CN104237480A - Test method for obtaining center porosity press-fit critical conditions - Google Patents
Test method for obtaining center porosity press-fit critical conditions Download PDFInfo
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- CN104237480A CN104237480A CN201410430971.XA CN201410430971A CN104237480A CN 104237480 A CN104237480 A CN 104237480A CN 201410430971 A CN201410430971 A CN 201410430971A CN 104237480 A CN104237480 A CN 104237480A
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Abstract
The invention discloses a test method for obtaining center porosity press-fit critical conditions. The method comprises the following steps: performing a press-fit test under different casting blank center porosity processes by utilizing a Gleeble3800 thermal simulated test machine, judging the press-fit condition in a mode of scanning a free surface on a fracture sample by using a scanning electron microscope, drawing a relational graph of heating temperature, deformation amount and deformation rate to the center porosity press-fit by taking the heating temperature as a horizontal coordinate and taking the deformation amount as a vertical coordinate, thereby obtaining the center porosity press-fit critical conditions. According to the method disclosed by the invention, the adopted test method is a physical simulation technology, the test cost is low, and the result is reliable. The test method disclosed by the invention also can be used for testing press-fit critical conditions of cracks and other internal defects.
Description
Technical field
The invention belongs to ferrous materials field tests, is more particularly a kind of method of testing fully utilizing hot modeling test machine and scanning electron microscope acquisition iron and steel slab center porosity pressing critical condition.
Background technology
In Heavy plate production process, due to the restriction such as slab thickness or mill capacity, easily there is the phenomenon of mechanical property instability in finished product sheet material, and the even appearance that has flaw detection does not conform to, and its main cause is that ratio of compression is too little, and the defects such as center porosity cannot caused by pressing.Adopt the continuous casting technologies such as electromagnetic agitation, although the strand inherent vices such as center porosity can be alleviated to a certain extent, cannot thoroughly eliminate all the time.In actual production process, also need to carry out pressing by conservative control rolling technological parameter.Because the parameter related to is more, site test cost is higher, and therefore, the research of this respect mainly adopts numerical simulation and physical simulation two kinds." healing of 45# steel implosion district and high-temperature laminating district metallographic structure analysis [J]. iron and steel .2002.10 (37): 524-528 " in a literary composition, the high-temperature laminating that the people such as Zhang Yongjun achieve precrack by Gleeble1500 hot modeling test machine is tested.But this literary composition lays particular emphasis on the tissue difference analyzing healing district and pressing district, does not study the impact of technological parameter.The Zhao Dewen of Northeastern University's rolling technique and tandem rolling robotization National Key Laboratory etc., by the numerical evaluation based on triangular velocity field, have drawn the critical dynamic geometry condition that heavy plate rolling central defect ftractures.Deng Wei, Zhang Lin etc. utilize again ANSYS Finite Element Simulation Software to calculate the critical compresibility of the thick strand central defect of pressing 400mm on this basis.Due to numerical simulation, this to be set up in model and a lot of hypothesis has all been made in the aspect such as boundary condition setting, therefore, still there is larger difference with actual conditions.
Summary of the invention
The object of this invention is to provide a kind of method of testing obtaining center porosity pressing critical condition, the method utilizes thermal modeling test to add the mode of electronic microscope photos, obtains the critical condition of center porosity pressing, for the formulation of on-the-spot rolling technological parameter provides theoretical foundation.
Object of the present invention is achieved through the following technical solutions:
Obtain a method of testing for center porosity pressing critical condition, it is characterized in that the method is carried out according to the following steps:
1. in the sampling of sotck thinkness center, be processed into the standard sample of Φ 10 × 15mm, sample is axially sotck thinkness direction;
2., before sample is installed, sample two ends are smeared high temperature lubricant and are padded upper tantalum piece respectively;
3., before experiment, sample bin vacuum tightness is evacuated to 4.0 × 10
-8below torr;
4. sample is heated to experimental temperature, insulation 30s, then carries out single pass pressing test with certain rate of deformation and deflection, and after distortion, power-off cools at random;
5. after having tested, cydariform sample upper and lower surface is respectively sawed out a notch, then puts into liquid nitrogen, take out after 1min, knock off and make fracture sample;
6. scanning electron microscope is utilized to analyze fracture, by judging center porosity pressing situation with or without Free Surface; If center porosity is not by pressing, when fracture process, the center porosity tension stress expansion be crushed, easily identifies; Free Surface is the principal character of center porosity, if fracture has Free Surface, then thinks center porosity not by complete pressing, otherwise nothing then.
7. take heating-up temperature as horizontal ordinate, deflection is ordinate, is depicted as heating-up temperature, deflection and the rate of deformation graph of a relation to center porosity pressing, obtains the critical condition of center porosity pressing.
The present invention, hot modeling test machine carries out single pass pressing test, and the model of hot modeling test machine is Gleeble3800.
Main Basis of the present invention and reason are:
1, center porosity mainly concentrates on sotck thinkness central area, and therefore must to get center just representative in sampling.Φ 10 × 15mm is the standard sample of Gleeble3800 hot modeling test machine compression test.Sample is axially slab thickness direction, mainly in order to make pressing test closer to the rolling deformation situation at scene.
2, sample two ends must smear high temperature lubricant and respectively the upper tantalum piece of pad be in order to sample deformation when pressing is tested evenly.
3, vacuumizing is to prevent sample center porosity to be oxidized in heating process.
4, be incubated 30s be in order to specimen temperature field evenly.Gleeble3800 hot modeling test machine conveniently can set rate of deformation, deflection and heating-up temperature three technological parameters.
5, kerf mouth and tapping nitrogen are all to make sample more easily rupture when knocking, and to obtain fresh fracture, are convenient to follow-up electron microscopic observation.
6, fracture is observed current the best way and is utilized scanning electron microscope exactly, if center porosity is not by pressing, when fracture process, the easy tension stress expansion of the center porosity be crushed, easily identifies.Why not selecting the method for metallographic to observe, is because metaloscope enlargement factor is limited, is difficult to identify the center porosity of non-pressing after flattening.Free Surface is the principal character of center porosity.If fracture has Free Surface, then can think that center porosity is not by complete pressing, otherwise nothing then.
7, by being depicted as heating-up temperature, deflection and the rate of deformation graph of a relation to center porosity pressing, observing critical condition and coming more directly perceived.
The present invention is by slab sampling core, Gleeble3800 hot modeling test machine is utilized to carry out the high-temperature laminating experiment of different technical parameters, and sample is dissected and scanning electron microscope analysis, thus determine the critical condition of center porosity pressing, for the formulation of on-the-spot rolling technological parameter provides theoretical foundation.
Tool of the present invention has the following advantages:
1, the present invention is analogue technique due to the method for testing adopted, and test required sample size little, process of the test can be carried out completely in the lab.Compare on-the-spot rolling test, experimentation cost is much lower.
2, the present invention due to adopt method of testing be physical simulation techniques, experimentation cost is low and result is more reliable.On the one hand, sampling in kind remains original pattern of center porosity substantially, and on the other hand, arranging of test parameters is basic according to actual production technique initialization, and do not need to do any hypothesis, therefore, experimental result is more reliable.
The present invention also can be used for the test of the inherent vice pressing critical conditions such as crackle.
Accompanying drawing explanation
Fig. 1 is the heating-up temperature of center porosity pressing, deflection and the rate of deformation critical condition curve map that embodiment obtains.
Embodiment
Below in conjunction with specific embodiment, a kind of method of testing obtaining center porosity pressing critical condition that the present invention relates to is described in detail.
Test steel grade is E36N, and slab thickness is 260mm, and center porosity grade is 1.0 grades.Thermal modeling test carries out on gleeble3800 hot modeling test machine, and fracture is observed and carried out in JSM6490 scanning electron microscope.Concrete operations are as follows:
1, sample in sotck thinkness center with flame cutting machine, be processed into the standard sample more than 50 of Φ 10 × 15mm on request, sample is axially sotck thinkness direction.
2, by K type thermopair in sample welding, for controlling heating-up temperature and collecting temperature data.After welding, sample two ends uniform application high temperature lubricant also pads upper tantalum piece respectively, and is installed in sample bin.
3, after sample installs, shut door, utilize two-stage vacuum system to start to vacuumize, when vacuum tightness is lower than 4.0 × 10
-8after torr, start test.
4, the TAB programming software that experimental technique is carried by hot modeling test machine sets.Heating-up temperature is set as 1000 DEG C, 1050 DEG C, 1100 DEG C and 1150 DEG C respectively, and deflection is respectively 10%, 20%, 30%, 40%, 50% and 60%, and rate of deformation is 1s
-1and 10s
-1; The rate of heat addition is 10 DEG C/s; Temperature retention time is 30s.After experimental technique executes, stop heating, sample is with apparatus cools.
5, when sample be cooled to be room temperature after, take off sample, put into lock-filters clamp and fasten, with bow saw, cydariform sample upper and lower surface is respectively sawed out a notch, then put into liquid nitrogen, take out after 1min, knock off and make fracture sample.
6, scanning electron microscope is utilized to analyze fracture, by judging center porosity pressing situation with or without Free Surface.
7, according to pressing situation data, critical condition is as shown in Figure 1 obtained.
From figure, not only can find out heating-up temperature, deflection and the rate of deformation affecting laws to the pressing of strand center porosity, also can obtain critical temperature and the critical strain amount condition of center porosity pressing under certain rate of deformation condition, illustrate that this kind of method of testing is feasible.
Claims (4)
1. obtain a method of testing for center porosity pressing critical condition, it is characterized in that the method is carried out according to the following steps:
1. in the sampling of sotck thinkness center, be processed into the standard sample of Φ 10 × 15mm, sample is axially sotck thinkness direction;
2., before sample is installed, sample two ends are smeared high temperature lubricant and are padded upper tantalum piece respectively;
3., before experiment, sample bin vacuum tightness is evacuated to 4.0 × 10
-8below torr;
4. sample is heated to experimental temperature, insulation, then carries out single pass pressing test with certain rate of deformation and deflection, and after distortion, power-off cools at random;
5. after having tested, cydariform sample upper and lower surface is respectively sawed out a notch, then puts into liquid nitrogen, take out after 1min, knock off and make fracture sample;
6. scanning electron microscope is utilized to analyze fracture, by judging center porosity pressing situation with or without Free Surface;
7. take heating-up temperature as horizontal ordinate, deflection is ordinate, is depicted as heating-up temperature, deflection and the rate of deformation graph of a relation to center porosity pressing, obtains the critical condition of center porosity pressing.
2. the method for testing of acquisition center porosity pressing critical condition according to claim 1, is characterized in that: step 4. in, hot modeling test machine carries out single pass pressing test, and the model of hot modeling test machine is Gleeble3800.
3. the method for testing of acquisition center porosity pressing critical condition according to claim 1, is characterized in that: step 4. in, temperature retention time is 30s.
4. the method for testing of acquisition center porosity pressing critical condition according to claim 1, is characterized in that: step 6. in, if center porosity is not by pressing, when fracture process, the expansion of the center porosity tension stress that is crushed, easily identifies; Free Surface is the principal character of center porosity, if fracture has Free Surface, then thinks center porosity not by complete pressing, otherwise nothing then.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104931318A (en) * | 2015-06-16 | 2015-09-23 | 中信戴卡股份有限公司 | Method for manufacturing test sample for wheel rim damage deformation |
| CN111208016A (en) * | 2020-02-12 | 2020-05-29 | 东北大学 | Continuous casting billet surface crack propagation critical strain measurement and crack propagation prediction method |
| CN112504874A (en) * | 2020-11-24 | 2021-03-16 | 河钢股份有限公司 | Method for effectively solving problem of bulging of welding thermal simulation test sample |
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| CN102654439A (en) * | 2011-03-02 | 2012-09-05 | 中国科学院金属研究所 | Method for evaluating welding degree of hole type defect in forge piece |
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2014
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Patent Citations (4)
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| JPS63157058A (en) * | 1986-12-22 | 1988-06-30 | Babcock Hitachi Kk | Service life predicting method for metal member |
| CN101984335A (en) * | 2010-09-20 | 2011-03-09 | 南京钢铁股份有限公司 | Method of analyzing product structure and properties by the utilization of samples prepared with thermo-stimulated test |
| CN102654439A (en) * | 2011-03-02 | 2012-09-05 | 中国科学院金属研究所 | Method for evaluating welding degree of hole type defect in forge piece |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104931318A (en) * | 2015-06-16 | 2015-09-23 | 中信戴卡股份有限公司 | Method for manufacturing test sample for wheel rim damage deformation |
| CN111208016A (en) * | 2020-02-12 | 2020-05-29 | 东北大学 | Continuous casting billet surface crack propagation critical strain measurement and crack propagation prediction method |
| CN111208016B (en) * | 2020-02-12 | 2021-02-26 | 东北大学 | Continuous casting billet surface crack propagation critical strain measurement and crack propagation prediction method |
| CN112504874A (en) * | 2020-11-24 | 2021-03-16 | 河钢股份有限公司 | Method for effectively solving problem of bulging of welding thermal simulation test sample |
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Application publication date: 20141224 |