Aluminum-calcium-magnesium-cerium composite alloy used for strong desulfurization, final desoxidation, and quenching and tempering of liquid steel

Abstract

The invention provides an aluminum-calcium-magnesium-cerium composite alloy used for strong desulfurization, final desoxidation, and microalloying quenching and tempering of liquid steel, belonging to the technical field of ferroalloy used for steelmaking. Based on aluminum deoxidization, the aluminum-calcium-magnesium-cerium composite alloy is added with alkaline-earth metal calcium and magnesium to conduct the strong desulphurization and the final desoxidation on the liquid steel so as to reduce inclusions in steel, and adopts rare earth-cerium and alloy elements such as titanium, niobium, vanadium and the like to conduct quenching and tempering, and microalloying on the liquid steel so as to change the morphology of the inclusions, lead the steel to be solidified, crystallized and refined, and optimize the steel performance. The aluminum-calcium-magnesium-cerium composite alloy contains the following chemical compositions (mass percent): 10-60% of aluminum, 10-30% of calcium, 10-30% of magnesium, 0.5-10% of cerium, less than or equal to 1% of impurities (carbon + silicon + phosphorus + sulphur), and the balance of ferrum; and for the purpose of achieving different microalloying, the composite alloy also can contain one or more microalloying elements of titanium, niobium, molybdenum, vanadium, tungsten and boron, and the weight percentage content of the microalloying elements is 0.1-10%. In the invention, the final desoxidation, the strong desulfurization, the microalloying and the quenching and tempering of the liquid steel is completed in one step, thus improving the refining efficiency and effect, and greatly improving the steel quality.

Description

technical field [0001] The invention belongs to the field of ferroalloys for steelmaking, and in particular relates to an aluminum-calcium-magnesium-cerium composite alloy for deep desulfurization, final deoxidation, microalloying and quenching and tempering of molten steel. Background technique [0002] With the rapid development of economy and technology, the quality requirements of steel are constantly increasing. Oxygen in steel will seriously reduce the mechanical properties of steel, especially the fatigue resistance. Therefore, deoxidation treatment is required in the steelmaking and refining process. Some special steel types , Such as bearing steel, anchor chain steel, rail steel, etc., the oxygen activity in the refined steel is lower than 0.001%, and the lower the better. Sulfur in steel is also a harmful element to most steel types (except free-cutting steel). Like oxygen in steel, sulfur-containing steel is prone to "hot embrittlement" during hot working, and sul...

AI Technical Summary

Problems solved by technology

[0003] At present, the alloys used for deoxidation are mainly: (1) silicon-manganese-aluminum alloy. The main disadvantage of this type of alloy is that the final deoxidation degree depends on the dissolved aluminum content in the steel. In the case of excess aluminum, the deoxidation ability of silicon and manganese is very low. Weak, excess silicon and manganese are easy to make the steel composition exceed the standard, especially some steels contain silicon, which will reduce the toughness of the steel; another deficiency is that for deep deoxidation, there must be excess aluminum, and the deoxidation product is a single Al 2 o 3 , not easy to float, stay in the molten steel to form inclusions, easy to block the nozzle and reduce the performance of the steel

(2) Aluminum-calcium alloys, which can form C 12 A 7 (12CaO·7Al 2 o 3 ) as the goal, which is beneficial to the discharge of aluminum deoxidation products. At the same time, calcium also has a strong deoxidation ability and is widely used in steelmaking. The main disadvantage of this type of alloy is that only calcium in this alloy has desulfurization ability, and calcium Solubility is limited, so the ability of this alloy to achieve simultaneous deep deoxidation and deep desulfurization is insufficient

Such as China's invention patent (application number 200510047547.8, title of invention: micro-low-carbon, low-silicon, low-phosphorus, low-sulfur aluminum-magnesium-calcium-iron alloy for steelmaking) proposes to use aluminum 20-80%, magnesium 5-20%, Calcium 1-15% composite alloy, this invention has the effect of deep desulfurization and final deoxidation, but the deficiency that this invention exists mainly is that although calcium and magnesium in the alloy have strong deep desulfurization and deoxidation capabilities at the same time, due to calcium, The vapor pressure of magnesium is very high, and the yield rate at the steelmaking temperature is low, which makes the alloy's ability to quench and temper the inclusions in the steel insufficient.

Chinese invention patent (Application No. 200610003456.9, invention name: molten steel refining modifier for steelmaking) proposes to prepare molten steel refining modifier with alkaline earth alloy and rare earth alloy, the composition used is: silicon 30-60%, barium 5-25% , 1-15% of rare earth, 1-15% of calcium, 1-15% of aluminum, 1-6% of titanium, the invention uses silicon as the matrix, elements barium, calcium, aluminum and titanium all have strong desulfurization ability, so silicon Therefore, the use of this modifier for steel types with strict requirements on silicon content will cause the silicon content to increase or even exceed the standard, so it is not suitable for smelting low-silicon or no-silicon steel. Steel grades of silicon, in addition, the product of silicon deoxidation SiO 2 , so that the basicity of the ladle top slag or covering slag is reduced, causing the molten steel to return to phosphorus and sulfur, and the high content of barium in the alloy is likely to cause barium poisoning, and the steel slag containing barium is also easy to pollute the environment

Chinese invention patent (application number 200610134330.5, invention name: manganese-based alkaline earth ferroalloy for steelmaking) proposes to add alkaline earth such as barium, calcium, magnesium, and strontium to manganese as a matrix for deoxidation and desulfurization and molten steel modification. Insufficient is that the yield of manganese (the proportion retained in molten steel) is the highest, which can easily cause the manganese content to increase or even exceed the standard, so it is not suitable for smelting low manganese steel types. In addition, higher content of barium is likely to cause barium poisoning , barium-containing steel slag is also easy to pollute the environment

[0004] In addition to the deficiencies of the above-mentioned liquid steel final deoxidation alloy and molten steel microalloying quenching and tempering agent, the current final deoxidation and microalloying of molten steel and the modification of molten steel often use different alloy sequences to add to the ladle, making the steel The process of final deoxidation, deep desulfurization and alloying modification of molten steel is relatively cumbersome, and the operation is also relatively complicated, which is prone to instability in the quality of molten steel, and the addition of alloys in multiple packages is also likely to increase the gas absorption of molten steel