A kind of method of testing the preceding grain size of square billet breaking down
Technical field
The invention belongs to technical filed of material metallographic test, a kind of method of testing the preceding grain size of square billet breaking down particularly is provided, austenite grain size before the breaking down of research square billet, formulation for the heating cycle of heating furnace, and formulate rational controlled rolling technology the data support is provided, detection method is easy, accurately.
Background technology
Controlled rolling is the emphasis of steel rolling process research always, reasonably the controlled rolling technological requirement to breaking down before austenite structure state, every time deflection, final material structure performance have in depth and understand, by obtain before the breaking down material composition, crystallite dimension and the boundary condition of desirable material structure performance two aspects, formulate steel rolling process parameters such as reasonable passage distortion distribution, process for cooling, so the research of the austenite structure state before the steel billet breaking down has very important meaning.
All the time, the method of the test of austenite grain size all is thermal simulation, quench after adopting austenitizing, picric acid heat etching method shows austenite grain boundary, thermal simulation is also adopted in the formulation of the rolling mill practice of square billet, after the austenite heating, size by test quenching back austenite grain size, formulate controlled rolling technology, this side's drawback has two aspects: one side detection method complexity, and narrow ranges of process parameters needs the suitable picric acid concentration of configuration, the heat time of invading is difficult to grasp the also bad assurance of the sharpness of crystal grain; On the other hand, obtain because austenite structure is thermal simulation after all, can't accurate get obtain square billet and go out heating furnace after, the structural state before the breaking down, the accuracy of data is worth discussion.This method provided by the invention, be equivalent to the original position analysis, structural state by the iron scale grain boundary oxidation of contact steel billet matrix after the de-scaling of test square billet, show the preceding austenitic grain size of breaking down exactly, principle is in the burning process, the austenite grain boundary position is at first oxidized, steel billet is no exception, water under high pressure utilization before the breaking down is cooled off fast on the one hand iron scale is cooled off fast, realize separating of iron sheet and steel billet simultaneously, preserve the replica of the preceding steel billet austenite crystal oxidation of breaking down, directly obtained the preceding austenite grain size data of square billet breaking down.
The invention provides a kind of method of studying the preceding austenite grain size of square billet breaking down, its detection method is simple, effective, has reflected the preceding austenite crystal state of square billet breaking down accurately, has enriched austenite structure research simultaneously.
Summary of the invention
The object of the present invention is to provide a kind of method of testing the preceding grain size of square billet breaking down, detect the preceding austenite grain size of square billet breaking down, simplified conventional heat etching method, solved and to have obtained preceding this difficult problem of austenite grain size data of square billet breaking down.
Testing procedure of the present invention is:
A. furnace temp is controlled at 980-1150 ℃, remaining oxygen 2.5-6%, 2.5-4 hour heat time heating time;
B. through high-pressure water descaling, water pressure 13-16Mpa obtained the square billet scale on surface after steel billet was come out of the stove;
C. iron scale is carried out ultrasonic cleaning 8-10 minute, be prepared into the scanning electron microscope analysis sample;
D. analyze iron scale and press close to the pattern of square billet matrix one side under scanning electron microscope, the Electronic Speculum Control of Voltage obtains square billet iron scale organization picture of grain boundary at 13-15Kv;
E. organize photo to utilize grain size before the breaking down of Imagetool software test square billet by grain boundary oxidation.
Imagetool software of the present invention is a kind of under familiar various typical organizations prerequisite, and can carry out image and the data processing software that basal ration characterizes to tissue.Major function is quantitatively artificial, promptly use quantitative metallography/stereology principle, it is quantitative with software to adopt numeral to take pictures, increase work efficiency, embody digitized characteristics, can determine outside crystallite dimension, phase number percent, the nucleation rate, also can determine crooked crystal boundary length easily, grain shape compares etc. and manually quantitatively to be difficult to the work finished.
Use the basic step of software statistics crystallite dimension:
1, activates this software.Open a graphic file.
2, if will survey crystallite dimension, calibrate Calibrate earlier.In settings menu, click Calibratespacial measurement; The straight line of standardized known length, and input length value are just finished calibration.
3, click the Distance wicket, measure, line of every picture, length value enters the Results window automatically, and provides mean value and variance.
4, be under the state of activation at the Results window, can preserve measurement data
The invention has the advantages that, provide a kind of more quick, directly perceived, clear, accurately test the method for austenite grain size before the square billet breaking down.After being used to analyze square billet and going out heating furnace, austenite crystal state before the breaking down for research square billet heating cycle, the control of breaking down austenite structure provide more direct, method and data easily, is convenient to the analysis and the research of the The whole control operation of rolling.
Description of drawings
Fig. 1 is that the replica scanning electron microscope of the inboard austenite grain boundary oxidation of iron scale before the 130 square billet ultra-low-carbon steel SWRCH-M6 breaking down is organized photo.
Fig. 2 is that the replica scanning electron microscope of the inboard austenite grain boundary oxidation of iron scale before the 130 square billet BP05 breaking down is organized photo.
Embodiment
Embodiment 1
The present invention produces among the 130 square billet ultra-low-carbon steel SWRCH-M6 in Shoudu Iron and Steel Co first wire rolling plants and is applied, and is used to study the preceding square billet austenite grain size size of breaking down, concrete steps:
A. the heating furnace remaining oxygen is controlled at 2.4%, and 1080 ℃ of soaking zone temperature, after square billet goes out heating furnace, after the dephosphorization of 14Mpa high pressure, obtain the square billet scale on surface at 2.5 hours heat time heating times;
B. iron scale was carried out after the ultrasonic cleaning 10 minutes, and be prepared into the scanning electron microscope analysis sample;
C. analyze iron scale under the scanning electron microscope and press close to the pattern of square billet matrix one side, scanning electron microscope voltage 15Kv obtains the square billet organization picture of grain boundary;
D. grain boundary oxidation organizes photo to utilize the preceding grain size of Imagetool software test square billet breaking down.
Embodiment 2
The present invention produces among the 130 square billet BP05 in Shoudu Iron and Steel Co first wire rolling plants and is applied, and is used to study the preceding square billet austenite grain size size of breaking down, concrete steps:
A. the heating furnace remaining oxygen is controlled at 2%, and 1050 ℃ of soaking zone temperature, after square billet goes out heating furnace, after the dephosphorization of 16Mpa high pressure, obtain the square billet scale on surface at 3 hours heat time heating times;
B. iron scale was carried out after the ultrasonic cleaning 10 minutes, and be prepared into the scanning electron microscope analysis sample;
C. analyze iron scale under the scanning electron microscope and press close to the pattern of square billet matrix one side, scanning electron microscope voltage 15Kv obtains the square billet organization picture of grain boundary;
D. grain boundary oxidation organizes photo to utilize the preceding grain size of Imagetool software test square billet breaking down.