A method for manufacturing a lightweight high-strength steel

Abstract

The application provides a preparation method of light high-strength steel and belongs to the technical field of advanced steel materials. The application removes crystallization water in return material through pre-baking of the return material; reduces volatilization loss of low-melting-point elements such as aluminum and manganese, and improves alloy composition utilization rate through heating in air; makes inclusions sufficiently melt out by controlling the heating rate, and reduces the content of inclusions; generates aluminum oxide and aluminum nitride by the reaction of aluminum added in the return material melt with oxygen and nitrogen, and removes the aluminum oxide and aluminum nitride in the form of dross to reduce the content of oxygen and nitrogen in the return material melt; adjusts the refining liquid after refining to ensure the composition content of the steel; and uses inert gas protection during casting to prevent secondary oxidation and nitrogen absorption.

Description

Technical Field

[0001] This invention belongs to the field of advanced steel materials technology, and specifically relates to a method for preparing lightweight high-strength steel. Background Technology

[0002] The rapid development of basic manufacturing has led to increasingly serious energy consumption and pollution emissions. In many mining operations, the annual consumption of wear-resistant parts exceeds 300,000 tons, resulting in economic losses of 5 billion yuan.

[0003] Lightweight high-strength steel is a new type of steel, comprising, by weight percentage, 7-9% aluminum, 18-27% manganese, 0.5-1.5% carbon, and the balance iron. The density of this new steel is no higher than 7.0 g / cm³. 3 This reduces material density by more than 10%, lowers equipment weight, and consequently reduces equipment operating power consumption by more than 3%. Furthermore, the tensile strength R of this type of steel... m Not less than 850 MPa, lower yield strength R eL Above 450MPa, the reduction of area Z is not less than 40%, and the notched impact absorption energy A KV (-40℃) Not less than 47J.

[0004] The existing main manufacturing processes for lightweight high-strength steel are electric arc furnace (EAF) - ladle refining furnace (LF) - vacuum degassing furnace (VD) - ingot casting (IC), or vacuum induction furnace (VIM). Both face significant cost pressures: EAF has high power consumption; LF requires the addition of large amounts of precious alloys such as electrolytic manganese, aluminum, and pure iron, resulting in high costs, large alloy additions, large temperature drops, difficulties in LF heating, difficulties in refining and slag adjustment, excessive refining time, and severe corrosion of the ladle lining refractory material by high alumina, easily leading to silicon reversion and excessive composition; using VIM, due to the addition of more than 25% lightweight alloys and the presence of a large amount of manganese (which volatilizes during smelting), the composition is difficult to control, and the requirements for furnace charge are extremely stringent; offline heat treatment has high energy consumption.

[0005] To reduce costs, existing technologies have attempted to use recycled materials. However, using recycled materials faces three major obstacles: impurity control, alloy composition utilization (mainly manganese), and inclusion removal. Existing manufacturing processes lack effective solutions to these challenges. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing lightweight, high-strength steel. The method provided by this invention can utilize recycled materials and effectively control impurities and inclusions, resulting in high utilization of alloy components.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing lightweight high-strength steel, comprising: The returned material is pre-baked to obtain dried material; the returned material is waste generated during the machining process of lightweight high-strength steel; the pre-baking temperature is 200~400℃ and the time is 15~60min; The dried material is heated in air until it is completely melted to obtain a return material melt; the heating rate is 200~300℃ / h. Aluminum is added to the molten recycled material for refining to obtain a refined liquid; the amount of aluminum added is not less than 1% of the mass of the recycled material. The refining liquid is prepared according to the composition of the target lightweight high-strength steel, and then smelted and cast in sequence to obtain lightweight high-strength steel; inert gas is used for protection during casting.

[0008] Preferably, the pre-baking temperature is 200~300℃.

[0009] Preferably, the pre-baking is carried out using the residual heat from the melting process.

[0010] Preferably, the preparation involves adding pure metal to the refining liquid.

[0011] Preferably, the pure metal includes one or more of iron, manganese, and aluminum.

[0012] Preferably, the amount of aluminum added is 1 to 2% of the mass of the recycled material.

[0013] Preferably, the melting temperature is 1500~1600℃.

[0014] Preferably, the holding time for melting is 15-20 minutes.

[0015] Preferably, the inert gas is argon.

[0016] Preferably, a heating agent and a heat-insulating agent are added after the casting is completed.

[0017] This invention provides a method for preparing lightweight high-strength steel, comprising: pre-baking recycled material to obtain dried material; wherein the recycled material is waste generated during the machining process of lightweight high-strength steel; the pre-baking temperature is 200~400℃, and the time is 15~60min; heating the dried material in an air atmosphere until it is completely melted to obtain recycled material melt; the heating rate is 200~300℃ / h; adding aluminum to the recycled material melt for refining to obtain a refined liquid; wherein the amount of aluminum added is not less than 1% of the mass of the recycled material; adjusting the refined liquid according to the composition of the target lightweight high-strength steel, and then sequentially performing melting and casting to obtain lightweight high-strength steel; wherein an inert gas is used for protection during casting. This invention removes the water of crystallization from the recycled material through pre-baking; reduces the volatilization loss of low-melting-point elements such as aluminum and manganese by heating in air, thereby improving the utilization rate of alloy components; controls the heating rate to ensure the complete melting of inclusions, reducing the inclusion content; reacts aluminum with oxygen and nitrogen in the recycled material melt to generate aluminum oxide and aluminum nitride, which are removed as slag, reducing the nitrogen and oxygen content in the recycled material melt; after refining, the refining solution is adjusted to ensure the composition content of the steel; and inert gas is used during casting to prevent secondary oxidation and nitrogen absorption. The results of the embodiments show that the steel ingots prepared by the method provided by this invention have a coarse / fine inclusion content of no higher than grade 0.5, no surface or flaw detection defects, and the content of each element meets the requirements for lightweight high-strength steel. The mechanical properties meet the requirements, and the utilization rate of manganese in the recycled material reaches 90%. Detailed Implementation

[0018] All raw materials used in this invention are not particularly limited in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0019] The purity of all raw materials used in this invention is not particularly limited. However, this invention preferably uses raw materials of industrial purity or conventional purity in the field of advanced steel materials technology.

[0020] This invention provides a method for preparing lightweight high-strength steel, comprising: The returned material is pre-baked to obtain dried material; the returned material is waste generated during the machining process of lightweight high-strength steel; the pre-baking temperature is 200~400℃ and the time is 15~60min; The dried material is heated in air until it is completely melted to obtain a return material melt; the heating rate is 200~300℃ / h. Aluminum is added to the molten recycled material for refining to obtain a refined liquid; the amount of aluminum added is not less than 1% of the mass of the recycled material. The refining liquid is prepared according to the composition of the target lightweight high-strength steel, and then smelted and cast in sequence to obtain lightweight high-strength steel; inert gas is used for protection during casting.

[0021] This invention pre-baks the returned material to obtain dried material.

[0022] In this invention, the recycled material is waste generated during the processing of lightweight high-strength steel; in the embodiments of this invention, the recycled material includes waste with different compositions generated during different processing processes; the recycled material is compounded according to the composition of the target lightweight high-strength steel before use; compounding the recycled material can improve the utilization rate of the recycled material and further reduce the preparation cost.

[0023] In this invention, the pre-baking temperature is 200~400℃, preferably 200~300℃; as one embodiment of this invention, the pre-baking temperature can be 200℃, 250℃, 300℃, 350℃, or 400℃. Pre-baking temperatures within the above range can remove the water of crystallization from the returned material while preventing oxidation.

[0024] In this invention, the pre-baking is preferably carried out using the residual heat from melting. Utilizing the residual heat from melting for pre-baking can save energy, reduce raw material transfer, and further reduce nitrogen and oxygen content.

[0025] In this invention, the pre-baking time is preferably 15 to 60 minutes, more preferably 15 to 30 minutes; the pre-baking time is within the above range, which can completely remove the water of crystallization in the returned material.

[0026] After obtaining the dried material, the present invention heats the dried material in an air atmosphere until it is completely melted to obtain a return material melt.

[0027] In this invention, the heating rate is 200~300℃ / h, preferably 230~280℃ / h; as one embodiment of this invention, the heating rate can be 210℃ / h, 220℃ / h, 240℃ / h, 250℃ / h, 260℃ / h, 270℃ / h, or 290℃ / h. This invention heats in an air atmosphere, which can reduce the volatilization loss of low-melting-point metals and improve the utilization rate of alloy components in recycled materials; the heating rate within the above range is beneficial for reducing elemental oxidation and further improving the utilization rate of recycled materials.

[0028] In one embodiment of the present invention, the heating device is a medium-frequency induction melting furnace, and the heating current can be 2000~3000A.

[0029] In one embodiment of the present invention, after the dried material is completely melted, slag can be removed to obtain a return material melt. The present invention does not have any particular limitations on the slag removal operation; conventional slag removal methods in the art can be used.

[0030] After obtaining the recycled material melt, the present invention adds aluminum to the recycled material melt for refining to obtain a refined liquid.

[0031] In this invention, the amount of aluminum added is not less than 1% of the mass of the recycled material, preferably 1-2% of the mass of the recycled material. This invention reduces the nitrogen and oxygen content in the recycled material melt by reacting aluminum with oxygen and nitrogen in the recycled material melt to generate aluminum oxide and aluminum nitride, which are removed in the form of slag. When the amount of aluminum added is within the above range, the nitrogen and oxygen content in the recycled material melt can be effectively removed.

[0032] After obtaining the refining liquid, the present invention adjusts the refining liquid according to the composition of the target lightweight high-strength steel, and then performs smelting and casting in sequence to obtain lightweight high-strength steel.

[0033] In this invention, the preferred method of blending is to add pure metals to the refining liquid to achieve the required content of each element for the target lightweight high-strength steel; the pure metals preferably include one or more of iron, manganese, and aluminum. As one embodiment of this invention, the manganese can be electrolytic manganese, and the aluminum can be aluminum granules with a purity of not less than 99.9%.

[0034] In this invention, the smelting temperature is preferably 1500~1600℃, more preferably 1550℃. A smelting temperature within this range is beneficial for the complete dissolution and uniform mixing of the elements, further improving the quality of the steel.

[0035] In this invention, the holding time for melting is preferably 15-20 minutes, more preferably 16-18 minutes. A holding time within this range facilitates the complete dissolution and uniform mixing of all elements, further improving the quality of the steel.

[0036] In this invention, an inert gas is used for protection during casting, preferably argon. Using argon for protection prevents secondary oxidation and nitrogen absorption, reduces nitrogen and oxygen content, and improves the quality of the steel.

[0037] In an embodiment of the present invention, the casting process is as follows: the casting system is baked and cleaned, argon gas is filled into the mold for 15 minutes, argon gas is continuously and gently blown into the ladle, the ladle is hoisted above the mold, and argon gas protection is applied during casting; after casting to the top cap, the casting speed is halved.

[0038] In this invention, after casting is completed, a heating agent and a heat-insulating agent are preferably added; as one embodiment of this invention, the heat-insulating agent is rice husk; the heating agent is added immediately after casting, and the rice husk is added after complete combustion. Adding the heating agent and the heat-insulating agent can reduce casting defects and further improve the quality of the steel.

[0039] In one embodiment of the present invention, after casting and solidification, the material is demolded and hot-fitted; the demolding time does not exceed 10 hours.

[0040] This invention removes the water of crystallization from the recycled material through pre-baking; reduces the volatilization loss of low-melting-point elements such as aluminum and manganese by heating in air, thereby improving the utilization rate of alloy components; controls the heating rate to ensure that inclusions are fully melted out, reducing the inclusion content; reacts aluminum with oxygen and nitrogen in the recycled material melt to generate aluminum oxide and aluminum nitride, which are removed as slag, reducing the nitrogen and oxygen content in the recycled material melt; after refining, the refining liquid is adjusted to ensure the composition content of the steel; and inert gas is used during casting to prevent secondary oxidation and nitrogen absorption.

[0041] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] The recycled materials used in this embodiment of the invention are of four types, and their composition analysis is shown in Table 1.

[0043] Table 1. Composition analysis of recycled materials used in the embodiments.

[0044] Example 1 A method for preparing lightweight high-strength steel, comprising the following steps: The recycled material (15% A, 15% B, 55% C, 15% D) was placed in a medium-frequency induction melting furnace, heated to 200°C, pre-baked for 20 minutes, and the current was set to 2000A. The material was heated at a heating rate of 260°C / h until it was completely melted to obtain the recycled material melt. After slag removal from the returned material melt, 1% aluminum by weight of the returned material is added for refining. After slag removal, a refined liquid is obtained. The refining liquid was analyzed for composition. According to the target lightweight high-strength steel composition requirements, as shown in Table 2, 7.0% of the mass of recycled aluminum particles (99.9% purity) were added. The mixture was then melted at 1550℃ and held for 15 minutes. It was then cast under argon protection. Immediately after casting, a heating agent was added. After complete combustion, rice husks were added. After complete solidification, the mixture was demolded to obtain lightweight high-strength steel.

[0045] Example 2 A method for preparing lightweight high-strength steel, the preparation process is the same as in Example 1, except that the composition of the recycled material is 20% A, 30% B, 30% C, and 20% D.

[0046] Table 2. Composition analysis of the refining solution in the examples.

[0047] Test Example 1 The composition analysis of the lightweight high-strength steels obtained in Examples 1 and 2 is shown in Table 3.

[0048] Table 3. Compositional analysis of the lightweight high-strength steel obtained in the examples.

[0049] The compositional analysis results show that the steel produced by this invention meets the compositional requirements for lightweight high-strength steel.

[0050] The utilization rate of returned material elements is calculated using the following formula: Return material element utilization rate = element content Quantity of molten steel / Total amount of elements added; The manganese utilization rates of the returned materials in Examples 1 and 2 were 90.0% and 90.2%, respectively.

[0051] Test Example 2 Inclusion analysis was performed on the lightweight high-strength steels obtained in Examples 1 and 2, and the results are shown in Table 4.

[0052] Table 4. Inclusion Analysis of Lightweight High-Strength Steel Obtained from Examples

[0053] As can be seen from Table 3, the inclusions in the steel ingots of this embodiment are grade 0.5.

[0054] Test Example 3 Surface observation of the lightweight high-strength steels obtained in Examples 1 and 2 showed no obvious defects; flaw detection tests also showed no defects.

[0055] The densities of the lightweight high-strength steels obtained in Examples 1 and 2 were tested using the water displacement method and were 6.98 g / cm³.3 6.985 g / cm 3 .

[0056] After residual water toughening, the lightweight high-strength steels obtained in Examples 1 and 2 were subjected to mechanical property tests (GB / T 228.1-2021 and GB / T 229-2020), and met the R... m ≥850MPa; R eL >450MPa; Z≥40%; A KV (-40℃)≥47J.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing lightweight high-strength steel, comprising: The returned material is pre-baked to obtain dried material; The returned material is waste generated during the machining process of lightweight high-strength steel; The pre-baking temperature is 200~400℃, and the time is 15~60min; The dried material is heated in air until it is completely melted to obtain a return material melt; the heating rate is 200~300℃ / h. Aluminum is added to the molten recycled material for refining to obtain a refined liquid; the amount of aluminum added is not less than 1% of the mass of the recycled material. The refining liquid is prepared according to the composition of the target lightweight high-strength steel, and then smelted and cast in sequence to obtain lightweight high-strength steel; inert gas is used for protection during casting.

2. The preparation method according to claim 1, characterized in that, The pre-baking temperature is 200~300℃.

3. The preparation method according to claim 1, characterized in that, The pre-baking is carried out using the residual heat from the melting process.

4. The preparation method according to claim 1, characterized in that, The preparation involves adding pure metal to the refining liquid.

5. The preparation method according to claim 4, characterized in that, The pure metal includes one or more of iron, manganese, and aluminum.

6. The preparation method according to claim 1, characterized in that, The amount of aluminum added is 1 to 2% of the mass of the returned material.

7. The preparation method according to claim 1, characterized in that, The melting temperature is 1500~1600℃.

8. The preparation method according to claim 7, characterized in that, The holding time for the melting process is 15-20 minutes.

9. The preparation method according to claim 1, characterized in that, The inert gas is argon.

10. The preparation method according to claim 1, characterized in that, After the casting is completed, a heating agent and a heat-insulating agent are added.

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