CN110343943B - High-nitrogen alloy enhancer and application thereof - Google Patents
High-nitrogen alloy enhancer and application thereof Download PDFInfo
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Abstract
The invention belongs to the field of ferrous metallurgy, and particularly relates to a high-nitrogen alloy enhancer and application thereof. The high-nitrogen alloy enhancer comprises the following raw materials in percentage by weight: 40-55% of ferrosilicon, 30-40% of silicomanganese alloy, 4-6% of silicon carbide and 10-20% of iron powder. Further, the chemical components of the high-nitrogen alloy enhancer comprise, by weight: c: 4.5% or less, Si: 25-45% of Mn: 10-15%, N: 16-30% of iron and inevitable impurities as the rest. The invention does not change the existing smelting and rolling equipment, thereby reducing the alloy cost and being popularized and used in other deformed steel and H-shaped steel production enterprises. The comprehensive utilization of low-price resources is realized, the consumption of vanadium alloy is reduced, the economic benefit of iron and steel enterprises is improved, and the environmental pressure caused by the exploitation of vanadium resources is reduced.
Description
Technical Field
The invention belongs to the field of ferrous metallurgy, and particularly relates to a high-nitrogen alloy enhancer and application thereof.
Background
A new standard (GB/T1499.2-2018) of the twisted steel is implemented in 2018 in 11/1.11, and a method for testing a macroscopic metallographic structure, a microscopic structure and the Vickers hardness of a section is added to the new standard. The waste heat quenching process (forced water penetration process) for producing a tempered martensite structure after rolling after the execution of the new standard is eliminated, and if the optimization improvement of the multi-element alloy optimization combination (alloy strengthening combination) and the controlled rolling and controlled cooling process is not carried out, the requirements of the new standard on the structure and the performance can be met only by greatly improving the content of silicon, manganese and vanadium elements in the steel. The price of vanadium-nitrogen alloy is higher (the price of vanadium-nitrogen alloy exceeds 20 ten thousand at present), and the cost of steel per ton is increased by about 34 yuan for every 0.01 percent of vanadium; the price of the niobium-iron alloy exceeds 20 ten thousand, and each ton of steel needs to be increased by nearly 40 yuan for each 0.01 percent of niobium increase), the price of silicon and manganese alloy also has great increase, which brings heavy pressure to the production cost of the twisted steel, reduces the contents of niobium, vanadium and the like in the steel, and has important practical significance for saving vanadium and niobium resources, improving the economic benefit of steel enterprises in China and reducing the environmental pressure.
Under the traditional production process and equipment conditions of straight threaded steel bars (with the diameter of 12-32 mm), the general way for improving the strength of the steel bars is as follows:
1) the microalloying treatment of Nb, V, Ti, B and the like is carried out by combining a controlled cooling process, so that the precipitation strengthening (precipitation strengthening) effect is improved;
2) the content of solid solution strengthening elements such as C, Si, Mn, Cr and the like is improved, and the solid solution strengthening effect is improved;
3) and controlled rolling and controlled cooling are carried out, so that the effects of phase change strengthening and fine grain strengthening are mainly improved.
After the new standard (GB/T1499.2-2018) of the twisted steel is executed, a method for increasing phase change strengthening and promoting fine grain strengthening by adopting a post-rolling waste heat quenching process (forced water penetration process) is eliminated. Therefore, on the basis of not adding or reducing noble metals of niobium and vanadium, the precipitation strengthening effect is ensured by replacing noble alloy elements with relatively cheap alloy elements, the solid solution strengthening effect is increased by optimally combining solid solution strengthening elements, and the fine grain strengthening effect is ensured by controlled cooling after rolling, which is a great trend. On the premise of meeting the requirements of new national standard performance and organization, the method prevents the steel bar cooling bed from being corroded, is the key technology of the process, and can effectively improve the economic benefit of steel enterprises.
Disclosure of Invention
The invention aims to solve the problems and provide a high-nitrogen alloy enhancer and application thereof.
The invention relates to an innovative process integrating molten steel smelting, casting blank heating, controlled cooling after twisted steel rolling and composite reinforced alloy preparation and use.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the invention provides a high-nitrogen alloy enhancer which comprises the following raw materials in percentage by weight: the raw materials mainly comprise 40-55% of ferrosilicon, 30-40% of silicomanganese (silicon content is 16-19%, manganese content is 64-68%, and the balance is iron and impurities), 4-6% of silicon carbide and 10-20% of iron powder.
Further, the preparation method of the high-nitrogen alloy enhancer comprises the following steps:
the raw materials are crushed, ground and fully mixed to be pressed into a block, and the size of the block is not limited in the invention, and can be any size meeting the requirement in the field, such as about 40mm multiplied by 50 mm.
And placing the material block on a push plate of a heating area of a push plate kiln, introducing nitrogen into the kiln body, performing nitriding treatment in the atmosphere of nitrogen protection, performing high-temperature heating treatment at 1600-1650 ℃, and performing cooling treatment to obtain the high-nitrogen alloy.
The high-nitrogen alloy enhancer comprises the following chemical components in percentage by weight: c: not more than 4.5% (as an option, C can be in the range of 1-4.5%), Si: 25-45% of Mn: 10-15%, N: 16-30% of iron and inevitable impurities as the rest.
The high-nitrogen alloy reinforcer of the invention is added with a certain amount of silicon carbide, the components contain a certain amount of C, and when nitrogen is introduced into a kiln body, Si synthesis can be carried out3N4The nitrogen content of the high-nitrogen alloy is improved through the carbothermic reduction reaction.
The invention also provides application of the high-nitrogen alloy enhancer in steel preparation, in particular application in the production of deformed steel bars and H-shaped steel.
Based on the application, the invention provides a preparation method of steel, which comprises the following steps:
(a) pretreating molten iron;
(b) when the S content of the molten iron is not more than 0.015 percent and the temperature of the molten iron is not less than 1280 ℃, primarily smelting the molten steel by adopting a converter;
(c) when the P content in the molten steel is not more than 0.020%, tapping into a steel ladle;
(d) adding a barium deoxidizer into the steel ladle when one third to one half of steel is tapped from the steel ladle, then adding VN alloy and the high-nitrogen alloy composite enhancer of the invention when the silicon-manganese alloy is added to one third to three quarters, adding 0.35-0.4 kg of VN alloy per ton of steel, and adjusting the content of V in molten steel to be 0.02-0.025%, wherein the adding amount of the high-nitrogen alloy composite enhancer is 0.3-0.7 kg per ton of steel;
(e) adjusting the Si content of the molten steel to be 0.25-0.45% and the Mn content to be 1.35-1.60%; the content of C is 0.22-0.25%;
(f) and carrying out soft argon blowing treatment on the molten steel.
According to the preparation method of the steel, 0.5-1 kg/t of silicon-calcium-barium is preferably adopted for pre-deoxidation in the step (d); VN is added to the molten steel downflow position in a mode of manually throwing a bag.
According to the preparation method of steel of the present invention, preferably, in the step (e), silicomanganese and ferrosilicon are used to control the Si content of the molten steel, silicomanganese is used to adjust the Mn content of the molten steel, and a graphite carburant is used to adjust the carbon content.
The method for producing steel according to the present invention, wherein preferably, the molten steel soft argon blowing time in the step (f) is not less than 8 minutes.
The method for producing steel according to the present invention preferably further comprises the step of performing continuous casting and slab rolling on the molten steel after step (f), wherein the slab heating time is controlled to be within 180 minutes, and the soaking temperature is not more than 1200. The initial rolling temperature is controlled to be between 1100 and 1150 ℃, the finish rolling temperature is controlled to be between 900 and 1020 ℃, and the final rolling temperature is controlled to be between 820 and 920 ℃.
According to the preparation method of the steel, the recovery temperature (throwing temperature) of the upper cooling bed of the steel is controlled to be 820-920 ℃ preferably after continuous casting and rolling.
The invention is suitable for any kind of steel, in particular to deformed steel and H-shaped steel. For example, but not limited to, a deformed steel bar having a chemical composition in weight percent: c: 0.22 to 0.25%, Si: 0.25 to 0.45%, Mn: 1.35-1.60%, V: 0.02-0.025 percent, less than or equal to 0.030 percent of P, less than or equal to 0.025 percent of S, and the balance of Fe and inevitable impurities.
Specifically, the key process of the invention is as follows:
after the molten steel is smelted in a converter, 0.5-1 kg of barium deoxidizer per ton of steel is added into each ton of steel, and if the molten steel has an over-oxidation phenomenon, such as the carbon content is lower than 0.05%, the amount of the deoxidizer can be properly increased so as to reduce the oxygen content in the steel. In the converter tapping process, when about one third of silicon-manganese alloy is added, VN alloy and 0.3-0.7 kg/ton steel high-nitrogen alloy composite enhancer are added; after the molten steel enters an argon station, large argon is required for stirring for not less than 3 minutes so as to homogenize the temperature and components of the molten steel; the molten steel components are controlled in the following ranges: c: 0.22 to 0.25%, Si: 0.25 to 0.45%, Mn: 1.35-1.60%, V: 0.02-0.025%, P is less than or equal to 0.030%, S is less than or equal to 0.025%; the heating time of the continuous casting billet is controlled within 180 minutes (if the time is exceeded, the furnace temperature of a heating section and a soaking section must be reduced to be below 1000 ℃), and the soaking temperature does not exceed 1200 ℃; controlling the return temperature (steel throwing temperature) of a steel bar upper cooling bed with the diameter of 20-25 mm at 830-900 ℃, controlling the return temperature (steel throwing temperature) of a steel bar upper cooling bed with the diameter of 12-18 mm at 820-900 ℃, and controlling the return temperature (steel throwing temperature) of a steel bar upper cooling bed with the diameter of 28-40 mm at 840-920 ℃;
the yield strength of the steel bar produced by the production process reaches 425-470 MPa, the yield ratio (tensile strength/yield strength) reaches more than 1.38, the metallographic structure of the steel bar is a pearlite + ferrite structure, the steel bar is not rusted after rolling, the surface quality is good, the using amount of vanadium-nitrogen alloy is reduced, and compared with the original process, the process reduces the vanadium content in the steel by more than 0.01%; compared with the original vanadium adding process, the process has the advantage that the cost per ton of steel is obviously reduced.
The high-nitrogen alloy composite reinforcer can also be used for low-alloy high-strength H-shaped steel, the steel-making process is the same as the production process of deformed steel, and the molten steel components are controlled in the following ranges: c: 0.16-0.20%, Si: 0.25 to 0.45%, Mn: 1.35-1.50 percent of Fe, 0.015-0.020 percent of V, less than or equal to 0.025 percent of P, less than or equal to 0.020 percent of S, and the balance of Fe and inevitable impurities; the heating time of the continuous casting billet is controlled within 200 minutes, and the soaking temperature is not more than 1210 ℃; the initial rolling temperature of H-shaped steel with the specification of 700 x 300mmQ345B is controlled to be 1150-1200 ℃, the initial rolling temperature of finish rolling is controlled to be 980-1050 ℃, and the final rolling temperature is controlled to be 850-920 ℃.
The invention has the following advantages:
the process is simple to operate, does not change the existing smelting and rolling equipment, can reduce the alloy cost, and can be popularized and used in other deformed steel and H-shaped steel production enterprises.
Comprehensive utilization of low-price resources is realized, the consumption of vanadium alloy is reduced, the economic benefit of iron and steel enterprises is improved, and the environmental pressure caused by exploitation of vanadium resources is reduced.
The invention can reduce the production cost of the twisted steel and the H-shaped steel, greatly improve the production level of the whole twisted steel and H-shaped steel industry, is worthy of further popularization, and can bring better economic benefit and social benefit.
Drawings
FIG. 1 is a schematic view of a process key control point flow when the high-nitrogen alloy composite enhancer of the invention is applied;
FIG. 2 is a metallographic structure of a deformed steel bar prepared in an example of the present invention; wherein a and b are conventional HRB400E steel, and c and d are the deformed steel bar of the invention.
Detailed Description
The present invention will be described in detail with reference to the following embodiments.
Example 1
Taking a 50-ton converter of Laiwu division of Shandong Steel works Limited as an example, the following operation process points are adopted, the yield strength of the steel bars of all specifications is more than 425MPa, the yield ratio is more than 1.40, and the surfaces of the steel bars are free of corrosion, and the method comprises the following specific steps:
1. chemical composition of prior HRB400E steel
The components of the prior HRB400E test steel are shown in Table 1
TABLE 1 HRB400E test Steel bar composition control (12-28 mm steel bar)
2. Control key points of steelmaking continuous casting process
1) An aluminum-containing deoxidizer is added for deoxidation in the early stage of tapping, and if the end point carbon content is less than 0.05%, the amount of the deoxidizer is increased by at least 20%.
2) The nitrogen gas is required to be stirred in the early stage and the middle stage of tapping, and the nitrogen gas is properly turned down in the later stage so as to prevent the slag from being discharged due to unclear vision in the later stage of tapping.
3) Adding a high-nitrogen alloy enhancer in time after one third of the silicon-manganese alloy is added (manually adding in a small scale test, 10kg of the enhancer is added in each small bag, and the enhancer can be added in a high-level bin after a normal amount is added), and stirring for not less than 3 minutes by using big nitrogen after tapping;
the high-nitrogen alloy enhancer comprises the following raw materials in percentage by weight: 45% of ferrosilicon powder, 30% of silicon-manganese alloy (the silicon content in the silicon-manganese alloy is 16%, the manganese content in the silicon-manganese alloy is 68%), 5% of silicon carbide and 20% of iron powder.
3. Rolling process control requirements
1) The initial rolling temperature: 980 and 1080 ℃.
2) The recovery temperature (casting temperature) of the cooling bed on the straight steel bars with the length of 20-25 mm is controlled to be 835-885 ℃, the recovery temperature (casting temperature) of the cooling bed on the straight steel bars with the length of 12-18 mm is controlled to be 825-880 ℃, and the recovery temperature (casting temperature) of the cooling bed on the steel bars with the length of 28-32 mm is controlled to be 840-870 ℃.
4. Actual production conditions
4.1 actual composition control
The actual composition control of the test steels prepared in this example is shown in Table 2
TABLE 2 control of actual composition of reinforcing bars (12 to 28mm reinforcing bars)
2 the actual composition control of the steel bars in the test shows that the C, Si and Mn are not changed much compared with the prior compositions, but the V is reduced by 0.01 percent and is relatively stable.
4.2 mechanical properties (12 to 28mm steel bar)
The actual mechanical property range of the test steel completely meets the enterprise standard, and the margin is large compared with the national standard, which is shown in Table 3
TABLE 3 mechanical properties of test steels (12 to 28mm steel bars)
4.3 metallographic structure
The metallographic structure is a pearlite + ferrite structure and completely meets the requirements of a new standard (GB/T1499.2-2018), and is shown in figures 2 a-2 d. As can be seen from the figure, the matrix structure of the steel bar is pearlite and ferrite, the structure is very uniform, and no abnormal structure exists. Compared with the prior deformed steel bar, the surface quality of the steel bar has no obvious difference.
Example 2
Taking a 120-ton converter of Laiwu division of Shandong Steel works Limited as an example, the yield strength of the H-shaped steel of each specification is more than 375MPa according to the following operating process key points, and the concrete steps are as follows:
1. chemical composition of existing Q345B steel
The compositions of the prior Q345B test H-section steel are shown in Table 1
TABLE 1Q 345B test H-section composition control (700X 300mm)
2. Control key points of steelmaking continuous casting process
1) An aluminum-containing deoxidizer is added for deoxidation in the early stage of tapping, and if the end point carbon content is less than 0.05%, the amount of the deoxidizer is increased by at least 20%.
2) The nitrogen gas is required to be stirred in the early stage and the middle stage of tapping, and the nitrogen gas is properly turned down in the later stage so as to prevent the slag from being discharged due to unclear vision in the later stage of tapping.
3) Adding a high-nitrogen alloy enhancer in time after one third of the silicon-manganese alloy is added (manually adding in a small scale test, 10kg of the enhancer is added in each small bag, and the enhancer can be added in a high-level bin after a normal amount is added), and stirring for not less than 3 minutes by using big nitrogen after tapping;
the high-nitrogen alloy enhancer comprises the following raw materials in percentage by weight: 50% of ferrosilicon powder, 30% of silicon-manganese alloy (the silicon content in the silicon-manganese alloy is 19%, the manganese content in the silicon-manganese alloy is 64%), 6% of silicon carbide and 14% of iron powder.
The heating time of the continuous casting billet is controlled within 200 minutes, and the soaking temperature is not more than 1210 ℃; the initial rolling temperature of H-shaped steel with the specification of 700 multiplied by 300mmQ345B is controlled between 1150-1200 ℃, the initial rolling temperature of finish rolling is controlled between 980-1050 ℃, and the final rolling temperature is controlled between 850-920 ℃.
3. Rolling process control requirements
1) The initial rolling temperature: 1150-1200 ℃.
2) The initial rolling temperature of the H-shaped steel with the specification of 700 multiplied by 300mmQ345B is controlled between 980 ℃ and 1050 ℃, and the final rolling temperature is controlled between 850 ℃ and 920 ℃.
4. Actual production conditions
4.1 actual composition control
The actual composition control of the test steels prepared in this example is shown in Table 2
TABLE 2 actual composition control of test steels (700X 300mmQ 345B)%
2 the actual composition control of the test steel showed less change in C, Si and Mn than the previous compositions, but the V was reduced by 0.012% and the composition control was relatively stable.
4.2 mechanical properties (700X 300mmQ345B)
The actual mechanical property range of the test steel completely meets the enterprise standard, and the margin is large compared with the national standard, which is shown in Table 3
TABLE 3 mechanical Properties of test steels
4.3 metallographic structure
The metallographic structure of the H-shaped steel of 700 multiplied by 300mmQ345B is a pearlite + ferrite structure without abnormal structures.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (4)
1. A method of making steel comprising the steps of:
(a) pretreating molten iron;
(b) when the S content of the molten iron is not more than 0.015 percent and the temperature of the molten iron is not less than 1280 ℃, primarily smelting the molten steel by adopting a converter;
(c) when the P content in the molten steel is not more than 0.020%, tapping into a steel ladle;
(d) adding a barium deoxidizer into the steel ladle when one third of steel is tapped from the steel ladle, then adding a VN alloy and a high-nitrogen alloy enhancer when the silicon-manganese alloy is added to one third of steel, and adjusting the V content of the molten steel to be 0.025-0.028%;
the high-nitrogen alloy enhancer comprises the following raw materials in percentage by weight: 40-55% of ferrosilicon powder, 30-40% of silicon-manganese alloy, 4-6% of silicon carbide and 10-20% of iron powder; the high-nitrogen alloy enhancer comprises the following chemical components in percentage by weight: c: 4.5% or less, Si: 25-45% of Mn: 10-15%, N: 16-30%;
the preparation method of the high-nitrogen alloy enhancer comprises the following steps:
the raw materials are smashed, ground and fully mixed, and then a material block is pressed;
placing the block material on a push plate of a push plate kiln temperature rising area, introducing nitrogen into a kiln body, performing nitriding treatment in the atmosphere of nitrogen protection, performing heating treatment at 1600-1650 ℃, and cooling to obtain high-nitrogen alloy;
(e) adjusting the Si content of the molten steel to be 0.25-0.45% and the Mn content to be 1.35-1.60%; the content of C is 0.22-0.25%;
(f) and (3) carrying out soft argon blowing treatment on the molten steel, and then carrying out continuous casting pouring and slab rolling on the molten steel, wherein the heating time of a continuous casting billet is controlled within 180 minutes, the soaking temperature is not more than 1200 ℃, and the return temperature of a steel on a cooling bed is controlled to be 820-920 ℃ after the continuous casting billet is rolled.
2. The method for preparing steel according to claim 1, wherein the pre-deoxidation is performed in the step (d) by using 0.5 to 1kg/t silicon calcium barium; VN is added to the molten steel downflow position in a mode of manually throwing a bag.
3. The method of manufacturing steel according to claim 1, wherein Si content of the molten steel is controlled using silicomanganese and ferrosilicon in the step (e), Mn content of the molten steel is adjusted using silicomanganese, and carbon content is adjusted using a graphite recarburizing agent.
4. The method of producing steel according to claim 1, wherein the molten steel soft argon blowing time in the step (f) is not less than 8 minutes.
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