WO2012129971A1 - Alloy for refining precipitates during production of steel and method of using same - Google Patents

Alloy for refining precipitates during production of steel and method of using same Download PDF

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Publication number
WO2012129971A1
WO2012129971A1 PCT/CN2012/070090 CN2012070090W WO2012129971A1 WO 2012129971 A1 WO2012129971 A1 WO 2012129971A1 CN 2012070090 W CN2012070090 W CN 2012070090W WO 2012129971 A1 WO2012129971 A1 WO 2012129971A1
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steel
alloy
molten steel
precipitates
refining
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PCT/CN2012/070090
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French (fr)
Chinese (zh)
Inventor
郑庆
杨健
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宝山钢铁股份有限公司
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Publication of WO2012129971A1 publication Critical patent/WO2012129971A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
    • 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
    • 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
    • C21C7/0037—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material
    • 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
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • 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
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • C21C2300/00—Process aspects
    • C21C2300/08—Particular sequence of the process steps

Definitions

  • the present invention relates to steel smelting technology, and more particularly to an alloy for refining precipitates in a steel production process and a method of using the same. Background technique
  • steels that are microalloyed using elements such as ⁇ , V, Nb, and niobium give full play to techniques such as fine grain strengthening and precipitation strengthening, and the steel strength is significantly improved while still maintaining high toughness and plasticity of the steel.
  • a typical example is a high-strength automotive panel with a strength of more than 100 MPa, and its plasticity can be maintained above 30%, and the brittle transition temperature can be as low as 30 °C or less, thereby achieving lightweight and safe performance of the automobile.
  • the improvement is not achieved by steel grades that have been solid solution strengthened or dislocation strengthened in the past.
  • the trace alloying elements in the steel mainly improve the strength of the steel by two mechanisms of fine grain strengthening and precipitation strengthening.
  • fine-grained strengthening is to refine the grain boundaries of the steel grains by pinning the fine grain precipitates such as carbides, nitrides or carbonitrides in the steel, so that the grain boundary ratio in the steel is increased and hindered. Dislocation slip produces reinforcement.
  • the effect of precipitation strengthening is also achieved by the precipitates, and the interaction of the precipitate particles and the slip dislocation directly strengthens the steel.
  • the enhancement increment is proportional to the 1/2 power of the volume fraction of the second phase particles and the 1/2 power of the particle size. Therefore, the precipitate phase becomes a key factor affecting the performance of the steel, and is a key factor for the strengthening and toughening of the steel.
  • the precipitate is a particle that is intentionally introduced to optimize the performance of the steel.
  • the performance is very unfavorable, and it is also the best to avoid in the composition design and physical quality control in actual production.
  • the method widely used for refining precipitates in the world is to reduce the solubility product of the elements forming precipitates, but this reduces the volume fraction (i.e., the number) of precipitates, and thus is not an effective method.
  • inclusions are inevitably present in the steel, which are oxides, slag and various oxides in the lining that enter the molten steel during the smelting process due to deoxidation or alloying, and precipitate during solidification of the molten steel.
  • Sulfides, oxides, etc. inclusions usually have a detrimental effect on the properties of steel, especially for inclusions with relatively large particle sizes, such as ten or tens of micron-sized inclusions, which generally affect steel fatigue.
  • Performance, toughness, steel grades with different performance requirements can also have an adverse effect on other properties of steel. Therefore, in order to protect the performance of the steel, it is also required to refine the inclusions.
  • the inclusions When the inclusions are sufficiently fine, the inclusions can effectively improve the properties of the steel, that is, become favorable particles.
  • the present alloy In the evaluation of the microscopic structure according to the present invention, it was also found that the present alloy has an effect of refining the inclusions in the steel. Summary of the invention
  • the object of the present invention is to provide an alloy for refining precipitates in a steel production process and a method for using the same, which can deoxidize molten steel by using a precipitate refining alloy without decomposing the content of precipitated elements, and utilize finely dispersed deoxidizing
  • the product acts as a nucleation particle of the precipitate, which increases the nucleation rate of the precipitate, while reducing the particle size of the precipitate and increasing the amount thereof.
  • An alloy used in the steel production process for refining precipitates, the weight percentage of which is: A1 78-95%, Mg 5-22% and unavoidable impurities.
  • Ca 0 10% and/or Sr 0 to 5% may be selectively added, by weight percentage. meter.
  • the method for using the alloy for refining precipitates in the steel production process of the present invention may be added to the steel in a refining stage outside the molten steel furnace in the form of a block, a granule, a powder or a cored wire according to actual conditions of steel making.
  • the total amount of alloy added is 0.010 ⁇ 0.025% of the total amount of molten steel, in weight percent; the temperature of molten steel is controlled from 1580 °C to 1620 °C, and the free oxygen in molten steel is controlled at 0.0001 ⁇ 0.0040%, in weight percent; after adding alloy The molten steel is stirred for not less than 5 minutes to ensure uniform dispersion.
  • Mg Forms an element for refining the particle.
  • Magnesium is a strong deoxidizer that can deoxidize molten steel or reduce the oxides formed by weaker deoxidizers such as manganese and silicon.
  • the resulting product is M g O, which is a very fine inclusion.
  • the average particle size is below 0.1 ⁇ m, and is easily and uniformly dispersed in the molten steel until the molten steel is solidified.
  • A1 Due to the high vapor pressure of magnesium, it is easy to vaporize at high temperatures, and magnesium is a reactive metal. Therefore, if metal magnesium is directly added to molten steel, the yield will be very low and the effect will be unstable. In order to increase the yield of magnesium, an alloying method must be employed. In the present invention, aluminum is used as an alloying element to form a solid solution of aluminum and magnesium to reduce magnesium activity and vapor pressure, and since aluminum is a commonly used alloying element and deoxidizer in steel, It can minimize the adverse effects of the alloy on molten steel.
  • Ca It is a commonly used inclusion modification element in steel. Calcium is added to steel to spheroidize the sulfide. At the same time, calcium can react with alumina in steel to form lower melting point of 7Al 2 (12CaO to remove steel. In the present invention, calcium can also effectively change the surface characteristics of MgO inclusions to make it more finely dispersed.
  • Sr is an alkaline earth metal.
  • the oxide formed by the addition of niobium to the steel can effectively change the surface characteristics of the MgO inclusions and act as an auxiliary nucleating agent.
  • Mg is a nucleation point element
  • magnesium is added to the steel to form fine MgO, which serves as the nucleation core of the precipitate. Since Mg is a strong active element and the vapor pressure is high, the addition of Al to the alloy can increase the yield of Mg. Ca and Sr are mainly used as surface-active elements to ensure deoxidation products. MgO is finely dispersed in steel.
  • the alloy of the present invention can be added to the steel in the form of a block, a granule, a powder or a cored wire depending on the actual conditions of the steelmaking.
  • the alloy is added as follows: The alloy is added in the refining stage of the steel, and the total amount is 0.010-0.025% of the total amount of molten steel. If the amount is too small, the number of nucleation points is insufficient, such as Too much, not only increases the cost, but the excess oxide inclusions will adversely affect the quality of the steel.
  • the temperature of the molten steel is controlled in the range of 1580 to 1620 °C, which is a suitable temperature for adjusting the composition of the molten steel. In this temperature range, the yield of the precipitated fine alloy is basically kept stable.
  • Oxygen level of molten steel is an important index to control the total amount of inclusions (ie, the purity of molten steel). At the same time, the oxygen content of molten steel needs to be refined and the amount of alloy is refined. (Total amount of alloy X is obtained. X is refined. ) Adapted. The free oxygen control in the molten steel is in the range of 0.0001 to 0.0040%.
  • the molten steel is stirred for not less than 5 minutes to ensure uniform dispersion.
  • the residual amount of each refined element after solidification of the molten steel is: Mg 20 ppm (0.0020%), and in the case of adding calcium and/or strontium, calcium 15 ppm, Sr ⁇ 5 ppm. Since the steel contains aluminum, the residue of aluminum is not counted.
  • the coarse precipitates in the steel are refined, and the total amount of precipitates in the steel is not reduced, but is greatly increased.
  • the cold-rolled steel sheets were sampled, and the particle size of all inclusions/precipitates was statistically analyzed using a 1000-fold optical microscope in 50 fields of view. The typical effect is shown in Fig. 1. Comparative tests on steels of the same composition show that after the refining treatment, the amount of inclusions and precipitates in the steel increases remarkably, the total number increases by more than 50%, and the particle size is remarkably refined, which is not only reflected in the decrease in average particle size. About 40%, also shown in large particle particles larger than 10 microns in particle size is almost eliminated.
  • the residual amount of magnesium in the steel is small, but the effect of refining the precipitate/inclusion is stable.
  • the residual amount of magnesium in the billet/ingot is 5 ⁇ 20ppm (0.0005 ⁇ 0.0020%), which greatly reduces the residual magnesium in the colleagues who maintain the process effect. The effect on steel.
  • the MgO inclusions introduced by this method are very fine and uniformly dispersed, so the total mass fraction is very low.
  • the formed MgO particle size is 0.01 ⁇ 0.10 ⁇ (micrometer), and the density is above 400/mm 2 (square mm).
  • the steel material undergoes heat treatment such as soaking and heat treatment, the MgO particle has no obvious coarsening.
  • the invention is an alloy specially designed for the refinement of precipitates in steel, and can effectively refine the precipitated phase such as ⁇ in steel, which is especially obvious and necessary when the solubility product of the precipitate forming element in steel is large. .
  • the alloy has the same refinement effect on the inclusions in the steel.
  • the prior patent mentions the refinement or dispersion of the inclusions, but has not touched the precipitates.
  • the precipitates and inclusions are greatly refined, and the amount thereof is remarkably increased. Since the precipitates have the effect of refining crystal grains and strengthening and toughening the steel, increasing the amount of precipitates is very important for improving the properties of the steel. Even in the case of refining inclusions, Japanese Patent No. JP2002256331A, JP2006124759A mentions fine inclusions, but does not provide specific comparative data, and does not mention the aspect of being able to increase the amount of small inclusions.
  • magnesium is used as a main precipitate refining element, but since the formed deoxidized product MgO has a very fine particle size, high density (400/mm 2 or more) is maintained in the steel, and the residual mass fraction of Mg is extremely low. , can minimize the adverse effects of magnesium on steel quality.
  • the same effect can not be achieved, which has a great relationship with the composition design of the alloy.
  • the Al-Mg-based alloy used in the present invention although some other magnesium-containing alloys are used in steel, such as Japanese Patent JP2002256331A (Ti-Mg), JP9287015A (Zr-Mg), JP2008266706A (Ca-Mg), etc. However, they are not used for the refinement of precipitates, but use magnesium as an inclusion crystal refining, desulfurization, and an increase in solidification and other axial crystallinity.
  • the alloy of the invention opens up a new field of application.
  • Figure 1 is a schematic diagram showing the comparison of the effects of fine precipitates.
  • FIG. 2 is a schematic illustration of the effect of the introduced MgO particles on the ⁇ precipitate.
  • the target steel grade is a high-strength automotive sheet.
  • the main component weights are: C 0.10%, Si 0.18%, Mn 1.52%, Al 0.03%, Nb 0.03%, Ti 0.06%, N 0.006%, S 0.0030%.
  • Thick The specification is 0.8mm, and the production process of steel is: hot metal pretreatment _ _ converter smelting one furnace outside refining one slab continuous casting one by one hot rolling one acid washing one cold rolling one one finished heat treatment.
  • the cold impact properties of the steel sheet were relatively poor, and about 20% of the steel sheets were cracked.
  • the fracture observation and metallographic analysis confirmed that the coarse TiN precipitates present in the steel were the main cause of deterioration of the cold performance.
  • the particle size of TiN is up to 14 microns, and it is observed that 500% of the metallographic phase shows that the total number of TiN particles is more than 5 microns.
  • the components are added in the refining process of the furnace to be A1 83%, Mg 7%, Ca 9%, and the balance is an impurity precipitated refining alloy, and the added amount is the weight of the molten steel. 0.023%.
  • the molten steel conditions for adding the alloy are: temperature 1608 °C, and the free oxygen of the molten steel is controlled at 0.0005%. After the addition of the alloy, the molten steel was stirred for 7 minutes and then continuously cast.
  • Example 2 The cold-shear test was carried out on the finished steel plate, and it was confirmed that all of them were qualified without cracking.
  • the sample was analyzed on the steel plate to confirm that the content of Mg in the steel was below 0.0020%.
  • the inclusion analysis confirmed that the grain size of TiN present in the steel was only 6 ⁇ m when observed by 500 times of metallography. Under the same conditions, the amount of TiN in the grain treated by this method increased by 8%. Left and right, TiN particles with a particle size of 5 microns or more are less than one tenth of the original. This method shows a good refining effect on the precipitate.
  • Example 2 Example 2
  • the steel grades targeted for Example 1 were tested using another precipitate refining alloy.
  • the composition of the precipitate refining alloy is: Al 79%, Mg 20%, and the balance is impurities, and the amount added is 0.016% by weight of the molten steel.
  • the molten steel conditions for adding the alloy are: temperature 1600 °C, and the free oxygen of the molten steel is controlled at 0.0035%. After the alloy was added, the molten steel was stirred for 7 minutes and then continuously cast.
  • the object steel grade is ordinary cold-rolled steel sheet.
  • the main components are: C 0.03%, Si 0.018%, Mn 0.25%, Al 0.03%, B 0.0026%, N 0.0034%, S 0.0030%.
  • the thickness specification is 0.5 ⁇ 2.0mm, and the steel production process is also as follows: hot metal pretreatment one-to-one converter smelting one-to-one furnace refining__slab continuous casting one-by-one hot-rolling one-by-one-one-one-one-one cold-rolling one-finished heat treatment.
  • hot metal pretreatment one-to-one converter smelting one-to-one furnace refining__slab continuous casting one-by-one hot-rolling one-by-one-one-one-one cold-rolling one-finished heat treatment.
  • there were about 30% cracks in the corners of continuous casting slabs ie, corner cracks). It was confirmed by research that coarse BN precipitates in steel caused brittleness in the temperature range of 800 ⁇ 900 °
  • the shrinkage rate is at least 5%, while the corresponding values of other steel grades are usually above 30%.
  • the high temperature brittleness causes the slab corners to be cracked due to mechanical stress and thermal stress during continuous casting, and the casting is reduced during the continuous casting stage.
  • Technical measures such as mechanical stress and thermal stress at the corner of the bill have not received significant results.
  • Sampling analysis of the slab confirmed that there is coarse BN precipitate in the steel, which is a hard precipitate with a maximum particle size of 6 ⁇ 8 microns, a common particle size of 0.5 ⁇ 2 microns, BN precipitates.
  • the number is in the range of 10 to 40/mm 2 , and it has been confirmed that the coarse BN precipitate is the main cause of the corner crack, so the BN in the steel is refined by the method.
  • the precipitated refined alloy composition added during the refining process is: A1 78%, Mg
  • the addition amount is 0.020% of the weight of molten steel.
  • the molten steel conditions for adding the alloy are: temperature 1590 °C, and the molten steel free oxygen is controlled at 0.00012%. After the alloy was added, the molten steel was stirred for 5 minutes and then continuously cast.
  • the monitoring of the quality of the continuous casting slab confirms that with this method, the corner crack of the slab is basically eliminated.
  • the high temperature tensile test of the cast blank confirmed that the brittleness of the steel in the temperature range of 800 to 900 °C was significantly improved, and the minimum necking rate was increased to 18%.
  • Sampling on the slab for component analysis confirmed that the Mg content of the steel was 0.0009%.
  • the inclusion analysis confirmed that the BN particle size in the steel was only 4 ⁇ m at most when observed by 500 times of metallography, and most of the BN particle size was in the range of 1 to 2 ⁇ m.
  • the precipitate refining alloy composition used was: A1 94%, Mg 5%, and the balance was an impurity, and the steel grades referred to in Example 3 were tested.
  • the molten steel free oxygen is controlled at 0.0005%, and the molten steel temperature is 1604 °C. After the alloy is added, the molten steel is stirred for 10 minutes and then continuously cast.
  • the slab quality monitoring and the slab sampling analysis confirmed that Example 4 achieved an effect similar to that of Example 3, confirming the effect of the precipitate refining alloy.
  • the precipitated fine alloy composition used was: A1 82%, Mg 6%, Ca 6%, Sr 5%, and the balance was an impurity, and the steel grades referred to in Example 3 were tested.
  • the molten steel free oxygen is controlled at 0. 0001%, the molten steel temperature is 1617 °C, and the molten steel is stirred for 15 minutes after the alloy is added. Analysis confirmed that the precipitate was effectively refined.

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Abstract

Disclosed are an alloy for refining precipitates during production of steel and a method of using same. The alloy has a composition, by weight percent, of Al 78 to 95%, Mg 5 to 22%, and unavoidable impurities. The alloy is added into steel in the form of pieces, granules, powders or cored wires at the secondary refining stage of molten steel, in a total amount of the alloy of 0.010 to 0.025% by weight based on the total amount of the molten steel. The temperature of the molten steel is controlled at 1580 to 1620°C, and the free oxygen in the molten steel is controlled at 0.0001 to 0.0040% by weight. After adding the alloy, the molten steel is stirred for a time period of no less than 5 minutes. By using the alloy for refining precipitates to deoxygenate the molten steel, the nucleation rate of precipitates can be increased, and at the same time the particle size of precipitates can be reduced and the number of precipitates can be increased.

Description

一种钢铁生产过程用于细化析出物的合金及其使用方法 技术领域  Alloy for refining precipitates in steel production process and method of using same
本发明涉及钢铁冶炼技术， 特别涉及一种钢铁生产过程用于细化析 出物的合金及其使用方法。 背景技术  The present invention relates to steel smelting technology, and more particularly to an alloy for refining precipitates in a steel production process and a method of using the same. Background technique
为满足用户的需求， 钢材的生产技术和实物性能在近三十年来得到 了很大的发展， 在技术方面的一个重要的突破是合金化理论的不断完善 和钢种数量和产量上的巨大飞跃。 特别是采用 Τι、 V、 Nb和 Β等元素进 行微合金化的钢种， 充分发挥细晶强化和析出强化等技术手段， 在钢材 强度得到显著提高的同时仍使钢材保持较高的韧性和塑性， 比较典型的 例子是高强度汽车板， 其强度可以达到 lOOOMPa以上， 而其塑性可以保 持在 30%以上， 脆性转变温度也可以低至一 30 °C以下， 从而实现汽车的 轻量化和安全性能的提高， 这是以往采用固溶强化或者位错强化的钢种 不能达到的。  In order to meet the needs of users, the production technology and physical properties of steel have been greatly developed in the past 30 years. An important breakthrough in technology is the continuous improvement of alloying theory and the huge leap in the quantity and output of steel. . In particular, steels that are microalloyed using elements such as Τι, V, Nb, and niobium give full play to techniques such as fine grain strengthening and precipitation strengthening, and the steel strength is significantly improved while still maintaining high toughness and plasticity of the steel. A typical example is a high-strength automotive panel with a strength of more than 100 MPa, and its plasticity can be maintained above 30%, and the brittle transition temperature can be as low as 30 °C or less, thereby achieving lightweight and safe performance of the automobile. The improvement is not achieved by steel grades that have been solid solution strengthened or dislocation strengthened in the past.
钢中的微量合金元素主要通过细晶强化和沉淀强化两种机制来使 钢的强度提高。 其中细晶强化是借助钢中微细的析出物如碳化物、 氮化 物或者碳氮化物来钉扎热变形时晶界的迁移使钢材晶粒得到细化， 从而 使钢中晶界比例增高而阻碍位错滑移产生强化。  The trace alloying elements in the steel mainly improve the strength of the steel by two mechanisms of fine grain strengthening and precipitation strengthening. Among them, fine-grained strengthening is to refine the grain boundaries of the steel grains by pinning the fine grain precipitates such as carbides, nitrides or carbonitrides in the steel, so that the grain boundary ratio in the steel is increased and hindered. Dislocation slip produces reinforcement.
细晶强化时，钢材的强度增量反比于晶粒大小的 1/2次方， 而钢材晶 粒大小 Dc遵循 Zener公式： Dc=A*d/f 其中 A为比例常数， d为析出物大小， f为析出物体积分数） ， 故细晶强化需要细小分散的析出物。 沉淀强化 的效果也是通过析出物来达到的， 析出物颗粒和滑移位错的交互作用直 接使钢强化。 其强化增量和第二相粒子的体积分数的 1/2次方和粒度的 1/2次方均成正比。 所以， 析出物相成为影响钢材性能的关键性因素， 是 钢得到强化和韧化的关键因素， 因此析出物是为了优化钢的性能有意引 入的质点。 为保证钢材具有良好的强度一塑性一韧性组合， 或者使钢材 具有优良的综合性能， 通常要求钢中析出物有较大的体积分数， 同时保 持适当的粒度， 但过于粗大的析出物颗粒对钢的性能是非常不利的， 也 是实际生产中在成分设计和实物质量控制中尽力需要避免的。 然而， 对于特定的析出物， 由于其粒度分布遵循一定的规律， 为得 到更大的质量分数， 一般需要相应提高微合金元素的含量， 就会相应增 大析出物的平均粒度， 钢中出现较大颗粒析出物粒子的几率也就增大 了。 即现有技术条件下使钢中析出物同时获得高的体积分数和保持细小 粒度是有矛盾的。 大颗粒的析出物会带来新的问题， 比较典型的例子是 使连铸板坯角部出现裂纹或者提高成品冷轧板的冷加工性能。 因此， 对 于微合金化钢种， 如何控制析出物的粒度， 特别是减小钢中出现大颗粒 析出物的几率， 是一个很突出的问题。 In fine grain strengthening, the strength increment of the steel is inversely proportional to the 1/2 power of the grain size, and the grain size Dc of the steel follows the Zener formula: Dc=A*d/f where A is the proportional constant and d is the size of the precipitate. , f is the precipitate volume fraction), so fine-grained strengthening requires finely dispersed precipitates. The effect of precipitation strengthening is also achieved by the precipitates, and the interaction of the precipitate particles and the slip dislocation directly strengthens the steel. The enhancement increment is proportional to the 1/2 power of the volume fraction of the second phase particles and the 1/2 power of the particle size. Therefore, the precipitate phase becomes a key factor affecting the performance of the steel, and is a key factor for the strengthening and toughening of the steel. Therefore, the precipitate is a particle that is intentionally introduced to optimize the performance of the steel. In order to ensure that the steel has a good strength-plastic-toughness combination, or to make the steel have excellent comprehensive properties, it is usually required that the precipitates in the steel have a large volume fraction while maintaining an appropriate particle size, but the excessively coarse precipitate particles are on the steel. The performance is very unfavorable, and it is also the best to avoid in the composition design and physical quality control in actual production. However, for a specific precipitate, since the particle size distribution follows a certain rule, in order to obtain a larger mass fraction, it is generally required to increase the content of the microalloying element correspondingly, which will correspondingly increase the average particle size of the precipitate, and the occurrence in the steel The probability of large particle precipitate particles increases. That is, it is contradictory to obtain a high volume fraction and a fine particle size in the steel under the prior art conditions. The precipitation of large particles brings about new problems. A typical example is the occurrence of cracks in the corners of the continuous casting slab or the improvement of the cold workability of the finished cold rolled sheet. Therefore, for microalloyed steel grades, how to control the particle size of precipitates, especially the possibility of large particle precipitates in steel, is a prominent problem.
目前国际上对于细化析出物广泛采用的是降低析出物形成元素的 溶度积的方法， 但这会减少析出物的体积分数 （即数量） ， 因此不是一 种有效的方法。  At present, the method widely used for refining precipitates in the world is to reduce the solubility product of the elements forming precipitates, but this reduces the volume fraction (i.e., the number) of precipitates, and thus is not an effective method.
另一方面， 钢中不可避免存在夹杂物， 这是在冶炼过程中因脱氧或 者合金化过程所形成的氧化物、 炉渣和炉衬中的各种氧化物进入钢水、 以及在钢液凝固过程中析出的硫化物、 氧化物等， 夹杂物通常对于钢的 性能有不利的影响， 特别是对于粒度比较大的夹杂物， 例如十个或者数 十个微米大小的夹杂物， 一般会显著影响钢的疲劳性能、 韧性， 对于不 同性能要求的钢种， 还会对钢的其它一些性能有不利影响。 因此， 为保 障钢的性能， 也要求对夹杂物进行细化。 当夹杂物足够微细化以后， 夹 杂物可以有效改善钢的性能， 即变成有利质点。 在本发明所涉及到的微 观组织评价中， 也发现本合金对于钢中的夹杂物有同等细化效果。 发明内容  On the other hand, inclusions are inevitably present in the steel, which are oxides, slag and various oxides in the lining that enter the molten steel during the smelting process due to deoxidation or alloying, and precipitate during solidification of the molten steel. Sulfides, oxides, etc., inclusions usually have a detrimental effect on the properties of steel, especially for inclusions with relatively large particle sizes, such as ten or tens of micron-sized inclusions, which generally affect steel fatigue. Performance, toughness, steel grades with different performance requirements can also have an adverse effect on other properties of steel. Therefore, in order to protect the performance of the steel, it is also required to refine the inclusions. When the inclusions are sufficiently fine, the inclusions can effectively improve the properties of the steel, that is, become favorable particles. In the evaluation of the microscopic structure according to the present invention, it was also found that the present alloy has an effect of refining the inclusions in the steel. Summary of the invention
本发明的目的在于提供一种钢铁生产过程用于细化析出物的合金 及其使用方法， 在不减少析出元素含量的条件下， 通过采用析出物细化 合金对钢水脱氧， 利用微细分散的脱氧产物作为析出物的形核质点， 提 高析出物的形核率， 同时减小析出物的粒度和增加其数量。  The object of the present invention is to provide an alloy for refining precipitates in a steel production process and a method for using the same, which can deoxidize molten steel by using a precipitate refining alloy without decomposing the content of precipitated elements, and utilize finely dispersed deoxidizing The product acts as a nucleation particle of the precipitate, which increases the nucleation rate of the precipitate, while reducing the particle size of the precipitate and increasing the amount thereof.
为达到上述目的， 本发明的技术方案是：  In order to achieve the above object, the technical solution of the present invention is:
一种钢铁生产过程用于细化析出物的合金， 其成分重量百分比为： A1 78-95% , Mg 5〜22%及不可避免杂质。  An alloy used in the steel production process for refining precipitates, the weight percentage of which is: A1 78-95%, Mg 5-22% and unavoidable impurities.
进一歩， 本发明合金对于钢中硫含量和铝含量比较高的钢种， 为强 化析出物细化效果， 可以选择性的加入 Ca 0〜10%和 /或 Sr 0〜5%， 以重 量百分比计。 本发明的用于钢铁生产过程用于细化析出物的合金的使用方法， 可 以根据炼钢的实际条件以块状、 粒状、 粉状或者以包芯线形式在钢水炉 外精炼阶段加入钢中， 合金加入总量为钢水总量的 0.010〜0.025%， 以 重量百分比计； 钢水温度控制 1580 °C〜1620 °C， 钢水中自由氧控制在 0.0001〜0.0040%， 以重量百分比计； 加入合金以后钢水搅拌时间不低 于 5分钟， 以保证均匀分散。 Further, in the steel of the present invention, for the steel having a relatively high sulfur content and aluminum content in the steel, in order to enhance the refining effect of the precipitate, Ca 0 10% and/or Sr 0 to 5% may be selectively added, by weight percentage. meter. The method for using the alloy for refining precipitates in the steel production process of the present invention may be added to the steel in a refining stage outside the molten steel furnace in the form of a block, a granule, a powder or a cored wire according to actual conditions of steel making. The total amount of alloy added is 0.010~0.025% of the total amount of molten steel, in weight percent; the temperature of molten steel is controlled from 1580 °C to 1620 °C, and the free oxygen in molten steel is controlled at 0.0001~0.0040%, in weight percent; after adding alloy The molten steel is stirred for not less than 5 minutes to ensure uniform dispersion.
在本发明的合金中：  In the alloy of the invention:
Mg: 为细化质点形成元素。 镁是一种强的脱氧剂， 能够对钢水脱 氧或者将较弱的脱氧剂如锰、 硅所形成的氧化物进行还原， 形成的产物 均是 MgO， 这是一种非常细小的夹杂物， 平均粒度在 0.1微米以下， 且 容易均匀分散地留存于钢水中直至钢水凝固。 Mg: Forms an element for refining the particle. Magnesium is a strong deoxidizer that can deoxidize molten steel or reduce the oxides formed by weaker deoxidizers such as manganese and silicon. The resulting product is M g O, which is a very fine inclusion. The average particle size is below 0.1 μm, and is easily and uniformly dispersed in the molten steel until the molten steel is solidified.
A1: 由于镁的蒸汽压高， 在高温下容易气化， 且镁为活泼金属， 故 若将金属镁直接加入钢水， 收得率将非常低， 且效果不稳定。 为了提高 镁的收得率， 必须采用合金化的方法， 本发明中采用铝作为合金元素使 铝和镁形成固溶体降低镁的活性和蒸汽压， 而且由于铝为钢中常用合金 元素和脱氧剂， 可以最大限度降低合金对钢水的不利影响。  A1: Due to the high vapor pressure of magnesium, it is easy to vaporize at high temperatures, and magnesium is a reactive metal. Therefore, if metal magnesium is directly added to molten steel, the yield will be very low and the effect will be unstable. In order to increase the yield of magnesium, an alloying method must be employed. In the present invention, aluminum is used as an alloying element to form a solid solution of aluminum and magnesium to reduce magnesium activity and vapor pressure, and since aluminum is a commonly used alloying element and deoxidizer in steel, It can minimize the adverse effects of the alloy on molten steel.
Ca: 为钢中常用的夹杂物改性元素， 钢中加入钙， 可以将硫化物球 化， 同时因钙可以和钢中的氧化铝反应形成较低熔点的 7Al2( 12CaO而 去除使钢纯净化， 本发明中钙还可以有效地改变 MgO夹杂物的表面特 性， 使之更加微细分散。 Ca: It is a commonly used inclusion modification element in steel. Calcium is added to steel to spheroidize the sulfide. At the same time, calcium can react with alumina in steel to form lower melting point of 7Al 2 (12CaO to remove steel. In the present invention, calcium can also effectively change the surface characteristics of MgO inclusions to make it more finely dispersed.
Sr: 为碱土金属， 锶加入钢中形成的氧化物能够有效改变 MgO夹杂 物的表面特性， 并起到辅助形核剂的作用。  Sr: is an alkaline earth metal. The oxide formed by the addition of niobium to the steel can effectively change the surface characteristics of the MgO inclusions and act as an auxiliary nucleating agent.
其中 Mg为形核质点元素， 镁加入钢中形成细小的 MgO , 作为析出 物的形核核心。 因 Mg为强活性元素且蒸汽压较高， 故合金中加入 Al， 可以提高 Mg的收得率。 Ca和 Sr主要作为表面活性元素保证脱氧产物 MgO在钢中微细分散。  Among them, Mg is a nucleation point element, and magnesium is added to the steel to form fine MgO, which serves as the nucleation core of the precipitate. Since Mg is a strong active element and the vapor pressure is high, the addition of Al to the alloy can increase the yield of Mg. Ca and Sr are mainly used as surface-active elements to ensure deoxidation products. MgO is finely dispersed in steel.
本发明合金可以根据炼钢的实际条件以块状、 粒状、 粉状或者以包 芯线形式加入钢中。为保证析出物的细化效果，合金按照以下方式加入： 合金在钢的炉外精炼阶段加入， 加入总量为钢水总量的 0.010— 0.025%, 加入量过少则形核质点数量不足， 如过多， 不但增大成本， 而 且所过量的氧化物夹杂将对钢质量造成不利影响。 钢水温度控制在 1580〜1620 °C范围， 这是钢水进行成分调整适宜温 度， 在该温度范围内， 析出物细化合金的收得率基本保持稳定。 The alloy of the present invention can be added to the steel in the form of a block, a granule, a powder or a cored wire depending on the actual conditions of the steelmaking. In order to ensure the refining effect of the precipitate, the alloy is added as follows: The alloy is added in the refining stage of the steel, and the total amount is 0.010-0.025% of the total amount of molten steel. If the amount is too small, the number of nucleation points is insufficient, such as Too much, not only increases the cost, but the excess oxide inclusions will adversely affect the quality of the steel. The temperature of the molten steel is controlled in the range of 1580 to 1620 °C, which is a suitable temperature for adjusting the composition of the molten steel. In this temperature range, the yield of the precipitated fine alloy is basically kept stable.
钢水氧位是控制夹杂物总量（即钢水纯净度）的重要指标， 同时 钢 水氧位需要和有效的析出物细化合金量（合金总量 X收得率 X细化质点形 成元素百分含量） 相适应。 钢水中自由氧控制在 0.0001〜0.0040%范围 为宜。  Oxygen level of molten steel is an important index to control the total amount of inclusions (ie, the purity of molten steel). At the same time, the oxygen content of molten steel needs to be refined and the amount of alloy is refined. (Total amount of alloy X is obtained. X is refined. ) Adapted. The free oxygen control in the molten steel is in the range of 0.0001 to 0.0040%.
加入合金以后钢水搅拌时间不低于 5分钟以保证均匀分散。  After the alloy is added, the molten steel is stirred for not less than 5 minutes to ensure uniform dispersion.
采用本析出物细化合金处理后， 钢水凝固以后， 各细化元素的残留 量为： Mg 20ppm( 0.0020%)，在加入钙和（或）锶的情况下，钙 15ppm， Sr ^ 5ppm。 因钢中含铝， 铝的残留不予统计。  After the precipitation of the precipitated alloy, the residual amount of each refined element after solidification of the molten steel is: Mg 20 ppm (0.0020%), and in the case of adding calcium and/or strontium, calcium 15 ppm, Sr ^ 5 ppm. Since the steel contains aluminum, the residue of aluminum is not counted.
采用本本发明方法处理的钢水， 钢中粗大的析出物得到细化， 同时 钢中析出物的总数量不但不会减少， 反而会大幅度增加。 经对冷轧钢板 取样，采用 1000倍光学显微镜 50个视场下对所有夹杂物 /析出物的粒度进 行统计分析， 典型效果如图 1。 对于同样成分的钢进行对比试验表明， 经过细化处理以后， 钢中夹杂物和析出物的数量显著增长， 总数增长 50%以上， 而粒度得到显著细化， 这不仅表现在平均粒度的减小约 40%, 也表现在粒径大于 10微米的大颗粒粒子近乎消除。  With the molten steel treated by the method of the present invention, the coarse precipitates in the steel are refined, and the total amount of precipitates in the steel is not reduced, but is greatly increased. The cold-rolled steel sheets were sampled, and the particle size of all inclusions/precipitates was statistically analyzed using a 1000-fold optical microscope in 50 fields of view. The typical effect is shown in Fig. 1. Comparative tests on steels of the same composition show that after the refining treatment, the amount of inclusions and precipitates in the steel increases remarkably, the total number increases by more than 50%, and the particle size is remarkably refined, which is not only reflected in the decrease in average particle size. About 40%, also shown in large particle particles larger than 10 microns in particle size is almost eliminated.
采用本发明合金处理的钢水， 钢中镁的残留量少， 但细化析出物 / 夹杂物的效果稳定。经多次试验和检测，采用本合金及相应的添加方式， 钢坯 /锭中镁的残留量在 5〜20ppm ( 0.0005〜0.0020%) ， 这在保持工艺 效果的同事极大限度地降低了残留镁对钢的影响。  In the molten steel treated with the alloy of the present invention, the residual amount of magnesium in the steel is small, but the effect of refining the precipitate/inclusion is stable. After repeated tests and tests, using this alloy and the corresponding addition method, the residual amount of magnesium in the billet/ingot is 5~20ppm (0.0005~0.0020%), which greatly reduces the residual magnesium in the colleagues who maintain the process effect. The effect on steel.
采用本方法引入了 MgO夹杂物非常细小且均匀分散，故其总的质量 分数很低。 经分析， 所形成的 MgO粒度在 0.01〜0.10μπι (微米） ， 密度 在 400个 /mm2 (平方毫米） 以上， 且钢材经过均热、 热处理等热过程以 后， MgO质点未见明显粗化。 The MgO inclusions introduced by this method are very fine and uniformly dispersed, so the total mass fraction is very low. After analysis, the formed MgO particle size is 0.01~0.10μπι (micrometer), and the density is above 400/mm 2 (square mm). After the steel material undergoes heat treatment such as soaking and heat treatment, the MgO particle has no obvious coarsening.
采用扫描电镜对对钢样进行观察和分析发现， 钢中的 Mg以 MgO的 形式存在于钢中， 外面包裹着不同的夹杂物或者析出物， 这表明 MgO的 作用是作为夹杂物和析出物的形核核心。正是由于本发明中 MgO作为夹 杂物和析出物形核核心这一特性， 使夹杂物和析出物的形核变得容易， 并增加其形核率， 使钢种的夹杂物和析出物的数量增加粒度减小。 典型 效果如图 2， 其中的析出相为 ΤιΝ。 本发明是一种专门针对钢中的析出物的细化而设计的合金， 可以有 效细化钢中象 ΤιΝ等析出相， 这在钢中析出物形成元素溶度积较大时尤 其明显和必要。 同时本合金对于钢中的夹杂物有同等的细化效果， 以往 的专利提及了夹杂物的细化或者分散化， 但还没有触及析出物。 Scanning electron microscopy was used to observe and analyze the steel samples. It was found that Mg in the steel exists in the form of MgO in the steel, and the outside is wrapped with different inclusions or precipitates, which indicates that the role of MgO is as inclusions and precipitates. The core of nucleation. It is precisely because of the characteristics of MgO as a core of inclusions and precipitates in the present invention that nucleation of inclusions and precipitates is facilitated, and the nucleation rate thereof is increased to cause inclusions and precipitates of steel species. The increase in the number of particles is reduced. The typical effect is shown in Fig. 2, in which the precipitated phase is ΤιΝ. The invention is an alloy specially designed for the refinement of precipitates in steel, and can effectively refine the precipitated phase such as ΤιΝ in steel, which is especially obvious and necessary when the solubility product of the precipitate forming element in steel is large. . At the same time, the alloy has the same refinement effect on the inclusions in the steel. The prior patent mentions the refinement or dispersion of the inclusions, but has not touched the precipitates.
本发明的有益效果：  The beneficial effects of the invention:
本发明一方面大幅度细化析出物和夹杂物， 同时显著增加其数量， 由于析出物具有细化晶粒和使钢强化和韧化的效果， 增加析出物数量对 于改善钢材性能非常重要。 即使在细化夹杂物方面， 日本专利 JP2002256331A, JP2006124759A均提及细化夹杂， 但未提供具体的对 比数据， 更未提及能够增加小夹杂物的数量这一方面。  In the aspect of the invention, the precipitates and inclusions are greatly refined, and the amount thereof is remarkably increased. Since the precipitates have the effect of refining crystal grains and strengthening and toughening the steel, increasing the amount of precipitates is very important for improving the properties of the steel. Even in the case of refining inclusions, Japanese Patent No. JP2002256331A, JP2006124759A mentions fine inclusions, but does not provide specific comparative data, and does not mention the aspect of being able to increase the amount of small inclusions.
本发明中采用镁作为主要的析出物细化元素， 但由于所形成的脱氧 产物 MgO粒度非常细小， 在钢中保持高密度（400个 /mm2以上） 的同时， Mg 的残留质量分数非常低， 可以最大限度减小镁对钢质量的不利影 响。 对于同样添加镁处理的相关专利， 如日本专利 JP10102131A等， 在 不能达到同样效果， 这和本合金的成分设计有很大关系。 In the present invention, magnesium is used as a main precipitate refining element, but since the formed deoxidized product MgO has a very fine particle size, high density (400/mm 2 or more) is maintained in the steel, and the residual mass fraction of Mg is extremely low. , can minimize the adverse effects of magnesium on steel quality. For related patents that also add magnesium treatment, such as Japanese patent JP10102131A, etc., the same effect can not be achieved, which has a great relationship with the composition design of the alloy.
具体到本发明所采用的 Al-Mg系合金，虽然也有一些其它的含镁合 金用于钢中， 如日本专利 JP2002256331A(Ti— Mg ) 、 JP9287015A ( Zr-Mg), JP2008266706A ( Ca-Mg) 等， 但均不是用于析出物细化， 而是将镁用作夹杂物细化、 脱硫和提高凝固等轴晶率。 本发明合金开辟 了一个新的应用领域。 附图说明  Specifically, the Al-Mg-based alloy used in the present invention, although some other magnesium-containing alloys are used in steel, such as Japanese Patent JP2002256331A (Ti-Mg), JP9287015A (Zr-Mg), JP2008266706A (Ca-Mg), etc. However, they are not used for the refinement of precipitates, but use magnesium as an inclusion crystal refining, desulfurization, and an increase in solidification and other axial crystallinity. The alloy of the invention opens up a new field of application. DRAWINGS
图 1为细化析出物效果对比示意图。  Figure 1 is a schematic diagram showing the comparison of the effects of fine precipitates.
图 2为引入的 MgO质点对 ΤιΝ析出物的效果的示意图。 具体实施方式 下面结合实施例对本发明进一歩详述。 实施例 1  Figure 2 is a schematic illustration of the effect of the introduced MgO particles on the ΤιΝ precipitate. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail in conjunction with the embodiments. Example 1
对象钢种为高强度汽车板， 主要成分重量为： C 0.10% ， Si 0.18%, Mn 1.52%, Al 0.03%, Nb 0.03%, Ti 0.06%, N 0.006%, S 0.0030%。 厚 度规格 0.8mm， 钢的生产流程为： 铁水预处理 _ _转炉冶炼一一炉外精 炼一一板坯连铸一一热轧一一酸洗一一冷轧一一成品热处理。 The target steel grade is a high-strength automotive sheet. The main component weights are: C 0.10%, Si 0.18%, Mn 1.52%, Al 0.03%, Nb 0.03%, Ti 0.06%, N 0.006%, S 0.0030%. Thick The specification is 0.8mm, and the production process of steel is: hot metal pretreatment _ _ converter smelting one furnace outside refining one slab continuous casting one by one hot rolling one acid washing one cold rolling one one finished heat treatment.
采用本发明方法之前， 钢板的冷冲性能比较差， 有约 20%的钢板开 裂， 经断口观察和金相分析， 证实钢中存在的粗大 TiN析出物是导致冷 冲性能恶化的主要原因。 TiN的粒径最大达 14微米， 采用 500倍金相观察 可见总数约 15%以上的 TiN粒径在 5微米以上。  Prior to the use of the method of the present invention, the cold impact properties of the steel sheet were relatively poor, and about 20% of the steel sheets were cracked. The fracture observation and metallographic analysis confirmed that the coarse TiN precipitates present in the steel were the main cause of deterioration of the cold performance. The particle size of TiN is up to 14 microns, and it is observed that 500% of the metallographic phase shows that the total number of TiN particles is more than 5 microns.
经采用本发明方法， 在炉外精炼过程中添加成分 （重量百分比， 下 同） 为 A1 83%， Mg 7%, Ca 9%, 余量为杂质的析出物细化合金， 添加 量为钢水重量的 0.023%。 添加合金时的钢水条件为： 温度 1608 °C， 钢水 自由氧控制在 0.0005%。 加入合金以后钢水搅拌时间 7分钟后进行连铸。  By using the method of the invention, the components (weight percentage, the same below) are added in the refining process of the furnace to be A1 83%, Mg 7%, Ca 9%, and the balance is an impurity precipitated refining alloy, and the added amount is the weight of the molten steel. 0.023%. The molten steel conditions for adding the alloy are: temperature 1608 °C, and the free oxygen of the molten steel is controlled at 0.0005%. After the addition of the alloy, the molten steel was stirred for 7 minutes and then continuously cast.
对成品钢板进行冷冲试验， 证实全部合格无开裂， 在钢板上取样作 成分分析证实钢中 Mg的含量在 0.0020%以下。 夹杂物分析证实： 经 500 倍的金相观察， 钢中存在的 TiN的粒径最大仅 6微米， 同等条件下， 采用 本方法处理的钢， 粒经在 1微米以下的 TiN数量增加了 8%左右， 而粒径 在 5微米以上的 TiN颗粒则不及原来的十分之一。显示出本方法对析出物 良好的细化效果。 实施例 2  The cold-shear test was carried out on the finished steel plate, and it was confirmed that all of them were qualified without cracking. The sample was analyzed on the steel plate to confirm that the content of Mg in the steel was below 0.0020%. The inclusion analysis confirmed that the grain size of TiN present in the steel was only 6 μm when observed by 500 times of metallography. Under the same conditions, the amount of TiN in the grain treated by this method increased by 8%. Left and right, TiN particles with a particle size of 5 microns or more are less than one tenth of the original. This method shows a good refining effect on the precipitate. Example 2
使用另外一种析出物细化合金对实施例 1所针对的钢种进行试验。 析出物细化合金的成分为： Al 79%、 Mg 20%、 余量为杂质， 添加 量为钢水重量的 0.016%。 添加合金时的钢水条件为： 温度 1600 °C， 钢 水自由氧控制在 0.0035%。 加入合金以后钢水搅拌时间 7分钟后进行连 铸。  The steel grades targeted for Example 1 were tested using another precipitate refining alloy. The composition of the precipitate refining alloy is: Al 79%, Mg 20%, and the balance is impurities, and the amount added is 0.016% by weight of the molten steel. The molten steel conditions for adding the alloy are: temperature 1600 °C, and the free oxygen of the molten steel is controlled at 0.0035%. After the alloy was added, the molten steel was stirred for 7 minutes and then continuously cast.
对成品钢板取样分析证实， 实施例 2取得了和实施例 1相接近的效 果。 实施例 3  Sampling analysis of the finished steel sheet confirmed that Example 2 achieved an effect similar to that of Example 1. Example 3
对象钢种普通冷轧钢板， 主要成分为： C 0.03% , Si 0.018% , Mn 0.25%, Al 0.03%, B 0.0026%, N 0.0034%, S 0.0030%。 厚度规格 0.5〜 2.0mm, 钢的生产流程同样为： 铁水预处理一一转炉冶炼一一炉外精炼 _ _板坯连铸一一热轧一一酸洗一一冷轧一一成品热处理。 之前， 有约近 30%连铸板坯角部出现裂纹 （即角裂） ， 经研究证实 钢中存在的粗大 BN析出物导致钢在 800〜900 °C温度区间出现脆性， 高 温拉伸断面颈缩率最低在 5%以下， 而其它钢种相应值通常在 30%以上， 高温脆性导致板坯角部在连铸过程中因受机械应力、 热应力而开裂， 在 连铸阶段采用减小铸坯角部机械应力和热应力等技术措施均未收到明 显效果。 经对铸坯取样分析证实， 钢中存在粗大的 BN析出物， 这是一 种硬质的析出物， 最大粒径达 6〜8微米， 常见的粒径在 0.5〜2微米， BN 析出物的数量在 10〜40个 /mm2 , 研究证实粗大的 BN析出物是导致角裂 的主要原因， 故采用本方法对钢中的 BN进行细化。 The object steel grade is ordinary cold-rolled steel sheet. The main components are: C 0.03%, Si 0.018%, Mn 0.25%, Al 0.03%, B 0.0026%, N 0.0034%, S 0.0030%. The thickness specification is 0.5~2.0mm, and the steel production process is also as follows: hot metal pretreatment one-to-one converter smelting one-to-one furnace refining__slab continuous casting one-by-one hot-rolling one-by-one-one-one-one-one cold-rolling one-finished heat treatment. Previously, there were about 30% cracks in the corners of continuous casting slabs (ie, corner cracks). It was confirmed by research that coarse BN precipitates in steel caused brittleness in the temperature range of 800~900 °C. The shrinkage rate is at least 5%, while the corresponding values of other steel grades are usually above 30%. The high temperature brittleness causes the slab corners to be cracked due to mechanical stress and thermal stress during continuous casting, and the casting is reduced during the continuous casting stage. Technical measures such as mechanical stress and thermal stress at the corner of the bill have not received significant results. Sampling analysis of the slab confirmed that there is coarse BN precipitate in the steel, which is a hard precipitate with a maximum particle size of 6~8 microns, a common particle size of 0.5~2 microns, BN precipitates. The number is in the range of 10 to 40/mm 2 , and it has been confirmed that the coarse BN precipitate is the main cause of the corner crack, so the BN in the steel is refined by the method.
在炉外精炼过程中添加的析出物细化合金成分为： A1 78% , Mg The precipitated refined alloy composition added during the refining process is: A1 78%, Mg
19% , Sr 3% , 添加量为钢水重量的 0.020%。 添加合金时的钢水条件为： 温度 1590 °C， 钢水自由氧控制在 0.00012%。 加入合金以后钢水搅拌时间 5分钟后进行连铸。 19%, Sr 3%, the addition amount is 0.020% of the weight of molten steel. The molten steel conditions for adding the alloy are: temperature 1590 °C, and the molten steel free oxygen is controlled at 0.00012%. After the alloy was added, the molten steel was stirred for 5 minutes and then continuously cast.
对连铸坯质量进行监测证实， 采用本方法， 铸坯角裂基本消除。 铸 坯高温拉伸测试证实， 钢种在 800〜900 °C温度区间的脆性得到明显改 善， 颈缩率最低值增大到 18%。 在铸坯上取样作成分分析证实钢中 Mg 的含量在 0.0009%。 夹杂物分析证实： 经 500倍的金相观察， 钢中存在的 BN的粒径最大仅 4微米， 绝大部分 BN粒径在 1〜2微米范围。 实施例 4  The monitoring of the quality of the continuous casting slab confirms that with this method, the corner crack of the slab is basically eliminated. The high temperature tensile test of the cast blank confirmed that the brittleness of the steel in the temperature range of 800 to 900 °C was significantly improved, and the minimum necking rate was increased to 18%. Sampling on the slab for component analysis confirmed that the Mg content of the steel was 0.0009%. The inclusion analysis confirmed that the BN particle size in the steel was only 4 μm at most when observed by 500 times of metallography, and most of the BN particle size was in the range of 1 to 2 μm. Example 4
使用的析出物细化合金成分为： A1 94%， Mg 5%， 余量为杂质， 对 实施例 3所针对的钢种进行试验。 钢水自由氧控制在 0.0005%， 钢水温度 1604 °C , 加入合金以后钢水搅拌时间 10分钟后进行连铸。 对铸坯质量监 测和铸坯取样分析证实， 实施例 4取得了和实施例 3相接近的效果， 证实 了析出物细化合金的效果。 实施例 5  The precipitate refining alloy composition used was: A1 94%, Mg 5%, and the balance was an impurity, and the steel grades referred to in Example 3 were tested. The molten steel free oxygen is controlled at 0.0005%, and the molten steel temperature is 1604 °C. After the alloy is added, the molten steel is stirred for 10 minutes and then continuously cast. The slab quality monitoring and the slab sampling analysis confirmed that Example 4 achieved an effect similar to that of Example 3, confirming the effect of the precipitate refining alloy. Example 5
使用的析出物细化合金成分为： A1 82% , Mg 6% , Ca 6% , Sr 5% , 余量为杂质， 对实施例 3所针对的钢种进行试验。 钢水自由氧控制在 0. 0001% , 钢水温度 1617 °C， 加入合金以后钢水搅拌时间 15分钟后进行 连铸。 分析证实析出物得到有效细化。  The precipitated fine alloy composition used was: A1 82%, Mg 6%, Ca 6%, Sr 5%, and the balance was an impurity, and the steel grades referred to in Example 3 were tested. The molten steel free oxygen is controlled at 0. 0001%, the molten steel temperature is 1617 °C, and the molten steel is stirred for 15 minutes after the alloy is added. Analysis confirmed that the precipitate was effectively refined.

Claims

权 利 要 求 Rights request
1. 一种钢铁生产过程用于细化析出物的合金， 其成分重量百分比为： A1 78-95% , Mg 5〜22%及不可避免杂质。 1. An alloy used in the steel production process for refining precipitates, the weight percentage of which is: A1 78-95%, Mg 5-22% and inevitable impurities.
2. 如权利要求 1所述的用于钢铁生产过程用于细化析出物的合金，其特 征是， 还包括 Ca 0〜10%和 /或 Sr 0〜5%， 以重量百分比计。  2. The alloy for refining precipitates for use in a steel production process according to claim 1, which further comprises Ca 0 to 10% and/or Sr 0 to 5% by weight.
3. 如权利要求 1或 2所述的钢铁生产过程用于细化析出物的合金的使用 方法， 可以根据炼钢的实际条件以块状、 粒状、 粉状或者以包芯线形式 在钢水炉外精炼阶段加入钢中， 合金加入总量为钢水总量的 0.010〜 0.025% , 以重量百分比计； 钢水温度控制 1580 °C〜1620 °C， 钢水中自 由氧控制在 0.0001〜0.0040%， 以重量百分比计； 加入合金以后钢水搅 拌时间不低于 5分钟， 以保证均匀分散。  3. The method for using an alloy for refining precipitates in the steel production process according to claim 1 or 2, which may be in the form of a block, a granule, a powder or a cored wire in a molten steel furnace according to actual conditions of steelmaking. The external refining stage is added to the steel. The total amount of the alloy added is 0.010~0.025% of the total molten steel, in terms of weight percentage; the molten steel temperature is controlled from 1580 °C to 1620 °C, and the free oxygen in the molten steel is controlled at 0.0001~0.0040%, by weight. Percentage meter; after adding the alloy, the molten steel stirring time is not less than 5 minutes to ensure uniform dispersion.
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