CN111842827B - Method for controlling center segregation of casting blank - Google Patents
Method for controlling center segregation of casting blank Download PDFInfo
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- CN111842827B CN111842827B CN202010623084.XA CN202010623084A CN111842827B CN 111842827 B CN111842827 B CN 111842827B CN 202010623084 A CN202010623084 A CN 202010623084A CN 111842827 B CN111842827 B CN 111842827B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
Abstract
The invention relates to the field of ferrous metallurgy, in particular to a method for controlling center segregation of a casting blank, which specifically comprises the following steps: (1) preparing alloy steel wires of the same kind as the target casting steel type; (2) calculating the enthalpy value of the tundish molten steel according to the actual temperature of the tundish molten steel; (3) calculating the heat required to be consumed for reaching the heat balance according to the target temperature of the molten steel in the tundish; (4) and (2) feeding the alloy steel wire in the step (1) into the molten tundish steel to supplement the heat. According to the invention, the casting temperature of the molten tundish steel in the continuous casting production process is effectively reduced, so that the problem of center segregation is solved, and the homogeneity of the casting blank is improved.
Description
Technical Field
The invention relates to the field of ferrous metallurgy, in particular to a method for controlling center segregation of a casting blank.
Background
With the rapid development of society, the steel material is the most popular metal material, and the quality and performance requirements of the steel material are higher and higher, which puts higher requirements on the blank quality of the steel product, including the chemical composition uniformity, purity and compactness of the blank, wherein the control of the chemical composition uniformity is also called segregation control, which is always the key and difficult point of research in the steel-making field, and the uniformity of the chemical composition directly affects the product structure and performance control. For example, as an important power transmission member, a gear steel is required to have high crushing resistance, pitting peeling resistance, good impact resistance, bending impact resistance, suitable hardenability, hardened layer depth, good core hardness, machinability, deformation and dimensional stability due to the characteristics of its service environment. The uniformity of chemical components lays an important foundation for the uniformity of the structure performance of the product in the processing process, and is favorable for solving the production problems of no bending deformation and the like in the processing and heat treatment processes. For high-carbon hard wire products, the serious solute enrichment in the center can cause the products to generate abnormal microstructures such as martensite, secondary cementite and the like, the drawing performance is seriously influenced, the problems of drawing wire breakage and the like can be caused, and the quality stability and the smooth production are influenced; and as heavy rail steel, the heavy rail steel is used as an important material for railway transportation construction, the quality of the steel rail directly influences the safety of railway transportation, the quality of the steel rail has important requirements on the uniformity of chemical components, local solute enrichment can cause heat treatment and welded joints to generate hard abnormal microstructures, the hard abnormal microstructures can become fatigue crack sources when loaded, and great potential safety hazards are brought. From this, it is known that the solute homogeneity is important for controlling the quality of the steel material.
However, the homogeneity of the steel products produced at present is not high, and the center segregation directly affects the performance of the finished steel products, for example, the fracture of a steel plate tensile sample is easy to generate the phenomena of tensile cracking or delamination.
Therefore, it is desirable to provide a new technical solution to solve the above problems.
Disclosure of Invention
The invention aims to overcome the problem of low homogeneity of steel products in the prior art, and provides a method for controlling center segregation of a casting blank.
In order to achieve the above object, an aspect of the present invention provides a method for controlling center segregation of a cast slab, including: (1) preparing alloy steel wires of the same kind as the target casting steel type; (2) calculating the enthalpy value of the tundish molten steel according to the actual temperature of the tundish molten steel; and (3) calculating the heat required to be consumed for reaching the heat balance according to the target temperature of the molten tundish steel; (4) and (2) feeding the alloy steel wire in the step (1) into the molten tundish steel to supplement the heat.
Preferably, the target temperature of the molten tundish steel in the step (3) is determined according to the liquidus temperature.
Preferably, the liquidus temperature is 1470-.
Preferably, the heat in the step (3) is generated by the enthalpy change of the cooling of the molten tundish steel.
Preferably, the speed of the wire feeding in the step (4) is calculated by the formula:
Vc*S*7.5*1000*(HTc-HTm)＝△H＝π*r2*Vs*7.8*1000*(HTsm-HTsc)
wherein Vc is casting pulling speed; s is the casting section area; tc is the actual temperature of the molten steel in the tundish, HTcThe enthalpy value is the original temperature of the molten steel of the tundish; tm is the target temperature of the molten steel in the tundish, HTmThe enthalpy value is the target temperature of the molten tundish steel; delta H is the enthalpy change of cooling of the molten steel in the tundish; r is the radius of the alloy steel wire; vs is the feed rate; hTsmThe enthalpy value of the alloy steel wire when the molten steel reaches the target temperature; tsc is the initial temperature of the alloy steel wire, HTscThe enthalpy value of the alloy steel wire at the initial temperature is shown.
Preferably, the wire feeding speed is determined by referring to the casting speed and the amount of the molten steel cast per unit time by each casting strand of the tundish.
Preferably, the casting pulling speed is 1.8-1.9 m/min.
Preferably, the wire feeding speed is 1.50-4.39 m/min.
Preferably, the related thermophysical property parameters in the speed calculation formula of the wire feeding can be calculated by software.
Preferably, step (4) is carried out in particular by a wire feeder.
According to the technical scheme, the alloy steel wires of the same type as the target casting steel type are formulated, the enthalpy value of the tundish molten steel is calculated according to the actual temperature of the tundish molten steel, the heat required to be consumed for achieving heat balance is calculated according to the target temperature of the tundish molten steel, and the alloy steel wires are fed into the tundish molten steel to supplement the heat. The method effectively reduces the casting temperature of the molten tundish steel in the continuous casting production process, thereby improving the problem of center segregation and improving the homogeneity of the casting blank.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a method for controlling center segregation of a casting blank, which comprises the following steps:
(1) preparing alloy steel wires of the same kind as the target casting steel type;
(2) calculating the enthalpy value of the tundish molten steel according to the actual temperature of the tundish molten steel;
(3) calculating the heat required to be consumed for reaching the heat balance according to the target temperature of the molten steel in the tundish;
(4) and (2) feeding the alloy steel wire in the step (1) into the molten tundish steel to supplement the heat.
According to the technical scheme, the alloy steel wires of the same type as the target casting steel type are formulated, the enthalpy value of the tundish molten steel is calculated according to the actual temperature of the tundish molten steel, the heat required to be consumed for achieving heat balance is calculated according to the target temperature of the tundish molten steel, and the alloy steel wires are fed into the tundish molten steel to supplement the heat. The method effectively reduces the casting temperature of the molten tundish steel in the continuous casting production process, thereby improving the problem of center segregation and improving the homogeneity of the casting blank.
According to the invention, the selection of the alloy steel wire in the step (1) is consistent with the target casting steel grade, so that impurity elements are prevented from being introduced into the molten tundish steel, and the generated casting blank is unqualified in component.
And (2) substituting the actual temperature of the molten tundish steel into a thermodynamic calculation formula for operation to obtain the enthalpy value of the molten tundish steel.
In the step (3), according to the target temperature (Tm) of the molten tundish steel, the enthalpy value (H) of the molten tundish steel at the target temperature can be obtained through a thermodynamic calculation formulaTm) The enthalpy value (H) of the tundish molten steel under the combination of the actual temperature (namely the original temperature of the molten steel transferred to the tundish, Tc) of the tundish molten steelTc) Therefore, the heat (delta H) required to be consumed by heat balance is obtained, namely the heat required to be provided by the alloy steel wire is required to reach the target temperature of the molten steel in the tundish.
And (4) executing wire feeding operation through the wire feeding machine, so that the heat required by the tundish molten steel reaching the target temperature is supplemented through wire feeding.
Specifically, the wire feeding speed calculation formula in the step (4) is as follows:
Vc*S*7.5*1000*(HTc-HTm)＝△H＝π*r2*Vs*7.8*1000*(HTsm-HTsc)
wherein Vc is casting drawing speed (m/min); s is the casting cross-sectional area (m)2) (ii) a Tc is the actual temperature of the molten steel in the tundish, HTcThe enthalpy value (kJ/kg) of the original temperature of the molten steel of the tundish; tm is the target temperature of the molten steel in the tundish, HTmThe enthalpy value (kJ/kg) of the target temperature of the molten tundish steel; the delta H is the enthalpy change of the cooling of the molten steel in the tundish, the heat consumed for maintaining heat balance is equal to the value of the enthalpy change of the heating of the steel wire; r is the radius (m) of the alloy steel wire; vs is the wire feed speed (m/min); hTsmThe enthalpy value (kJ/kg) of the alloy steel wire when the molten steel reaches the target temperature is the value of the enthalpy of the alloy steel wire and the value of the enthalpy of the molten steel at the target temperature HTmEqual in size; tsc is the initial temperature of the alloy steel wire, HTscThe enthalpy value (kJ/kg) of the alloy steel wire at the initial temperature is shown.
When the feed speed is calculated by the above formula, the related thermophysical property parameters (such as H)Tc、HTmAnd deltah) can be obtained by direct calculation by software.
The target temperature of the tundish molten steel is determined according to the liquidus temperature (also called primary crystal temperature, which refers to the highest temperature at which an object starts to change from a liquid state to a solid state), and the specific value is determined by combining the specific chemical components of the steel and various process parameters. The liquidus temperature in the invention is preferably 1470-1472 ℃, and certainly, the liquidus temperature is not limited to 1470-1472 ℃, so long as the purpose of reducing the casting temperature of the tundish molten steel in the continuous casting production process can be achieved, and the problem of the center segregation of the casting blank can be improved.
The wire feeding speed needs to be determined by referring to the casting speed and the amount of liquid steel cast by each tundish casting flow in unit time, and specific numerical values need to be calculated by substituting each parameter into a wire feeding speed calculation formula. In the invention, the casting pulling speed is preferably 1.8-1.9m/min, the wire feeding speed is preferably 1.50-4.39m/min, and the method is not limited to the method, and specific values can be flexibly selected according to different continuous casting processes, so long as the casting temperature of the molten tundish steel in the continuous casting production process can be reduced, thereby improving the problem of central segregation of the casting blank and improving the homogeneity of the casting blank.
According to the technical scheme, the alloy steel wires of the same type as the target casting steel type are formulated, the enthalpy value of the tundish molten steel is calculated according to the actual temperature of the tundish molten steel, the heat required to be consumed for achieving heat balance is calculated according to the target temperature of the tundish molten steel, and the alloy steel wires are fed into the tundish molten steel to supplement the heat. The method effectively reduces the casting temperature of the molten tundish steel in the continuous casting production process, thereby improving the problem of center segregation and improving the homogeneity of the casting blank.
The present invention will be described in detail below by way of examples.
Example 1
This example is a steel mill using the method of the present invention to produce SWRH82B hard wire products with 160mm X160 mm cross-sections.
The specific execution flow is as follows: casting pulling speed Vc is 1.8 m/min; casting cross-section area S0.16 0.0256m2(ii) a Enthalpy value H of original temperature of molten steel in tundishTc1261.2 kJ/kg; enthalpy value H of target temperature of molten steel in tundishTm1258.0 kJ/kg; the radius r of the alloy steel wire is 0.005 m; the heat enthalpy value H of the alloy steel wire when the molten steel of the tundish is at the target temperatureTsm＝HTm1258.0(kJ/kg), enthalpy value H at initial temperature of alloy steel wireTsc＝50kJ/kg。
Substituting the obtained value into a wire feeding speed calculation formula to calculate that the wire feeding speed Vs is 1.50 m/min. The casting temperature at the casting position in the simultaneous continuous casting production can be reduced from 1479 ℃ to 1475 ℃, and the liquidus temperature of the steel is calculated to be 1470 ℃ by combining the specific chemical components of the steel.
Besides the above key technical points, the present invention needs to be implemented according to requirements, and other continuous casting system processes are required to be implemented according to conventional implementation.
Through the chemical test of drilling sample segregation on the test casting blank of the embodiment, the following conclusion can be obtained: the length proportion of the equiaxed crystal area of the casting blank reaches 48.2 percent of the section size of the casting blank, and the segregation degree of the central C element reaches 1.06. The casting blank has good corner quality, uniform thickness distribution along the circumferential direction, good full-section homogeneity, loose center and low-power center segregation quality rating index control. The center of the product has no microscopic martensite abnormal structure, and the drawing process is smooth.
Example 2
This example is a steel mill using the method of the present invention to produce SWRH82B hard wire products with 160mm X160 mm cross-sections.
The specific execution flow is as follows: casting pulling speed Vc is 1.7-1.8 m/min; casting cross-section area S0.16 0.0256m2(ii) a Enthalpy value H of original temperature of molten steel in tundishTc1270.1 kJ/kg; enthalpy value H of target temperature of molten steel in tundishTm1261.2 kJ/kg; the radius r of the alloy steel wire is 0.005 m; the heat enthalpy value H of the steel wire when the molten steel of the tundish is at the target temperatureTsm＝HTm1261.2(kJ/kg), enthalpy value H at initial temperature of alloy steel wireTsc＝50kJ/kg。
Substituting the obtained value into a wire feeding speed calculation formula to calculate that the wire feeding speed Vs is 3.93-4.16 m/min. The casting temperature at the casting position can be reduced from 1498 ℃ to 1479 ℃ and the liquidus temperature is calculated to be 1472 ℃ in combination with the specific chemical composition of the steel grade.
Besides the above key technical points, the present invention needs to be implemented according to requirements, and other continuous casting system processes are required to be implemented according to conventional implementation.
Through the chemical test of drilling sample segregation on the test casting blank of the embodiment, the following conclusion can be obtained: the length proportion of the equiaxed crystal area of the casting blank reaches 45.2 percent of the section size of the casting blank, and the segregation degree of the central C element reaches 1.08. The casting blank has good corner quality, uniform thickness distribution along the circumferential direction, good full-section homogeneity, loose center and low-power center segregation quality rating index control. The center of the product has no microscopic martensite abnormal structure, and the drawing process is smooth.
Example 3
This example is a steel mill using the method of the present invention to produce SWRH82B hard wire products with 160mm X160 mm cross-sections.
The specific execution flow is as follows: casting pulling speed Vc 1.8-1.9 m/min; casting cross-section area S0.16 0.0256m2(ii) a Enthalpy value H of original temperature of molten steel in tundishTc1270.1 kJ/kg; enthalpy value H of target temperature of molten steel in tundishTm1261.2 kJ/kg; the radius r of the alloy steel wire is 0.005 m; the heat enthalpy value H of the alloy steel wire when the molten steel of the tundish is at the target temperatureTsm＝HTm1263.2(kJ/kg), enthalpy value H at initial temperature of alloy steel wireTsc＝50kJ/kg。
Substituting the obtained value into a wire feeding speed calculation formula to calculate that the wire feeding speed Vs is 4.16-4.39 m/min. The casting temperature at the casting position can be reduced from 1498 ℃ to 1481 ℃ and the liquidus temperature is 1471 ℃ calculated in conjunction with the specific chemical composition of the steel grade.
Besides the above key technical points, the present invention needs to be implemented according to requirements, and other continuous casting system processes are required to be implemented according to conventional implementation.
Through the chemical test of drilling sample segregation on the test casting blank of the embodiment, the following conclusion can be obtained: the length proportion of the equiaxed crystal area of the casting blank reaches 45.7 percent of the section size of the casting blank, and the segregation degree of the central C element reaches 1.07. The casting blank has good corner quality, uniform thickness distribution along the circumferential direction, good full-section homogeneity, loose center and low-power center segregation quality rating index control. The center of the product has no microscopic martensite abnormal structure, and the drawing process is smooth.
The above examples illustrate that, by adopting the present invention, the low-cost casting temperature control is realized by continuous casting of steel billets for high-carbon hard wire products with 160mm × 160mm cross-section SWRH82B, low-temperature casting is realized, the quality control of the cast blank is good, zero defects are found at the corners of the cast blank, the thickness of the shell of the blank is uniformly distributed along the circumferential direction, the homogeneity of the whole cross-section of the cast blank is good, the quality rating index control of center porosity and center segregation is good, the center of the product has no micro martensite abnormal structure, and the drawing process is smooth.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (7)
1. A method for controlling center segregation of a casting blank is characterized by comprising the following steps:
(1) preparing alloy steel wires of the same kind as the target casting steel type;
(2) calculating the enthalpy value of the tundish molten steel according to the actual temperature of the tundish molten steel;
(3) calculating the heat required to be consumed for reaching the heat balance according to the target temperature of the molten steel in the tundish;
(4) feeding the alloy steel wire in the step (1) into the molten tundish steel to supplement the heat;
the wire feeding speed calculation formula in the step (4) is as follows:
Vc*S*7.5*1000*(HTc-HTm)＝△H＝π*r2*Vs*7.8*1000*(HTsm-HTsc)
wherein Vc is casting pulling speed; s is the casting section area; tc is the actual temperature of the molten steel in the tundish, HTcThe enthalpy value is the original temperature of the molten steel of the tundish; tm is the target temperature of the molten steel in the tundish, HTmThe enthalpy value is the target temperature of the molten tundish steel; delta H is the enthalpy change of cooling of the molten steel in the tundish; r is the radius of the alloy steel wire; vs is the feed rate; hTsmThe enthalpy value of the alloy steel wire when the molten steel reaches the target temperature; tsc is the initial temperature of the alloy steel wire, HTscThe enthalpy value of the alloy steel wire at the initial temperature is obtained;
the casting drawing speed is 1.8-1.9 m/min;
the wire feeding speed is 1.50-4.39 m/min.
2. The method for controlling center segregation of a casting slab according to claim 1, wherein the target temperature of the molten tundish steel in the step (3) is determined according to the liquidus temperature.
3. The method for controlling the center segregation of a cast slab as claimed in claim 2, wherein the liquidus temperature is 1470-1472 ℃.
4. The method for controlling center segregation of a cast slab according to claim 1, wherein the heat in the step (3) is generated by enthalpy change of cooling of molten tundish steel.
5. The method of controlling center segregation of a cast slab according to claim 1, wherein the wire feeding speed is determined with reference to a casting speed and an amount of molten steel poured per unit time for each tundish casting flow.
6. The method for controlling the center segregation of a casting slab according to claim 1, wherein the related thermophysical property parameters in the wire feeding speed calculation formula are calculated by software.
7. The method for controlling the center segregation of a cast slab according to claim 1, wherein the step (4) is performed by a wire feeder.
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| CN1363439A (en) * | 2001-07-20 | 2002-08-14 | 南京理工大学 | Conticasting technology for feeding rare-earth wires into tundish |
| CN102430729A (en) * | 2011-11-15 | 2012-05-02 | 内蒙古包钢钢联股份有限公司 | Method for preparing thinned steel continuous casting round billet crystal grains |
| CN105033216A (en) * | 2015-08-26 | 2015-11-11 | 东北大学 | Method for determining steel belt feeding process parameter of crystallizer in thick slab continuous casting process |
| CN105598402A (en) * | 2016-01-22 | 2016-05-25 | 东北大学 | Core-covered wire fed by steel continuous casting crystallizer and method for dynamically controlling wire feeding process |
| CN107177716A (en) * | 2017-05-24 | 2017-09-19 | 马鞍山市兴达冶金新材料有限公司 | A kind of production method for Large Heat Input Welding micro alloyed steel |
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2020
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1363439A (en) * | 2001-07-20 | 2002-08-14 | 南京理工大学 | Conticasting technology for feeding rare-earth wires into tundish |
| CN102430729A (en) * | 2011-11-15 | 2012-05-02 | 内蒙古包钢钢联股份有限公司 | Method for preparing thinned steel continuous casting round billet crystal grains |
| CN105033216A (en) * | 2015-08-26 | 2015-11-11 | 东北大学 | Method for determining steel belt feeding process parameter of crystallizer in thick slab continuous casting process |
| CN105598402A (en) * | 2016-01-22 | 2016-05-25 | 东北大学 | Core-covered wire fed by steel continuous casting crystallizer and method for dynamically controlling wire feeding process |
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