CN110983171A - Method for producing as-cast high-strength all-ferrite nodular cast iron differential case by sand-lined iron mold - Google Patents
Method for producing as-cast high-strength all-ferrite nodular cast iron differential case by sand-lined iron mold Download PDFInfo
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- CN110983171A CN110983171A CN201911324646.4A CN201911324646A CN110983171A CN 110983171 A CN110983171 A CN 110983171A CN 201911324646 A CN201911324646 A CN 201911324646A CN 110983171 A CN110983171 A CN 110983171A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/06—Permanent moulds for shaped castings
- B22C9/068—Semi-permanent moulds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/22—Moulds for peculiarly-shaped castings
- B22C9/24—Moulds for peculiarly-shaped castings for hollow articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/08—Making cast-iron alloys
- C22C33/10—Making cast-iron alloys including procedures for adding magnesium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/04—Cast-iron alloys containing spheroidal graphite
Abstract
The invention relates to a method for producing a cast-state high-strength full-ferrite nodular cast iron differential case by sand-lined iron molds, which comprises the following steps of selecting 60-80 mass percent of pig iron, 20-40 mass percent of scrap steel or 35-65 mass percent of pig iron, 15-30 mass percent of scrap steel and 15-45 mass percent of scrap returns, and carrying out spheroidization and in-ladle inoculation on the selected materials, wherein the mass percent of each element in molten iron is as follows: 2.80-3.50% of C, 3.30-4.50% of Si, less than or equal to 0.50% of Mn, less than or equal to 0.05% of P, less than or equal to 0.025% of S and 0.035-0.065% of Mg; adopting an iron mold sand-lined molding mold and a core making mold, and naturally cooling a casting in the iron mold after pouring; and filling the differential case obtained by opening the casting into an iron box, stacking and naturally cooling. The invention has simple flow, strong process reliability, high process yield, high production efficiency and low production cost, and is suitable for mass production.
Description
Technical Field
The invention belongs to the technical field of sand-lined metal molds casting, and particularly relates to a method for producing an as-cast high-strength full-ferrite nodular cast iron differential case by sand-lined metal molds, which can thoroughly solve the problems of shrinkage cavity and shrinkage porosity inside the differential case, and has uniform hardness and tensile strength distribution and excellent processability in a casting body.
Background
The existing cast nodular cast iron technology achieves a certain grade of mark in the national standard of nodular cast iron by adding alloying elements such as Cu, Mn and the like and controlling the content of pearlite stable elements. Mainly shows that the cast high-grade nodular cast iron has less ferrite content, more pearlite content, high tensile strength and low elongation; on the contrary, the cast low-grade nodular cast iron has the advantages of high ferrite content, low pearlite content, low tensile strength and high elongation. However, this technique cannot be applied to high-strength all-ferritic spheroidal graphite cast iron differential housing castings.
The sand-lined iron mold casting is an advanced casting process formed by coating a layer of precoated sand on an inner cavity of an iron mold. Because the sand coating layer is thin, the casting is cooled in the cavity quickly, and the pearlite nodular cast iron is easy to obtain. Chinese patent No. CN201210296150.2 discloses a casting mold and a casting method for casting an automobile differential case by using metal mold sand, the method includes: the molten iron contains 3.70-3.85% of C, 2.5-2.8% of Si, 0.010-0.016% of S, less than 0.15% of P, 0.027-0.050% of Mg, 0.020-0.035% of Re and the balance of Fe by mass percent; the molten iron is inoculated for three times, high-efficiency Si-Ba-Ca inoculant accounting for 0.7 percent of the weight of the molten iron is placed on nodulizer for nodulizing treatment in the nodulizing treatment, when the nodulizing reaction is finished, the high-efficiency inoculant accounting for 0.4 percent of the weight of the molten iron is added along with the flow when the molten iron is poured, the high-efficiency Si-Ba-Ca inoculant accounting for 0.15 percent of the weight of the molten iron and having the granularity of 1 millimeter is poured along with the flow when the molten iron is poured, and the molten iron is inoculated instantaneously. Above-mentioned technical scheme differential casing material is QT500, and its base member tissue belongs to mixed base member nodular cast iron, belongs to the trade mark of the conventional requirement in the casting field. In addition, chinese patent No. CN201611187967.0 discloses a method for casting a passenger car differential shell by sand lined iron mold, which comprises the following steps: pouring, namely pouring by adopting QT450-10 molten iron, wherein the molten iron comprises the following chemical components in percentage by mass: 3.7-3.8% of C, Si: 1.6% -1.9%, Mn: 0.3-0.4% of Cu, 0.2-0.5%; opening the box, and opening the box buckle 20 minutes after pouring; the casting is solidified for 25 minutes, and then falls into a box and is freely cooled. Above-mentioned technical scheme passenger car differential shell material is QT450-10 trade mark, belongs to low-grade ferrite base body nodular cast iron, also belongs to the trade mark of the conventional requirement in the casting field, still need add more expensive Cu and can reach its regulation trade mark, and manufacturing cost is higher, and the casting is poured the back and is loosened the case card and open the case time long, and production efficiency is low.
Therefore, the prior sand-lined metal mold casting has no application in the production of high-strength full-ferrite nodular cast iron differential case castings.
Disclosure of Invention
Aiming at the problems, the invention provides a method for producing an as-cast high-strength full-ferrite nodular cast iron differential case by sand coating of an iron mold, which can thoroughly solve the problems of shrinkage cavity and shrinkage porosity in the differential case, has uniform hardness and tensile strength distribution in a casting body and has excellent processability, so as to fill the defects of the prior art.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the method for producing the cast-state high-strength full-ferrite nodular cast iron differential case by using the sand-lined iron mold comprises the following steps of selecting 60-80 mass percent of pig iron, 20-40 mass percent of scrap steel or 35-65 mass percent of pig iron, 15-30 mass percent of scrap steel and 15-45 mass percent of scrap returns, and carrying out spheroidization and in-package inoculation on the selected materials, wherein the mass percent of each element in molten iron is as follows: 2.80-3.50% of C, 3.30-4.50% of Si, less than or equal to 0.50% of Mn, less than or equal to 0.05% of P, less than or equal to 0.025% of S and 0.035-0.065% of Mg; adopting an iron mold modeling mold and a core making mold, and naturally cooling a casting in the iron mold after pouring; and filling the differential case obtained by opening the casting into an iron box, stacking and naturally cooling.
The method for producing the as-cast high-strength full-ferrite nodular cast iron differential case by sand coating of the iron mold comprises the following steps:
(1) ingredients
60-80% of pig iron and 20-40% of scrap steel are selected as raw materials for furnace burden; or selecting 35-65% of pig iron, 15-30% of scrap steel and 15-45% of scrap returns by mass percent;
(2) spheroidizing and in-ladle inoculation
Putting the materials prepared in the step (1) into an electric furnace to obtain molten iron with the temperature of 1470-1550 ℃, and pouring the molten iron into a ladle for spheroidization and ladle inoculation; wherein, the mass percentages of all elements in the molten iron after spheroidization and in-ladle inoculation are as follows: 2.80-3.50% of C, 3.30-4.50% of Si, less than or equal to 0.50% of Mn, less than or equal to 0.05% of P, less than or equal to 0.0.025% of S and 0.035-0.065% of Mg;
(3) pouring
Pouring the molten iron subjected to spheroidizing treatment and in-ladle inoculation in the step (2), wherein the temperature of the molten iron is controlled to be 1330-1440 ℃ during pouring;
(4) cooling down
After the iron liquid in the step (3) is poured, naturally cooling the casting in the iron mold for 6-8 minutes, then loosening the box clamp, and naturally cooling for 4-6 minutes after loosening the box clamp;
(5) unpacking
Opening the box after the cooling in the step (4) is finished, wherein the surface temperature of the casting is 400-600 ℃;
(6) boxing
And (4) loading the castings obtained in the step (5) into an iron box through a manipulator, stacking and naturally cooling.
The method for producing the cast-state high-strength full-ferrite nodular cast iron differential case by sand coating of the iron mold comprises the following steps: and (3) adding a rare earth magnesium nodulizer with the mass percentage of 0.9-1.2% into the ladle of the step (2). And (3) adding a silicon-barium-iron alloy inoculant with the mass percentage of 0.7-1.1% into the ladle of the step (2). And (3) adding an SRCB high-efficiency compound inoculant with the mass percentage of 0.06-0.08% during pouring.
Has the advantages that:
the method for producing the cast-state high-strength full-ferrite nodular cast iron differential case by sand-coating the iron mold has simple process, does not need to add expensive alloying materials such as Cu, Mn and the like, obtains the high-strength full-ferrite nodular cast iron differential case by reasonable furnace burden proportion, chemical components of molten iron, in-package inoculation amount, box loosening time, box opening time and the like, saves the method for obtaining the same-material casting by increasing the tensile strength, the elongation and the ferrite amount by carrying out heat treatment again, has strong process reliability, uniform distribution of hardness and tensile strength in the casting body, good processing performance and long service life of a cutter, thereby greatly reducing the production cost and improving the economic benefit of enterprises.
Meanwhile, the invention also has the following advantages:
(1) under the condition that the differential case is not subjected to heat treatment, the material requirements of the cast high-strength full-ferrite nodular cast iron differential can be stably obtained by adopting the existing iron mold sand-lined casting production line, namely the tensile strength (MPa) is more than or equal to 600MPa, the yield strength (MPa) is more than or equal to 470MPa, the elongation (%) > is more than or equal to 10%, the ferrite amount (F) is more than or equal to 95%, the energy conservation and emission reduction can be promoted, and the economic benefit is remarkable;
(2) the invention can thoroughly solve the problems of shrinkage cavity and shrinkage porosity in the differential shell;
(3) the cast-state high-strength full-ferrite nodular cast iron differential case produced by the method does not need to be added with expensive alloying materials such as Cu and Mn, so that the production cost is reduced;
(4) the invention has high production efficiency and high casting process yield;
(1) the invention is produced on the existing iron mold sand-lined production line, and the capital investment is less.
The invention has simple flow, strong process reliability, high process yield, high production efficiency and low production cost, and is suitable for mass production.
Detailed Description
The invention relates to a method for producing a cast-state high-strength full-ferrite nodular cast iron differential case by sand-coating an iron mold, which comprises the following steps of selecting 60-80 mass percent of pig iron, 20-40 mass percent of scrap steel or 35-65 mass percent of pig iron, 15-30 mass percent of scrap steel and 15-45 mass percent of scrap returns, and carrying out spheroidization and in-package inoculation on the selected materials, wherein the mass percent of each element in molten iron is as follows: 2.80-3.50% of C, 3.30-4.50% of Si, less than or equal to 0.50% of Mn, less than or equal to 0.05% of P, less than or equal to 0.025% of S and 0.035-0.065% of Mg; adopting an iron mold modeling mold and a core making mold, and naturally cooling a casting in the iron mold after pouring; and filling the differential case obtained by opening the casting into an iron box, stacking and naturally cooling.
The method specifically comprises the following steps:
(1) ingredients
60-80% of pig iron and 20-40% of scrap steel are selected as raw materials for furnace burden; or selecting 35-65% of pig iron, 15-30% of scrap steel and 15-45% of scrap returns by mass percent;
(2) spheroidizing and in-ladle inoculation
Putting the mixture obtained in the step (1) into an electric furnace to obtain molten iron with the temperature of 1470-1550 ℃, adding a rare earth magnesium nodulizer with the mass percent of 0.9-1.2% into a molten iron ladle, adding a silicon-barium ferroalloy inoculant with the mass percent of 0.7-1.1% into the molten iron ladle, and pouring the molten iron into the molten iron ladle for nodulizing and in-ladle inoculation; wherein, the mass percentages of all elements in the molten iron after spheroidization and in-ladle inoculation are as follows: 2.80-3.50% of C, 3.30-4.50% of Si, less than or equal to 0.50% of Mn, less than or equal to 0.05% of P, less than or equal to 0.0.025% of S and 0.035-0.065% of Mg;
(3) pouring
Pouring the molten iron subjected to spheroidizing treatment and in-ladle inoculation in the step (2), wherein the temperature of the molten iron is controlled to be 1330-1440 ℃ during pouring, and an SRCB high-efficiency compound inoculant with the mass percentage of 0.06-0.08% is added during pouring;
(4) cooling down
After the iron liquid in the step (3) is poured, naturally cooling the casting in the iron mold for 6-8 minutes, then loosening the box clamp, and naturally cooling for 4-6 minutes after loosening the box clamp;
(5) unpacking
Opening the box after the cooling in the step (4) is finished, wherein the surface temperature of the casting is 400-600 ℃;
(6) boxing
And (4) loading the castings obtained in the step (5) into an iron box through a manipulator, stacking and naturally cooling.
Wherein, 0.9 to 1.2 percent by mass of rare earth magnesium nodulizer is added into the ladle in the step (2), the model of the rare earth magnesium nodulizer is QRMG8Re3, the chemical components are Re of 2.5 to 4.0 percent, Mg of 7.0 to 9.0 percent, Ca of 2.0 to 3.5 percent, Si of 35.0 to 44.0 percent, Mn of less than or equal to 4.0 percent, Ti of less than or equal to 1.0 percent, MgO of less than or equal to 1.0 percent and Al of less than or equal to 0.5 percent;
after a silicon barium ferroalloy inoculant accounting for 0.7-1.1 percent by mass is added into the ladle in the step (2), the molten iron is poured into the ladle for spheroidization and ladle inoculation, wherein the silicon barium ferroalloy inoculant is FeBa5Si60, and comprises the chemical components of Ba being more than or equal to 5.0 percent, Si being more than or equal to 60 percent, Al being less than or equal to 3.0 percent, Mn being less than or equal to 0.40 percent, C being less than or equal to 0.20 percent, P being less than or equal to 0.04 percent and S being less than or equal to 0.04 percent;
and (3) adding 0.06-0.08% by mass of SRCB efficient compound inoculant during pouring, wherein the chemical components of the SRCB efficient compound inoculant are 55-65% of Si, 1.5-2.5% of Ca, 1.0-3.0% of Ba, 1.0-2.0% of Re, 0.6-1.5% of Al, less than 0.04% of P and less than 0.02% of S.
The invention is further described below with reference to specific examples:
the material requirement of a certain automobile differential shell is DIN EN 1563 GJS-600-10, wherein the mechanical property is as follows: the tensile strength (MPa) is more than or equal to 600MPa, the yield strength (MPa) is more than or equal to 470MPa, the percentage elongation (%) is more than or equal to 10%, and the Hardness (HB) is 200-; metallographic structure: the ferrite (F) is more than or equal to 95 percent, the graphite is 5-8 grade, the spheroidization rate is more than or equal to 80 percent, and the content of free carbide is less than or equal to 1 percent. The differential case is produced by the method of the present invention, and specific examples are as follows.
Example 1
The method comprises the following specific steps:
(1.1) batching, wherein the main furnace charge is selected from pig iron with the mass of 891Kg and scrap steel with the mass of 363Kg, and the adding amount of the ferrosilicon is 50.3 Kg; wherein the mass percentages of the elements before spheroidization and in-ladle inoculation are as follows: 3.25% of C, 3.22% of Si, 0.17% of Mn, 0.030% of P and 0.013% of S;
(1.2) spheroidizing and in-ladle inoculation
Putting the mixture into an electric furnace to obtain liquid iron with the temperature of 1483 ℃, pouring the liquid iron into a ladle to perform spheroidization and in-ladle inoculation, wherein the addition amount of a spheroidizing agent is 13.8Kg, and the addition amount of an in-ladle inoculant is 12.5 Kg; wherein, the mass percentages of the elements after spheroidization and in-ladle inoculation are as follows: 3.13% of C, 4.27% of Si, 0.17% of Mn, 0.032% of P, 0.009% of S and 0.047% of Mg;
(1.3) casting
Pouring 14 boxes of molten iron with the water outlet weight of 1208Kg and the backwater weight of 101Kg into the spheroidized and inoculated molten iron in the ladle in the step (1.2), wherein the pouring temperature of a first box of the casting is 1401 ℃, and the pouring temperature of a last box of the casting is 1342 ℃;
(1.4) Cooling
Naturally cooling the casting in the iron mold after the iron liquid pouring in the step (1.3) is finished, loosening the box clamp at intervals of 6 minutes and 15 seconds, and opening the box at intervals of 5 minutes;
(1.5) unpacking
Opening the box after the cooling in the step (1.4) is finished; the surface temperature of the casting is 572 ℃ when the box is opened, and the ambient temperature is 26 ℃;
(1.6) boxing
And (4) loading the casting obtained in the step (1.5) into an iron box through mechanical arm demoulding, stacking and naturally cooling.
(1.7) test results
In the embodiment 1 of the invention, the same ladle is used for pouring, the final box and the first box of casting bodies are sampled, one blank and 10 pieces are taken from one box of casting, and the results of metallographic structure and mechanical property inspection are as follows:
metallographic structure: (Table 1)
Mechanical properties: (Table 2)
In the embodiment 1 of the invention, the same ladle is poured with molten iron, all castings of the No. 2 box and the No. 13 box are subjected to X-ray flaw detection, and the castings do not have shrinkage cavities and shrinkage porosity, so that the technical condition requirements of customers are met.
Example 2
The method comprises the following specific steps:
(2.1) compounding
The main furnace charge is selected from 809Kg of pig iron and 443Kg of scrap steel, and the adding amount of ferrosilicon is 55.0 Kg; wherein the mass percentages of the elements before spheroidization and in-ladle inoculation are as follows: 3.01% of C, 3.49% of Si, 0.15% of Mn, 0.027% of P and 0.016% of S.
(2.2) spheroidizing and in-ladle inoculation
Putting the mixture obtained in the step (1.1) into an electric furnace to obtain a liquid iron with the temperature of 1496 ℃, pouring the liquid iron into a foundry ladle to perform spheroidization and ladle inoculation, wherein the addition amount of a spheroidizing agent is 13.8Kg, and the addition amount of an inoculant in the ladle is 12.5 Kg; wherein, the mass percentages of the elements after spheroidization and in-ladle inoculation are as follows: 2.93% of C, 4.48% of Si, 0.16% of Mn, 0.037% of P, 0.012% of S and 0.041% of Mg;
(2.3) casting
Pouring 14 boxes of molten iron with the water outlet weight of 1205Kg and the backwater weight of 106Kg into the spheroidized and inoculated molten iron in the ladle in the step (1.2), wherein the pouring temperature of a first box of the casting is 1392 ℃, and the pouring temperature of a last box of the casting is 1340 ℃;
(2.4) Cooling
Naturally cooling the casting in the iron mold after the iron liquid pouring in the step (1.3) is finished, loosening the box clamp at intervals of 6 minutes and 05 seconds, and opening the box at intervals of 5 minutes;
(2.5) unpacking
Opening the box after the cooling in the step (1.4) is finished; the surface temperature of the casting is 523 ℃ when the box is opened, and the environmental temperature is 22 ℃;
(2.6) boxing
And (4) loading the casting obtained in the step (1.5) into an iron box through mechanical arm demoulding, stacking and naturally cooling.
(2.7) test results
In the embodiment 2 of the invention, the same ladle is used for pouring, the final box and the first box of casting bodies are sampled, one blank and 10 pieces are taken from one box of casting, and the results of metallographic structure and mechanical property inspection are as follows:
metallographic structure: (Table 3)
Mechanical properties: (Table 4)
In the embodiment 2 of the invention, the same ladle is poured with molten iron, all castings in the 2 nd box and the 13 th box are subjected to X-ray flaw detection, and the castings do not have shrinkage cavities and shrinkage porosity, so that the technical condition requirements of customers are met.
Example 3
The method comprises the following specific steps:
(3.1) compounding
The main furnace charge selects 946Kg pig iron and 304Kg scrap steel, the adding amount of the ferrosilicon is 32.1 Kg; wherein the mass percentages of the elements before spheroidization and in-ladle inoculation are as follows: 3.49% of C, 2.35% of Si, 0.13% of Mn, 0.035% of P and 0.018% of S.
(3.2) spheroidizing and in-ladle inoculation
Putting the mixture obtained in the step (1.1) into an electric furnace to obtain a liquid iron with the temperature of 1491 ℃, pouring the liquid iron into a foundry ladle to perform spheroidization and ladle inoculation, wherein the addition amount of a spheroidizing agent is 13.8Kg, and the addition amount of an inoculant in the ladle is 12.5 Kg; wherein, the mass percentages of the elements after spheroidization and in-ladle inoculation are as follows: 3.35% of C, 3.34% of Si, 0.13% of Mn, 0.031% of P, 0.015% of S and 0.049% of Mg;
(3.3) casting
Pouring 14 boxes of molten iron with the water outlet weight of 1210Kg and the backwater weight of 98Kg into the molten iron subjected to spheroidizing treatment and ladle inoculation in the step (1.2), wherein the pouring temperature of a first box of the casting is 1385 ℃, and the pouring temperature of a last box of the casting is 1331 ℃;
(3.4) Cooling
Naturally cooling the casting in the iron mold after the iron liquid pouring in the step (1.3) is finished, loosening the box clamp at intervals of 6 minutes and 32 seconds, and opening the box at intervals of 5 minutes;
(3.5) unpacking
Opening the box after the cooling in the step (1.4) is finished; the surface temperature of the casting is 553 ℃ when the box is opened, and the ambient temperature is 22 ℃;
(3.6) boxing
And (4) loading the casting obtained in the step (1.5) into an iron box through mechanical arm demoulding, stacking and naturally cooling.
(3.7) test results
In the embodiment 3 of the invention, the same ladle is used for pouring, the final box and the first box of casting bodies are sampled, one blank and 10 pieces are taken from one box of casting, and the results of metallographic structure and mechanical property inspection are as follows:
metallographic structure: (Table 5)
Mechanical properties: (Table 6)
In the embodiment 3 of the invention, the same ladle is poured with molten iron, all castings of the No. 2 box and the No. 13 box are subjected to X-ray flaw detection, and the castings do not have shrinkage cavities and shrinkage porosity, so that the technical condition requirements of customers are met.
Example 4
The method comprises the following specific steps:
(4.1) compounding
The main furnace charge is selected from 721Kg of pig iron, 279Kg of scrap steel and 253Kg of scrap returns, and the adding amount of ferrosilicon is 35.7 Kg; wherein the mass percentages of the elements before spheroidization and in-ladle inoculation are as follows: 3.24% of C, 3.26% of Si, 0.15% of Mn, 0.033% of P and 0.016% of S.
(4.2) spheroidizing and in-ladle inoculation
Putting the mixture obtained in the step (2.1) into an electric furnace to obtain a liquid iron with the temperature of 1491 ℃, pouring the liquid iron into a foundry ladle to perform spheroidization and ladle inoculation, wherein the addition amount of a spheroidizing agent is 13.8Kg, and the addition amount of an inoculant in the ladle is 12.5 Kg; wherein, the mass percentages of the elements after spheroidization and in-ladle inoculation are as follows: 3.08 percent of C, 4.22 percent of Si, 0.16 percent of Mn, 0.029 percent of P, 0.011 percent of S and 0.048 percent of Mg;
(4.3) casting
Pouring 14 boxes of molten iron with the water outlet weight of 1202Kg and the backwater weight of 95Kg into the spheroidized and inoculated molten iron in the ladle in the step (2.2), wherein the pouring temperature of a first box of the casting is 1405 ℃, and the pouring temperature of a last box of the casting is 1349 ℃;
(4.4) Cooling
Naturally cooling after the iron liquid in the step (2.3) is poured, loosening the box clamp at an interval of 6 minutes and 07 seconds, and opening the box at an interval of 5 minutes;
(4.5) unpacking
Opening the box after the cooling in the step (2.4) is finished; the surface temperature of the casting is 595 ℃ when the box is opened, and the ambient temperature is 26 ℃;
(4.6) boxing
And (3) loading the casting obtained in the step (2.5) into an iron box through mechanical arm demoulding, stacking and naturally cooling.
(4.7) test results
In the embodiment 4 of the invention, the same ladle is used for pouring, the final box and the first box of casting bodies are sampled, one blank and 10 pieces are taken from one box of casting, and the results of metallographic structure and mechanical property inspection are as follows:
metallographic structure: (Table 7)
Mechanical properties: (Table 8)
In the embodiment 4 of the invention, the same ladle is poured with molten iron, all castings of the No. 2 box and the No. 13 box are subjected to X-ray flaw detection, and the castings do not have shrinkage cavities and shrinkage porosity, so that the technical condition requirements of customers are met.
Example 5
The method comprises the following specific steps:
(5.1) compounding
The main furnace charge selects pig iron with the mass of 613Kg, scrap steel with the mass of 319Kg and foundry returns with the mass of 325Kg, and the adding amount of ferrosilicon is 36.4 Kg; wherein the mass percentages of the elements before spheroidization and in-ladle inoculation are as follows: 3.04% of C, 3.47% of Si, 0.19% of Mn, 0.036% of P and 0.020% of S.
(5.2) spheroidizing and in-ladle inoculation
Putting the mixture obtained in the step (2.1) into an electric furnace to obtain molten iron with the temperature of 1488 ℃, pouring the molten iron into a foundry ladle to perform spheroidization and in-ladle inoculation, wherein the addition amount of a spheroidizing agent is 13.8Kg, and the addition amount of an in-ladle inoculant is 12.5 Kg; wherein, the mass percentages of the elements after spheroidization and in-ladle inoculation are as follows: 2.89% of C, 4.45% of Si, 0.17% of Mn, 0.031% of P, 0.018% of S and 0.052% of Mg;
(5.3) casting
Pouring 14 boxes of iron liquid which is spheroidized and inoculated in the ladle in the step (2.2) with the weight of effluent 1207Kg and the weight of backwater 109Kg, wherein the pouring temperature of the first box of the casting is 1390 ℃, and the pouring temperature of the last box of the casting is 1351 ℃;
(5.4) Cooling
Naturally cooling after the iron liquid pouring in the step (2.3) is finished, loosening the box clamp at intervals of 6 minutes and 43 seconds, and opening the box at intervals of 5 minutes;
(5.5) unpacking
Opening the box after the cooling in the step (2.4) is finished; the surface temperature of the casting is 536 ℃ when the box is opened, and the environmental temperature is 20 ℃;
(5.6) boxing
And (3) loading the casting obtained in the step (2.5) into an iron box through mechanical arm demoulding, stacking and naturally cooling.
(5.7) test results
In the embodiment 5 of the invention, the same ladle is used for pouring, the final box and the first box of casting bodies are sampled, one blank and 10 pieces are taken from one box of casting, and the results of metallographic structure and mechanical property inspection are as follows:
metallographic structure: (watch 9)
Mechanical properties: (watch 10)
In the embodiment 5 of the invention, the same ladle is poured with molten iron, all castings of the No. 2 box and the No. 13 box are subjected to X-ray flaw detection, and the castings do not have shrinkage cavities and shrinkage porosity, so that the technical condition requirements of customers are met.
Example 6
The method comprises the following specific steps:
(6.1) compounding
The main furnace charge is selected from 776Kg of pig iron, 238Kg of scrap steel and 233Kg of foundry returns, and the adding amount of ferrosilicon is 19.6 Kg; wherein the mass percentages of the elements before spheroidization and in-ladle inoculation are as follows: 3.49% of C, 2.35% of Si, 0.23% of Mn, 0.040% of P and 0.012% of S.
(6.2) spheroidizing and in-ladle inoculation
Putting the mixture obtained in the step (2.1) into an electric furnace to obtain a liquid iron with the temperature of 1499 ℃, pouring the liquid iron into a foundry ladle to perform spheroidization and ladle inoculation, wherein the addition amount of a spheroidizing agent is 13.8Kg, and the addition amount of an inoculant in the ladle is 12.5 Kg; wherein, the mass percentages of the elements after spheroidization and in-ladle inoculation are as follows: 3.37% of C, 3.39% of Si, 0.19% of Mn, 0.038% of P, 0.010% of S and 0.043% of Mg;
(6.3) casting
Pouring 14 boxes of molten iron with the water outlet weight of 1213Kg and the backwater weight of 98Kg into the molten iron subjected to spheroidizing treatment and in-ladle inoculation in the step (2.2), wherein the pouring temperature of the first box of the casting is 1392 ℃, and the pouring temperature of the last box of the casting is 1339 ℃;
(6.4) Cooling
Naturally cooling after the iron liquid in the step (2.3) is poured, loosening the box clamp at intervals of 6 minutes and 27 seconds, and opening the box at intervals of 5 minutes;
(6.5) unpacking
Opening the box after the cooling in the step (2.4) is finished; the surface temperature of the casting is 503 ℃ when the box is opened, and the environmental temperature is 29 ℃;
(6.6) boxing
And (3) loading the casting obtained in the step (2.5) into an iron box through mechanical arm demoulding, stacking and naturally cooling.
(6.7) test results
In example 6 of the invention, the same ladle is used for pouring, the final box and the first box of casting bodies are sampled, one blank and 10 pieces are taken from one box of casting, and the results of metallographic structure and mechanical property inspection are as follows:
metallographic structure: (watch 11)
Mechanical properties: (watch 12)
In the embodiment 6 of the invention, the same ladle is poured with molten iron, all castings of the No. 2 box and the No. 13 box are subjected to X-ray flaw detection, and the castings do not have shrinkage cavities and shrinkage porosity, so that the technical condition requirements of customers are met.
Example 7
The method comprises the following specific steps:
(7.1) compounding
The main furnace charge is selected from 452Kg of pig iron, 241Kg of scrap steel and 559Kg of scrap returns, and the adding amount of ferrosilicon is 23.2 Kg; wherein the mass percentages of the elements before spheroidization and in-ladle inoculation are as follows: 3.03% of C, 3.42% of Si, 0.16% of Mn, 0.036% of P and 0.011% of S.
(7.2) spheroidizing and ladle inoculation
Putting the mixture obtained in the step (2.1) into an electric furnace to obtain a liquid iron with the temperature of 1490 ℃, pouring the liquid iron into a foundry ladle to perform spheroidization and ladle inoculation, wherein the addition amount of a spheroidizing agent is 13.8Kg, and the addition amount of an inoculant in the ladle is 12.5 Kg; wherein, the mass percentages of the elements after spheroidization and in-ladle inoculation are as follows: 2.95% of C, 4.46% of Si, 0.15% of Mn, 0.036% of P, 0.009% of S and 0.048% of Mg;
(7.3) casting
Pouring 14 boxes of molten iron with the water outlet weight of 1205Kg and the backwater weight of 100Kg into the spheroidized and inoculated molten iron in the ladle in the step (2.2), wherein the pouring temperature of the first box of the casting is 1386 ℃, and the pouring temperature of the last box of the casting is 1335 ℃;
(7.4) Cooling
Naturally cooling after the iron liquid in the step (2.3) is poured, loosening the box clamp at intervals of 6 minutes and 59 seconds, and opening the box at intervals of 5 minutes;
(7.5) unpacking
Opening the box after the cooling in the step (2.4) is finished; the surface temperature of the casting is 483 ℃ when the box is opened, and the ambient temperature is 25 ℃;
(7.6) boxing
And (3) loading the casting obtained in the step (2.5) into an iron box through mechanical arm demoulding, stacking and naturally cooling.
(7.7) test results
In example 7 of the invention, the same ladle is used for pouring, the final box and the first box of casting bodies are sampled, one blank and 10 pieces are taken from one box of casting, and the results of metallographic structure and mechanical property inspection are as follows:
metallographic structure: (watch 13)
Mechanical properties: (watch 14)
In embodiment 7 of the invention, the same ladle is poured with molten iron, and X-ray flaw detection is carried out on all castings of the No. 2 box and the No. 13 box, so that the castings do not have the phenomena of shrinkage cavity and shrinkage porosity, and the technical condition requirements of customers are met.
The invention relates to a method for producing an as-cast high-strength full-ferrite nodular cast iron differential case by sand-coating an iron mold, which adopts reasonable charge mixture ratio, molten iron chemical components, in-ladle inoculation amount, box loosening time and box opening time, does not need to add expensive alloying materials such as Cu, Mn and the like to obtain the metallographic structure and the mechanical property technical requirements of the as-cast high-strength full-ferrite nodular cast iron differential case, and does not have the phenomena of shrinkage cavity and shrinkage porosity through cast body dissection and X-ray flaw detection. Compared with the prior art, the invention also has the following advantages:
(1) the casting can stably obtain as-cast high-strength full-ferrite nodular cast iron, so that the heat treatment cost is saved, and the production cost is reduced;
(2) the hardness and tensile strength in the casting body are uniformly distributed, the matrix structure is ferrite, the machining performance is good, the service life of the cutter is long, and the machining cost is reduced;
(3) the problems of shrinkage cavity and shrinkage porosity in the differential shell can be thoroughly solved;
(4) the production efficiency is high, and the casting process yield is high;
(5) the pearlite stabilizing element can be relaxed in the charge proportioning, so that the use amount of scrap steel can be increased, and the production cost is reduced.
Claims (5)
1. A method for producing a cast-state high-strength full-ferrite nodular cast iron differential case by sand-lined iron molds comprises the following steps of selecting 60-80 mass percent of pig iron, 20-40 mass percent of scrap steel or 35-65 mass percent of pig iron, 15-30 mass percent of scrap steel and 15-45 mass percent of scrap returns, and carrying out spheroidization and in-package inoculation on the selected materials, wherein the mass percent of each element in molten iron is as follows: 2.80-3.50% of C, 3.30-4.50% of Si, less than or equal to 0.50% of Mn, less than or equal to 0.05% of P, less than or equal to 0.025% of S and 0.035-0.065% of Mg; adopting an iron mold sand-lined molding mold and a core making mold, and naturally cooling a casting in the iron mold after pouring; and filling the differential case obtained by opening the casting into an iron box, stacking and naturally cooling.
2. The method of sand lined metal molds for producing an as-cast high strength all-ferritic spheroidal graphite cast iron differential housing according to claim 1, comprising the steps of:
(1) ingredients
60-80% of pig iron and 20-40% of scrap steel are selected as raw materials for furnace burden; or selecting 35-65% of pig iron, 15-30% of scrap steel and 15-45% of scrap returns by mass percent;
(2) spheroidizing and in-ladle inoculation
Putting the materials prepared in the step (1) into an electric furnace to obtain molten iron with the temperature of 1470-1550 ℃, and pouring the molten iron into a ladle for spheroidization and ladle inoculation; wherein, the mass percentages of all elements in the molten iron after spheroidization and in-ladle inoculation are as follows: 2.80-3.50% of C, 3.30-4.50% of Si, less than or equal to 0.50% of Mn, less than or equal to 0.05% of P, less than or equal to 0.0.025% of S and 0.035-0.065% of Mg;
(3) pouring
Pouring the molten iron subjected to spheroidizing treatment and in-ladle inoculation in the step (2), wherein the temperature of the molten iron is controlled to be 1330-1440 ℃ during pouring;
(4) cooling down
After the iron liquid in the step (3) is poured, naturally cooling the casting in the iron mold for 6-8 minutes, then loosening the box clamp, and naturally cooling for 4-6 minutes after loosening the box clamp;
(5) unpacking
Opening the box after the cooling in the step (4) is finished, wherein the surface temperature of the casting is 400-600 ℃;
(6) boxing
And (4) loading the castings obtained in the step (5) into an iron box through a manipulator, stacking and naturally cooling.
3. The method of sand lined metal molds for producing an as-cast high strength all-ferritic spheroidal graphite cast iron differential housing according to claim 2, wherein: and (3) adding a rare earth magnesium nodulizer with the mass percentage of 0.9-1.2% into the ladle of the step (2).
4. The method of sand lined metal molds for producing an as-cast high strength all-ferritic spheroidal graphite cast iron differential housing according to claim 2, wherein: and (3) adding a silicon-barium-iron alloy inoculant with the mass percentage of 0.7-1.1% into the ladle of the step (2).
5. The method of sand lined metal molds for producing an as-cast high strength all-ferritic spheroidal graphite cast iron differential housing according to claim 2, wherein: and (3) adding an SRCB high-efficiency compound inoculant with the mass percentage of 0.06-0.08% during pouring.
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