CN111235481A - Casting alloy for plastic mold and preparation method thereof - Google Patents
Casting alloy for plastic mold and preparation method thereof Download PDFInfo
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- KTUFCUMIWABKDW-UHFFFAOYSA-N oxo(oxolanthaniooxy)lanthanum Chemical compound O=[La]O[La]=O KTUFCUMIWABKDW-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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Abstract
A casting alloy for plastic molds and a preparation method thereof are disclosed, wherein the mass percentage of each element is Cr: 4.0-4.8, Nb: 0.8 to 1.3, La: 0.5-1.2, B: 1.3-1.6, C: 0.60 to 0.70, Mn: 0.5 to 1.0, Si: 1.0 or less, P: less than or equal to 0.1, S: less than or equal to 0.06 percent, and the balance being iron. Melting the raw materials at 1480-1600 ℃ to fully melt the pure iron and the ferrochrome; cooling the melt to 1300-1360 ℃, adding lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.1-0.15% of the total amount of the ingredients; and preserving the temperature for about 6-12 minutes, and casting the alloy when the temperature of the melt is 1250-1350 ℃. The hardness of the cast ingot reaches HRC 48-54, and the impact toughness reaches 8.0 ℃12.0J/cm2The bending strength is 1460-1812 MPa, and the surface roughness is less than 0.32 μm.
Description
Technical Field
The invention belongs to the field of high-toughness plastic molds, and relates to a high-toughness casting mold of rare earth lanthanum modified fine grain boride and a martensite matrix phase and a preparation method thereof, which can be popularized and applied to formed parts of plastic molds and relevant high-toughness and high-corrosion-resistance wear-resistant occasions.
Technical Field
The working conditions of the plastic die are different from those of a cold punching die, and the plastic die generally needs to work at 150-200 ℃ and also needs to bear the influence of temperature except under the action of certain pressure. The steel for plastic molds should meet the following requirements:
(1) strength property: the plastic deformation failure can be caused by the compression and heating of the cavity surface of the plastic mold, and particularly when a small mold works on large-tonnage equipment, the plastic deformation is easy to generate overload. When the strength and toughness of the material adopted by the plastic mould are insufficient, plastic deformation failure and fracture are easily caused.
(2) Heat resistance: with the advent of high speed molding machinery, plastic articles have been moving faster. The molding temperature is 200-350 ℃, and if the plastic has poor flowability, the molding speed is high, so that the molding surface temperature of the mold part exceeds 400 ℃ in a very short time. In order to ensure the precision and small deformation of the die in use, the die steel has high heat resistance. When the transient temperature of the amorphous/nanocrystalline alloy related to the project reaches 800 ℃, the mechanical property can not be obviously changed, but when the amorphous/nanocrystalline alloy is used as a plastic mould, the thermal fatigue damage of the amorphous/nanocrystalline alloy still has potential possibility due to the thermal cycle effect under the stress action for a long time, and related indexes such as high-temperature endurance strength and thermal fatigue strength need to be measured.
(3) Sufficient wear resistance and excellent machinability
With the expansion of the use of plastic products, inorganic materials such as glass fiber are often added into the plastic to enhance the plasticity, and the addition of the additives greatly reduces the fluidity of the plastic, which causes the abrasion of a mold, so that the chess is required to have good wear resistance. Most plastic forming dies need certain cutting processing and fitter repairing besides electric spark processing. In order to prolong the service life of the cutting tool, the work hardening is small in the cutting process. In order to avoid the influence of the deformation of the mold on the accuracy, it is desirable that the machining residual stress be kept to a minimum.
In general, wear resistance increases with increasing hardness, but increasing hardness makes machining difficult, and therefore the hardness range should be determined reasonably.
(4) Mirror processability and dimensional thermal stability
The surface of the cavity is smooth, the molding surface is required to be polished into a mirror surface, and the surface roughness is lower than 0.4 mu m, so that the appearance of the plastic pressing piece is ensured and the demoulding is convenient. The material has uniform tissue, small residual stress and small size change rate caused by temperature change, and is favorable for ensuring the size precision and the surface roughness of the die.
(5) Corrosion resistance
In the forming process, corrosive gas may be released and decomposed by heating to generate corrosive gas, such as HC1, HF, etc., so that the mold may be corroded and damaged at the air flow passage, and thus, the mold steel is required to have good corrosion resistance.
The primary problem in mold manufacture is the mold material. In recent years, although the mold industry in China is rapidly developed, a huge market is provided for domestic mold steel, and the improvement of the yield, variety, specification and quality level of domestic mold steel is driven. At present, the annual output of domestic die steel reaches about 60 ten thousand tons, but the domestic die steel cannot completely meet the requirements of the domestic die market in terms of variety and quality. With the continuous development of the die industry in China, die steel products in China are greatly dependent on import, the external dependence is as high as about 50%, and particularly, the import quantity of steel for high-grade dies is continuously increased. The import of the steel for molds comes mainly from countries such as Japan, Germany, Sweden, Austria, Korea, etc.
In the manufacturing cost of the plastic mold, the machining and polishing account for 70-80%, because the precision and the finish degree of the part are high, the preparation process of the plastic mold is extremely strict, and taking a mold core as an example, the preparation process comprises a plurality of steps of flash, rough grinding, milling machine, bench work, rough machining, fine grinding, fine machining, electric spark machining, mold saving and the like. The complicated preparation process also leads the production period of the die to be very long, and puts strict requirements on the design and the material selection of the die, thereby limiting the innovation and the personalized design of plastic products.
S136 is high-grade stainless die steel, is AISI420 improved medium-carbon high-chromium high-grade stainless steel of AsAB (ASSAB) of Windor Steel products company, Sweden, is refined outside the furnace and then subjected to electroslag remelting, has a finer and cleaner structure, has excellent acid and corrosion resistance, mechanical properties, mirror polishing property, hardenability, heat treatment deformation stability and machinability, and is widely applied to production of actual plastic dies. The main technical indexes of the S136 alloy are as follows: the bending strength is more than or equal to 1800MPa, and the hardness is 46-56 HRC; the surface roughness is lower than 0.4 mu m; the plane fracture toughness is more than or equal to 30 MPa.m1/2(ii) a The impact toughness is more than or equal to 8J/cm2(ii) a The self-corrosion current density is less than or equal to 10 in 3.5 percent NaCl aqueous solution at the temperature of 25 DEG C-5A/cm2。
Disclosure of Invention
The invention aims to provide a casting alloy for plastic molds and a preparation method thereof, wherein the alloy mainly comprises Fe, Cr, Nb, B, C and La as main components, and the element B is M2The main forming elements of the B hard phase, Cr promote a matrix to form a high-hardness martensite phase, Nb and C elements form a high-hardness particle precipitation phase, and rare earth lanthanum is adopted for modification and refinement of the phases.
The invention selects high-toughness and high-hardness FeCrNbLaBC alloy, and the multi-element eutectic alloy containing Fe, Cr, Ni, La, B, C and other elements, wherein the mass percent of each element is Cr: 4.0-4.8, Nb: 0.8 to 1.3, La: 0.5-1.2, B: 1.3-1.6, C: 0.60 to 0.70, Mn: 0.5 to 1.0, Si: 1.0 or less, P: less than or equal to 0.1, S: less than or equal to 0.06 percent, and the balance being iron. Wherein Mn and Si are beneficial impurity elements, and P, S is a harmful impurity element.
Preferably, the mass percentage of the Nb element is as follows: 0.9 to 1.1.
Preferably, the La element comprises the following components in percentage by mass: 0.6 to 0.8.
Preferably, the total mass percentage of the B element and the C element is 2.0-2.3.
B has low solubility in iron matrix and is easy to form M with Fe and Cr elements2B compound, M represents Fe and Cr elements, and the addition of Cr: 4.0-4.8% and B: 1.3-1.6%, mainly for obtaining high hardness M2B, a particle phase.
The content of C is 0.52-0.66%, the matrix structure is mainly in a mixed phase transformation area of lath martensite and sheet martensite when undergoing martensite phase transformation, and the martensite phase transformation is easy to occur in the area and has better toughness. During the actual smelting, a part of C is required to be supplemented as La2O3The reducing agent(s) of (2) is consumed in the smelting process.
Nb is a strong carbide forming element, forms an NbC particle precipitation phase with C, exists between matrix phase grains, inhibits the growth of a primary crystal phase, and destroys M2The network continuous state of the B hard phase improves the toughness and hardness of the material.
The Cr element and the C element form a hard particle phase, replace part of the Fe element to be dissolved into boride and also be dissolved into the Fe matrix phase, so that the effects of solid solution strengthening and promotion of the matrix phase to form high-hardness martensite are achieved, and the bonding effect is related to the improvement of the corrosion resistance of the alloy.
La element is used as a modification element to refine the hard particles and the matrix grains, so that the alloy has a mirror polishing effect.
The contents of other Mn, Si, P and S impurities refer to the standard of cast iron alloy, and the method is favorable for industrial production and batching.
When the alloy is prepared specifically, ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron, lanthanum oxide, pure iron and the like can be prepared according to the component requirements. Some of the raw materials and their compositions are listed in table 1.
TABLE 1 raw materials and compositions applicable to the preparation of the alloys of the invention
The raw material components of table 2 are not exclusive, and the specific components are determined by the raw materials that are actually available. Wherein the ferrochrome, ferrocolumbium, chromium metal and ferroboron provide the dosage of Cr, Nb and B of the alloy, and the high-carbon ferrochrome is used for balancing the content of C. The pure iron can be electrician pure iron, electromagnetic pure iron or industrial pure iron, and the industrial scrap steel can also be used as the raw material of Fe.
With lanthanum oxide (La)2O3) Is a donor of La element, La2O3Can be reduced by C element at high temperature to obtain simple substance La which is dissolved in matrix phase to play the role of deteriorating and refining tissue. La2O3Or lanthanum nitrate and lanthanum carbonate can be used for replacing the lanthanum nitrate and the lanthanum carbonate, and the lanthanum nitrate and the lanthanum carbonate can be decomposed at high temperature to obtain La2O3。
The specific smelting and casting process comprises the following steps:
after the corresponding raw materials are weighed according to the component requirement, the consumption of the lanthanum oxide C needs to be calculated during the batching, namely about 0.067 percent of the element C needs to be consumed when each 1 percent of the element La is added. The alloy can be prepared by smelting in an induction furnace, a vacuum induction furnace and the like. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1480-1600 ℃ so that the pure iron and the ferrochrome are fully melted; then reducing the power of the electric furnace, reducing the temperature of the melt to 1300-1360 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.1-0.15% of the total amount of the ingredients; and continuously preserving the heat for about 6-12 minutes, and rapidly casting the alloy when the temperature of the melt is 1250-1350 ℃.
The casting method can refer to the production method of high-chromium cast iron parts, such as common sand mold casting or investment casting, lost foam casting, metal mold casting, ceramic mold casting, die casting and other special casting methods. The ingot can be directly used without reheating and quenching.
The size specification of the plastic mould forming part blank prepared by the casting method is close to that of the forming part, and only simple rough machining, fine grinding, finish machining, electric spark surface polishing machining, mould saving and other procedures are needed in the follow-up process.
The invention is mainly characterized in that B, C element, Cr and Nb element with high-hardness particle phase are adopted, the matrix is promoted to form martensite, and the alloy structure is refined through La modification, so that the alloy has mirror polishing effect. The integral hardness of the cast ingot reaches HRC 48-54, and the impact toughness reaches 8.0-12.0J/cm2The bending strength reaches 1460-1812 MPa, and the surface roughness is lower than 0.32 mu m after the surface is polished; the self-corrosion current density is less than or equal to 10 in 3.5 percent NaCl aqueous solution at the temperature of 25 DEG C-5A/cm2The high-grade stainless die steel can be used for plastic die-formed parts instead of part of S136.
Drawings
FIG. 1 cast structure of example 2 of the invention;
FIG. 2 Tafel plot measured at electrochemical workstation of example 4 of the present invention;
FIG. 3 example 5 of the present invention shows a fracture scanning morphology of a casting;
FIG. 4 roughness of the surface of the casting of example 6 of the present invention after polishing.
Detailed Description
The various melting and casting methods of the present invention are not limited by the following examples, and any modifications and variations within the scope of the claims of the present invention are within the scope of the present invention.
High-carbon ferrochrome, micro-carbon ferrochrome, metal chromium, ferroboron, lanthanum oxide, industrial pure iron and the like are selected as raw materials and are prepared into the alloy within the component range required by the invention.
Example 1 after weighing the corresponding raw materials according to the required mixture ratio of the componentsAnd when the material is prepared, 0.067 percent of C element is supplemented according to each 1 percent of La element added. And smelting by adopting a vacuum induction furnace to prepare the alloy. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1580 ℃ to fully melt the pure iron and the ferrochrome; then reducing the power of the electric furnace, reducing the temperature of the melt to 1350 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.12 percent of the total amount of the ingredients; and keeping the temperature for about 8 minutes, and quickly casting the alloy when the temperature of the melt is 1340 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.7, Nb: 1.2, La: 1.1, B: 1.5, C: 0.68, Mn: 0.9, Si: 0.8, P: 0.045, S: 0.04 and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC52, and the impact toughness reaches 10.8J/cm2The bending strength reaches 1760MPa, and the surface roughness is lower than 0.18 mu m after surface polishing; self-corrosion current density of 3.2X 10 in 3.5% NaCl aqueous solution at 25 deg.C-6A/cm2。
Example 2 after weighing the corresponding raw materials according to the component proportion, adding 0.067% of C element for each 1% of La element added during the material preparation. And smelting by adopting an induction furnace to prepare the alloy. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1520 ℃ to fully melt the pure iron and the ferrochrome; then reducing the power of the electric furnace, reducing the temperature of the melt to 1340 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.14 percent of the total amount of the ingredients; and keeping the temperature for about 10 minutes, and quickly casting the alloy when the temperature of the melt is 1280 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.5, Nb: 0.96, La: 0.98, B: 1.50, C: 0.70, Mn: 0.7, Si: 0.9, P: 0.09, S: less than or equal to 0.05 and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC50, and the impact toughness reaches 11.0J/cm2The bending strength reaches 1782MPa, and the surface roughness is lower than 0.21 mu m after surface polishing; self-corrosion current density of 5.2X 10 in 3.5% NaCl aqueous solution at 25 deg.C-6A/cm2. FIG. 1 is a metallographic photograph of the alloy showing that the matrix phase of the alloy is lath martensite, relatively fine; the eutectic phase of the crystal boundary no longer presents a continuous network structure, andmany fine, spheroidized second phases are now present, indicating that the alloy has high toughness.
Example 3 after weighing the corresponding raw materials according to the component proportion, adding 0.067% of C element for each 1% of La element added during the material preparation. The alloy is prepared by smelting in a vacuum induction furnace and the like. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1550 ℃ to fully melt the pure iron and the ferrochrome; then reducing the power of the electric furnace, reducing the temperature of the melt to 1350 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.12 percent of the total amount of the ingredients; and keeping the temperature for about 9 minutes, and quickly casting the alloy when the temperature of the melt is 1290 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.5, Nb: 1.2, La: 1.0, B: 1.6, C: 0.60, Mn: 0.6, Si: 0.9, P: 0.06, S: 0.04 and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC53, and the impact toughness reaches 10.8J/cm2The bending strength reaches 1728MPa, and the surface roughness is lower than 0.12 mu m after surface polishing; self-corrosion current density of 2.6X 10 in 3.5% NaCl aqueous solution at 25 deg.C-6A/cm2。
Example 4 after weighing the corresponding raw materials according to the component proportion, adding 0.067% of C element for each 1% of La element added during the material preparation. And smelting by adopting an induction furnace to prepare the alloy. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1560 ℃ to fully melt the pure iron and the ferrochrome; then reducing the power of the electric furnace, reducing the temperature of the melt to 1350 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.13 percent of the total amount of the ingredients; and keeping the temperature for about 9 minutes, and quickly casting the alloy when the temperature of the melt is 1290 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.6, Nb: 0.8, La: 0.6, B: 1.5, C: 0.65, Mn: 0.76, Si: 0.80, P: 0.08, S: 0.05 and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC52, and the impact toughness reaches 9.0J/cm2The bending strength reaches 1662MPa, and the surface roughness is lower than 0.22 μm after surface polishing. FIG. 2 is a Tafel plot of the alloy showing the alloy at 25 ℃ in 3.5% aqueous NaClHas a self-etching current density of 3.809 × 10-6A/cm2。
Example 5 after weighing the corresponding raw materials according to the component proportion, adding 0.067% of C element for each 1% of La element added during the material mixing. The alloy can be prepared by smelting in an induction furnace, a vacuum induction furnace and the like. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1600 ℃ so that the pure iron and the ferrochrome are fully melted; then reducing the power of the electric furnace, reducing the temperature of the melt to 1360 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum with the total amount of 0.1 percent of the ingredients; and keeping the temperature for about 6 minutes, and quickly casting the alloy when the temperature of the melt is 1350 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.0, Nb: 0.8, La: 0.5, B: 1.3, C: 0.60, Mn: 1.0, Si: 0.8, P: 0.07, S: 0.04 and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC48, and the impact toughness reaches 10.3J/cm2The bending strength reaches 1625MPa, and the surface roughness is lower than 0.20 μm after the surface is polished; self-corrosion current density of 5X 10 in 3.5% NaCl aqueous solution at 25 deg.C-6A/cm2. FIG. 3 is a morphology chart of the alloy bending fracture, which shows that the fracture surface of the alloy is mainly cleavage fracture, the fracture surface is very fine and uneven, so that a large amount of micro fracture surfaces are required to be cracked before fracture, and relatively high energy is required to be consumed, so that the alloy has relatively high fracture toughness.
Example 6 after weighing the corresponding raw materials according to the component proportion, adding 0.067% of C element for each 1% of La element added during the material preparation. The alloy can be prepared by smelting in an induction furnace, a vacuum induction furnace and the like. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1480 ℃ so that the pure iron and the ferrochrome are fully melted; then reducing the power of the electric furnace, reducing the temperature of the melt to 1300 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.15 percent of the total amount of the ingredients; and keeping the temperature for about 12 minutes, and quickly casting the alloy when the temperature of the melt is 1250 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.8, Nb: 1.3, La: 0.8, B: 1.6, C: 0.70, Mn: 0.5Si: 1.0, P: 0.08, S: 0.05 and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC54, and the impact toughness reaches 8.0J/cm2The bending strength reaches 1612 MPa. FIG. 4 is a photograph of yard fibers after the surface of the alloy ingot was polished, showing that the surface roughness was 0.1007 μm. Electrochemical work station determines the self-corrosion current density of the alloy at 25 ℃ in 3.5% NaCl aqueous solution and 7.8 multiplied by 10-6A/cm2。
Example 7 after weighing the corresponding raw materials according to the component proportion, adding 0.067% of C element for each 1% of La element added during the batching. The alloy is prepared by smelting in a vacuum induction furnace and the like. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1560 ℃ to fully melt the pure iron and the ferrochrome; then reducing the power of the electric furnace, reducing the temperature of the melt to 1320 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.12% of the total amount of the ingredients; and keeping the temperature for about 9 minutes, and quickly casting the alloy when the temperature of the melt is 1320 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.3, Nb: 0.8, La: 0.5, B: 1.6, C: 0.60, Mn: 0.9, Si: 0.9, P: 0.09, S: 0.04 and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC48, and the impact toughness reaches 11.0J/cm2The bending strength reaches 1712MPa, and the surface roughness is lower than 0.32 μm after surface polishing; self-corrosion current density of 1X 10 in 3.5% NaCl aqueous solution at 25 deg.C-5A/cm2。
Example 8 after weighing the corresponding raw materials according to the component proportion, adding 0.067% of C element for each 1% of La element added during the batching. And smelting by adopting an induction furnace to prepare the alloy. Firstly, melting ferrochrome (high carbon, medium carbon and micro carbon), ferrocolumbium, ferroboron and pure iron at 1500 ℃ to fully melt the pure iron and the ferrochrome; then reducing the power of the electric furnace, reducing the temperature of the melt to 1350 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.1 percent of the total amount of the ingredients; and keeping the temperature for about 12 minutes, and quickly casting the alloy when the temperature of the melt is 1250 ℃. The mass percentage of each element in the FeCrNbLaBC alloy is Cr: 4.0, Nb: 1.3, La: 0.7, B: 1.3,c: 0.70, Mn: 1.0, Si: 1.0, P: 0.1, S: 0.06, and the balance of iron. The integral hardness of the obtained cast ingot reaches HRC52, and the impact toughness reaches 12.0/cm2The bending strength reaches 1656MPa, and the surface roughness is lower than 0.22 μm after surface polishing; self-corrosion current density of 4.2X 10 in 3.5% NaCl aqueous solution at 25 deg.C- 6A/cm2。
The properties of the cast alloys prepared in the examples were measured as follows:
1. hardness tests were conducted on the cast metals of the examples using an HR-150A Rockwell hardness machine under a load of 150Kg, and the average value was taken after five points were struck.
2. The impact toughness of the cast metal of the example was tested using a JBS-300B impact tester with a measuring range of 150J, and an average value was taken after five samples were taken.
3. Three-point bending tests were carried out on example cast metals using an electronic universal testing machine, with sample dimensions of 2X 5X 50mm rectangular test specimens with a span of 30mm, and the bending strength of three identically treated samples was averaged.
4. The sample surface roughness was examined by Atomic Force Microscopy (AFM) on the example cast metal, with the parameters set: the scanning range is 10 μm, the scanning frequency is 2Hz, and the scanning speed is 512 times. The sample polishing process comprises the following steps: the mosaic height is less than or equal to 10mm, and the size is 5 multiplied by 10 mm; sequentially using 320-mesh, 600-mesh, 1200-mesh and 2000-mesh sandpaper for coarse grinding for 2min, 3min and 5min, wherein the pressure is 7N, and the rotating speed is 400 r/min; then rough polishing is carried out, the material of the polishing cloth is velvet, the polishing pressure is 13N, the polishing time is 10min, the rotating speed is 450r/min, and the grinding material is alumina powder (0.5 mu m); fine polishing, wherein the polishing cloth is made of flocking, the polishing pressure is 10N, the polishing time is 15min, the rotating speed is 450r/min, and the grinding material is diamond spray (the granularity is 0.25); and after polishing, carrying out alcohol ultrasonic cleaning and drying.
5. The self-corrosion current density measurements were performed on the example cast metals using an electrochemical workstation with an electrolyte of 25 ℃ in 3.5% aqueous NaCl and a scan rate of 0.0005V/s.
Claims (5)
1. A casting alloy for plastic molds, characterized in that: the mass percentage of each element is Cr: 4.0-4.8, Nb: 0.8 to 1.3, La: 0.5-1.2, B: 1.3-1.6, C: 0.60 to 0.70, Mn: 0.5 to 1.0, Si: 1.0 or less, P: less than or equal to 0.1, S: less than or equal to 0.06 percent, and the balance being iron.
2. A casting alloy for plastic molds as claimed in claim 1, wherein: the Nb elements comprise the following components in percentage by mass: 0.9 to 1.1.
3. A casting alloy for plastic molds as claimed in claim 1, wherein: the La element comprises the following components in percentage by mass: 0.6 to 0.8.
4. A casting alloy for plastic molds as claimed in claim 1, wherein: the total mass percentage of the element B and the element C is 2.0-2.3.
5. The method for producing a casting alloy for a plastic mold as claimed in any one of claims 1 to 4, wherein: after weighing the corresponding raw materials according to the component requirement, calculating the consumption of C of lanthanum oxide during batching, namely, about 0.067 percent of C is consumed when every 1 percent of La is added, melting the other raw materials except lanthanum at the melting temperature of 1480-1600 ℃, so that pure iron and ferrochrome are fully melted; then reducing the power of the electric furnace, reducing the temperature of the melt to 1300-1360 ℃, adding the prepared lanthanum oxide, and deoxidizing by using pure aluminum accounting for 0.1-0.15% of the total amount of the ingredients; and continuously preserving the heat for 6-12 minutes, and rapidly casting the alloy when the temperature of the melt is 1250-1350 ℃.
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