CN111876558B - Method for producing peritectic high-strength steel based on LF + VD process and accurately controlling carbon content - Google Patents
Method for producing peritectic high-strength steel based on LF + VD process and accurately controlling carbon content Download PDFInfo
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- CN111876558B CN111876558B CN202010707014.2A CN202010707014A CN111876558B CN 111876558 B CN111876558 B CN 111876558B CN 202010707014 A CN202010707014 A CN 202010707014A CN 111876558 B CN111876558 B CN 111876558B
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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
- C21C7/10—Handling in a vacuum
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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
- C21C7/0025—Adding carbon material
Abstract
The invention discloses a method for accurately controlling carbon content in peritectic high-strength steel produced based on an LF + VD process, which comprises the following steps: firstly, controlling the carbon content at the end point of a converter to be less than or equal to 0.080%, and carburetting by using a carburant after tapping; secondly, adopting a carburant for recarburization in the LF furnace process, simultaneously considering recarburization rules of a steel ladle and an electrode, and controlling the exit of the LF furnace to control the carbon content; thirdly, a VD process is adopted, a steel ladle bearing molten steel to be processed is hung into a vacuum processing position, and the carbon content, the manganese content and the like of the molten steel are measured; and fourthly, starting a VD (vacuum degassing) vacuum system to carry out vacuum treatment on the molten steel, and after the vacuum treatment, adding carbon-containing alloy to adjust the carbon content of the molten steel according to the measured data of carbon and manganese in the molten steel and the carburization range of the steel ladle in a vacuum state in the third step so as to meet the target requirement of the steel content of finished products. The invention can be suitable for VD and VOD vacuum processes, and breaks through the bottleneck that VD and VOD can not accurately control the carbon content of molten steel.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to a method for producing peritectic high-strength steel by using an LF + VD (ladle furnace and vacuum distillation) process in a steelmaking process and accurately controlling the carbon content.
Background
The high-strength steel has strict requirements on the gas content of molten steel, such as nitrogen, hydrogen, oxygen and the like in the molten steel, the lower the gas content is, the more stable the quality of a steel billet is, and thus the requirement on the low gas content of the high-strength steel is ensured by a vacuum degassing process in the smelting process. The carbon content of the peritectic high-strength steel is 0.10-0.15% in terms of composition, peritectic reaction occurs in the continuous casting solidification process of molten steel, so that the instantaneous volume fluctuation is large, and further the fluctuation of the liquid level of a continuous casting crystallizer is increased, particularly for some slab continuous casting machines with large width and thickness, such as continuous casting machines with the width being more than or equal to 1600mm and the thickness being 150mm, because the peritectic reaction is strong, the liquid level of the crystallizer fluctuates greatly, so that the stable automatic control of the liquid level of the crystallizer can not be realized, and the continuous casting process is directly influenced. The intensity of the peritectic reaction is directly related to the carbon content in the molten steel, and production practices show that when the carbon content is more than or equal to 0.13 percent, the fluctuation of the liquid level of the crystallizer in the continuous casting process is relatively small, the automatic control process of the liquid level of the crystallizer can be stably adopted, and the stable production of the peritectic high-strength steel of the ultra-wide slab continuous casting machine is further realized. In addition, the control range of carbon in the component design of some peritectic high-strength steels is 0.12% -0.14%, and under the background, the stable and smooth production can be realized only by accurately controlling the carbon content within the range of 0.13% -0.14%.
Therefore, when a VD furnace production process is adopted, how to accurately control the carbon content in the steel-making LF + VD refining process within the range of 0.13% -0.14% is the key for stably producing peritectic high-strength steel by adopting an ultra-wide slab continuous casting machine.
Disclosure of Invention
The invention aims to provide a method for accurately controlling the carbon content in peritectic high-strength steel produced based on an LF + VD process, which effectively solves the molten steel smelting problem in the production of the peritectic high-strength steel by an ultra-wide slab caster, reduces the peritectic reaction degree through accurate hit of the carbon content of the molten steel, and realizes a metallurgical process for stable and smooth production of the peritectic high-strength steel of the ultra-wide slab caster.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for accurately controlling the carbon content in peritectic high-strength steel produced based on an LF + VD process is characterized in that when the LF + VD refining process is adopted, the control accuracy of the carbon content of a finished product can reach within 0.01 percent, and the method specifically comprises the following steps:
firstly, controlling the carbon content at the end point of a converter to be below 0.08%, and controlling the carbon content of molten steel by adopting a carburant to carburize after tapping to be-0.050% of the target lower limit of the carbon content of a finished steel billet product and-0.030% of the target lower limit of the carbon content of the finished steel billet product;
secondly, adopting a carburant for recarburization in the LF furnace process, simultaneously considering recarburization rules of a steel ladle and an electrode, and controlling the carbon content of the LF furnace to be in a range from-0.010 percent of the target lower limit of the carbon content of a finished steel billet product to-0.005 percent of the target lower limit of the carbon content of the finished steel billet product;
thirdly, a VD process is adopted, a steel ladle bearing molten steel to be processed is hung into a vacuum processing position, and the carbon content, the manganese content and the like of the molten steel are measured;
and fourthly, starting a VD (vacuum degassing) vacuum system to carry out vacuum treatment on the molten steel, and after the vacuum treatment, adding carbon-containing alloy to adjust the carbon content of the molten steel according to the measured data of carbon and manganese in the molten steel and the carburization range of the steel ladle in a vacuum state in the third step so as to meet the target requirement of the steel content of finished products.
Further, the refractory material adopted by the ladle is magnesia carbon.
Further, the carburant in the first step and the second step is carbon powder.
Further, the carbon-containing alloy adopted in the fourth vacuum treatment process is high-carbon ferromanganese.
Further, the fourth step of vacuum treatment lasts for 15-20min, and the vacuum pressure is kept below 67Pa for 10-15 min.
Compared with the prior art, the invention has the beneficial effects that:
1. after the metallurgical technology is adopted, in the LF + VD refining technology, the carbon content of the molten steel can be stably controlled within 0.01 percent; the invention can be suitable for VD and VOD vacuum processes, breaks through the bottleneck that VD and VOD can not accurately control the carbon content of molten steel, has a higher development space for steel enterprises adopting VD and VOD production processes in terms of process, and is simple and reliable in the whole process control process.
2. In the VD production process, firstly, because a steel ladle is placed in a vacuum tank for molten steel vacuum treatment by the VD process, magnesium in a steel ladle refractory material is volatile in a vacuum state, so that melting loss of a steel ladle magnesia carbon brick is unstable, and molten steel recarburization is caused; secondly, in the VD vacuum treatment process of the molten steel, due to the technical characteristics of VD, sampling cannot be carried out in the vacuum treatment process; after VD vacuum treatment is finished, if conventional carbon powder is adopted to adjust the carbon content of molten steel, the carbon powder floats on the surface layer of steel slag due to being lighter, and the carbon powder is limited to melt on the premise of meeting the requirement that molten steel is not exposed and stirred, so that the recarburization absorption rate of the carbon powder adopted after VD vacuum treatment is unstable. Based on the factors, the precise control of the carbon content in the LF and VD smelting process is difficult. The peritectic high-strength steel produced based on the LF and VD processes provided by the invention can control the carbon content of the finished steel billet to be within 0.010%, and the purpose of accurately controlling the carbon content of the finished steel billet by the LF and VD processes is realized.
Drawings
Figure 1 is a hit of the carbon content of the finished peritectic high strength steel AQ690D produced using the present invention.
Detailed Description
In order to make the technical solutions and advantages of the present invention clearer, the present invention is further described below with reference to specific examples.
Example 1
Taking 150t converter steel output, the peritectic high-strength steel AQ690D with carbon content of 0.130-0.140% and manganese content of 1.35-1.50% is produced as an example.
The adopted smelting process route is as follows: molten iron pretreatment → converter → LF → vacuum treatment process (VD) → ultra-wide slab caster (1600 + 3250mm in width, 150mm in thickness).
The carbon content control in the smelting process comprises the following specific steps.
Firstly, controlling the carbon content to be less than or equal to 0.080% at the smelting end point of the converter, adjusting the carbon content of molten steel by using carbon powder in the tapping process, and adjusting the carbon content of the molten steel by using the carbon powder after tapping to achieve the target of 0.080-0.100%. Generally, when a 150t converter dephosphorizes to below 0.015 percent, the carbon content in molten steel is 0.040 to 0.060 percent, the manganese content is 0.08 to 0.12 percent, 2900kg of ferro-silico-manganese (FeMn 68Si 18) is added in the tapping process, the carbon content in the molten steel is 0.070 to 0.090 percent, then 20kg of carbon powder is added, the carbon content in the molten steel can reach 0.080 to 0.100 percent, and the manganese content is 1.32 to 1.36 percent;
secondly, in the LF furnace process, a molten steel sample is taken from a station to detect the carbon and manganese content in the molten steel, the carbon content in the molten steel is determined by sampling at the later stage of smelting, because the carbon content in the molten steel is generally 0.100-0.120% in the smelting process, carbon powder is adopted to finely adjust the carbon content in the molten steel to 0.120-0.125%, and ferro-silico-manganese or low-carbon ferromanganese is adopted to adjust the manganese content in the molten steel to 1.35-1.38%;
and thirdly, a VD process, namely hoisting the steel ladle into a vacuum tank, taking a molten steel sample to detect the carbon and manganese content in the molten steel and carrying out vacuum treatment, wherein the carbon content in the molten steel is accurately controlled according to the following basis in the vacuum treatment process: firstly, sampling components of molten steel when VD enters a station; secondly, under the condition of VD vacuum treatment for 15min to 20min, the carburetion amount of the 150t magnesium-carbon steel ladle is 0.007 percent to 0.009 percent; sampling and detecting the carbon and manganese content in the molten steel after VD vacuum treatment is finished, wherein the carbon content in the molten steel is 0.127-0.134%, and if the carbon content in the molten steel is 0.130-0.134%, the target is hit; if the carbon content in the molten steel is between 0.127 and 0.130, the target is not hit, the carbon content in the molten steel is adjusted by adopting 0 to 80kg of high-carbon ferromanganese (FeMn68C7.0), the target can be hit after the carbon content in the molten steel is adjusted, and the manganese content in the molten steel is increased by less than or equal to 0.04 percent, namely the manganese content is 1.35 to 1.42 percent.
Figure 1 is a hit of the carbon content of the finished peritectic high strength steel AQ690D produced using the present invention. In 222 furnace steel produced, the carbon content of a finished product billet of 220 furnace steel meets the target requirement, and the hit rate is 99.10%.
Comparative example
Taking the peritectic high-strength steel Q690D with the carbon content of 0.130-0.140% as an example when the steel output of a 150t converter is 150 t.
After tapping of the converter, the process parameters of the comparative example are the same as those of example 1, except that the VD carbon control process is different, and the other processes are the same.
In the VD process, the conventional carbon control process is to sample and test after the VD vacuum treatment is finished, and according to the test result, if the carbon content does not meet the target requirement, the carbon powder is used for increasing the carbon content in the molten steel.
Example 1 and comparative example were collected for 10 months and hits were compared to finished carbon as shown in figure 1. As can be seen from the graph 1, through comparison of test data of 10 months, in the 101-furnace steel produced by the smelting process of the embodiment 1, the carbon content of the finished product completely meets the target requirement, and the qualification rate is 100%; in the comparative example, 16 of the 86-furnace steel were not subjected to the target requirement, and the yield was 81.40%. Therefore, the smelting method provided by the invention has the advantage that the process stability is obviously improved.
Finally, it should be noted that the above-mentioned description is only for illustrating the technical solution of the present invention and not for limiting, and other modifications or equivalent substitutions made by the technical solution of the present invention by those skilled in the art should be covered in the scope of the claims of the present invention as long as they do not depart from the spirit of the technical solution of the present invention.
Claims (2)
1. A method for accurately controlling the carbon content in peritectic high-strength steel produced based on an LF + VD process is characterized in that when the LF + VD refining process is adopted, the control accuracy of the carbon content of a finished product reaches within 0.01 percent, and the method specifically comprises the following steps:
firstly, controlling the carbon content at the end point of a converter to be below 0.08%, and controlling the carbon content of molten steel by adopting a carburant to carburize after tapping to be-0.050% of the target lower limit of the carbon content of a finished steel billet product and-0.030% of the target lower limit of the carbon content of the finished steel billet product;
secondly, adopting a carburant for recarburization in the LF furnace process, simultaneously considering recarburization rules of a steel ladle and an electrode, and controlling the carbon content of the LF furnace to be in a range from-0.010 percent of the target lower limit of the carbon content of a finished steel billet product to-0.005 percent of the target lower limit of the carbon content of the finished steel billet product;
thirdly, a VD process is adopted, a steel ladle bearing molten steel to be processed is hung into a vacuum processing position, and the carbon content and the manganese content of the molten steel are measured;
fourthly, starting a VD vacuum system to carry out vacuum treatment on the molten steel, and after the vacuum treatment, adding carbon-containing alloy to adjust the carbon content of the molten steel according to the measured data of carbon and manganese in the molten steel and the recarburization range of the steel ladle in a vacuum state in the third step so as to achieve the target requirement of the content of finished steel;
the recarburizing agent in the first step and the second step is carbon powder;
the carbon-containing alloy adopted in the fourth step of vacuum treatment is high-carbon ferromanganese;
and the fourth step of vacuum treatment lasts for 15-20min, and the vacuum pressure is kept below 67Pa for 10-15 min.
2. The method for accurately controlling the carbon content in the peritectic high-strength steel produced based on the LF + VD process as claimed in claim 1, wherein the refractory material adopted by the steel ladle is magnesia carbon.
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| CN102345061B (en) * | 2011-06-28 | 2013-06-12 | 南阳汉冶特钢有限公司 | Q690D quality structural medium steel plate and production method thereof |
| CN102864275A (en) * | 2012-09-25 | 2013-01-09 | 鞍钢股份有限公司 | Control method of aluminum content of heavy rail steel |
| CN103276148A (en) * | 2013-06-07 | 2013-09-04 | 鞍钢股份有限公司 | Method for reducing influence of casting residue recovery on LF liquid steel carburization |
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