two and be attached to the current measurement module of selecting change-over switch, the analog to digital conversion circuits of two shared path control deivce controls of current measurement module in the said current measurement circuit; One of them current measurement module uses before welding, and its amplifier amplification coefficient is 100～500; Another current measurement module uses in welding process, and its amplifier amplification coefficient is 10～100.
As a kind of improvement, the resistance value of said precision resistance is 0.5～10m Ω, indicate the resistance error be no more than ± 0.5%, temperature-coefficient of electrical resistance (temperature is floated) is no more than 20ppm.
Beneficial effect of the present invention:
Through the method among the present invention, for the electric smelting sleeve of a certain specification, as long as the welding heat input of given needs, electro-fusion welding machine just can be confirmed rational welding automatically.Target is to confirm that electric fusion joint can obtain under the prerequisite of enough welding heat inputs, cold welding can not take place and cross the weldering defective.
On existing digital welding machine, can add this control method easily, become and have anti-cold welding and weld the novel electro-fusion welding machine of function with crossing.This novel electro-fusion welding machine is applicable to the electric smelting sleeve of existing whole specifications, need not do the improvement on any structure or on the circuit to the electric smelting sleeve.This electro-fusion welding machine can be based on detected weld interface adjustment input voltage; And in welding process, monitor input power in real time and calculate the input heat; To guarantee that resistance wire was avoided the generation of common weld defects such as weldering, cold welding to pipe fitting and the enough heats of tubing transmission in the electro-fusion welding termination process from welding machine control angle.
Description of drawings
Fig. 1 is a circuit measuring module diagram in the electro-fusion welding machine.
The specific embodiment
Realization principle of the present invention is:
With the welding total heat input is control variables, is monitored parameters with the weld interface temperature results of measuring, and serves as the control parameter with the welding input voltage of resistance wire, adjusts the welding input power of electric fusion joint in real time.Variation through resistance wire in the real-time monitoring electro-fusion welding termination process detects the weld interface temperature; Under the target of guaranteeing sufficient welding heat input; Avoid causing electric fusion joint to produce the weldering defective, or produce the cold welding defective because the weld interface temperature is not enough because of the weld interface temperature is too high.
The resistance value of resistance wire can raise and linear the increase along with temperature in the electro-fusion welding termination process, and its version is shown below:
R＝R
0[1+α
t(T-T
0)] (1)
In the formula: R
0Be the initial resistance of electric fusion joint, Ω; R is the resistance value of measuring in real time, Ω; T
0Be original ambient temperature, ℃; α
tBe the resistance wire temperature coefficient, ℃
-1T is the resistance wire real time temperature, ℃.
According to (1) formula, the real time temperature T of resistance wire can be expressed as:
Shi Jianfeng etc. discover (Jianfeng Shi, JinyangZheng, et.al.ASME Journal of PressureVessel Technology, vol.131): have certain temperature difference T between polythene material around the resistance wire and the resistance wire; Temperature difference T increases rapidly earlier in welding beginning back, in welding process, reduces rapidly then, and is stabilized at last between 20～60 ℃.
Therefore,
In the formula: T
PEBe the temperature of polythene material around the resistance wire, ℃.
If T
mFor the complete melt temperature of polyethylene (℃), T
dFor the polyethylene cracking temperature (℃).As long as in welding process, make T all the time
PESatisfy:
T
m＜T
PE＜T
d (4)
Just can guarantee that weldering or cold welding defective can not appear in electric fusion joint.
In welding process, detect the resistance change of resistance wire in real time, can obtain the poly real time temperature of weld interface according to formula (3).Based on the relation control welding input voltage of weld interface polyethylene temperature and melt temperature and cracking temperature, thereby the control bonding power also finally reaches the effect of control weld interface temperature.Welding process real time record bonding power, and accumulation calculating welding heat input, when welding heat input reached setting, welding finished.
It is to be noted; When the electric fusion joint of a certain specification is welded; Its total input heat Q comprehensively confirms according to the wiring region width of electric smelting sleeve and used material (promptly considering the heat of the required absorption of material fusion); Usually the manufacturer by the electric smelting sleeve confirms through test, can be considered the proper property data of electric smelting sleeve, and the controller that is used for directly importing electro-fusion welding machine is as initial parameter.Be heating resistor owing to what use in the electric smelting sleeve simultaneously; Very little for welding heat in heating on the welding machine and the electromagnetic energy loss on the resistance wire; (common bonding power is between 1-10kW, and the consumption in welding machine can not surpass 10W) can ignore.Therefore can be similar to and think that the thermal efficiency of electro-fusion welding machine is 100%, promptly the energy of welding machine all is converted into welding heat input.
For the electric smelting sleeve of a certain specification, as long as the welding heat input of given needs, electro-fusion welding machine just can be confirmed rational welding automatically.Target is to confirm that electric fusion joint can obtain under the prerequisite of enough welding heat inputs, cold welding can not take place and cross the weldering defective.
Specific embodiment:
(1) obtains electric fusion joint welding input parameter
Behind the electro-fusion welding machine power connection, welding machine just begins to detect whether connected the electric smelting sleeve.Usually the resistance value in the electric smelting sleeve applies a low-voltage dc voltage U through the output termination at electro-fusion welding machine between 0.5～10 Ω
t, detect electric current simultaneously.If detecting electric current passes through, and numerical value is at 0.1U
t～2U
tBetween the time, think that circuit connects.After treating current stabilization, the current values that records through circuit is I
t, then the initial resistivity value of electric smelting sleeve is:
Simultaneously, recording the ambient temperature value of this moment through temperature measuring equipment is T
0Welding heat input that electric fusion joint is required and temperature-coefficient of electrical resistance can be imported through manual, also can be through inquiring about acquisition in the welding machine internal database.
(2) the electro-fusion welding termination process is divided into two control stages and carries out
Phase I is before the complete fusion of weld interface, the 39.5V constant voltage welding of adopting existing electro-fusion welding machine generally to adopt, every resistance value of measuring an electric smelting sleeve internal resistance wire at a distance from Δ t=0.5s.If continuously the detected resistance wire temperature value of 5s is all more than poly complete melt temperature, then think the polyethylene fusion fully of weld interface, electric smelting welding phase I end.The resistance wire temperature value adopts (3) formula to calculate.Every voltage in the interocclusal record welding process and electric current variation when Δ t.
In the second stage of electric smelting welding, the welding input voltage of resistance wire is controlled in real time according to the temperature of weld interface.When the weld interface temperature is high, reduce the welding input voltage of resistance wire; When the weld interface temperature is low, improve the welding input voltage.The welding input voltage carries out proportion control according to the polyethylene temperature that records, and can regulate by following formula:
In the formula, T
PEBe the poly real time temperature of weld interface, calculate according to (4) formula; U
0For initial weldingvoltage, be generally 39.5V; K is a proportional control factor, common desirable 1.0; U is the current weldingvoltage that needs control output.
In the welding process, every voltage in the interocclusal record welding process and electric current variation when Δ t.Obtain electric current I in resistance wire voltage U and the resistance wire according to every at a distance from Δ t record, but the input heat in the approximate calculation Δ t time.If the electro-fusion welding termination process has experienced t
Wn=n Δ t second.If (weldingvoltage and the electric current in the individual cycle of i≤n) is respectively U to i
iAnd I
i, t then
WnTotal input heat of electro-fusion welding machine is in second:
Q
n＝(U
1I
1+U
2I
2+L+U
nI
n)·Δt (7)
Work as Q
nDuring more than or equal to the required heat of electric fusion joint, welding finishes.
For realizing above-mentioned functions, need the current measurement circuit of existing electro-fusion welding machine be improved.
Comprise precision resistance (resistance value is 0.5～10m Ω) and current measurement circuit in the welding circuit of electro-fusion welding machine.Comprise two and be attached to the current measurement module of selecting change-over switch, the analog to digital conversion circuits of two shared path control deivce controls of current measurement module in the said current measurement circuit; One of them current measurement module uses before welding, and its amplifier amplification coefficient is 100～500, can be described as the light current measuring circuit; Another current measurement module uses in welding process, and its amplifier amplification coefficient is 10～100, can be described as the forceful electric power measuring circuit.
Before the electric smelting welding, controller is connected the light current measuring circuit.In the electro-fusion welding termination process, controller is connected the forceful electric power measuring circuit.The main distinction of light current measuring circuit and forceful electric power measuring circuit is the amplifier of different amplification coefficients.Measurement result is input to and is used for calculating before the welding in the controller and the real-time resistance value of welding process.
Claims (4)
1. one kind can prevent to produce cold welding and cross the electric smelting welding method of welding defective, comprising:
(1) in welding process, measures the electric current and the voltage of welding circuit in real time, to obtain the resistance change situation of resistance wire in the electric smelting sleeve; Through the voltage of control welding circuit, to realize control to resistance wire resistance value and bonding power; Simultaneously, the temperature T of polythene material around the resistance wire in the control welding process
PEAll the time satisfy:
T
m＜T
PE＜T
d
Wherein, T
mBe the temperature of the complete fusion of polyethylene, ℃; T
dBe the temperature of polyethylene cracking, ℃;
To T
PEControl be according to following formula, the resistance value through resistance wire in the control electric smelting sleeve realizes:
In the formula, α
tBe the resistance wire temperature coefficient, ℃
-1R is the resistance value of measuring in real time, Ω; R
0Be the initial resistivity value of electric fusion joint, Ω; T
0Be original ambient temperature, ℃; Δ T is polythene material and the temperature difference between the resistance wire around the resistance wire, and its value is 20～60 ℃;
(2) the real-time bonding power of resistance wire in the record welding process, and accumulation calculating welding heat input, when welding heat input reached the numerical value of the required total input heat Q of electric smelting sleeve completion welding, welding finished.
2. method according to claim 1 is characterized in that, before beginning welding, input electric smelting sleeve is accomplished the numerical value of the required total input heat Q of welding in the controller of bonding machine; When welding heat input reaches the numerical value of total input heat Q, cut off the power supply of welding circuit automatically.
3. electro-fusion welding machine that is used to realize the said method of claim 1; Comprise precision resistance and current measurement circuit in its welding circuit; It is characterized in that; Comprise two and be attached to the current measurement module of selecting change-over switch, the analog to digital conversion circuits of two shared path control deivce controls of current measurement module in the said current measurement circuit; One of them current measurement module uses before welding, and its amplifier amplification coefficient is 100～500; Another current measurement module uses in welding process, and its amplifier amplification coefficient is 10～100.
4. electro-fusion welding machine according to claim 3 is characterized in that, the resistance value of said precision resistance is 0.5～10m Ω, indicate the resistance error be no more than ± 0.5%, temperature-coefficient of electrical resistance is no more than 20ppm.
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| CN103407158A (en) * | 2013-07-19 | 2013-11-27 | 广东联塑科技实业有限公司 | Method for determining optimal welding time of PE electric melt pipe fitting |
| CN105588654A (en) * | 2016-03-26 | 2016-05-18 | 宁波市宇华电器有限公司 | Electric melting pipe fitting welding temperature detection system and detection method |
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| CN103407158A (en) * | 2013-07-19 | 2013-11-27 | 广东联塑科技实业有限公司 | Method for determining optimal welding time of PE electric melt pipe fitting |
| CN105588654A (en) * | 2016-03-26 | 2016-05-18 | 宁波市宇华电器有限公司 | Electric melting pipe fitting welding temperature detection system and detection method |
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| CN105799159A (en) * | 2016-03-26 | 2016-07-27 | 宁波市宇华电器有限公司 | Electric-molten pipe welding machine and electric-molten pipe welding method |
| CN108656561B (en) * | 2018-06-20 | 2023-12-26 | 诸暨市逍遥管道科技有限公司 | Intelligent monitoring device and method for electric fusion welding of plastic pipeline |
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| CN109177177A (en) * | 2018-07-23 | 2019-01-11 | 广东东方管业有限公司 | A kind of electric melting pipe fittings welding method and electric melting pipe fittings welding machine |
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| CN110239104A (en) * | 2019-05-05 | 2019-09-17 | 诸暨市逍遥管道科技有限公司 | The method that DC inversion electro-fusion welding machine output voltage compensates automatically |
| CN113619127A (en) * | 2021-06-27 | 2021-11-09 | 浙江大学 | Electric melting pipe welding method based on resistance wire resistance temperature coefficient automatic measurement |
| CN113878880A (en) * | 2021-09-14 | 2022-01-04 | 浙江大学 | Intelligent electric melting welding temperature control method and device |
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Application publication date: 20120627 Assignee: NINGBO AOPU PIPE TECHNOLOGY CO., LTD. Assignor: Zhejiang University Contract record no.: 2013330000400 Denomination of invention: Electrofusion welding process for preventing generation of cold welding and over welding defects and electrofusion welder License type: Exclusive License Record date: 20131220 |
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