CN115852261A - Mirror surface plastic die steel with uniform section hardness and manufacturing method thereof - Google Patents
Mirror surface plastic die steel with uniform section hardness and manufacturing method thereof Download PDFInfo
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- 238000005496 tempering Methods 0.000 claims description 23
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Abstract
The invention discloses mirror surface plastic die steel with uniform section hardness and a manufacturing method thereof, wherein the mirror surface die steel comprises the following chemical components in percentage by mass: c:0.35 to 0.45%, si:0.40 to 0.60%, mn:0.40 to 0.70%, cr:6.50 to 8.00%, ni:0.10 to 0.30%, mo:0.50 to 0.70%, V:0.50 to 0.70%, al: 0.020-0.060%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, O is less than or equal to 0.0015%, N: 0.020-0.040%, the manufacturing method comprises the steps of electrode blank preparation, electrode blank annealing, electroslag remelting, heating forging, forge piece annealing, heat treatment and the like. The mirror surface plastic die steel manufactured by the invention has high hardness and good hardenability, the whole section hardness of the mirror surface plastic die steel is stably kept at 49-52 HRC, the maximum section hardness difference is less than or equal to 2HRC, the hardness distribution is uniform, and the high requirement of the field on the hardness distribution uniformity of the large-section mirror surface plastic die steel is completely met.
Description
Technical Field
The invention belongs to the technical field of plastic die steel, and particularly relates to mirror surface plastic die steel with uniform section hardness and a manufacturing method thereof.
Background
With the development of the plastic industry, the demand for transparent plastic parts and bright appearance parts is rapidly increased, and the mirror surface performance becomes an important index for evaluating the technological performance of plastic die steel. The high mirror surface mold requires that the material must have high purity and high hardness uniformity to ensure that the polishing performance meets the high requirements of the appearance of the plastic product. In addition, the increasing demand for large-scale high-surface-quality plastic products requires that the molds be enlarged more and more, and the production difficulty of plastic mold steel is increased.
Therefore, continuously improving the mechanical properties and the structural properties of the plastic die steel is a key direction for research and improvement of those skilled in the art, and although a certain exploration has been made in the prior art in the aspects of improving the purity of steel and improving the mirror surface properties of die steel by strictly controlling the metallurgical process, how to effectively improve the purity and the hardness uniformity from the sources of chemical composition design, manufacturing process and the like, especially the uniformity of hardness distribution of large-section plastic die steel is a technical problem that needs to be solved urgently by those skilled in the art.
Disclosure of Invention
In order to solve the above problems, the present invention provides a mirror surface plastic mold steel having uniform section hardness and a method for manufacturing the same.
The invention provides a manufacturing method of mirror surface plastic die steel with uniform section hardness, which comprises the following steps:
preparing an electrode blank: proportioning raw materials according to the component content requirement of a mirror surface die steel target product, carrying out an electric furnace smelting process, an LF refining process and a VD treatment process, and then casting into an electrode blank, wherein the component content of the mirror surface die steel target product is as follows according to the mass fraction: c:0.35 to 0.45%, si:0.40 to 0.60%, mn:0.40 to 0.70%, cr:6.50 to 8.00%, ni:0.10 to 0.30%, mo:0.50 to 0.70%, V:0.50 to 0.70%, al: 0.020-0.060%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, O is less than or equal to 0.0015%, N: 0.020-0.040%, and the balance of Fe and inevitable impurities;
(II) annealing the electrode blank: preheating the electrode blank at 350-450 ℃ for 2-3 h, raising the temperature to 700-750 ℃ at the speed of 80-100 ℃/h, then preserving the heat, calculating the heat preservation time according to 1.5-2.0 min/mm based on the diameter of the electrode blank, and then cooling the electrode blank in a furnace to below 200 ℃ at the speed of less than or equal to 40 ℃/h and discharging the electrode blank;
(III) electroslag remelting: after the annealed electrode blank is subjected to surface grinding treatment, caF is adopted 2 CaO and Al 2 O 3 Smelting the ternary slag system, adding a deoxidizing agent in the smelting process, and smelting to obtain an electroslag ingot;
(IV) heating and forging: carrying out hot feeding on an electroslag ingot into a furnace, keeping the temperature of 630-700 ℃ for 2-3 h, heating to 800-850 ℃ within 2-4 h, keeping the temperature for 3-6 h, heating to 1220-1260 ℃ within 4-6 h, keeping the temperature for 15-20 h, discharging the electroslag ingot out of the furnace, forging into a steel plate, controlling the start forging temperature to be 1100-1180 ℃, and controlling the finish forging temperature to be more than or equal to 900 ℃;
(V) annealing the forged piece: charging the steel plate at the temperature of below 300 ℃, heating the steel plate to the temperature of between 630 and 700 ℃ at the speed of between 60 and 80 ℃/h, preserving the heat for 2 to 3 hours, heating the steel plate to the temperature of between 850 and 900 ℃ at the speed of less than or equal to 60 ℃/h, preserving the heat for 10 to 15 hours, cooling the steel plate to the temperature of between 400 and 500 ℃ after the heat preservation is finished, and discharging the steel plate for air cooling;
(VI) heat treatment: the method comprises a quenching process and a tempering process, wherein in the quenching process, the annealed steel plate is heated to 850-900 ℃ at the speed of 60-80 ℃/h and then is kept warm for 5-8 h, then the steel plate is heated to 1010-1050 ℃ at the speed of 60-80 ℃/h and then is kept warm, the heat preservation time is calculated according to the thickness of the steel plate at 2-3 min/mm, the steel plate is taken out of a furnace and is quenched to the room temperature by water, in the tempering process, the quenched steel plate is heated to 500-550 ℃ at the speed of less than or equal to 60 ℃/h and then is kept warm, the heat preservation time is calculated according to the thickness of the steel plate at 3-4 min/mm, and the steel plate is taken out of the furnace and is cooled to the room temperature by air.
Further, in the manufacturing method of the mirror surface plastic die steel with uniform section hardness, in the electrode blank preparation step, an electric furnace smelting process is carried out in an eccentric bottom tapping electric furnace by adopting an oxidation method smelting process, when the C of molten steel in the electric furnace is less than or equal to 0.09 percent, the P is less than or equal to 0.008 percent and the temperature is more than or equal to 1640 ℃, tapping is sent into an LF furnace, steel and slag remaining operation is adopted during tapping, aluminum is added during tapping for precipitation deoxidation, and slag making materials are added for making new slag; the LF refining process comprises the following steps: introducing argon gas to stir after molten steel arrives at a station, white slag is produced in the whole refining process, the alkalinity R is controlled to be 3.2-4.5, calcium silicate powder is adopted for diffusion deoxidation, the white slag holding time is controlled to be more than or equal to 20min, fine adjustment of components is carried out after full deoxidation, and the molten steel is taken out of the station and transferred to a VD furnace when the temperature is 1650-1670 ℃; the VD processing procedure comprises the following steps: vacuumizing the molten steel after arriving at a station, controlling the vacuum degree in the furnace to be less than or equal to 67Pa, keeping the vacuum degree for 20-30 min, performing aluminum alloying by adopting an aluminum wire feeding mode, stirring by adopting argon, keeping the slag surface to be slightly moved without exposing the molten steel in the argon stirring process, stopping argon blowing after the components are uniformly stirred, changing the bottom blowing of high-purity nitrogen into bottom blowing of high-purity nitrogen, blowing nitrogen for 6-10 min at the flow rate of 600NL/min for performing nitrogen alloying, and leaving the station when the temperature is 1560-1580 ℃, wherein the [ H ] in the discharged molten steel is controlled to be less than or equal to 1.0ppm.
Furthermore, in the method for manufacturing the mirror surface plastic die steel with uniform section hardness, the slag-making material in the electric furnace smelting process comprises ferrosilicon, fluorite and lime.
Further, in the above method for manufacturing mirror surface plastic mold steel with uniform section hardness, caF is used in the step of electroslag remelting 2 CaO and Al 2 O 3 CaF in ternary slag system 2 CaO and Al 2 O 3 The ratio of the deoxidizer to the silicon calcium powder is controlled to be 6.
Further, in the above method for manufacturing mirror surface plastic die steel with uniform section hardness, in the step of heating and forging, the forging is performed in a manner of "two-pier two-drawing", and the forging ratio is controlled to be 5 or more.
Further, in the above method for manufacturing mirror surface plastic die steel having uniform section hardness, the diameter of the electrode blank cast in the electrode blank manufacturing step is controlled to be 450mm, the diameter of the electroslag ingot smelted in the electroslag remelting step is controlled to be 790mm or 830mm, the thickness of the steel plate forged in the heating forging step is controlled to be 150 to 300mm, the tempering temperature of the steel plate having a thickness of 100 to 200mm is controlled to be 530 to 550 ℃ and the tempering temperature of the steel plate having a thickness of more than 200mm is controlled to be 510 to 540 ℃.
The mirror surface plastic die steel with uniform section hardness provided by the invention is manufactured by the manufacturing method, and the mirror surface plastic die steel comprises the following chemical components in percentage by mass: c:0.35 to 0.45%, si:0.40 to 0.60%, mn:0.40 to 0.70%, cr:6.50 to 8.00%, ni:0.10 to 0.30%, mo:0.50 to 0.70%, V:0.50 to 0.70%, al: 0.020-0.060%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, O is less than or equal to 0.0015%, N: 0.020-0.040%, and the balance of Fe and inevitable impurities.
Optionally, in the mirror-surface plastic mold steel with uniform section hardness, the mirror-surface plastic mold steel comprises the following chemical components in percentage by mass: c:0.36%, si:0.47%, mn:0.53%, P:0.011%, S:0.002%, cr:6.83%, ni:0.16%, mo:0.53%, V:0.54%, al:0.043%, N:0.026%, and the balance of Fe and inevitable impurities.
Optionally, in the mirror surface plastic mold steel with uniform section hardness, the mirror surface plastic mold steel comprises the following chemical components in percentage by mass: c:0.37%, si:0.46%, mn:0.52%, P:0.008%, S:0.002%, cr:7.12%, ni:0.21%, mo:0.54%, V:0.56%, al:0.051%, N:0.025%, and the balance of Fe and inevitable impurities.
Optionally, in the mirror surface plastic mold steel with uniform section hardness, the mirror surface plastic mold steel comprises the following chemical components in percentage by mass: c:0.36%, si:0.51%, mn:0.56%, P:0.009%, S:0.002%, cr:7.30%, ni:0.28%, mo:0.56%, V:0.58%, al:0.049%, N:0.028%, and the balance of Fe and inevitable impurities.
The mirror surface plastic die steel with uniform section hardness and the manufacturing method thereof have the following advantages and beneficial effects:
1. the mirror surface plastic die steel manufactured by the invention has high hardness and good hardenability, the hardness of the whole section of the mirror surface plastic die steel is stably kept at 49-52 HRC, the maximum section hardness difference is less than or equal to 2HRC, the hardness distribution is uniform, and the high requirement of the field on the hardness distribution uniformity of the large-section mirror surface plastic die steel is completely met;
2. the manufacturing method of the mirror surface plastic die steel with uniform section hardness can fully play the reinforcing role of the microalloy and control uniform precipitation, eliminate white points, improve the transverse performance of products, refine crystal grains and realize tissue homogenization and compactness, thereby meeting the mirror surface polishing requirement of the die steel and ensuring the performances of corrosion resistance, wear resistance and the like. Through test determination, the flaw detection grade of the mirror plastic die steel manufactured by the invention meets the 4-grade requirement of GB/T6402-2008, the grain size is more than or equal to 8 grade, the polishing performance is excellent, the mirror plastic die steel can be polished to 10000#, the polishing rate is as high as 95 percent, and the mirror plastic die steel is particularly suitable for manufacturing plastic dies with strict requirements on dimensional accuracy, surface roughness and the like and complex cavities.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic view showing the results of the full thickness hardness curve test of the mirror surface plastic mold steel manufactured by the method for manufacturing mirror surface plastic mold steel having uniform section hardness according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
In one aspect of the present invention, the method for manufacturing mirror surface plastic mold steel having uniform sectional hardness according to the present invention comprises the steps of:
preparing an electrode blank: proportioning raw materials according to the component content requirement of a mirror surface die steel target product, carrying out an electric furnace smelting process, an LF refining process and a VD treatment process, and then casting into an electrode blank, wherein the component content of the mirror surface die steel target product is as follows according to the mass fraction: c:0.35 to 0.45%, si:0.40 to 0.60%, mn:0.40 to 0.70%, cr:6.50 to 8.00%, ni:0.10 to 0.30%, mo:0.50 to 0.70%, V:0.50 to 0.70%, al: 0.020-0.060%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, O is less than or equal to 0.0015%, and N:0.020 to 0.040 percent, and the balance of Fe and inevitable impurities;
(II) annealing the electrode blank: preheating the electrode blank at 350-450 ℃ for 2-3 h, raising the temperature to 700-750 ℃ at the speed of 80-100 ℃/h, then preserving the heat, calculating the heat preservation time according to 1.5-2.0 min/mm based on the diameter of the electrode blank, and then cooling the electrode blank in a furnace to below 200 ℃ at the speed of less than or equal to 40 ℃/h and discharging the electrode blank;
(III) electroslag remelting: after the annealed electrode blank is subjected to surface grinding treatment, caF is adopted 2 CaO and Al 2 O 3 Smelting the ternary slag system, adding a deoxidizing agent in the smelting process, and smelting to obtain an electroslag ingot;
(IV) heating and forging: carrying out hot feeding on an electroslag ingot into a furnace, keeping the temperature of 630-700 ℃ for 2-3 h, heating to 800-850 ℃ within 2-4 h, keeping the temperature for 3-6 h, heating to 1220-1260 ℃ within 4-6 h, keeping the temperature for 15-20 h, discharging the electroslag ingot out of the furnace, forging into a steel plate, controlling the start forging temperature to be 1100-1180 ℃, and controlling the finish forging temperature to be more than or equal to 900 ℃;
(V) annealing the forged piece: charging the steel plate at the temperature of below 300 ℃, heating the steel plate to the temperature of between 630 and 700 ℃ at the speed of between 60 and 80 ℃/h, preserving the heat for 2 to 3 hours, heating the steel plate to the temperature of between 850 and 900 ℃ at the speed of less than or equal to 60 ℃/h, preserving the heat for 10 to 15 hours, cooling the steel plate to the temperature of between 400 and 500 ℃ after the heat preservation is finished, and discharging the steel plate for air cooling;
(VI) heat treatment: the method comprises a quenching process and a tempering process, wherein in the quenching process, the annealed steel plate is heated to 850-900 ℃ at the speed of 60-80 ℃/h and then is kept warm for 5-8 h, then the steel plate is heated to 1010-1050 ℃ at the speed of 60-80 ℃/h and then is kept warm, the heat preservation time is calculated according to the thickness of the steel plate at 2-3 min/mm, the steel plate is taken out of a furnace and is quenched to the room temperature by water, in the tempering process, the quenched steel plate is heated to 500-550 ℃ at the speed of less than or equal to 60 ℃/h and then is kept warm, the heat preservation time is calculated according to the thickness of the steel plate at 3-4 min/mm, and the steel plate is taken out of the furnace and is cooled to the room temperature by air.
In the manufacturing method of the mirror surface plastic die steel with uniform section hardness, in the electrode blank preparation step, an electric furnace smelting process is carried out in an eccentric bottom tapping electric furnace by adopting an oxidation method smelting process, when the C of molten steel in the electric furnace is less than or equal to 0.09 percent, the P is less than or equal to 0.008 percent and the temperature is more than or equal to 1640 ℃, tapping is sent into an LF furnace, steel and slag remaining operation is adopted during tapping, aluminum is added in the tapping process for precipitation deoxidation, and slag making materials are added to make new slag; the LF refining process comprises the following steps: introducing argon gas to stir after molten steel arrives at a station, white slag is produced in the whole refining process, the alkalinity R is controlled to be 3.2-4.5, calcium silicate powder is adopted for diffusion deoxidation, the white slag holding time is controlled to be more than or equal to 20min, fine adjustment of components is carried out after full deoxidation, and the molten steel is taken out of the station and transferred to a VD furnace when the temperature is 1650-1670 ℃; the VD processing procedure comprises the following steps: vacuumizing the molten steel after arriving at a station, controlling the vacuum degree in the furnace to be less than or equal to 67Pa, keeping the vacuum degree for 20-30 min, performing aluminum alloying by adopting an aluminum wire feeding mode, stirring by adopting argon, keeping the slag surface to be slightly moved without exposing the molten steel in the argon stirring process, stopping argon blowing after the components are uniformly stirred, changing the bottom blowing of high-purity nitrogen into bottom blowing of high-purity nitrogen, blowing nitrogen for 6-10 min at the flow rate of 600NL/min for performing nitrogen alloying, and leaving the station when the temperature is 1560-1580 ℃, wherein the [ H ] in the discharged molten steel is controlled to be less than or equal to 1.0ppm.
Further, the slag-making material in the electric furnace smelting process comprises ferrosilicon, fluorite and lime.
In the method for manufacturing mirror surface plastic die steel with uniform section hardness, caF is adopted in the electroslag remelting step 2 CaO and Al 2 O 3 CaF in ternary slag system 2 CaO and Al 2 O 3 The ratio of the deoxidizer to the silicon calcium powder is controlled to be 6.
In the manufacturing method of the mirror surface plastic die steel with uniform section hardness, the forging is carried out in a mode of two piers and two pulls in the heating and forging step, and the forging ratio is controlled to be more than 5.
In the method for manufacturing mirror surface plastic die steel with uniform section hardness, in the tempering process of the heat treatment step, the tempering temperature of a steel plate with the thickness of 100-200 mm is controlled to be 530-550 ℃, and the tempering temperature of a steel plate with the thickness of more than 200mm is controlled to be 510-540 ℃.
In the method for manufacturing mirror plastic die steel with uniform section hardness, the diameter of the electrode blank obtained by casting in the electrode blank preparation step is controlled to be 450mm, the diameter of the electroslag ingot obtained by smelting in the electroslag remelting step is controlled to be 790mm or 830mm, and the thickness of the steel plate forged in the heating and forging step is controlled to be 150-300 mm.
In another aspect of the present invention, the mirror surface plastic mold steel having uniform sectional hardness according to the present invention is manufactured by the above manufacturing method, and the mirror surface plastic mold steel having uniform sectional hardness has chemical components in mass fraction of: c:0.35 to 0.45%, si:0.40 to 0.60%, mn:0.40 to 0.70%, cr:6.50 to 8.00%, ni:0.10 to 0.30%, mo:0.50 to 0.70%, V:0.50 to 0.70%, al: 0.020-0.060%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, O is less than or equal to 0.0015%, N: 0.020-0.040%, and the balance of Fe and inevitable impurities.
In the mirror surface plastic die steel having uniform section hardness and the method for manufacturing the same according to the present invention, the reason why the chemical composition of the mirror surface plastic die steel is controlled in the mass fraction is as follows:
c: the steel can obviously improve the hardness and hardenability of the steel, is the most economical hardening element, can obviously reduce the plasticity and the toughness of the steel if the carbon content is too high, can be combined with chromium, molybdenum and the like to form carbide, and reduces the chromium and the molybdenum in a matrix, thereby reducing the corrosion resistance, and the content of C in the invention is controlled to be 0.35-0.45%.
Si: used as a deoxidizer in the steelmaking process; meanwhile, the solid solution in austenite can inhibit the formation of pearlite, promote bainite/martensite phase transformation, improve the strength of the steel plate and improve the hardenability. But the excessive content of Si can increase the risk of cracks of the casting blank and the steel plate, and the Si content is selected to be 0.40-0.60 percent.
Mn: effective elements for deoxidation and desulfurization can delay the occurrence of high-temperature ferrite phase transformation so as to improve the strength and hardenability of the steel, and if the content of Mn is too high, the hot workability is reduced. The invention controls the content of added Mn to be 0.40-0.70%.
Cr: important corrosion resistance elements in steel. The strength and hardenability of steel can be improved, but too high Cr and Mn are added into the steel at the same time, surface cracks are easily formed in the steel rolling process, so the Cr content of the invention is limited to 6.50-8.00%.
Ni: the invention has strong capability of stabilizing austenite and expanding austenite, can improve the toughness of steel and the hardenability, the mirror surface die steel in China is divided into a Ni-containing type and a Ni-free type according to the Ni content, the invention adopts a low-Ni scheme, and the Ni content is controlled to be 0.10-0.30%
Mo: the strong carbide element can improve the hardenability of the steel plate, can also increase the tempering resistance of the steel, and can reduce the tempering brittleness caused by the element when being used with chromium and manganese. The Mo content of the invention is limited to 0.50-0.70%.
V: vanadium has strong affinity with carbon and nitrogen, forms corresponding carbon and nitride with the vanadium, is dispersed and distributed, refines the structure, reduces the overheating sensitivity of steel and increases the tempering stability. The V content of the invention is controlled between 0.50 and 0.70 percent.
Al: the strong deoxidizing element can be combined with N to form AlN, can play a role in refining grains, and has a content of less than 0.020wt.%, and the above effects are not obvious. The Al content in the steel is controlled to be 0.020-0.060%.
N: the interstitial elements can increase the hardness of martensite, and when V, al, etc. are present in the steel, N forms carbonitrides with them, and austenite grain growth can be effectively suppressed. The control range of the N content of the steel is 0.020-0.040%.
The effect of the alloy elements is as follows: the hardenability and the strength of the steel plate are improved through alloy elements such as Cr, ni, mo and the like, the hardness of the core part of the steel plate with large thickness is ensured, the tempering stability of the steel plate is improved, and the tempering process window of the steel plate is enlarged; v, al and carbon nitride can be formed in steel, so that the growth of crystal grains is prevented, and the performance uniformity of the steel plate is improved; si, mn and other elements are beneficial to obtaining a relatively stable martensite structure after rolling, so that the whole module can obtain a higher and more uniform hardness value.
The mirror surface plastic mold steel having uniform sectional hardness and the method for manufacturing the same according to the present invention will be described in detail with reference to specific examples.
Example 1
The mirror surface plastic die steel with uniform section hardness in the embodiment 1 of the invention comprises the following chemical components in percentage by mass: c:0.36%, si:0.47%, mn:0.53%, P:0.011%, S:0.002%, cr:6.83%, ni:0.16%, mo:0.53%, V:0.54%, al:0.043%, N:0.026%, and the balance of Fe and inevitable impurities.
The manufacturing method of the mirror surface plastic die steel with uniform section hardness, provided by the embodiment 1 of the invention, comprises the following steps:
(I) electrode blank preparation
(1) Preparing materials: the raw materials are proportioned according to the following component content requirements of a mirror surface die steel target product: c:0.36%, si:0.47%, mn:0.53%, P:0.011%, S:0.002%, cr:6.83%, ni:0.16%, mo:0.53%, V:0.54%, al:0.043%, N:0.026%, and the balance of Fe and inevitable impurities;
(2) Electric furnace smelting: carrying out primary smelting by adopting an eccentric bottom tapping electric furnace, tapping when the C content of molten steel in the electric furnace is 0.08%, the P content is 0.007% and the temperature is 1667 ℃, adopting a steel and slag remaining operation, adding aluminum for deoxidation in the tapping process, and adding ferrosilicon, fluorite and lime to make new slag in the tapping process;
(3) LF refining: introducing argon gas for stirring after molten steel arrives at a station, controlling the alkalinity of white slag in the whole refining process at R = 3.2-4.5, performing diffusion deoxidation by adopting calcium silicate powder, controlling the white slag retention time at 24min, performing fine component adjustment after full deoxidation, and hoisting and transferring to a VD furnace when the temperature is 1660 ℃;
(4) VD treatment: vacuumizing the molten steel after the molten steel arrives at a station, keeping the vacuum degree in the furnace for 25min after the vacuum degree reaches less than or equal to 67Pa, sampling and analyzing after vacuum treatment, carrying out Al alloying by adopting an Al wire feeding mode, stirring by adopting argon, keeping the slag surface to be slightly moved without exposing the molten steel in the argon stirring process, stopping argon blowing after uniformly stirring the components, changing the bottom blowing of high-purity nitrogen into the bottom blowing of high-purity nitrogen for carrying out nitrogen alloying, blowing nitrogen for 9min at the flow rate of 600NL/min, adjusting the pressure according to the rolling state of the liquid level, discharging the molten steel when the temperature is 1570 ℃, controlling the [ H ] in the discharged molten steel to be 0.6ppm, and then carrying out ladle pouring to obtain an electrode blank with the diameter of 450 mm;
(II) annealing of electrode blank
Preheating the electrode blank at 400 ℃ for 2h, then heating to 740 ℃ at the speed of 90 ℃/h, preserving heat for 680min, then cooling to 180 ℃ in a furnace, and discharging;
(III) electroslag remelting
Polishing the surface of the annealed electrode blank, and then adopting CaF 2 CaO and Al 2 O 3 Smelting ternary slag with the proportion of 6;
(IV) heating forging
Carrying out hot feeding and charging on the electroslag ingot, keeping the temperature at 650 ℃ for 3h, then heating to 830 ℃ within 3h, keeping the temperature for 5h, then heating to 1250 ℃ within 5h, keeping the temperature for 16h, discharging and forging, forging the electroslag ingot into a steel plate by adopting a 'two-pier two-drawing' mode, controlling the forging ratio to be 6, controlling the forging starting temperature to be 1150 ℃, controlling the final forging temperature to be 910 ℃, and obtaining the steel plate with the specification of 170 multiplied by 1010 multiplied by 6100mm;
(V) annealing of forgings
Charging the steel plate at the temperature of below 300 ℃, heating to 680 ℃ at the speed of 70 ℃/h, preserving heat for 3h, heating to 870 ℃ at the speed of 50 ℃/h, preserving heat for 13h, cooling to 430 ℃ in a furnace, and discharging from the furnace for air cooling;
(VI) Heat treatment
Quenching: heating the annealed steel plate to 880 ℃ at the speed of 70 ℃/h, preserving heat for 4h, then heating to 1020 ℃ at the speed of 70 ℃/h, preserving heat for 6h, and quenching with water to room temperature;
tempering: and heating the quenched steel plate to 530 ℃ at the speed of 60 ℃/h, preserving the heat for 10h, and then air-cooling to room temperature.
Example 2
The mirror surface plastic die steel with uniform section hardness in the embodiment 2 of the invention comprises the following chemical components in percentage by mass: c:0.37%, si:0.46%, mn:0.52%, P:0.008%, S:0.002%, cr:7.12%, ni:0.21%, mo:0.54%, V:0.56%, al:0.051%, N:0.025%, and the balance of Fe and inevitable impurities.
The manufacturing method of the mirror surface plastic die steel with uniform section hardness, provided by the embodiment 2 of the invention, comprises the following steps:
(I) electrode blank preparation
(1) Preparing materials: the raw materials are proportioned according to the following component content requirements of a mirror surface die steel target product: c:0.37%, si:0.46%, mn:0.52%, P:0.008%, S:0.002%, cr:7.12%, ni:0.21%, mo:0.54%, V:0.56%, al:0.051%, N:0.025%, and the balance of Fe and inevitable impurities;
(2) Electric furnace smelting: carrying out primary smelting by adopting an eccentric bottom tapping electric furnace, tapping when the C content of molten steel in the electric furnace is 0.07%, the P content is 0.007% and the temperature is 1658 ℃, adopting steel and slag retention operation, adding aluminum for deoxidation in the tapping process, and adding ferrosilicon, fluorite and lime to make new slag in the tapping process;
(3) LF refining: introducing argon gas and stirring after molten steel arrives at a station, controlling the alkalinity of white slag in the whole refining process at R = 3.2-4.5, performing diffusion deoxidation by adopting calcium silicate powder, controlling the white slag retention time to be 26min, performing component fine adjustment after full deoxidation, and hoisting and transferring to a VD furnace when the temperature is 1657 ℃;
(4) VD treatment: vacuumizing the molten steel after arriving at a station, keeping the vacuum degree in the furnace for 24min after reaching 67Pa or less, sampling and analyzing after vacuum treatment, performing Al alloying by adopting an Al wire feeding mode, stirring by adopting argon, keeping the slag surface to be slightly moved without exposing the molten steel in the argon stirring process, stopping argon blowing after uniformly stirring the components, changing the process of bottom blowing of high-purity nitrogen into the process of nitrogen alloying, blowing nitrogen for 10min at the flow of 600NL/min, adjusting the pressure according to the rolling state of the liquid level, discharging the molten steel when the temperature is 1575 ℃, controlling the [ H ] in the discharged molten steel to be 0.7ppm, and then pouring in a ladle to obtain an electrode blank with the diameter of 450 mm;
(II) annealing of electrode blank
Preheating the electrode blank at 400 ℃ for 2h, then heating to 750 ℃ at a speed of 90 ℃/h, preserving heat for 730min, then cooling the furnace to 150 ℃, and discharging;
(III) electroslag remelting
Polishing the surface of the annealed electrode blank, and then adopting CaF 2 CaO and Al 2 O 3 Smelting ternary slag with the proportion of 6Smelting to obtain an electroslag ingot with the diameter of 830 mm;
(IV) heating forging
Carrying out hot feeding and charging on the electroslag ingot, keeping the temperature at 650 ℃ for 3h, then heating to 830 ℃ within 3h, keeping the temperature for 5h, then heating to 1250 ℃ within 5h, keeping the temperature for 16h, discharging and forging, forging the electroslag ingot into a steel plate by adopting a two-pier and two-drawing mode, controlling the forging ratio to be 6.2, controlling the forging starting temperature to be 1170 ℃, controlling the final forging temperature to be 920 ℃, and obtaining the steel plate with the specification of 230 multiplied by 1010 multiplied by 4400mm;
(V) annealing of forgings
Charging the steel plate at the temperature of below 300 ℃, heating to 680 ℃ at the speed of 70 ℃/h, preserving heat for 3h, heating to 880 ℃ at the speed of 50 ℃/h, preserving heat for 13h, cooling to 450 ℃ in the furnace, and discharging from the furnace for air cooling;
(VI) Heat treatment
Quenching: heating the annealed steel plate to 880 ℃ at the speed of 70 ℃/h, preserving heat for 4h, then heating to 1020 ℃ at the speed of 70 ℃/h, preserving heat for 9h, and quenching with water to room temperature;
tempering: and heating the quenched steel plate to 530 ℃ at the speed of 60 ℃/h, preserving the heat for 14h, and then air-cooling to room temperature.
Example 3
The mirror surface plastic die steel with uniform section hardness in the embodiment 3 of the invention comprises the following chemical components in percentage by mass: c:0.36%, si:0.51%, mn:0.56%, P:0.009%, S:0.002%, cr:7.30%, ni:0.28%, mo:0.56%, V:0.58%, al:0.049%, N:0.028%, and the balance of Fe and inevitable impurities.
The manufacturing method of the mirror surface plastic die steel with uniform section hardness, provided by the embodiment 3 of the invention, comprises the following steps:
(I) electrode blank preparation
(1) Preparing materials: the raw materials are proportioned according to the following component content requirements of a mirror surface die steel target product: c:0.36%, si:0.51%, mn:0.56%, P:0.009%, S:0.002%, cr:7.30%, ni:0.28%, mo:0.56%, V:0.58%, al:0.049%, N:0.028%, the balance being Fe and inevitable impurities;
(2) Electric furnace smelting: carrying out primary smelting by adopting an eccentric bottom tapping electric furnace, tapping when the C content of molten steel in the electric furnace is 0.08%, the P content is 0.009% and the temperature is 1658 ℃, adopting steel and slag retention operation, adding aluminum for deoxidation in the tapping process, and adding ferrosilicon, fluorite and lime to make new slag in the tapping process;
(3) LF refining: introducing argon gas for stirring after molten steel arrives at a station, controlling the alkalinity of white slag in the whole refining process at R = 3.2-4.5, performing diffusion deoxidation by adopting calcium silicate powder, controlling the white slag retention time to be 25min, performing fine component adjustment after full deoxidation, and hoisting and transferring to a VD furnace when the temperature is 1662 ℃;
(4) VD treatment: vacuumizing the molten steel after arriving at a station, keeping the vacuum degree in the furnace for 25min after reaching 67Pa or less, sampling and analyzing after vacuum treatment, carrying out Al alloying by adopting an Al wire feeding mode, stirring by adopting argon, keeping the slag surface to be slightly moved without exposing the molten steel in the argon stirring process, stopping argon blowing after uniformly stirring the components, changing into bottom blowing of high-purity nitrogen for carrying out nitrogen alloying, blowing nitrogen for 10min at the flow of 600NL/min, adjusting the pressure according to the rolling state of the liquid level, leaving the station at the temperature of 1572 ℃, controlling [ H ] in the discharged molten steel to be 0.6ppm, and then carrying out ladle pouring to obtain an electrode blank with the diameter of 450 mm;
(II) annealing of electrode blank
Preheating the electrode blank at 400 ℃ for 2h, then heating to 750 ℃ at the speed of 90 ℃/h, preserving the heat for 740min, then cooling to 152 ℃ in a furnace, and discharging;
(III) electroslag remelting
The annealed electrode blank is subjected to surface polishing treatment and then CaF 2 CaO and Al 2 O 3 Smelting the ternary slag with the ratio of (6);
(IV) heating forging
Carrying out hot feeding and charging on the electroslag ingot, keeping the temperature at 650 ℃ for 3h, then heating to 830 ℃ within 3h, keeping the temperature for 5h, then heating to 1250 ℃ within 5h, keeping the temperature for 17h, discharging and forging, forging the electroslag ingot into a steel plate by adopting a two-pier and two-drawing mode, controlling the forging ratio to be 6.1, controlling the forging starting temperature to be 1173 ℃, controlling the final forging temperature to be 910 ℃, and obtaining the steel plate with the specification of 260 multiplied by 1010 multiplied by 4400mm;
(V) annealing of forgings
Charging the steel plate at the temperature of below 300 ℃, heating to 680 ℃ at the speed of 70 ℃/h, preserving heat for 3h, heating to 880 ℃ at the speed of 50 ℃/h, preserving heat for 14h, cooling to 450 ℃ in a furnace, discharging from the furnace, and air-cooling;
(VI) Heat treatment
Quenching: heating the annealed steel plate to 880 ℃ at the speed of 70 ℃/h, preserving heat for 4h, heating to 1030 ℃ at the speed of 70 ℃/h, preserving heat for 10h, and quenching in water to room temperature;
tempering: and heating the quenched steel plate to 530 ℃ at the speed of 60 ℃/h, preserving the heat for 15h, and then air-cooling to room temperature.
The mirror surface plastic die steel products manufactured by the three embodiments of the invention are subjected to flaw detection, the flaw detection level meets the 4-level requirement of GB/T6402-2008, the full thickness hardness of the mirror surface plastic die steel products is detected, the full thickness hardness curve detection result of the mirror surface plastic die steel is shown in figure 1, and the surface hardness, the core hardness and the maximum section hardness difference of the mirror surface plastic die steel products are shown in table 1.
TABLE 1 hardness test results for mirror plastic die steel products
| Thickness/mm of product | Surface Hardness (HRC) | Core Hardness (HRC) | Maximum section hardness difference (HRC) | |
| Example 1 | 170 | 51.5 | 50 | 1.5 |
| Example 2 | 230 | 50.7 | 49.1 | 1.6 |
| Example 3 | 260 | 51 | 49.2 | 1.8 |
Obviously, the full section hardness of the mirror surface plastic die steel manufactured by the manufacturing method of the mirror surface plastic die steel with uniform section hardness is stably maintained at 49-52 HRC (Rockwell hardness), and the maximum section hardness difference is less than or equal to 2HRC.
In conclusion, compared with the prior art, the mirror surface plastic die steel with uniform section hardness and the manufacturing method thereof have the following advantages and beneficial effects:
1. the mirror surface plastic die steel manufactured by the invention has high hardness and good hardenability, the hardness of the whole section of the mirror surface plastic die steel is stably kept at 49-52 HRC, the maximum section hardness difference is less than or equal to 2HRC, the hardness distribution is uniform, and the high requirement of the field on the hardness distribution uniformity of the large-section mirror surface plastic die steel is completely met;
2. the manufacturing method of the mirror plastic die steel with uniform section hardness can fully play the microalloy strengthening role, control uniform precipitation, eliminate white spots, improve the transverse performance of products, refine crystal grains and realize tissue homogenization and compactness, thereby meeting the mirror polishing requirements of the die steel and ensuring the performances of corrosion resistance, wear resistance and the like. Through test determination, the flaw detection grade of the mirror plastic die steel manufactured by the invention meets the 4-grade requirement of GB/T6402-2008, the grain size is more than or equal to 8 grade, the polishing performance is excellent, the mirror plastic die steel can be polished to 10000#, the polishing rate is as high as 95 percent, and the mirror plastic die steel is particularly suitable for manufacturing plastic dies with strict requirements on dimensional accuracy, surface roughness and the like and complex cavities.
It is to be noted that, in this document, the term "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion, so that an article or an apparatus including a series of elements includes not only those elements but also other elements not explicitly listed or inherent to such article or apparatus.
It should be further noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and are not limited thereto; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or alterations do not depart from the spirit of the invention.
Claims (10)
1. The manufacturing method of the mirror surface plastic die steel with uniform section hardness is characterized by comprising the following steps of:
preparing an electrode blank: proportioning raw materials according to the component content requirement of a mirror surface die steel target product, carrying out an electric furnace smelting process, an LF refining process and a VD treatment process, and then casting into an electrode blank, wherein the component content of the mirror surface die steel target product is as follows according to the mass fraction: c:0.35 to 0.45%, si:0.40 to 0.60%, mn:0.40 to 0.70%, cr:6.50 to 8.00%, ni:0.10 to 0.30%, mo:0.50 to 0.70%, V:0.50 to 0.70%, al: 0.020-0.060%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, O is less than or equal to 0.0015%, and N:0.020 to 0.040 percent, and the balance of Fe and inevitable impurities;
(II) annealing the electrode blank: preheating the electrode blank at 350-450 ℃ for 2-3 h, raising the temperature to 700-750 ℃ at the speed of 80-100 ℃/h, then preserving the heat, calculating the heat preservation time according to 1.5-2.0 min/mm based on the diameter of the electrode blank, and then cooling the electrode blank in a furnace to below 200 ℃ at the speed of less than or equal to 40 ℃/h and discharging the electrode blank;
(III) electroslag remelting: after the annealed electrode blank is subjected to surface grinding treatment, caF is adopted 2 CaO and Al 2 O 3 Smelting the ternary slag system, adding a deoxidizing agent in the smelting process, and smelting to obtain an electroslag ingot;
(IV) heating and forging: carrying out hot feeding on an electroslag ingot into a furnace, keeping the temperature at 630-700 ℃ for 2-3 h, heating to 800-850 ℃ within 2-4 h, keeping the temperature for 3-6 h, heating to 1220-1260 ℃ within 4-6 h, keeping the temperature for 15-20 h, taking the electroslag ingot out of the furnace, forging the electroslag ingot into a steel plate, controlling the initial forging temperature to be 1100-1180 ℃, and controlling the final forging temperature to be not less than 900 ℃;
(V) annealing the forged piece: charging the steel plate at the temperature of below 300 ℃, heating the steel plate to the temperature of between 630 and 700 ℃ at the speed of between 60 and 80 ℃/h, preserving the heat for 2 to 3 hours, heating the steel plate to the temperature of between 850 and 900 ℃ at the speed of less than or equal to 60 ℃/h, preserving the heat for 10 to 15 hours, cooling the steel plate to the temperature of between 400 and 500 ℃ after the heat preservation is finished, and discharging the steel plate for air cooling;
(VI) heat treatment: the method comprises a quenching process and a tempering process, wherein in the quenching process, the annealed steel plate is heated to 850-900 ℃ at the speed of 60-80 ℃/h and then is kept warm for 5-8 h, then the steel plate is heated to 1010-1050 ℃ at the speed of 60-80 ℃/h and then is kept warm, the heat preservation time is calculated according to the thickness of the steel plate at 2-3 min/mm, the steel plate is taken out of a furnace and is quenched to the room temperature by water, in the tempering process, the quenched steel plate is heated to 500-550 ℃ at the speed of less than or equal to 60 ℃/h and then is kept warm, the heat preservation time is calculated according to the thickness of the steel plate at 3-4 min/mm, and the steel plate is taken out of the furnace and is cooled to the room temperature by air.
2. The method for manufacturing mirror surface plastic mold steel with uniform section hardness according to claim 1, wherein in the electrode blank preparation step, the electric furnace smelting process is performed in an eccentric bottom tapping electric furnace by using an oxidation method melting smelting process, when the C of the molten steel in the electric furnace is less than or equal to 0.09%, the P is less than or equal to 0.008% and the temperature is more than or equal to 1640 ℃, the molten steel is fed into an LF furnace, steel and slag remaining operation is adopted during tapping, aluminum is added during tapping for precipitation and deoxidation, and slag making materials are added to make new slag; the LF refining process comprises the following steps: introducing argon gas to stir after molten steel arrives at a station, white slag is produced in the whole refining process, the alkalinity R is controlled to be 3.2-4.5, calcium silicate powder is adopted for diffusion deoxidation, the white slag holding time is controlled to be more than or equal to 20min, fine adjustment of components is carried out after full deoxidation, and the molten steel is taken out of the station and transferred to a VD furnace when the temperature is 1650-1670 ℃; the VD processing procedure comprises the following steps: vacuumizing the molten steel after arriving at a station, controlling the vacuum degree in the furnace to be less than or equal to 67Pa, keeping the vacuum degree for 20-30 min, performing aluminum alloying by adopting an aluminum wire feeding mode, stirring by adopting argon, keeping the slag surface to be slightly moved without exposing the molten steel in the argon stirring process, stopping argon blowing after the components are uniformly stirred, changing the bottom blowing of high-purity nitrogen into bottom blowing of high-purity nitrogen, blowing nitrogen for 6-10 min at the flow rate of 600NL/min for performing nitrogen alloying, and leaving the station when the temperature is 1560-1580 ℃, wherein the [ H ] in the discharged molten steel is controlled to be less than or equal to 1.0ppm.
3. A method for manufacturing mirror surface plastic die steel with uniform section hardness as claimed in claim 2, wherein the slag-making material in the electric furnace smelting process comprises ferrosilicon, fluorite, lime.
4. The method for manufacturing mirror surface plastic mold steel with uniform section hardness according to claim 1, wherein CaF is used in the electroslag remelting step 2 CaO and Al 2 O 3 CaF in ternary slag system 2 CaO and Al 2 O 3 The ratio of the deoxidizer to the silicon calcium powder is controlled to be 6.
5. The method for manufacturing mirror-surface plastic die steel with uniform section hardness according to claim 1, wherein in the step of hot forging, the forging is performed in a two-pier two-draw manner, and the forging ratio is controlled to be 5 or more.
6. A method for manufacturing mirror surface plastic mold steel with uniform sectional hardness as claimed in claim 1, wherein the diameter of the electrode slab poured in the electrode slab manufacturing step is controlled to 450mm, the diameter of the electroslag ingot smelted in the electroslag remelting step is controlled to 790mm or 830mm, the thickness of the steel plate forged in the heating forging step is controlled to 150 to 300mm, the tempering temperature of the steel plate with a thickness of 100 to 200mm in the tempering step is controlled to 530 to 550 ℃, and the tempering temperature of the steel plate with a thickness of more than 200mm in the tempering step is controlled to 510 to 540 ℃.
7. A mirror-surface plastic mold steel having uniform sectional hardness, which is manufactured by the mirror-surface plastic mold steel manufacturing method having uniform sectional hardness according to any one of claims 1 to 6, and which has chemical compositions in mass fraction of: c:0.35 to 0.45%, si:0.40 to 0.60%, mn:0.40 to 0.70%, cr:6.50 to 8.00%, ni:0.10 to 0.30%, mo:0.50 to 0.70%, V:0.50 to 0.70%, al: 0.020-0.060%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, O is less than or equal to 0.0015%, N:0.020 to 0.040 percent, and the balance of Fe and inevitable impurities.
8. The mirror-surface plastic mold steel with uniform section hardness according to claim 7, wherein the mirror-surface plastic mold steel comprises the following chemical components in mass fraction: c:0.36%, si:0.47%, mn:0.53%, P:0.011%, S:0.002%, cr:6.83%, ni:0.16%, mo:0.53%, V:0.54%, al:0.043%, N:0.026%, and the balance of Fe and inevitable impurities.
9. The mirror-surface plastic mold steel with uniform sectional hardness according to claim 7, wherein the mirror-surface plastic mold steel has a chemical composition of, in mass fraction: c:0.37%, si:0.46%, mn:0.52%, P:0.008%, S:0.002%, cr:7.12%, ni:0.21%, mo:0.54%, V:0.56%, al:0.051%, N:0.025%, and the balance of Fe and inevitable impurities.
10. The mirror-surface plastic mold steel with uniform sectional hardness according to claim 7, wherein the mirror-surface plastic mold steel has a chemical composition of, in mass fraction: c:0.36%, si:0.51%, mn:0.56%, P:0.009%, S:0.002%, cr:7.30%, ni:0.28%, mo:0.56%, V:0.58%, al:0.049%, N:0.028%, and the balance of Fe and inevitable impurities.
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| US20230012944A1 (en) * | 2019-12-31 | 2023-01-19 | Longnan Longyi Heavy Rare-Earth Technology Co., Ltd. | Hot-Work Die Steel Electroslag Remelted Ingot and Manufacturing Method Thereof |
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