CN111482564A - Method for judging cause of transverse crack on corner of plate blank surface - Google Patents
Method for judging cause of transverse crack on corner of plate blank surface Download PDFInfo
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- CN111482564A CN111482564A CN202010244623.9A CN202010244623A CN111482564A CN 111482564 A CN111482564 A CN 111482564A CN 202010244623 A CN202010244623 A CN 202010244623A CN 111482564 A CN111482564 A CN 111482564A
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Abstract
The invention discloses a method for judging the cause of transverse corner cracks on the surface of a slab, which is used for analyzing the cause of corner cracks aiming at the corner cracks of the slab.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy, in particular to a method for judging the cause of transverse cracks on corners of the surfaces of slabs.
Background
The production of defect-free casting blanks is a desired goal of continuous casting plant production, but is limited by factors such as production conditions and is difficult to achieve in practice. The defects of the continuous casting slab comprise surface defects, internal quality defects, shape defects and the like, while transverse cracks of the surface corner of the slab are the most common defects of the casting slab, the reason for the transverse cracks of the surface corner of the slab is extremely complicated, and the defects of the casting slab are related to physical and chemical phenomena generated in the solidification process of molten steel in a continuous casting machine, so that the reason for the transverse cracks of the surface corner of the slab must be found in the actual production, corresponding measures are made, and the surface quality of the slab is controlled.
The chinese patent application No. 201310124647.0 discloses that the determination is performed by using metallographic and scanning electron microscope examination methods, and it is observed whether a copper-rich region having a copper content of more than 0.2% by weight exists as a basis for determining the generation of cracks caused by copper embrittlement. The method analyzes the generation reason of the corner cracks by inspecting the characteristics of the corner cracks of the slab through a metallographic microscope and a scanning electron microscope.
Chinese patent application No. 201710895478.9 discloses a process for determining the location of a corner transverse crack by microstructure analysis and a temperature zone in which the corner transverse crack occurs. According to the invention, the characteristics of the corner cracks of the slab are inspected through a metallographic microscope and a scanning electron microscope, and the production process condition of the casting blank is analyzed, so that the generation reason of the corner cracks is judged.
Chinese patent application No. 201410083414.5 discloses a method for determining a subsurface crack defect of a continuous cast slab, which determines a subsurface crack defect ratio corresponding to a measured actual nitrogen content of molten steel using a subsurface crack index map, thereby determining a subsurface crack defect degree of the continuous cast slab obtained after the molten steel is continuously cast.
Disclosure of Invention
The invention aims to provide a method for judging the generation reason of the transverse corner cracks on the surface of a slab, which analyzes the generation reason of the corner cracks aiming at the corner cracks of the slab and provides a basis for making corresponding measures so as to control the surface quality of the slab.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for determining the cause of transverse cracks on the corner of the surface of a plate blank comprises the following steps:
s1, manufacturing a sample aiming at the corner transverse crack defect on the surface of the slab, and grinding the sample to the observable degree of a metallographic microscope;
s2, observing the appearance and characteristics of the corner cracks by adopting a metallographic microscope, wherein the appearance and characteristics at the corner cracks at least comprise the length, the width and the number of the cracks;
s3, observing the microstructure of the crack by adopting a scanning electron microscope, wherein the microstructure at least comprises grain size, tissue condition, decarburization phenomenon and inclusion, and carrying out EDS (electron-dispersive spectroscopy) analysis on the crack area and the surrounding matrix;
s4, analyzing the production process parameter conditions of the casting blank aiming at the corner crack sample, wherein the conditions at least comprise the liquid level fluctuation condition of a crystallizer, the pulling speed change condition and the casting blank temperature condition of a secondary cooling area;
s5, the corner transverse cracks of the analyzed slab surface are mainly classified into the following two types:
the first type of corner transverse cracks are characterized in that: the length is long (more than 150um), the width is wide (more than 2mm), the number is small (generally less than 6), inclusions are in cracks, the main components are similar to the covering slag, the transverse cracks of the corners are generated in the crystallizer, the cracks are expanded due to secondary cooling, and the main reasons for the generation are that the vibration marks of the casting blank are deep, the liquid level fluctuation of the crystallizer is large, and the pulling speed change is large;
the second type of corner transverse cracks are characterized in that: the length is short (less than 100um), the width is narrow (less than 2mm), the number is large (generally more than 10), no inclusion exists in the cracks, the corner transverse cracks are generated under the action of thermal stress, friction force and straightening stress of a secondary cooling area, and the generation reasons are mainly that the corner temperature of the casting blank is too low and the casting blank is straightened in a brittle temperature area.
Further, the size of the test piece was 20mm × 20mm × 20 mm.
Furthermore, the sample is ground by sand paper or polishing cloth to the extent that the sample can be observed by a metallographic microscope.
Compared with the prior art, the invention has the beneficial technical effects that:
and (3) inspecting the characteristics of the corner cracks of the slab by adopting a metallographic microscope and a scanning electron microscope, and analyzing the production process condition of the casting blank so as to judge the generation reason of the corner cracks.
The method for judging the reason for the transverse corner crack on the surface of the plate blank is simple, strong in operability and low in cost in the judging process, can avoid the talents and financial resources wasted by adopting other methods because the reason for the transverse corner crack is not found, improves the working efficiency, saves the cost and has a wide application prospect.
Drawings
The invention is further illustrated in the following description with reference to the drawings.
FIGS. 1 and 2 are metallographic results of corner cracks of SS400B specimens according to the invention;
FIGS. 3 and 4 show the metallurgical results of corner cracks of L245M specimens of the present invention.
Detailed Description
Example 1:
the steel is SS400B, the surface of a slab is taken to have corner transverse crack defects, the sample is processed into 20mm × 20mm × 20mm, the sample is ground to the observable degree of a metallographic microscope by using abrasive paper, polishing cloth and the like, the corner cracks appear in the vibration trace valley of the corner, the maximum width of the corner cracks is 200 mu m, the maximum length of the corner cracks is 5mm, and 4 cracks are observed in total, as shown in figures 1 and 2, the structure condition of the corner cracks is observed by adopting metallographic corrosion, no decarburized layer and no inclusion are generated, the grain size is normal and is the same as the grain size of a matrix, the main components in the cracks are Fe, Na, Si, Mg, Ca and O, iron oxide and protective slag, the constant pulling speed is ensured to be 1.3m/min during production of the furnace, the liquid level fluctuation of the crystallizer is normal, the superheat degree is 27 ℃, the section of a casting blank is 1250mm × 230mm, the operation requirements are met, and the chemical components meet the standard requirements.
Example 2:
l M steel type, a corner transverse crack defect on the surface of a slab is taken, the sample is processed into 20mm × mm 6320 mm, sand paper, polishing cloth and the like are adopted to grind the sample to the observable degree of a metallographic microscope, the width of the corner crack is 20-100 mu M, the length of the corner crack is less than 2mm, 15 cracks are observed in total, as shown in figures 3 and 4, metallographic corrosion is adopted to observe the structure condition of the corner crack, no decarburized layer and no impurities exist, the grain size is normal and is the same as that of a matrix, the main components outside and inside the crack are Fe and O and are ferric oxide, the furnace ensures that the constant drawing speed is 1M/min during production, the liquid level fluctuation of a crystallizer is normal, the superheat degree is 29 ℃, the section of a casting blank is 1650mm × mm, the operation specification requirements are met, the chemical components meet the standard requirements, the straightening temperature of a narrow side corner part is 860 ℃, the high-temperature tensile property of the steel type is analyzed, the brittleness interval is 800 ℃, and the straightening temperature of the corner part is analyzed under the cold stress generated in a straightening region under the action of cold stress and the straightening stress generated under the action of the brittle stress.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (3)
1. A method for judging the cause of transverse cracks on the corner of the surface of a plate blank is characterized by comprising the following steps: the method comprises the following steps:
s1, manufacturing a sample aiming at the corner transverse crack defect on the surface of the slab, and grinding the sample to the observable degree of a metallographic microscope;
s2, observing the appearance and characteristics of the corner cracks by adopting a metallographic microscope, wherein the appearance and characteristics at the corner cracks at least comprise the length, the width and the number of the cracks;
s3, observing the microstructure of the crack by adopting a scanning electron microscope, wherein the microstructure at least comprises grain size, tissue condition, decarburization phenomenon and inclusion, and carrying out EDS (electron-dispersive spectroscopy) analysis on the crack area and the surrounding matrix;
s4, analyzing the production process parameter conditions of the casting blank aiming at the corner crack sample, wherein the conditions at least comprise the liquid level fluctuation condition of a crystallizer, the pulling speed change condition and the casting blank temperature condition of a secondary cooling area;
s5, the corner transverse cracks of the analyzed slab surface are mainly classified into the following two types:
the first type of corner transverse cracks are characterized in that: the casting mold has the advantages that the casting mold is long in length, wide in width and small in quantity, impurities are contained in cracks, the main components of the cracks are similar to those of the casting mold, the corner transverse cracks are generated in the mold, the cracks are expanded due to secondary cooling, and the main reasons for the generation are that the casting blank has deep oscillation marks, the liquid level fluctuation of the mold is large, and the pulling speed change is large;
the second type of corner transverse cracks are characterized in that: the length is short, the width is narrow, the number is large, no inclusion exists in cracks, the corner transverse cracks are generated under the action of thermal stress, friction force and straightening stress of a secondary cooling zone, and the generation reasons are mainly that the corner temperature of the casting blank is too low and straightening is carried out in a brittle temperature zone.
2. The method of determining the cause of the transverse crack in the corner of the slab surface according to claim 1, wherein the size of the sample is 20mm × 20mm × 20 mm.
3. The method for determining the cause of the transverse crack in the corner of the slab surface according to claim 1, wherein: the sample is ground with sandpaper or polishing cloth to a level observable by a metallographic microscope.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113414361A (en) * | 2021-05-19 | 2021-09-21 | 包头钢铁（集团）有限责任公司 | Method for reducing transverse cracks of corner part of slab surface |
| CN113664166A (en) * | 2021-06-30 | 2021-11-19 | 武汉钢铁有限公司 | Method for measuring depth of vibration mark |
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| JP2012207283A (en) * | 2011-03-30 | 2012-10-25 | Toyota Central R&D Labs Inc | Heat resistant and high strength aluminum alloy and method for producing the same |
| CN104043801A (en) * | 2014-06-16 | 2014-09-17 | 北京首钢股份有限公司 | Secondary cooling method for controlling cross cracks in corner of microalloy steel slab |
| CN104165971A (en) * | 2014-08-07 | 2014-11-26 | 国家电网公司 | Method for analyzing power linking metal fitting failure |
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| CN110565006A (en) * | 2019-09-16 | 2019-12-13 | 西安理工大学 | rod end joint bearing based on structure enabling material and preparation method |
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2020
- 2020-03-31 CN CN202010244623.9A patent/CN111482564A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012207283A (en) * | 2011-03-30 | 2012-10-25 | Toyota Central R&D Labs Inc | Heat resistant and high strength aluminum alloy and method for producing the same |
| CN104043801A (en) * | 2014-06-16 | 2014-09-17 | 北京首钢股份有限公司 | Secondary cooling method for controlling cross cracks in corner of microalloy steel slab |
| CN104165971A (en) * | 2014-08-07 | 2014-11-26 | 国家电网公司 | Method for analyzing power linking metal fitting failure |
| CN104807667A (en) * | 2015-04-30 | 2015-07-29 | 内蒙古包钢钢联股份有限公司 | Analytical sampling and analytical method for failure of H-section steel |
| CN107598108A (en) * | 2017-09-28 | 2018-01-19 | 江西理工大学 | A kind of method for judging continuous casting billet and transverse corner crack line place process occurring |
| CN109239079A (en) * | 2018-09-11 | 2019-01-18 | 包头钢铁（集团）有限责任公司 | The method of Hot Metal in Beam Blank production H profile steel web crackle and straightening cracks failure analysis |
| CN110565006A (en) * | 2019-09-16 | 2019-12-13 | 西安理工大学 | rod end joint bearing based on structure enabling material and preparation method |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113414361A (en) * | 2021-05-19 | 2021-09-21 | 包头钢铁（集团）有限责任公司 | Method for reducing transverse cracks of corner part of slab surface |
| CN113664166A (en) * | 2021-06-30 | 2021-11-19 | 武汉钢铁有限公司 | Method for measuring depth of vibration mark |
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