CN103344674A - Method for detecting pearlite content of ductile cast iron - Google Patents
Method for detecting pearlite content of ductile cast iron Download PDFInfo
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- CN103344674A CN103344674A CN2013103000615A CN201310300061A CN103344674A CN 103344674 A CN103344674 A CN 103344674A CN 2013103000615 A CN2013103000615 A CN 2013103000615A CN 201310300061 A CN201310300061 A CN 201310300061A CN 103344674 A CN103344674 A CN 103344674A
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Abstract
The invention relates to a method for detecting the pearlite content of ductile cast iron. N representative ductile cast iron samples (200-300*phi24) are prepared and are heat-treated by using different heat treatment processes to obtain the ductile cast iron with different matrix structures; the pearlite content of each sample is detected by using the traditional metallographic detection method, and then is detected by an eddy current detection method. The detection results show that the pearlite content of the ductile cast iron and eddy current values have a linear relationship, and the error values of the two detection methods are within 3%, and can meet the accuracy requirements of industrial application.
Description
Technical field
The present invention relates to a kind of detection method of content of pearlite in alloy, especially relate to a kind of detection method of spheroidal-graphite cast iron content of pearlite in alloy.
Background technology
The traditional detection method of spheroidal-graphite cast iron content of pearlite in alloy is the metallographic detection method, and this method wastes time and energy, destroys product, belongs to sampling Detection, and testing result is subjected to the randomness influence, can't adapt to quick, accurate, the economic detection requirement of modern production.Spheroidal-graphite cast iron mainly is made of pearlite, ferrite and globular graphite, and wherein ferrite is the extremely low solid solution of carbon content, and its electromagnetic property is near pure iron, and pearlite then is the mechanical impurity of ferrite and cementite.
Summary of the invention
Above-mentioned technical matters of the present invention is mainly solved by following technical proposals:
A kind of detection method of spheroidal-graphite cast iron content of pearlite in alloy is characterized in that, adopts eddy current detection method to detect the content of spheroidal-graphite cast iron medium pearlite.
In the detection method of above-mentioned a kind of spheroidal-graphite cast iron content of pearlite in alloy, adopt eddy current testing instrument to detect, wherein, detection probe is a pair of reflective probe, adopts in parallel the driving, receives separately, specifically may further comprise the steps:
Step 1, sample casting and thermal treatment, sample blank dimension is Ф 30X300, rough-cast is heat-treated after finishing, and carries out machine work after thermal treatment is finished, and the sample final size is long 200～300mm, diameter is the cylindrical of 23.9mm～24.1mm, the N spare of materialsing from tested spheroidal-graphite cast iron is tested, and wherein, N spare sample comprises 55 the sample from pearl 5 to pearl that obtains by the actual measurement of traditional metallographic grid method;
Step 2, the probe of eddy current testing instrument is driven parameter after setting completed, put into sample to be detected and detect, sample places the probe center position, make instrument get back to the equilibrium position earlier when detecting beginning, the displayed value when being detected sample to put in the probe is as measured value;
Step 3, carry out the measurement of EDDY CURRENT resistance value, after the duplicate step of laying equal stress at least three times comes to the same thing to the EDDY CURRENT resistance value, after taking out current institute's test specimens and changing sample repeated execution of steps 2 to step 3 until all tests detect finish after, depict linearity curve; This linearity curve is the content of pearlite in alloy curve of tested spheroidal-graphite cast iron.
In the detection method of above-mentioned a kind of spheroidal-graphite cast iron content of pearlite in alloy, in the described step 2, probe drives parameter and comprises mensuration frequency, driving, gain and phase place, and described mensuration frequency adopts 10Hz～100Hz; Drive and adopt 5V～8V; 10dB～30dB is adopted in gain; Phase place adopts 0 °～360 °.
In the detection method of above-mentioned a kind of spheroidal-graphite cast iron content of pearlite in alloy, in the described step 3, the measuring method of impedance signal comprises automatic measurement and manual measurement, and described step 3 is selected to measure automatically or manual measurement at random.
In the detection method of above-mentioned a kind of spheroidal-graphite cast iron content of pearlite in alloy, in the described step 1, heat treatment step comprises following substep:
Step 1.1 is put into annealing furnace with sample;
Step 1.2 is warming up to maximum temperature between 900-930 ℃ to sample;
Step 1.3 is at maximum temperature place insulation 1-2h;
Step 1.4, sample cool to 750-780 ℃ of insulation 1-4h with the furnace;
When cooling to 550 ℃ with the furnace, step 1.5, sample from stove, take out air cooling to room temperature.
Therefore, the present invention has following advantage: 1, the present invention adopts the technological means of Non-Destructive Testing, and starting material are not had any damage; 2, traditional metallographic method need pass through buck, polishing, burn into is taken a picture and grid calculates, and detection speed is slow, and the present invention adopts eddy detection technology by setting up the corresponding relation between EDDY CURRENT value and the content of pearlite in alloy, and detection speed is fast.
Description of drawings
Accompanying drawing 1 is EDDY CURRENT principle schematic involved in the present invention.
Accompanying drawing 2a is the synoptic diagram of selecting eddy current signal in the embodiment of the invention.
Accompanying drawing 2b is the demonstration result of eddy current signal section in the extensive diagnostic window selected in the embodiment of the invention.
Accompanying drawing 3a is the measuring method synoptic diagram (measuring automatically) of embodiment of the invention middle impedance value.
Accompanying drawing 3b is the measuring method synoptic diagram (manual measurement) of embodiment of the invention middle impedance value.
Accompanying drawing 4 is spheroidal-graphite cast iron EDDY CURRENT curves in the embodiment of the invention.
Accompanying drawing 5 is method flow synoptic diagram of the present invention.
Embodiment
Below by embodiment, and by reference to the accompanying drawings, technical scheme of the present invention is described in further detail.
Embodiment:
One, at first introduces the test principle of eddy current detection method.
EDDY CURRENT is a kind of lossless detection method that is based upon on the electromagnetic induction principle basis, and it is applicable to conductive material.Because electromagnetic induction, when conductor is in the magnetic field of variation or during with respect to Movement in Magnetic Field, just has induced current to exist in the conductor, these characteristics of current are: have the closed-loop path of one's own in conductor inside, be the whirlpool shape and flow, therefore be referred to as eddy current.Because the variation of conductor self various factors, thereby cause faradic variation, utilize this phenomenon and declare and know that conductor nature, status detection method namely are detection method of eddy.
The EDDY CURRENT ultimate principle as shown in Figure 1, in the time of near test specimen is placed in the coil that is connected with exchange current, the alternating magnetic field that enters test specimen can in test specimen, generate direction and excitation field perpendicular, be the electric current (eddy current) that the eddy current shape flows, this eddy current can produce a magnetic field opposite with the excitation field direction reduces the former magnetic field part ground in the coil, thereby causes the variation of coil impedance.
Spheroidal-graphite cast iron mainly is made of pearlite, ferrite and globular graphite, and wherein ferrite is the extremely low solid solution of carbon content, and its electromagnetic property is near pure iron, and pearlite then is the mechanical impurity of ferrite and cementite.By ferromagnetics as can be known, the size of the initial permeability of spheroidal-graphite cast iron depends primarily on the reversible displacement of domain wall, and the reversible displacement of domain wall is subjected to the influence of accumulation state, grain size of magnetization Ms, impurity etc., for spheroidal-graphite cast iron, globular graphite in its tissue can be regarded impurity as, because it is agglomerating that it is assembled, distributing has surpassed several magnetic domain scopes, little to the domain wall displacement influence.Because the ferrite type in the matrix is similar to pure iron, its saturation magnetization Ms approximately is pearlitic 10 times.And initial permeability and Ms
2Be directly proportional, so what of ferrite content affect initial permeability consumingly.This just lays a good foundation for the method that adopts low-intensity magnetic field detects the spheroidal-graphite cast iron content of pearlite in alloy.
The preparation of 2 samples.
(1) casting of sample and processing: smelting equipment is 1.5 tons of middle frequency furnaces (KGPS750/0.5) that Xi'an Boda Electric Furnace Co., Ltd. produces, adopt rare earth magnesium nodularizer (Mg7.89%, Re3.51%, Si42.82%, Yu Tie), inovulant is VI270(Ba2%, Ca1%, Si70～75%, Yu Tie), the agent of skimming is volcanic debris (ISHIKAWALITE), and foundry sand is clay-bonded sand.
After the sample casting is finished, adopt direct-reading spectrometer to detect chemical constitution, the results are shown in Table shown in 1.
Table 1
The basic configuration of sample is long 200～300mm, and diameter 24mm's is cylindrical, and material is QT500, and quantity is N spare, and blank dimension is 300 * Φ 30, and blank is machined to required size by machining process.
It should be noted that this melting step carries out in the sample first being processed, if what adopt is melted sample, then can directly heat-treat step.
(2) Shi Yan thermal treatment: ask the heat treated step of detailed presentations, comprise temperature, time, the setting of pressure and other parameters, by different Technologies for Heating Processing, the sample that has prepared 55 a series of different content of pearlite in alloy from pearl 5 to pearl has carried out Preliminary detection by the grid method to the content of pearlite in alloy of each sample.
In this step, pearl 5 expression content of pearlite in alloy are 5%, and pearl 55 expression content of pearlite in alloy are 55%.Content of pearlite in alloy is not known, but obtain by traditional metallographic grid method actual measurement, preparation is 55 a series of samples from pearl 5 to pearl, adopt eddy-current method to detect to these samples again, obtain the relation curve between content of pearlite in alloy and the EDDY CURRENT value, the recycling curve detects the sample of unknown content of pearlite in alloy, to reach the purpose that detects content of pearlite in alloy more fast.
The test of 3 EDDY CURRENT.
3.1 test apparatus and interface
Detecting the equipment that adopts is the EEC-39RFT++ intelligent all-digital eight frequency far-field eddy detectors that Xiamen Ai Desen (EDDYSUN) Electronics Co., Ltd. produces, and detection probe is a pair of reflective probe, adopts in parallel the driving, separately reception.This instrument can effectively suppress to pop one's head in when detecting lift from, the influence of disturbing factor such as skin effect.Detecting the software that adopts is that far-field eddy detects software RFT-39++for98NTXP.According to equipment characteristic, more low magnetic field intensity is more low owing to detect frequency, so should adopt low frequency in the testing process.
3.2 probe drives the parameter setting
The parameter that arranges that probe drives has frequency, coupling and driving, and the waveform that parameter arranges in the rear hatch should be straight line or sinusoidal waveform, if then wave amplitude can not be above 1/2 of window size, in order to avoid cause saturated for sinusoidal waveform; If waveform is the counterbalance effect ideal of two probes of straight line explanation.The detected parameters setting of instrument is shown in Table 2:
Table 2
3.3 sample is placed and signal is selected
After parameter settings such as frequency, gain and phase place are finished, putting into sample to be detected detects, sample places the probe center position, presses balance key " SPACE " earlier when detecting beginning and makes instrument get back to the equilibrium position, and the displayed value when being detected sample to put in the probe is as measured value.
After treating signal stabilization, employing drags the method for right mouse button and select one section eddy current signal in the 1st, the 2nd display window, shown in Fig. 2 a: the oa section is inserted preceding eddy current signal for detected sample among the figure, the ab section is the eddy current jump signal when inserting sample, the bc section is that sample inserts the eddy current signal after stablizing, and the cd section is the eddy current jump signal when extracting sample.Fig. 2 b is the selected demonstration result of eddy current signal section in the extensive diagnostic window.
3.4 the measurement of EDDY CURRENT resistance value
At the selected one section eddy current signal of extensive diagnostic window, demonstrate corresponding impedance signal in the impedance window.As shown in Figure 3.
The measuring method of impedance signal is divided into two kinds of automatic measurement and manual measurements, and Fig. 3 a is method for automatic measurement, only needs when measuring automatically after selected one section eddy current signal, to click " amplitude-phase is measured automatically " button and get final product in the extensive diagnostic window; Need drag two end points of the selected impedance signal of right mouse button during manual measurement, impedance this moment beneath window will demonstrate the resistance value that records.The impedance signal amplitude that records among Fig. 3 is 224, and this value is the distance between two end points in the impedance diagram, and namely the screen between two end points is counted, and measures automatically and the result of manual measurement should be identical.
In the testing process, each sample counterpoise retrial is tested more than 3 times, and test findings is identical, and repeatability is good.
4 testing results.
Table 3 is the testing result of pearlite sample;
Table 3
By table (3) as can be seen, be 30HZ when measuring frequency, drive be 7, gain is 15, when phase place is 230 °, the detection resolution maximum of pearlite sample, (wherein total coordinate is Figure 10 for the relation curve between measured value under this condition and the content of pearlite in alloy
Measured value, horizontal ordinate are content of pearlite in alloy, and unit is %).
4 conclusions.
(1) by preparing the spheroidal-graphite cast iron sample of different content of pearlite in alloy, adopt metallographic grid method that the content of pearlite in alloy of each sample is checked earlier, adopt eddy current detection method that content of pearlite in alloy is detected again, testing result shows, has linear relationship between spheroidal-graphite cast iron content of pearlite in alloy and the EDDY CURRENT value.
(2) content of pearlite in alloy is more low, and then ferrite content is more high, and then saturation magnetization is more high, and corresponding magnetic permeability is more high, and measured value is also just more high.
(3) error amount of the content of pearlite in alloy that records of the spheroidal-graphite cast iron content of pearlite in alloy that records by detection method of eddy and metallographic method can satisfy the accuracy requirement of commercial Application less than 3%.
Specific embodiment described herein only is that the present invention's spirit is illustrated.Those skilled in the art can make various modifications or replenish or adopt similar mode to substitute described specific embodiment, but can't depart from spirit of the present invention or surmount the defined scope of appended claims.
Claims (5)
1. the detection method of a spheroidal-graphite cast iron content of pearlite in alloy is characterized in that, adopts eddy current detection method to detect the content of spheroidal-graphite cast iron medium pearlite.
2. the detection method of a kind of spheroidal-graphite cast iron content of pearlite in alloy according to claim 1 is characterized in that, adopts eddy current testing instrument to detect, and wherein, detection probe is a pair of reflective probe, adopts in parallel the driving, receives separately, specifically may further comprise the steps:
Step 1, sample casting and thermal treatment, sample blank dimension is Ф 30X300, rough-cast is heat-treated after finishing, after finishing, thermal treatment carries out machine work, the sample final size is long 200 ~ 300mm, and diameter is the cylindrical of 23.9mm～24.1mm, and the N spare of materialsing from tested spheroidal-graphite cast iron is tested; Wherein, N spare sample comprises 55 the sample from pearl 5 to pearl that obtains by the actual measurement of traditional metallographic grid method;
Step 2, the probe of eddy current testing instrument is driven parameter after setting completed, put into sample to be detected and detect, sample places the probe center position, make instrument get back to the equilibrium position earlier when detecting beginning, the displayed value when being detected sample to put in the probe is as measured value;
Step 3, carry out the measurement of EDDY CURRENT resistance value, after the duplicate step of laying equal stress at least three times comes to the same thing to the EDDY CURRENT resistance value, after taking out current institute's test specimens and changing sample repeated execution of steps 2 to step 3 until all tests detect finish after, depict linearity curve; This linearity curve is the content of pearlite in alloy curve of tested spheroidal-graphite cast iron.
3. the detection method of a kind of spheroidal-graphite cast iron content of pearlite in alloy according to claim 1 is characterized in that, in the described step 2, probe drives parameter and comprises mensuration frequency, driving, gain and phase place, and described mensuration frequency adopts 10 Hz～100Hz; Drive and adopt 5V～8V; 10 dB～30dB is adopted in gain; Phase place adopts 0 °～360 °.
4. the detection method of a kind of spheroidal-graphite cast iron content of pearlite in alloy according to claim 1 is characterized in that, in the described step 3, the measuring method of impedance signal comprises automatic measurement and manual measurement, and described step 3 is selected to measure automatically or manual measurement at random.
5. the detection method of a kind of spheroidal-graphite cast iron content of pearlite in alloy according to claim 1 is characterized in that, in the described step 1, heat treatment step comprises following substep:
Step 1.1 is put into annealing furnace with sample;
Step 1.2 is warming up to maximum temperature between 900-930 ℃ to sample;
Step 1.3 is at maximum temperature place insulation 1-2h;
Step 1.4, sample cool to 750-780 ℃ of insulation 1-4h with the furnace;
When cooling to 550 ℃ with the furnace, step 1.5, sample from stove, take out air cooling to room temperature.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106524957A (en) * | 2016-09-22 | 2017-03-22 | 武汉钢铁股份有限公司 | Method for measuring dimension of pearlite colony |
| CN111175126A (en) * | 2020-01-19 | 2020-05-19 | 锦州捷通铁路机械股份有限公司 | Method for measuring ratio of ductile and brittle areas on impact fracture of nodular cast iron |
Citations (2)
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|---|---|---|---|---|
| CN86108323A (en) * | 1986-12-06 | 1987-06-24 | 武汉工学院 | Fast determining device of ball as cast state iron crankshaft pearlite |
| CN102735684A (en) * | 2012-06-29 | 2012-10-17 | 马钢(集团)控股有限公司 | Quantitative detection method for ferrite content in wheel steel |
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2013
- 2013-07-17 CN CN2013103000615A patent/CN103344674A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN86108323A (en) * | 1986-12-06 | 1987-06-24 | 武汉工学院 | Fast determining device of ball as cast state iron crankshaft pearlite |
| CN102735684A (en) * | 2012-06-29 | 2012-10-17 | 马钢(集团)控股有限公司 | Quantitative detection method for ferrite content in wheel steel |
Non-Patent Citations (1)
| Title |
|---|
| 张思全等: "球墨铸铁珠光体含量涡流无损智能检测", 《科学技术与工程》, vol. 10, no. 34, 31 December 2010 (2010-12-31), pages 8417 - 8420 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106524957A (en) * | 2016-09-22 | 2017-03-22 | 武汉钢铁股份有限公司 | Method for measuring dimension of pearlite colony |
| CN111175126A (en) * | 2020-01-19 | 2020-05-19 | 锦州捷通铁路机械股份有限公司 | Method for measuring ratio of ductile and brittle areas on impact fracture of nodular cast iron |
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Application publication date: 20131009 |