CN102944610A

CN102944610A - Method for detecting weld defect of stainless steel runner blade of water turbine

Info

Publication number: CN102944610A
Application number: CN2012105023903A
Authority: CN
Inventors: 龙毅; 谢国胜; 龙思成; 谢阿萌
Original assignee: HUNAN XIANGDIAN BOILER PRESSURE VESSEL EXAMINATION CENTER CO Ltd; State Grid Corp of China SGCC; Electric Power Research Institute of State Grid Hunan Electric Power Co Ltd
Current assignee: HUNAN XIANGDIAN BOILER PRESSURE VESSEL EXAMINATION CENTER CO Ltd; State Grid Corp of China SGCC; Electric Power Research Institute of State Grid Hunan Electric Power Co Ltd
Priority date: 2012-11-30
Filing date: 2012-11-30
Publication date: 2013-02-27

Abstract

The invention discloses a method for detecting a weld defect of a stainless steel runner blade of a water turbine, comprising the following steps of: 1, selecting an instrument; 2, calibrating the instrument; 3, drawing a rejection judging line for detection: (1) making a reference block; and (2) testing the detected surface of the reference block through a wedge block by using a probe of the instrument, recording the current gain of the instrument and the height values of reflection wave amplitudes of through holes at different heights in the reference block, drawing points according to the height values of the reflection wave amplitudes on a two-dimensional coordinate system, and connecting the points into a smooth curve to draw the rejection judging line; 4, detecting the weld of the blade; and 5, recording the defect: displaying the height of an echo signal according to the instrument and comparing the height of the echo signal with the rejection judging line by taking the rejection judging line as a reference, making corresponding marks on the surface of the blade, and finally detecting whether the blade has a defect according to the marks on the surface of the blade. By using the method, the weld defect of the stainless steel runner blade can be reliably, conveniently and rapidly detected.

Description

A kind of detection method of hydraulic turbine stainless steel rotary wheel blade weld defect

Technical field

The invention belongs to lossless detection method, be specifically related to a kind of detection method of hydraulic turbine stainless steel rotary wheel blade weld defect, be applicable to the detection to big-and-middle-sized Francis turbine stainless steel rotary wheel blade crown, lower girth joint.

Background technology

In recent years the big-and-middle-sized Francis turbine that newly generates electricity, turbine blade generally adopts Low Carbon Martensite Stainless Steel ZG0Cr13Ni4-6Mo, but after the shorter time of operation, near the crown of runner, lower ring and the blade outlet connecting portion, penetrating crack has often just appearred, some unit even the extreme case that the runner bucket same position is repaired repeatedly cracking repeatedly occurs has a strong impact on safety, the stable operation of hydropower unit.

The way that thorough solution stainless steel rotary wheel crackle relatively gears to actual circumstances is to utilize the servicing machine meeting, removes crackle and also repaired, but crucial effective discovery crackle or other inherent vices that is early.And present blade interior quality determining method is main or the conventional Ultrasound wave technology, it is to utilize the probe of ultrasonoscope and with the supporting voussoir of probe blade is detected, to the stainless steel rotary wheel weld seam detection time, its limitation is: 1) coarse grains of turbine blade material causes hyperacoustic attenuation coefficient and noise signal large, and detection sensitivity reduces; 2) blade shape of three-dimension curved surface causes ultrasonic wave acoustic beam to be propagated at inside workpiece and is difficult to prediction, thereby is difficult to the flaw indication that interpretation detects and the positioning and quantitative that carries out defective; 3) rotary wheel of water turbine detects in labour and is subjected to the restriction in space, only can cause coverage rate detected in the welding joint limited with probe scanning on blade, and acoustic beam is difficult to consistent with the direction that dangerous defective effectively detects.So, must study new detection method, guarantee effectively to detect all defect, guarantee the safe and reliable operation of hydraulic generator unit.

Summary of the invention

The technical problem to be solved in the present invention is, the shortcoming large for conventional sense technology for detection stainless steel rotary wheel blade weld defect difficulty, that sensitivity is low, a kind of detection method of hydraulic turbine stainless steel rotary wheel blade weld defect is proposed, utilize the deflection of ultrasonic phased array technology acoustic beam and focusing performance, to stainless steel rotary wheel blade weld defect implement reliably, easily and fast detection, in order in time find, process defective, avoid causing the runner failure accidents because of weld defect.

Technical solution of the present invention is:

The detection method of hydraulic turbine stainless steel rotary wheel blade weld defect, carry out according to following steps:

Step 1, selection instrument: instrument adopts and is equipped with probe and voussoir and has the sector scan function, and minimum continuously adjustable gain is not less than the ultrasonic phased array instrument of 76db; Probe requires frequency 2.25MHz, is no less than 64 wafers, and the single wafer size is 0.5 * 10mm to the maximum, and wafer gap is 0.1mm to the maximum; Wedge angle is 45 °, and size is not more than 40 * 30mm;

Step 2, calibrating instrument: the scanning type of setting instrument is sector scan; The beginning angle is 30 °; Angle at the end is 70 °; Focusing distance should be greater than vane thickness value 5mm to be detected;

Step 3, drafting detect with declaring scrap wire:

1), make reference block: reference block is tool length * wide * high rectangular strip body, and the length of reference block * high face is provided with the through hole of some differing heights, and two of reference block are long * wide as detection faces;

2), daubing coupling agent on the detection faces of reference block, with the probe of instrument by testing on the detection faces of voussoir to reference block, the reflection wave width of cloth height value of the through hole of differing heights in the current gain of register instrument and the reference block, reflection wave width of cloth height value is fastened described point at two-dimensional coordinate, and connect to be depicted as with level and smooth curve and declare scrap wire;

Step 4, detection blade weld seam: near daubing coupling agent blade crown to be detected, lower girth joint, be close to and perpendicular to blade axis of a weld to be detected with the voussoir on the instrument probe, do the sawtooth pattern scanning and detect, the scope that probe moves forward and backward should be greater than 2 times vane thickness;

Step 5, defect record: to declare scrap wire as reference, surpass when declaring scrap wire when instrument display echoed signal height in the testing process, judge that this reflecting body is defective, make corresponding mark at blade surface, and the height coordinate value record defective depth of burial corresponding according to echoed signal; When the echoed signal height is lower than when declaring scrap wire, refuse record; Finally can detect blade according to the mark of blade surface and whether have defective.

The length of described reference block is respectively 320mm, 40mm, 100mm, the internal diameter of through hole is 3mm, through hole amounts to 8, wherein per 4 through holes are one group, press upper and lower vertical layout in short transverse, spacing was 20mm between through hole was upper and lower, and wherein the starting altitude of one group of through hole is 10mm; The starting altitude of another group through hole is 20mm; The distance of two groups of through holes and side is 40mm.

Principle of the present invention is: if there is a defective in a steel workpiece, because the existence of this defective, caused the interface that has formed between defective and the Steel material between the different medium, acoustic impedance between the interface is different, after the ultrasound wave of emission runs into this interface, will reflect, the energy that reflects is received by probe again, certain position of horizontal ordinate will show the waveform of a reflection wave in display screen, and this position of horizontal ordinate is exactly the degree of depth of defective in detected material.

The invention has the beneficial effects as follows: overcome the difficulties such as material grains is thick, detection space restriction, vane thickness variation when using this method to detect, have simple, safe, reliable, highly sensitive characteristics, therefore loose to the environmental requirement that detects, and convenient and swift, especially the butt welded seam inherent vice can effectively detect and put in place, thereby improved significantly detection efficiency and detection sensitivity, in order in time find, process defective, avoided causing the runner failure accidents because of weld defect.

Description of drawings

Fig. 1 is the schematic diagram of reference block of the present invention and instrument scanning in reference block.

Fig. 2 be the present invention draw declare scrap wire.

Fig. 3 is the schematic diagram of instrument scanning on blade to be detected.

Fig. 4 be blade draw when detecting declare scrap wire and echoed signal demonstration figure.

Fig. 5 is the characterization processes process flow diagram.

Embodiment

No. 2 unit crowns in certain hydroelectric power plant, lower ring and blade are the 0Crl3Ni5Mo martensite stainless steel material, are connected into runner with crown, lower boxing after the blade compression molding, and maximum blade thickness is about 50mm.Unit is since putting into operation, and all there is crackle in various degree in runner bucket at crown, lower ring outlet edge, and the crackle of indivedual blades is also more serious.To hydroturbine blade add in weldering triangle muscle process during the maintenance of C level in November, 2010, removes clean and triangle muscle welding quality for guaranteeing the blade weld metal crack, and runner bucket and crown, lower ring splicing welding joint have been carried out the ultrasonic phased array detection.Concrete grammar is as follows:

Step 1, selection instrument: the Omniscan-MX type phased array instrument that the present invention adopts RD-Tech company to produce, has the sector scan function, continuous adjustable gain 80db, apparatus preparation probe and voussoir, frequency probe 2.25MHz, 64 wafers, single wafer are of a size of 0.5 * 10mm, wafer gap is 0.1mm; Wedge angle is 45 °, is of a size of 24 * 16mm.

Step 2, calibrating instrument: the scanning type of setting instrument is sector scan; The beginning angle is 30 °; Angle at the end is 70 °; Focusing distance: 57mm.

Step 3, draw to detect with declaring scrap wire, referring to Fig. 1:

1), make reference block: reference block is the rectangular strip body 1 of the long L of tool * wide W * high H, and the length of reference block * high face is provided with the through hole 2 of some differing heights, and two long L of reference block * wide W face is as detection faces; The long L of reference block, wide W, high H are respectively 320mm, 40mm, 100mm, the internal diameter Φ of through hole 2 is 3mm, through hole 2 amounts to 8, wherein per 4 through holes 2 are one group, press upper and lower vertical layout in short transverse, distance s 2 was 20mm between through hole 2 was upper and lower, and wherein the starting altitude s1 of one group of through hole 2 is 10mm; The starting altitude s4 of another group through hole 2 is 20mm; Two groups of through holes 2 are 40mm with side apart from s3;

2), daubing coupling agent on the detection faces of reference block, with the probe of instrument by testing on the detection faces of voussoir to reference block, the reflection wave width of cloth height value (number percent) of the through hole of differing heights in the current gain of register instrument and the reference block, reflection wave width of cloth height value is fastened described point at two-dimensional coordinate, and connect to be depicted as with level and smooth curve and declare scrap wire, as shown in Figure 2.

Table 1 is the reflection wave height of Φ 3 * 40mm through hole 2 when instrument gain is 38db in the reference block.

Table 1 reference block regular reflector testing result

Step 4, detection blade weld seam, referring to Fig. 3: near the daubing coupling agent crown weld seam 501 of blade 5 to be detected, lower girth joint 502, be close to and perpendicular to blade axis of a weld to be detected with the voussoir 3 on the instrument probe, doing the sawtooth pattern scanning detects, the scope that moves forward and backward of probe should be greater than 100mm, namely greater than 2 times vane thickness;

Step 5, defect record: referring to Fig. 4, declaring scrap wire as reference, the testing process Instrumental shows that echoed

signal

1,3 height are lower than and declares scrap wire, refuses record; The height of echoed signal 2 surpasses declares the scrap wire height, judge that this reflecting body is defective, should be to give record at blade, and be about 33mm according to the degree of depth that depth coordinate marks this defective, finally can detect the position that blade exists defective and defective according to the mark of blade surface.

The flow process of above-mentioned detection method as shown in Figure 5.

Claims

1. the detection method of a hydraulic turbine stainless steel rotary wheel blade weld defect is characterized in that carrying out according to following steps:

Step 3, drafting detect with declaring scrap wire:

2. the detection method of hydraulic turbine stainless steel rotary wheel blade weld defect according to claim 1, the length that it is characterized in that described reference block is respectively 320mm, 40mm, 100mm, the internal diameter of through hole is 3mm, through hole amounts to 8, wherein per 4 through holes are one group, by upper and lower vertical layout, spacing was 20mm between through hole was upper and lower in short transverse, and wherein the starting altitude of one group of through hole is 10mm; The starting altitude of another group through hole is 20mm; The distance of two groups of through holes and side is 40mm.