CN110835670B - High-wear-resistance high-hardness easy-cutting high-end mirror surface plastic die steel and preparation method thereof - Google Patents
High-wear-resistance high-hardness easy-cutting high-end mirror surface plastic die steel and preparation method thereof Download PDFInfo
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- C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
Abstract
The invention provides high-wear-resistance high-hardness free-cutting high-end mirror surface plastic die steel and a preparation method thereof, wherein the die steel comprises the following components in percentage by weight: c: 0.50% -0.57%, Si: 0.70% -1.00%, Mn: 1.40-1.90%, P is less than or equal to 0.015%, S is less than or equal to 0.015%, Cr: 1.50% -2.30%, Mo: 0.28% -0.38%, B: 0.001% -0.002%, solid strengthening-lubricant: 1.75 to 1.98 percent, and the balance of Fe and inevitable impurities. The preparation method comprises smelting, continuous casting, soaking, two-stage controlled rolling and heat treatment; the plastic die steel has high hardness of 67HRC-69HRC, the homogeneity degree reaches 2HRC, the transverse impact performance reaches 80J-83J, the longitudinal impact performance reaches 88J-90J, which is far higher than that of the imported plastic die steel 1.2738, and the surface quality of the polished plastic die steel reaches the national standard of 14 grade.
Description
Technical Field
The invention belongs to the field of metal materials, and particularly relates to free-cutting high-end mirror surface plastic die steel with high wear resistance and high hardness and a preparation method thereof.
Background
Nowadays, the mold yield value for plastic molding in industrially developed countries is the first in the total mold yield, and the requirements on the mold steel material mainly include proper mechanical properties, good cutting processability, good polishing, pattern etching, corrosion resistance and the like according to the performance difference of plastic varieties, the requirements on shape size and quality precision. In the production link of the mold, compared with the production cost of a mold steel module, the cost required by product machining is often higher and can reach 80% of the cost of the whole mold in the production of some special products, meanwhile, the shortening of the life cycle of the product and the acceleration of the updating speed force down the compression of the production time of the mold, and the good machining performance becomes an important index for judging the quality of the mold steel material.
In order to improve the cutting performance and other comprehensive mechanical properties of plastic die steel in combination with market demands, various appropriate alloy elements are generally added into the material, so that the adjustment of the proportion, the optimization of the component design and the production process become the key points of the research of various national scholars.
The invention discloses a novel plastic die steel SPM and a preparation method thereof (application number: 201811595815.3), and the SPM comprises the following components by mass percent: 0.25% -0.29%, Si: 0.15% -0.35%, Mn: 1.4% -1.6%, Cr: 1.25% -1.45%, Mo: 0.40% -0.60%, Ni: 1.1% -1.2%, V: 0.1 to 0.15 percent. Compared with the existing steel type 718, the mass fraction of C, Cr is reduced, the contents of Mo and Ni are improved, the alloy element V is increased, the alloy cost is improved, and the homogeneity degree of 4HRC cannot meet the requirement of the performance uniformity of high-quality steel.
The invention discloses a novel plastic die steel with high toughness, high polishing and high corrosion resistance and a preparation method thereof (application number: 201811524548.0), and the plastic die steel adopts the technical scheme that the components are as follows: 0.18% -0.3%, Si: 0.1% -0.5%, Mn: 0.3% -0.48%, Cr: 11.5% -12.8%, Mo: 0.15% -0.4%, V: 0.4% -0.7%, Ni: 0.3% -0.59%, rare earth: 0.003-0.009%. The hardness of the plastic die steel is 42.2-47.7HRC, the impact energy is 368-399J, the tempering stability is obviously improved, the wear resistance is more excellent, and the like, but the hardness uniformity is poor. Patent No. 201711181166.8, a plastic die steel with corrosion resistance and a method for manufacturing the same, wherein C: 0.45% -0.55%, Si: 0.40% -0.80%, Mn: 0.80% -1.60%, V: 0.10% -0.25%, N: 0.007% -0.015%, Al: 0.005% -0.050%, Ni: 3.5% -4.0%, Cr: 8.5% -10.5%, Cu: 0.25 to 0.45 percent of the total Cr and Ni, 12 to 14.5 percent of the total Cr and Ni, complicated production process route and long raw tea period, which adopt forging-heat preservation tempering-rough processing, hot rolling-high temperature tempering-fine processing, forging-tempering-cooling, and is not in line with the development direction of the current die manufacturing industry.
The invention relates to a free-cutting plastic die steel and a heat treatment method thereof (application number: 201510897021.2), and discloses a plastic die steel, which comprises the following components: 0.26-0.28, Mn: 1.4-1.8, Si: 0.4-0.5, Cr: 1.3-1.5, Mo: 0.2-0.4, S: 0.06-0.07, Pb: 0.06-0.07, N is less than or equal to 0.01, P is less than or equal to 0.025, Cu is less than or equal to 0.1, and Ni is less than or equal to 0.15, and S and Pb are added into the components to improve the cutting performance of the die steel, so that the die steel has higher hardness, but the impact toughness and the performance homogeneity cannot be ensured.
The invention discloses a heat treatment process of plastic die steel (application number: 201711004718.8). The technical scheme adopts three times of continuous tempering treatment, the total tempering time is 10-16h, the full section hardness is 30-35HRC, the production cost is high, the production period is long, and the product hardness is not improved.
The invention discloses a high-toughness plastic die steel and a production method thereof (application number: 201711181181.2), and the plastic die steel comprises the following components: 0.55-0.75, Mn: 2.00% -3.50%, Mo: 0.45% -0.50%, Cr: 2.00% -3.00%, Sr: 0.40% -0.60%, Ni: 0.80% -1.20%, S: 0.02% -0.04%, V: 0.20% -0.30%, Ca: 0.004%. The heat treatment process of normalizing and tempering is adopted to refine crystal grains, the impact toughness is higher, and the easy cutting effect is obvious, but specific performance indexes are not available and cannot be compared.
The invention discloses plastic die steel and a preparation method thereof (application number: 200710038193.X), wherein Cu in the plastic die steel is as follows: 0.6% -2.3%, Ni: 0.36-1.00%, the ratio of Ni/Cu is greater than 1/3 and less than or equal to 1/2, the ratio of Ni/Cu is low, a copper-enriched layer is easily formed on the surface of steel, the combination between a matrix and the surface is crisp, the grain boundary strength is low, cracks are easily formed at high temperature, and cracking occurs.
The surface hardness of a plastic die steel plate disclosed in the invention of an alloy plastic die steel plate and a production method thereof (application No. 200910312255.0) is more than or equal to 280HB, and cannot represent the section hardness and cannot explain the problem of homogeneity of the steel plate.
In conclusion, China should continue to strengthen the development and research of high-end die steel, combine advantages of self energy, technology and the like to form a series of self, and enable the production of plastic die steel in China to reach standardization and refinement.
Disclosure of Invention
The invention aims to overcome the problems and the defects and provide high-wear-resistance high-hardness free-cutting high-end mirror surface plastic die steel and a preparation method thereof, which have the advantages of high cost and die steel performance, high wear resistance, high hardness, low surface roughness, excellent comprehensive performance of free-cutting and high-efficiency production process.
The purpose of the invention is realized as follows:
the high-wear-resistance high-hardness free-cutting high-end mirror surface plastic die steel comprises the following components in percentage by weight: c: 0.50% -0.57%, Si: 0.70% -1.00%, Mn: 1.40-1.90%, P is less than or equal to 0.015%, S is less than or equal to 0.015%, Cr: 1.50% -2.30%, Mo: 0.28% -0.38%, B: 0.001% -0.002%, solid strengthening-lubricant: 1.75 to 1.98 percent, and the balance of Fe and inevitable impurities.
The solid strengthening-lubricating agent in the die steel comprises the following components in parts by weight: ti: mg: al: fe ═ (2.0-3.1): (1.0-2.1): (3.0-4.1): (212.5-237.5), ball-milling Ti, Mg, Al and Fe in a planetary ball mill for more than 24 hours to form a supersaturated solid solution, forming by adopting a hot isostatic pressing mode, and dispersing and distributing the Ti, Mg and Al in the die steel in a nano-scale oxide form. Smelting in a steel ladle, and performing a series of processes such as continuous casting, rolling, heat treatment and the like, wherein the interaction of various elements of the solid strengthening-lubricating agent and alloy elements in the die steel can form fine and dispersed nano-structure oxides which are uniformly distributed in the steel, and the functions of the nano-structure oxides are as follows: firstly, the nano-scale oxide is uniformly dispersed in the steel, so that the strength and the hardness can be obviously improved, the crystal grains can be refined, the fine-grain strengthening effect is achieved, and the toughness is improved; secondly, the nanometer oxide particles can be used as a plastic binder and a solid lubricant to reduce the abrasion during compensation and friction, and particularly, the oxide particles are dispersed in a material matrix to effectively reduce the abrasion of a cutter and improve the cutting performance.
The invention has the following design reasons:
c: the martensite steel is the most traditional and economic strengthening element in steel, and alloy carbides precipitated by dispersion can be formed in the steel. In the case of plastic die steel, a part of carbon in the steel enters the matrix of the steel to cause solid solution strengthening, and another part of carbon combines with carbide-forming elements in the alloying elements to form alloyed carbides. When the steels with different C contents are subjected to heat treatment to the same hardness, the steels with high C contents have better wear resistance, and the wear resistance of the die steel is improved along with the increase of the C contents. In order to ensure the comprehensive performance of the plastic die steel and improve the wear resistance, the content of the C is selected to be 0.50-0.57%.
Si: the steel is solid-dissolved in ferrite without forming carbide, is an important solid-solution strengthening element, can obviously improve the strength and hardness of the steel, can improve the quenching temperature and improves the hardenability. Si is also an effective element for improving the tempering resistance, the diffusion speed of carbon in ferrite is reduced, carbides separated out during tempering are not easy to aggregate, and the tempering stability is improved. The Si content in the range of less than 1% hardly reduces the plasticity of the steel, and although addition of an appropriate amount of Si contributes to improvement of the toughness of the steel, spheroidized carbides become larger in size and increase in spacing with increase in the Si content, promote segregation, form a band-shaped structure, and make the transverse properties lower than the longitudinal properties. Therefore, the content of Si added is 0.70-1.00%.
Mn: the Mn-containing steel is a solid solution strengthening element in the steel, so that crystal grains are refined, the ductile-brittle transition temperature is reduced, and the property and the shape of an oxide formed during solidification of the steel can be changed by the Mn-containing steel. Meanwhile, the high-melting-point FeS has larger affinity with S, so that the formation of low-melting-point FeS on grain boundaries can be avoided, and the hot workability of the steel is improved. The content of Mn added is 1.40-1.90%.
P, S: the excessive addition of a certain amount of S can affect the homogeneity and the purity of steel, the addition of a certain amount of S can improve the cutting performance of the steel, the S is distributed in the steel in a MnS form, MnS inclusions cut off the continuity of a matrix structure and play a role in lubrication, so the cutting performance of the material is improved, but the excessive S exists in the steel and is easy to form eutectic compounds with O, Mn, Fe and the like in the steel, the eutectic compounds are remained on a grain boundary in a film form after molten steel is solidified in the continuous casting molten steel cooling process, and microcracks are generated in the steel due to the existence of the eutectic compounds with low melting points during rolling, and the S content and the total oxygen content in the steel are difficult to be accurately controlled, so that S series addition elements are not adopted as forming elements of the easy-cutting phase, and the addition of P is not more than 0.015 percent and not more than 0.015 percent of S are selected.
Cr: chromium has a favourable effect on the wear resistance, high temperature strength, as well as on the as-rolled hardness, toughness and hardenability of the steel. Part of the chromium is dissolved in the matrix to play a role in solid solution strengthening, and the other part of the chromium is combined with the carbon to form carbide. Chromium is dissolved in austenite during quenching and heating and is dissolved in martensite after quenching, so that the tempering softening resistance of the steel can be improved, the chromium is separated out from a matrix during tempering, alloy carbides are generally formed, and the chromium tends to coarsen along with the increase of the tempering temperature and the prolonging of time. The invention selects the Cr content of 1.50-2.30%.
Mo: the alloy elements added into the steels of DIN 1.2738, GB 3Cr2MnNiMo, Swedish 718 and the like are mainly Ni, but the cores are not easy to be completely quenched, and block-shaped ferrite is easy to appear, which affects the homogeneity of the steel structure and performance. Meanwhile, Ni can improve the toughness of steel and reduce the heat conductivity coefficient, so that the deformation force is large during cutting and machining, and meanwhile, turning is not easy to peel off, so that cutting heat is not easy to dissipate, the temperature of the hard alloy cutter is increased quickly, and a plurality of turning chips are wound on a sample, so that the surface of the sample is rough finally. Therefore, the content of Mo is increased without adding Ni. With molybdenum in the steel improving the quality of the steelHardenability while forming Mo in the steel2C and MoC carbides, both of which have high hardness and high decomposition temperature. The C curve of the steel grade of the invention can be shifted to the right by increasing the content of Mo, the ferrite-pearlite curve in a high-temperature area can be obviously shifted to the right, and the occurrence of core ferrite is avoided. The content of Mo added in the invention is 0.28-0.38%.
B: boron atoms solid-dissolved in austenite tend to segregate to austenite grain boundaries due to the size effect, inhibit ferrite nucleation at the grain boundaries, and strongly improve hardenability of steel. When the same ocean permeability is obtained, the addition of the alloy elements is more beneficial to the weldability of the steel than other alloy elements, and a large amount of expensive alloy elements such as nickel, chromium, molybdenum and the like can be saved. Research shows that the mechanical property of the steel plate is obviously influenced by adding the ultra-micro boron, the strength of the boron-containing steel plate is far higher than that of the steel plate without boron under the same rolling and heat treatment conditions, and the influence of the boron on the comprehensive mechanical property of the steel plate is more obvious especially for thick-specification steel plates. Therefore, the content of the B selected and added in the invention is 0.001-0.002%.
Solid fortification-lubricants: the solid strengthening-lubricating agent consists of Ti, Mg, Al and Fe elements, and the components of the solid strengthening-lubricating agent are as follows by weight: mg: al: fe ═ (2.0-3.1): (1.0-2.1): (3.0-4.1): (212.5-237.5). And ball-milling the 4 kinds of powder in a planetary ball mill for 24 hours to form a supersaturated solid solution, and forming by adopting a hot isostatic pressing mode. The steel is put into a steel ladle for smelting, fine and dispersed nano-structure oxides can be formed and uniformly distributed in the steel, and the steel has the following two functions: firstly, the nano-scale oxide is uniformly dispersed in the steel, so that the strength and the hardness can be obviously improved, the crystal grains can be refined, the fine-grain strengthening effect is achieved, and the toughness is improved; and secondly, the nano-scale oxide particles can be used as a plastic binder and a solid lubricant to reduce the abrasion during compensation and friction, and particularly, the oxide particles are dispersed in a material matrix to effectively reduce the abrasion of a cutter and improve the cutting performance. In terms of cutting performance, oxides are considered as harmful inclusions in the past, sulfides are considered as favorable inclusions, the solid strengthening-lubricating agent formed by four components of Ti, Mg, Al and Fe is dispersed and uniformly distributed in a matrix, harmful oxides formed by other elements are wrapped or decomposed, the lubricating effect is achieved, and the strength and the toughness can be remarkably improved by refining grains. The solid strengthening-lubricating agent has different effects due to different proportions of the added elements and contents in steel, and the mechanical property of the steel plate is reduced due to insufficient or excessive addition, so that the content of the solid strengthening-lubricating agent is 1.75-1.98% by selecting.
The second technical scheme of the invention provides a preparation method of high-wear-resistance high-hardness free-cutting high-end mirror surface plastic die steel, which comprises smelting, continuous casting, soaking, two-stage controlled rolling and heat treatment;
soaking the raw materials: keeping the temperature of the continuous casting blank at 1150-1200 ℃ for 240-280 min;
two-stage controlled rolling: rolling at 1050-1100 deg.c, the first two rolling reduction rates in the rolling stage being 18-22%, the final rolling temperature in the finishing rolling stage being 840-920 deg.c, and the first two rolling reduction rates in the finishing rolling stage being 20-24%; obtaining the finished product of steel plate with the thickness of 20-180mm, and the finishing rolling temperature of the steel plate is close to AC3The temperature can reduce segregation or the occurrence probability of segregation, and the air cooling is carried out to 400-500 ℃ and then the mixture is loaded into a heat treatment furnace, so that the production efficiency can be improved, the energy can be saved, and the loss of coal gas can be reduced.
The heat treatment is step-by-step quenching plus 2 times tempering; the method specifically comprises the following steps:
the step-by-step quenching process comprises the following steps:
heating to 890-910 ℃; keeping the temperature for 20min to 100min, and then air-cooling to 850 ℃ to 880 ℃; preserving the heat for 30min-150min, and then cooling to room temperature by water;
and (3) tempering for 2 times: then, carrying out tempering treatment on the steel plate for 2 times; tempering temperature: keeping the temperature at 350-400 ℃ for 40-240 min.
The step quenching process of 890-910 ℃ multiplied by 20min-100min + 850-880 ℃ multiplied by 30min-150min and water cooling to room temperature is adopted, the process can obviously refine the crystal grains of the die steel, the structure is more uniform step by step, and the comprehensive mechanical property of the steel plate is improved, because the quenching is based on the phase transition critical point of the material, the material forms fine and uniform austenite crystal grains in the heating process, and the material is rapidly cooled to below the martensite start transformation temperature at the cooling speed higher than the critical cooling speed to perform martensite transformation, so that a fine martensite structure is obtained. Compared with the conventional quenching process, the step-by-step quenching can ensure that the martensite transformation process is smoother and more uniform, thereby obtaining finer structure, refining the crystal grains of the plastic die steel material and ensuring that the structure distribution is more uniform.
Then, carrying out tempering treatment on the steel plate for 2 times; tempering temperature: keeping the temperature at 350-400 ℃ for 40-240 min. The invention adopts 2 times of tempering processes, and has the two reasons that firstly, compared with the primary tempering, the secondary tempering can more effectively eliminate the residual stress generated during the quenching of the material and avoid the microcracks of the material; secondly, the internal microscopic structure of the material can be better stabilized, so that the material has better comprehensive performance.
The invention has the beneficial effects that: the invention adopts Ni-removing Mo-increasing and B-microalloying and simultaneously adds a proper amount of solid strengthening-lubricating agent. The plastic die steel is produced by adopting the process of continuous casting, soaking, two-stage controlled rolling, step quenching and secondary tempering, so that the plastic die steel has the high hardness of 67HRC-69HRC, the homogeneity degree reaches 2HRC, the transverse impact performance reaches 80J-83J, the longitudinal impact performance reaches 88J-90J, and the hardness is far higher than that of the imported plastic die steel 1.2738. After the plastic die steel is polished, the surface roughness is Ra0.005-0.01 mu m, reaches the national standard 14 grade (highest grade), and simultaneously has good wear resistance and easy cutting. The high-end mirror surface die steel provided by the invention conforms to the future development direction of die steel, and is high-quality die steel with development potential.
Drawings
FIG. 1 is a comparison of the wear loss of the inventive example steel and the comparative example steel.
FIG. 2 is a graph showing the surface roughness after polishing of the steel according to the example of the present invention and the steel according to the comparative example,
FIG. 3 shows the amount of wear at the tip of the steel according to the example of the present invention and the steel according to the comparative example.
Detailed Description
The present invention is further illustrated by the following examples.
According to the embodiment of the invention, the smelting-continuous casting-soaking-two-stage controlled rolling-heat treatment is carried out according to the component proportion of the technical scheme.
The continuous casting blank is kept at 1150-1200 ℃ for 240-280 min, rolling is started at 1050-1100 ℃, the reduction rate of the first two passes is 18-22%, finish rolling is carried out at 840-920 ℃ in the finish rolling stage, the reduction rate of the first two passes is 20-24%, and a steel plate with the thickness of 20-180mm is obtained; air cooling to 400-500 deg.c and loading into heat treating furnace;
the heat treatment is step-by-step quenching plus 2 times tempering; the method specifically comprises the following steps:
the step-by-step quenching process comprises the following steps: heating to 890-910 ℃; keeping the temperature for 20min to 100min, and then air-cooling to 850 ℃ to 880 ℃; preserving the heat for 30min-150min, and then cooling to room temperature by water;
and (3) tempering for 2 times: then, carrying out tempering treatment on the steel plate for 2 times; tempering temperature: keeping the temperature at 350-400 ℃ for 40-240 min.
The compositions of the steels of the examples of the invention are shown in table 1. The composition ratio of the steel solid strengthening-lubricating agent in the embodiment of the invention is shown in Table 2. The main process parameters of the heating rolling of the steel of the embodiment of the invention are shown in Table 3. The main process parameters of the heat treatment of the steel of the embodiment of the invention are shown in Table 4. The Rockwell hardness of the steels of the examples of the invention is shown in Table 5. The impact properties of the steels of the examples of the invention are shown in Table 6.
TABLE 1 composition (wt%) of steels of examples of the present invention
TABLE 2 Steel solid strengthening-Lubricant composition in wt% of inventive examples
TABLE 3 heating-Rolling Main Process parameters of steels according to the examples of the invention
TABLE 4 Heat treatment of steels of examples of the invention
TABLE 5 Rockwell hardness of steels according to examples of the invention
TABLE 6 impact properties of steels of examples of the invention
In order to describe the present invention, the above embodiments are properly and fully described by way of examples, and the above embodiments are only used for illustrating the present invention and not for limiting the present invention, and those skilled in the relevant art can make various changes and modifications without departing from the spirit and scope of the present invention, and any modifications, equivalent substitutions, improvements, etc. should be included in the protection scope of the present invention, and the protection scope of the present invention should be limited by the claims.
Claims (3)
1. The high-wear-resistance high-hardness free-cutting high-end mirror surface plastic die steel is characterized by comprising the following components in percentage by weight: c: 0.50% -0.57%, Si: 0.70% -1.00%, Mn: 1.40-1.90%, P is less than or equal to 0.015%, S is less than or equal to 0.015%, Cr: 1.50% -2.30%, Mo: 0.28% -0.38%, B: 0.001% -0.002%, solid strengthening-lubricant: 1.75-1.98 percent, and the balance of Fe and inevitable impurities; the solid strengthening-lubricating agent in the die steel comprises the following components in parts by weight: ti: mg: al: fe = (2.0-3.1): (1.0-2.1): (3.0-4.1): (212.5-237.5).
2. The high-wear-resistance high-hardness free-cutting high-end mirror surface plastic die steel as claimed in claim 1, wherein components Ti, Mg, Al and Fe of the solid strengthening-lubricating agent in the die steel are ball-milled in a ball mill for more than 24h to form a supersaturated solid solution, and the Ti, Mg and Al are dispersed and distributed in the die steel in a form of nano-scale oxides.
3. A method for preparing the high wear resistance, high hardness and easy cutting high-end mirror surface plastic die steel as claimed in claim 1 or 2, which comprises smelting, continuous casting, soaking, two-stage controlled rolling and heat treatment; the method is characterized in that:
soaking the raw materials: keeping the temperature of the continuous casting blank at 1150-1200 ℃ for 240-280 min;
two-stage controlled rolling: rolling at 1050-1100 ℃, wherein the reduction rate of the first two passes of the rolling stage is 18-22%, the finish rolling temperature of the finish rolling stage is 840-920 ℃, and the reduction rate of the first two passes of the finish rolling stage is 20-24%; then air-cooling to 400-500 deg.C, loading into heat treatment furnace;
and (3) heat treatment: step-by-step quenching and 2 times tempering;
the method specifically comprises the following steps:
the step-by-step quenching process comprises the following steps: heating to 890-910 ℃; keeping the temperature for 20min to 100min, and then air-cooling to 850 ℃ to 880 ℃; preserving the heat for 30min-150min, and then cooling to room temperature by water;
and (3) tempering for 2 times: then, carrying out tempering treatment on the steel plate for 2 times;
tempering temperature: keeping the temperature at 350-400 ℃ for 40-240 min, and cooling to room temperature.
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| CN112251686B (en) * | 2020-09-29 | 2022-03-18 | 中国科学院金属研究所 | Ultrahigh-strength nanocrystalline 4Cr5MoWSi die steel and preparation method thereof |
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