CN103926314A - Supersonic flaw detection method of weld joint - Google Patents
Supersonic flaw detection method of weld joint Download PDFInfo
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- CN103926314A CN103926314A CN201410045564.7A CN201410045564A CN103926314A CN 103926314 A CN103926314 A CN 103926314A CN 201410045564 A CN201410045564 A CN 201410045564A CN 103926314 A CN103926314 A CN 103926314A
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Abstract
A supersonic flaw detection method of a weld joint is characterized in that another two detection channels are arranged on a TOFD detector, creep wave probe scanning of the upper portion of the weld joint and transverse wave probe scanning of the lower portion of the weld joint are carried out while TOFD scanning in order to simultaneously carry out three detections. The respective advantages of UT detection and the TOFD detection are fully utilized, and the whole weld joint can be all-directionally detected through one time scanning. The method has the advantages of high detection efficiency and high accuracy.
Description
Technical field
The present invention relates to the ultrasound examination of station boiler high-alloy steel pipe welding seam, other special material UT (Ultrasonic Testing) also can be consulted and used.
Background technology
Electrical production, safety is above all.In firepower power station, have numerous high-temperature and pressure pipeline, its danger is well-known.And the numerous weld seams of the number existing in pipeline are weakest links of pipe safety.Therefore, at power station installation phase, carrying out welding detection has a great responsibility.
The evaluation that the test to various detection method defect detection rates of foreign study mechanism draws is: manual UT, 50-70%; TOFD, 70-90%; Mechanical scanning UT+TOFD, 80-95%.Ray detection 75%.But because manual UT is affected by human factors, at most critical pipings and ASME territory of use, strictly limit use.Mechanical scanning UT+TOFD is subject to reasons in structure to be not suitable for again on-the-spot pipe detection.Remaining ray detection and TOFD detect and have again obviously limitation:
1, radiographic inspection limitation
A, ray detection are subject to the strict control of national policy because of its radiologic hazard, and scene can only single work post work, has reduced testing efficiency, has hindered whole project progress.
B, ray detection penetration power are limited, if the pipe welding seam that is greater than 45mm for wall thickness adopts radiographic inspection, must offer flaw detection hole at weld seam avris.The not only butt welded seam of offering in flaw detection hole causes weak link, and welding and thermal treatment are all increased to sizable workload.Therefore many pipelines do not allow to offer flaw detection hole.The required time of detecting a flaw is in the case multiplied.Single 40mm medium caliber seam inspection time at least needs more than 2 hours.
C, the not high increase with detecting size of flaw detection accuracy rate, radiographic inspection sharpness, sensitivity sharply decline.Particularly ray can only obtain the vertical view information of defect, and for the length that judges the important indicator thickness direction of defect harmfulness degree, ray is very difficult.
2, TOFD flaw detection limitation
At the root of weld and upper surface, there is blind area.And this blind area scope Dangerous defect such as crater crack and incomplete root penetration position occurred frequently just.If do not carried out additive method, assist flaw detection.Potential safety hazard is larger.
Limitation in view of above 2 kinds of detection methods.In the urgent need to a kind of new characterization processes.According to field welding common deficiency and the least detectable harm defect of testing, make simulating test pieces for this reason.By carrying out multiple detection method knot, detect. by contrast, show that UT+TOFD detects as optimum detection scheme.
Summary of the invention
The present invention is exactly when TOFD detects, opens up two other sense channel on TOFD checkout equipment.In TOFD scanning, butt welded seam carries out top creeping wave probe scanning, and shear wave probe scanning is carried out in bottom.Three kinds of detections are carried out simultaneously.This technology has following advantage:
1, detection efficiency is high.A scanning can cover whole weld seam, and detecting simple and efficient, the most frequently used non-parallel scanning only needs a people can operate, and probe only need or not to do Zigzag scan along weld seam two side shiftings, and detection efficiency is high.
2, data record comprehensively.The equal real time record of all detection data in testing process, and the processing of available computer, record data can be used for long-range interpretation and result is reviewed.
3, detect non-blind area.In testing process, utilize TOFD technology to analyze weld seam middle part.The transverse wave double-bevel detector scanning root of weld.Creeping wave probe scanning face of weld.Avoid detecting the appearance of blind area.Guarantee Detection accuracy.
Embodiment
1, data review is prepared
Before examinations, should understand more workpiece situation, weld seam situation and want to detect the information such as defect situation, this will be conducive to design better detection scheme.These information comprise: at workpiece processed, should be appreciated that and manufacture and design standard, inspection project approach, manufacturing process, equipment, environmental baseline; To equipment in use, should also be clear that the problem of service condition, failure condition and check discovery last time etc.; Field condition while should be appreciated that weldability, welding line structure form, welding method, the welding of material and the defect type that need to detect etc.
2, detected workpiece is prepared
Check weld appearance, reinforcement width and height, whether the thickness of the mother metal on both sides is consistent etc.The wide PCS that may affect of scanning face one side reinforcement arranges; The weld seam wide lower surface that causes in bottom detects blind area increase; Uniform thickness attachment weld may not cause a plurality of bottom surfaces ripple; Whether the scanning face of inspection situation is smooth, and whether width meets scanner is placed.Remove surperficial spatter, iron filings, grease and other impurity.Check whether roughness affects coupling, and General Requirements machining surface Ra is no more than 6.3 μ m, shot-peening table and Ra is no more than 12.5 μ m; Determine and marker detection region, draw axis of a weld and surveyed area width; Require to remove the weld seam of reinforcement, reinforcement should be polished to concordant with contiguous mother metal; The weld seam that retains reinforcement, if face of weld has undercut, larger protuberance and depression etc. also should carry out suitable reconditioning, and makes rounding off in order to avoid affects the evaluation of testing result; If necessary, the inspection whether mother metal that can butt welded seam both sides has layering and tear, this contributes to explain banded signal in D/B scanning.
3, select ultrasonic probe
Selecting properly probe kind and frequency.Selected probe should be short pulse, and the pulse length of straight-through ripple and bottorm echo is no more than two cycles.The frequency that guarantees time sense selects requirement to be: the time window of straight-through ripple and end ripple signal at least reaches 20 signal periods; For guaranteeing signal to noise ratio (S/N ratio), to decaying, large coarse grain material can suitably reduce frequency; The selection of frequency also should be considered with wafer diameter and wave beam Diffusion Synthetic.Selecting properly head angle and wafer size, draw the expansion of wave beam and synthetic check overlay area by artificial calculating or use related software.For non-parallel scanning, generally need to select undersized probe to obtain large overlay area, although large-sized probe can provide higher energy beam coverage little.
4, the mensuration of probe parameter
Measure the time that Probe index, forward position and ultrasound wave are propagated in probe voussoir.Assay method is for directly to contact two probes, finds out the position of its Gao Bo in instrument, and the intermediate points of two probe contacts are Probe index, and an overlapping half-distance is forward position, swept that signal is readable to be gone out the time that ultrasound wave is propagated in probe voussoir by A
5, probe spacing (PCS) is set
With 2/3T criterion or other suitable selections, determine the centre distance of use probe.Probe is arranged on scanning frame, confirms that reinforcement width and the scanning face of PCS and weld seam can adapt.
6, select TOFD probe group number and necessary scanning number of times
According to rules, require to determine and use several groups of probes and carry out scanning several times, with the degree of depth and the width range of weld seam that ensuring coverage is detected.If need to use one group of above TOFD probe, should repeatedly select according to above 3,4 steps.Tackle each group probe and carry out parameter optimization according to each self-monitoring region, comprise frequency, wafer size and the centre distance etc. of probe.
7, select A sweep acquisition parameter
Select digitization frequencies, should with time resolution require consistent, to obtain enough wave amplitude resolution characteristiies.Digitization frequencies is generally 5 times of nominal probe frequency; Selection filtering arranges, to obtain best signal to noise ratio (S/N ratio).Minimum bandwidth should be the nominal probe frequency of 0.5 to 2 times; Selective excitation pulse width arranges, to obtain the shortest signal and maximum Depth resolution; Signalization mean value is to minimum requirements, to obtain a rational signal to noise ratio (S/N ratio); Set pulse repetition rate, require to match with acquisition speed.
8, setup times window
If be a scanning at depth direction, time window can arrange according to straight-through ripple or wave mode conversion end ripple.Whether the reference position of window should be arranged on straight-through ripple and arrive before receiving transducer, and window width should be arranged on after a wave mode transformed wave of workpiece bottom, to have signal to show after observing bottom reflection compressional wave signal.Some near surface flaw, its compressional wave signal appears near straight-through ripple, thereby is difficult to observe.But these defects can produce simultaneously with shear wave form, propagate signal because and transverse wave velocity is approximately half of compressional wave, after these signals appear at bottom reflection compressional wave signal, observe these signals to finding and verifying that some defect is useful.If carry out subregion scanning at depth direction, the straight-through ripple of some subregion and end ripple, just must pass through calculating and setting time window to these scanning districts, and check in reference block.
Claims (7)
1. a weld seam supersonic detection method, is characterized in that, opens up two other sense channel on TOFD checkout equipment, and in TOFD scanning, butt welded seam carries out top creeping wave probe scanning, and shear wave probe scanning is carried out in bottom, and three kinds of detections are carried out simultaneously.
2. weld seam supersonic detection method according to claim 1, is characterized in that, selected probe should be short pulse, and the pulse length of straight-through ripple and bottorm echo is no more than two cycles.
3. weld seam supersonic detection method according to claim 2, is characterized in that, the time window of described straight-through ripple and end ripple signal at least reaches 20 signal periods.
4. weld seam supersonic detection method according to claim 2, it is characterized in that, two probes are directly contacted, in instrument, find out the position of its Gao Bo, the intermediate point of two probe contacts is Probe index, an overlapping half-distance is forward position, is swept that signal is readable to be gone out the time that ultrasound wave is propagated in probe voussoir by A.
5. weld seam supersonic detection method according to claim 2, is characterized in that, determines the centre distance of use probe with 2/3T criterion or other suitable selections.
6. weld seam supersonic detection method according to claim 4, is characterized in that, described A sweep characteristic parameter is selected to require consistent digitization frequencies with time resolution, is generally 5 times of nominal probe frequency.
7. weld seam supersonic detection method according to claim 3, is characterized in that, the reference position of described time window should be arranged on straight-through ripple and arrive before receiving transducer, and window width should be arranged on after a wave mode transformed wave of workpiece bottom.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201410045564.7A CN103926314A (en) | 2014-01-27 | 2014-01-27 | Supersonic flaw detection method of weld joint |
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| CN201410045564.7A CN103926314A (en) | 2014-01-27 | 2014-01-27 | Supersonic flaw detection method of weld joint |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105987951A (en) * | 2015-01-28 | 2016-10-05 | 宝山钢铁股份有限公司 | Crack detection method recognizing types of defects in edge of weld joint |
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2014
- 2014-01-27 CN CN201410045564.7A patent/CN103926314A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105987951A (en) * | 2015-01-28 | 2016-10-05 | 宝山钢铁股份有限公司 | Crack detection method recognizing types of defects in edge of weld joint |
| CN105987951B (en) * | 2015-01-28 | 2018-12-07 | 宝山钢铁股份有限公司 | Identify the method for detection of weld seam edge defect type |
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Application publication date: 20140716 |
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| WD01 | Invention patent application deemed withdrawn after publication |