Split type tundish spray forming military and civilian dual-use high-strength boron steel and heat treatment process

Abstract

A split type tundish spray forming military dual-use high-strength boron steel and heat treatment process, characterized in that the content of alloying elements is: C 0.36-0.42wt%, Si 0.30-0.80wt%, Mn 2.40-3.80wt%, Cr 1.20-1.60wt%, Ni 0.3-0.6wt%, S 0.05-0.10wt%, P 0.05-0.10wt%, B 0.001-0.003wt%, the balance is Fe. The material smelting utilizes the characteristics of rapid solidification of spray forming, eliminates the macrosegregation in alloy steel, and makes the alloying elements uniformly distributed. At the same time, the split type tundish is used for smelting, the purity of liquid steel before spray steel is improved, the problems of the whole tundish that cannot be reused after pouring once, and the slag liquid is too much and the fluidity is not good are overcome, the uniform liquid steel temperature is reached and the inclusions are removed, the solidification of the easy loose part of the steel deposition billet is improved, so that the high-quality high-density spray high-strength steel is prepared. It can also effectively establish the liquid level of molten steel, so as to promote the floating of inclusions in the process of opening and pouring, and reduce the probability of inclusions blocking the liquid duct and entering the final ingot. By adding Ni, B and other micro-alloying elements in the steel, fine Fe2B particles are formed, the growth of dendritic grain boundary in austenite grain is limited, and then the grain growth is prevented.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spray deposition high alloy structural steel, and relates to a split type tundish spray forming high strength alloy steel and a heat treatment process. TECHNICAL BACKGROUND

[0002] The alloy structural steel has better hardenability and comprehensive mechanical properties than the carbon steel, and is widely used in various fields of military and civilian use, such as ships, vehicles, ammunition, weapons and the like. In the military aspect, with the development of weapon equipment, the alloy structural steel selected for the body material in the military ammunition industry gradually develops towards high performance; at present, the body steel mainly includes 50SiMnVB (823), 40CrMnSiB and the like, and the annual demand is 30-50 thousand tons / year, wherein the 40CrMnSiB steel mainly adopts the process flow of: electric furnace or converter smelting→LF→VD / RH→forging or rolling (bar)→heat treatment→performance detection→product processing, and the material performance can reach: after heat treatment, the tensile strength Rm is greater than or equal to 1050 MPa, the elongation A50 is greater than or equal to 12%, the reduction of area Z is greater than or equal to 45%, and K1c is greater than or equal to 50 MPam1 / 2, and the strong and tough matching performance can ensure that the material component can meet certain bearing and fragment damage element functions as a support body, and is only suitable for use in low load environment; however, if the steel is applied in a high impact load environment, there are still problems of poor fracture toughness and insufficient high impact resistance, and through improving the smelting process, improving the material grain size and improving the impact resistance of the material, the application of the material in the military high impact load structure has significant military significance. At the same time, the material can also be used in the civilian aspect, replace some high-speed steels or steels for knives and blades with high impact resistance requirements, and can create good social and economic benefits for the development of civilian high-strength steel.

[0003] The spray deposition, that is, the spray forming technology, as a short process rapid solidification material preparation technology, has great potential in improving the performance of steel materials, can overcome the problems of carbide segregation and grain coarsening of the alloy steel, can make the carbon remain in a solid solution state or a fine and dispersed state, the alloy steel has fine grains and uniform structure, and thus the material has good mechanical properties. Through the search of domestic and foreign patent standards, there is no related report on the spray deposition smelting and application of the CrMnSiB component system steel; therefore, the domestic research and development of the spray deposition military and civilian high-strength boron steel involved in the present technology is a beneficial attempt. SUMMARY

[0004] The application aims to: meet the room temperature mechanical properties: R p0.2The high-toughness impact-resistant military and civilian dual-purpose high-strength boron steel with a strength of ≥1350MPa, A ≥9%, Z ≥40%, and KIC ≥90MPam1 / 2 can be used for military large-caliber grenade body components, and can also be used for civilian high-life cutter steel, bearings, plastic molds, gears and the like.

[0005] The present application solves the above problems by adopting the technical scheme of:

[0006] A split type tundish spray forming military and civilian dual-purpose high-strength boron steel, the alloy element content is: C 0.36-0.42wt%, Si 0.30-0.80wt%, Mn 2.40-3.80wt%, Cr 1.20-1.60wt%, Ni 0.3-0.6wt%, S 0.05-0.10wt%, P 0.05-0.10wt%, B 0.001-0.003wt%, the balance is Fe.

[0007] When the material is smelted, 0.001-0.003wt% B is added to prevent grain growth, Cr, Mn and Ni elements are added to improve the strength and toughness of the material, S and B alloy elements are added to improve the cutting performance, and the influence of reducing carbon and increasing Mn on the fragmentation of the body material under military detonation conditions is compensated.

[0008] The split type tundish is used to transfer molten metal, and the molten metal is atomized to form a deposited ingot after being sprayed and deposited.

[0009] The tundish structure is split type, the outer layer of the tundish wall is a steel plate layer, the steel plate layer is sequentially provided with a heat preservation layer, a permanent layer and a working layer from outside to inside, and a cross section is arranged at the heat preservation layer, the permanent layer and the working layer of the built-in slag stop plate and can be disassembled.

[0010] The heat treatment method is that the rod or plate after forging is heated to 860℃±10℃, and is kept for 30-50min, and is oil-cooled or water-cooled to room temperature; then the rod or plate is heated to 350-700℃, and is kept for 120-180min, and is water-cooled or oil-cooled to room temperature, so that the material has high strength and toughness.

[0011] As a preferred heat treatment method, the rod or plate after forging is heated to 860℃, and is kept for 45min, and is oil-cooled to room temperature; then the rod or plate is heated to 400℃, and is kept for 150min, and is water-cooled to room temperature. This heat treatment has the best effect and is most suitable for the product of the present application.

[0012] The slag stop plate is made of 45# steel, and the shape of the molten steel outlet is "2".

[0013] The present application has the following beneficial effects:

[0014] By using the rapid solidification characteristics of spray forming, macrosegregation in alloy steel is eliminated, and alloy elements are uniformly distributed. Meanwhile, by using the split type tundish, the purity of liquid steel before spray steel casting is improved, the problems of non-reusable after one-time casting of the whole tundish, and the problems of much slag and poor fluidity are overcome, so that the uniform steel liquid temperature is reached, the inclusions are removed, the solidification of the easy-porosity part of the steel deposition billet is improved, and the high-quality high-density spray high-strength steel is prepared. The liquid level of the molten steel can be effectively established, so as to promote the floating of inclusions in the opening and casting processes, and reduce the probability of inclusions blocking the liquid guide pipe and entering the final ingot. By adding micro-alloying elements such as Ni and B in the steel, fine Fe2B particles are formed, the growth of dendritic boundaries in the austenite grain is limited, and the grain growth is prevented. After the austenite grain is refined, fine α-ferrite in the final carbon steel is formed, without affecting the thermal plasticity of the steel, so that the material has higher strength and plasticity, and the application range is wider. As the steel bar for military projectile, the diameter is 80mm-200mm, which can be used for large-caliber grenade projectile steel, and the breaking property is equivalent to that of the traditional large-caliber grenade material, so that the requirement of high-impact penetration of large-caliber grenade can be met. Meanwhile, the material is used in impact-resistant cutters and plastic molds, and the service life of the cutter and the mold made of the material is increased by more than 47% compared with the cutter and the mold made of M35 high-speed steel. BRIEF DESCRIPTION OF DRAWINGS

[0015] Table 1 Performance of forged state material of lower limit composition of example one

[0016] Table 2 Performance of forged state material of upper limit composition of example two

[0017] Table 3 Performance of forged state material of middle limit composition of example three

[0018] Table 4 Breaking property test results of forged state material of middle limit composition of example three (combined with 122 large-caliber grenade and 50SiMnVB material)

[0019] Table 5 Cutting performance test results of forged state material of middle limit composition of example three

[0020] Figure 1 Crystal phase diagram of forged state material of lower limit composition of example one

[0021] Figure 2 Crystal phase diagram of forged state material of upper limit composition of example two

[0022] Figure 3 Crystal phase diagram of forged state material of middle limit composition of example three

[0023] Figure 4 Yield strength of example one, example two and example three after quenching at 870℃ and tempering at different temperatures

[0024] Figure 5Example 1, Example 2, Example 3 elongation after quenching at 870℃ and tempering at different temperatures

[0025] Figure 6 Example 1, Example 2, Example 3 reduction of area after quenching at 870℃ and tempering at different temperatures DETAILED DESCRIPTION

[0026] The application will be further described in conjunction with the accompanying drawings and specific examples.

[0027] Example 1: The alloy composition is C 0.36wt%, Si 0.30wt%, Mn 2.40wt%, Cr 1.2wt%, Ni 0.3wt%, S 0.05wt%, P 0.05wt%, B 0.001wt%, and the balance is Fe. After quenching at 870℃ for 50min, oil cooling to room temperature; and then tempering at 650℃ for 180min, the R p0.2 , A, Z and other properties are shown in Table 1, and the grain size and phase diagram are shown in Figure 1 .

[0028] Example 2

[0029] The alloy composition is C 0.42wt%, Si 0.80wt%, Mn 3.80wt%, Cr 1.6wt%, Ni 0.6wt%, S 0.10wt%, P 0.1wt%, B 0.003wt%, and the balance is Fe. After quenching at 870℃ for 50min, oil cooling to room temperature; and then tempering at 650℃ for 180min, the R p0.2 , A, Z and other properties are shown in Table 2, and the grain size and phase diagram are shown in Figure 2 .

[0030] Example 3

[0031] The alloy composition is C 0.40wt%, Si 0.55wt%, Mn 3.10wt%, Cr 1.4wt%, Ni 0.4wt%, S 0.08wt%, P 0.08wt%, B 0.002wt%, and the balance is Fe. After quenching at 870℃ for 50min, oil cooling to room temperature; and then tempering at 650℃ for 180min, the R p0.2 , A, Z and other properties are shown in Table 3, and the grain size and phase diagram are shown in Figure 3 , the crushing test results are shown in Table 4, and the cutting performance test results are shown in Table 5.

[0032] The yield strength, elongation and reduction of area of the upper, middle and lower limit components after quenching at 870 DEG C and tempering at different temperatures are shown in Tables 1-4. Figure 4 , 5 and 6.

[0033] The outer layer of the cladding wall of the cladding is a steel plate layer, the steel plate layer is sequentially provided with a heat preservation layer, a permanent layer and a working layer from outside to inside, and the cross section of the built-in slag baffle is arranged at the positions corresponding to the heat preservation layer, the permanent layer and the working layer and is detachable. The slag baffle is made of 45# steel, the shape of the molten steel outlet is "2", and there is a buffer force, so that the slag effect is also obvious.

[0034] The above embodiments of the present application are described in detail in combination with the drawings, and those skilled in the art can make various changes to the present application according to the above description. Therefore, some details in the embodiments should not constitute a limitation on the present application, and the scope of protection of the present application will be defined by the appended claims.

[0035] Table 1: Performance of lower limit component forged state material in Example One

[0036]

[0037] Table 2: Performance of upper limit component forged state material in Example Two

[0038]

[0039] Table 3: Performance of middle limit component forged state material in Example Three

[0040]

[0041] Table 4: Fracture test results of middle limit component forged state material in Example Three

[0042]

[0043] Table 5: Cutting performance test results of middle limit component in Example Three

[0044]

[0045]

Claims

1. A split-type tundish spray forming military and civilian dual-use high-strength boron steel, characterized in that, The alloy element content is: C 0.36-0.42wt%, Si 0.30-0.80wt%, Mn 2.40-3.80wt%, Cr 1.20-1.60wt%, Ni 0.3-0.6wt%, S 0.05-0.10wt%, P 0.05-0.10wt%, B 0.001-0.003wt%, and the balance is Fe; the spray forming adopts a split type tundish, the tundish body is provided with a steel plate layer outside the tundish wall, the steel plate layer is sequentially provided with a heat preservation layer, a permanent layer and a working layer from outside to inside, and the inner stopper plate is provided with a detachable cross section corresponding to the heat preservation layer, the permanent layer and the working layer; the split type tundish spray forming can improve the liquid steel purity before the spray steel pouring; The 0.001-0.003wt% B is added during the material smelting to prevent the grain growth, the Cr, Mn and Ni elements are added to improve the strength and toughness of the material, the S and B alloy elements are added to improve the cutting performance and compensate the influence of the reduced carbon and the increased Mn on the fragmentation of the projectile body material under the military detonation condition; the spray forming makes the alloy elements uniformly distributed; The stopper plate material is 45# steel, and the shape of the stream steel port is a "2" shape.

2. The split-type tundish spray forming military and civilian dual-use high-strength boron steel according to claim 1, characterized in that, The alloy composition is: C 0.40wt%, Si 0.55wt%, Mn 3.10wt%, Cr 1.4wt%, Ni 0.4wt%, S 0.08wt%, P 0.08wt%, B 0.002wt%, and the balance is Fe.

3. The split-type tundish spray forming military and civilian dual-use high-strength boron steel according to claim 1, characterized in that, The alloy composition is: C 0.42wt%, Si 0.80wt%, Mn 3.80wt%, Cr 1.6wt%, Ni 0.6wt%, S 0.10wt%, P 0.1wt%, B 0.003wt%, and the balance is Fe.

4. The split-type tundish spray forming military and civilian dual-use high-strength boron steel according to claim 1, characterized in that, The alloy composition is: C 0.36wt%, Si 0.30wt%, Mn 2.40wt%, Cr 1.2wt%, Ni 0.3wt%, S 0.05wt%, P 0.05wt%, B 0.001wt%, and the balance is Fe.

5. The heat treatment process for the split-type tundish spray forming military and civilian dual-use high-strength boron steel according to any one of claims 1-4, characterized in that: The bar after the spray boron steel billet forging is heated to 860℃±10℃, and is kept for 30-50min, and is oil-cooled or water-cooled to room temperature; and then is heated to 350-700℃, and is kept for 120-180min, and is water-cooled to room temperature.

6. The heat treatment process of claim 5, wherein the heat treatment process is a military and civilian dual-use high-strength boron steel process. The bar after the forging is heated to 860℃, and is kept for 45min, and is oil-cooled to room temperature; and then is heated to 400℃, and is kept for 150min, and is water-cooled to room temperature.

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