CN114317862B - Preparation method of integrated vermicular core-spun yarn and thin-wall vermicular iron casting - Google Patents
Preparation method of integrated vermicular core-spun yarn and thin-wall vermicular iron casting Download PDFInfo
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Abstract
The invention discloses an integrated vermicular core-spun yarn and a preparation method of a thin-wall vermicular iron casting, wherein the integrated vermicular core-spun yarn comprises an outer skin and alloy powder wrapped in the outer skin, wherein the alloy powder comprises the following components in percentage by weight: 10 to 15 weight percent of Mg; 55 to 65 weight percent of Si; 3 to 5 weight percent of Ba; 0.8-1.5 wt% of Al; 2-4 wt% of C; and the balance of Fe. The integrated vermicular cored wire is used in the preparation process of the thin-wall vermicular iron casting. The invention can not only reduce the generation of magnesium oxide and the occurrence probability of slag holes, but also supplement the burning loss of carbon element, stabilize the carbon equivalent and liquidus temperature of molten iron, and is favorable for promoting the precipitation of graphite and reducing the white cast tendency; the preparation process of the thin-wall vermicular cast iron can be simplified, and the production cost is reduced.
Description
Technical Field
The invention belongs to the technical field of vermicular cast iron manufacturing, and particularly relates to an integrated vermicular cored wire and a preparation method of a thin-wall vermicular iron casting.
Background
With the development of low emission and light weight requirements of internal combustion engines, light weight requirements are required for many parts. For example, flywheel housings, which are essential components of internal combustion engines, are required to be thin-walled and lightweight by high-strength vermicular cast iron materials. The vermiculizer is used as a key raw material for forming and growing vermicular graphite, and the components and the quality of the vermicular graphite determine the performance of the thin-wall vermicular iron casting, so that the vermicular graphite has very important function.
The vermiculizer prepared by the smelting method has burning loss in the smelting and crushing processes, so that inert magnesium oxide exists in the vermiculizer, and the probability of slag holes is increased. The existing vermiculizer is generally rare earth magnesium silicon iron, the rare earth can play a role in purifying molten iron and widening the vermiculizing range to a certain extent, but the problems of graphite form deterioration, white cast tendency increase and the like can be caused by the addition of the rare earth element, particularly for thin-wall castings, the defects of the rare earth element can be very obvious because the casting cooling speed is high and the white cast tendency is large, and the advantages of delaying decline and the like can not be reflected.
In view of this, there is an urgent need to develop an integrated vermicular cored wire suitable for use in the preparation of thin-walled vermicular iron castings to reduce the generation of magnesium oxide and the occurrence probability of slag holes, and at the same time, supplement the burning loss of carbon element, stabilize the carbon equivalent and liquidus temperature of molten iron, facilitate the precipitation of graphite and reduce the white cast tendency; the preparation process of the thin-wall vermicular iron casting can be simplified.
Disclosure of Invention
Aiming at overcoming at least one of the defects in the prior art, the invention solves the technical problem of providing a preparation method of an integrated vermicular cored wire and a thin-wall vermicular iron casting; the magnesium oxide can be reduced, the probability of slag hole occurrence can be reduced, the burning loss of carbon elements can be supplemented, the carbon equivalent and the liquidus temperature of molten iron can be stabilized, the graphite precipitation can be promoted, and the white cast tendency can be reduced; the preparation process of the thin-wall vermicular iron casting can be simplified.
In order to solve the technical problem, an embodiment of the invention provides an integrated vermicular core-spun yarn, which comprises an outer skin and alloy powder wrapped in the outer skin;
wherein the alloy powder comprises the following components in percentage by weight:
Mg:10wt％～15wt％；
Si:55wt％～65wt％；
Ba:3wt％～5wt％；
AL:0.8wt％～1.5wt％；
C:2wt％～4wt％；
the balance of Fe.
Further, the alloy powder is formed by mixing three materials of magnesium powder, silicon-barium alloy powder and graphitized carburant, wherein the particle sizes of the magnesium powder, the silicon-barium alloy powder and the graphitized carburant are 12-18 meshes.
Further, the outer skin is made of a steel strip of type 08 AL.
Furthermore, the diameter of the integrated vermicular cored wire is 10-13 mm, the weight of the wire is 450-600 g/m, and the core dose is 300-450 g/m.
The embodiment of the invention provides a preparation method of a thin-wall vermicular cast iron, which comprises the following steps:
s1, smelting: adding a mixture of pig iron, a vermicular iron returns, scrap steel and a graphitizing carburant into an electric furnace to be molten iron;
s2, adjusting the content of the molten iron components: and (3) regulating the weight percentage of each chemical element component in the molten iron obtained in the step (S1) to the following range through stokehole analysis: 3.7 to 3.85 percent of C, 2.1 to 2.2 percent of Si, 0 to 0.3 percent of Mn, 0.008 to 0.015 percent of S, 0 to 0.03 percent of P and 0 to 0.01 percent of Ti;
s3, alloying treatment: adding alloy elements into a 2-ton smelting ladle with the height-diameter ratio of 1.5, and then adding the molten iron obtained in the step S2 into the 2-ton smelting ladle for alloying treatment;
s4, vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in the 2-ton smelting ladle by adopting the integrated vermicular cored wire;
s5, pouring: and (5) transferring the molten iron obtained in the step (S4) to a casting cavity for pouring, and naturally cooling after pouring to obtain the thin-wall vermicular iron casting.
Further, in the step S4, the temperature of the vermicular wire feeding treatment is 1440-1460 ℃, the wire feeding speed is 20-30 m/min, and the adding amount of the integrated vermicular cored wire is 6-12 m according to the sulfur content in the molten iron obtained in the step S2.
Further, in the step S1, the ratio of pig iron, scrap steel and compacted iron returns is 2;
and the alloy elements added in the step S3 are Cu or/and Sn.
Further, the weight percentage of each chemical element component in the thin-wall vermicular iron casting obtained in the step S5 is as follows:
C:3.7wt％～3.85wt％，S:0.008wt％～0.015wt％，Si:2.2wt％～2.3wt％，Mn:0wt％～0.3wt％，P:0～0.03wt％，Ti:0wt％～0.01wt％，Mg:0.014wt％～0.018wt％,Cu:0.5wt％～0.7wt％，Sn:0.05wt％～0.07wt％。
further, the preparation method further includes a step performed between step S4 and step S5 of: the slag skimming, temperature measurement and component detection are sequentially carried out.
Further, the tensile strength of the thin-wall vermicular iron casting obtained in the step S5 is more than 450MPa, the elongation is more than 1.5%, the vermicular rate is 80% -95%, the hardness is 200-250 HBW, the pearlite is more than 75%, and the carbide is less than 1%.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
the integrated vermicular core-spun yarn comprises an outer skin and alloy powder wrapped in the outer skin, wherein the alloy powder comprises the following components in percentage by weight: 10 to 15 weight percent of Mg; 55 to 65 weight percent of Si; 3 to 5 weight percent of Ba; 0.8-1.5 wt% of Al; 2-4 wt% of C; and the balance of Fe. The integrated vermicular cored wire is used in the preparation process of the thin-wall vermicular iron casting.
The integrated vermicular cored wire is prepared by a mechanical mixing method, does not contain rare earth elements, and contains a certain amount of carburant and barium elements. Compared with the vermiculizer prepared by smelting, the vermiculizer can reduce the generation of magnesium oxide, thereby reducing the probability of slag holes; the burning loss of carbon elements in the molten iron in the vermicular treatment process can be compensated, and the carbon equivalent and the liquidus temperature of the molten iron are stabilized; the existence of the silicon-barium component can also play a role in inoculation, and in addition, the silicon-barium component does not contain rare earth elements, so that the graphite precipitation is promoted to be added to reduce the chilling tendency; the method has the advantages that the addition of the inoculated core-spun yarn is not needed after the integrated vermicular core-spun yarn is adopted, the preparation process of the thin-wall vermicular iron casting is simplified, and the production cost is reduced.
In conclusion, the magnesium oxide can be reduced, the probability of slag holes can be reduced, the burning loss of carbon elements can be supplemented, the carbon equivalent and the liquidus temperature of molten iron can be stabilized, and the graphite precipitation can be promoted and the white cast tendency can be reduced; the preparation process of the thin-wall vermicular iron casting can be simplified, and the production cost is reduced.
Drawings
FIGS. 1.1 and 1.2 are the metallographic images of the graphite and the matrix of the thin-walled vermicular iron obtained by the preparation method provided in example 1;
FIGS. 2.1 and 2.2 are the matrix metallographic images of the graphite metallographic images of the thin-walled vermicular iron obtained by the preparation method provided in example 2;
FIGS. 3.1 and 3.2 are the matrix metallographic images of the graphite metallographic images of the thin-walled vermicular iron obtained by the preparation method provided in example 3;
FIGS. 4.1 and 4.2 are the matrix metallographic images of the thin-walled compacted graphite obtained by the preparation method provided in example 4;
FIGS. 5.1 and 5.2 are the matrix metallographic images of the thin-walled vermicular iron obtained by the preparation method provided in example 5;
fig. 6.1 and fig. 6.2 are the matrix metallographic images of the thin-walled vermicular iron obtained by the preparation method provided in example 6.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
To facilitate an understanding of the invention, some terms used in the art are explained below:
vermicular cast iron (compacted iron for short): this is a cast iron in which graphite is mostly vermicular and a small amount of spheroidal graphite is incorporated.
A vermiculizer: certain metals or alloys added to the liquid iron in order to obtain vermicular graphite cast iron.
Core-spun yarn: a material obtained by winding alloy powder from a strip-shaped steel strip is added to molten iron by a wire feeding method to react the alloy powder with the molten iron.
The integrated vermicular cored wire of the invention comprises the following components: the vermicular cast iron core-spun yarn is characterized in that a vermiculizer and an inoculant are integrated into one core-spun yarn, and the vermicular cast iron core-spun yarn can be produced without inoculation.
White cast iron tendency: the method is characterized in that no graphite is separated out in the crystallization process, all carbon in the casting exists in the form of a permeated carbon body, and a fracture is silvery white. White cast iron has high hardness, but has poor toughness and is difficult to process, and therefore, is rarely used as it is in industrial applications.
Rare earth elements: the lanthanide elements in the periodic table of the elements and the total of seventeen metal elements of scandium and yttrium are called.
The smelting method comprises the following steps: the preparation process of the vermicular agent comprises the steps of fusing required elements together by a smelting method to form an alloy, and crushing the alloy to a certain granularity.
Mechanical mixing method: a vermiculizer (such as vermicular cored wire) which is prepared by mechanically mixing the required materials uniformly.
The invention provides an integrated vermicular core-spun yarn, which comprises an outer skin and alloy powder wrapped in the outer skin;
wherein the alloy powder comprises the following components in percentage by weight:
Mg:10wt％～15wt％。
Si:55wt％～65wt％。
Ba:3wt％～5wt％。
AL:0.8wt％～1.5wt％。
C:2wt％～4wt％；
and the balance of Fe.
Wherein the alloy powder is formed by mixing three materials of magnesium powder, silicon-barium alloy powder and graphitized carburant, the particle sizes of the magnesium powder, the silicon-barium alloy powder and the graphitized carburant are 12-18 meshes (namely 0.018-1.7 mm).
The outer skin is preferably made of a steel strip of type 08AL, but may be made of other materials, and is not particularly limited herein.
In the invention, the diameter of the integrated vermicular cored wire is 10-13 mm, the weight of the wire is 450-600 g/m, and the core dose is 300-450 g/m.
The integrated vermicular cored wire is prepared by a mechanical mixing method, does not contain rare earth elements, and contains a certain amount of carburant and barium elements. Compared with the vermiculizer prepared by smelting, the vermiculizer can reduce the generation of magnesium oxide, thereby reducing the probability of slag holes; the burning loss of carbon elements in the molten iron in the vermicular treatment process can be compensated, and the carbon equivalent and the liquidus temperature of the molten iron are stabilized; the existence of the silicon-barium component can play a role in inoculation, and in addition, the silicon-barium component does not contain rare earth elements, so that the graphite precipitation is facilitated to be added to reduce the chilling tendency; the method has the advantages that the addition of the inoculated core-spun yarn is not needed after the integrated vermicular core-spun yarn is adopted, the preparation process of the thin-wall vermicular iron casting is simplified, and the production cost is reduced.
The invention also provides a preparation method of the thin-wall vermicular cast iron, which comprises the following steps:
s1, smelting: adding a mixture of pig iron, vermicular iron return stock, scrap steel and a graphitizing carburant into an electric furnace to be melted into molten iron.
Preferably, the ratio of pig iron to scrap steel to compacted iron returns is 2; the graphitizing carburant is preferably 2 to 5 percent of the total amount of pig iron, scrap steel and vermicular iron returns.
S2, adjusting the content of the molten iron components: and (3) regulating the weight percentage of each chemical element component in the molten iron obtained in the step (S1) to the following range through stokehole analysis: 3.7 to 3.85 weight percent of C, 2.1 to 2.2 weight percent of Si, 0 to 0.3 weight percent of Mn, 0.008 to 0.015 weight percent of S, 0 to 0.03 weight percent of P and 0 to 0.01 weight percent of Ti.
S3, alloying treatment: adding alloy elements into a 2-ton smelting ladle with the height-diameter ratio of 1.5, and then adding the molten iron obtained in the step S2 into the 2-ton smelting ladle for alloying treatment; the alloy element is Cu or/and Sn. In the present invention, cu and Sn are preferred; in the present invention, 0.5 to 1.0wt% of Cu, 0.05 to 0.10wt% of Sn, more preferably 0.6 to 0.9wt% of Cu, and 0.06 to 0.09wt% of Sn are used. More preferably, cu is 12Kg, sn:1.2Kg.
S4, vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in a 2-ton smelting ladle by adopting the integrated vermicular cored wire; in the step S4, the temperature of the vermicular wire feeding treatment is 1440-1460 ℃, the wire feeding speed is 20-30 m/min (preferably 25 m/min), and the adding amount of the integrated vermicular cored wire is 6-12 m according to the sulfur content in the molten iron obtained in the step S2.
The method adopts the wire feeding method to replace the punching method to produce the thick and large vermicular cast iron piece, has small generated smoke dust, is environment-friendly, improves the absorption rate and has stable production process.
S5, pouring: and (5) transferring the molten iron obtained in the step (S4) to a casting cavity for pouring, and naturally cooling after pouring to obtain the thin-wall vermicular iron casting. Wherein the casting temperature is preferably 1320-1410 ℃, and more preferably 1340-1390 ℃; the casting time is preferably 20s to 8min.
The thin-wall vermicular iron casting obtained in the step S5 comprises the following chemical element components in percentage by weight:
C:3.7wt％～3.85wt％，S:0.008wt％～0.015wt％，Si:2.2wt％～2.3wt％，Mn:0wt％～0.3wt％，P:0～0.03wt％，Ti:0wt％～0.01wt％，Mg:0.014wt％～0.018wt％,Cu:0.5wt％～0.7wt％，Sn:0.05wt％～0.07wt％。
the above preparation method further includes a step performed between step S4 and step S5 of: the slag skimming, temperature measurement and component detection are sequentially carried out.
The tensile strength of the thin-wall vermicular iron casting obtained in the step S5 is more than 450MPa, the elongation is more than 1.5%, the vermicular rate is 80% -95%, the hardness is 200-250 HBW, the pearlite is more than 75%, and the carbide is less than 1%.
In order to further illustrate the present invention, the following examples are provided for illustrative purposes.
Example 1:
the integrated creeping cored wire adopted by the embodiment is as follows: the diameter was 13mm, the thread weight was 450g/m and the core dose was 300g/m. The components and the weight percentage of the alloy powder are 10wt% of Mg; 58wt% of Si;
4wt% of Ba; 1.2wt% of AL; 3wt% of C; and the balance of Fe.
The molten iron in the step S2 is adjusted to have the following components: 3.8wt% of C, 2.15wt% of Si, 0.22wt% of Mn, 0.008wt% of S, 0.013wt% of P and 0.006wt% of Ti.
In step S3 — alloying treatment, 12Kg of Cu and 1.2Kg of Sn were added to a 2-ton melting ladle having a height-diameter ratio of 1.5.
Step S4, in the vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in a 2-ton smelting ladle by adopting the integrated vermicular cored wire of the embodiment; wherein the temperature of the vermicular wire feeding treatment is 1450 ℃, the wire feeding speed is 25m/min, and the addition amount of the integrated vermicular cored wire is 11m according to the sulfur content in the molten iron obtained in the step S2.
The thin-wall vermicular iron casting obtained by final pouring comprises the following chemical element components in percentage by weight:
C:3.755wt％，S:0.008wt％，Si:2.25wt％，Mn:0.21wt％，P:0.013wt％，Ti:0.006wt％，Mg:0.014wt％,Cu:0.62wt％，Sn:0.064wt％。
the thin-wall vermicular iron casting prepared by the method and prepared by the integrated vermicular cored wire has the tensile strength of more than 467MPa, the elongation of 2 percent, the vermicular rate of 90 percent, the hardness of 212HBW, pearlite of 85 percent and carbide of less than 1 percent (see figure 1.1 and figure 1.2)
Example 2:
the integrated creeping cored wire adopted by the embodiment is as follows: the diameter was 13mm, the thread weight was 500g/m and the core dose was 350g/m. The components and the weight percentage of the alloy powder are that Mg accounts for 12wt%; 55wt% of Si;
4wt% of Ba; 1.2wt% of AL; 3wt% of C; and the balance of Fe.
The molten iron in the step S2 is adjusted to have the following components: 3.82wt% of C, 2.10wt% of Si, 0.24wt% of Mn, 0.008wt% of S, 0.013wt% of P and 0.006wt% of Ti.
In the step S3-alloying treatment, 12Kg of Cu and 1.2Kg of Sn are added to a 2-ton melting ladle having an aspect ratio of 1.5.
Step S4, in the vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in a 2-ton smelting ladle by adopting the integrated vermicular cored wire of the embodiment; wherein the temperature of the vermicular wire feeding treatment is 1452 ℃, the wire feeding speed is 25m/min, and the adding amount of the integrated vermicular cored wire is 8m according to the sulfur content in the molten iron obtained in the step S2.
The thin-wall vermicular iron casting obtained by final pouring comprises the following chemical element components in percentage by weight:
C:3.752wt％，S:0.008wt％，Si:2.2wt％，Mn:0.24wt％，P:0.013wt％，Ti:0.006wt％，Mg:0.015wt％，Cu:0.63wt％，Sn:0.064wt％。
the thin-wall vermicular iron casting prepared by the method and prepared by the integrated vermicular cored wire has the tensile strength of more than 472MPa, the elongation of 2 percent, the vermicular rate of 90 percent, the hardness of 215HBW, 85 percent of pearlite and less than 1 percent of carbide (see fig. 2.1 and 2.2).
Example 3:
the integrated vermicular cored wire adopted in the embodiment: the diameter was 13mm, the thread weight was 530g/m and the core dose was 380g/m. The components and the weight percentage of the alloy powder are 15wt% of Mg; 62wt% of Si;
4wt% of Ba; 1.0wt% of AL; 3wt% of C; the balance of Fe.
The molten iron in the step S2 is adjusted to have the following components: 3.85wt% of C, 2.18wt% of Si, 0.20wt% of Mn, 0.008wt% of S, 0.014wt% of P and 0.007wt% of Ti.
In step S3 — alloying treatment, 12Kg of Cu and 1.2Kg of Sn were added to a 2-ton melting ladle having a height-diameter ratio of 1.5.
Step S4, in the vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in a 2-ton smelting ladle by adopting the integrated vermicular cored wire of the embodiment; wherein the temperature of the vermicular wire feeding treatment is 1455 ℃, the wire feeding speed is 25m/min, and the addition of the integrated vermicular cored wire is 6m according to the sulfur content in the molten iron obtained in the step S2.
The thin-wall vermicular iron casting obtained by final pouring comprises the following chemical element components in percentage by weight:
C:3.8wt％，S:0.008wt％，Si:2.26wt％，Mn:0.25wt％，P:0.015wt％，Ti:0.007wt％，Mg:0.014wt％，Cu:0.65wt％，Sn:0.064wt％。
the thin-wall vermicular iron casting prepared by the method and prepared by the integrated vermicular cored wire has the tensile strength of more than 460MPa, the elongation of 2 percent, the vermicular rate of 85 percent, the hardness of 210HBW, pearlite 85 percent and carbide less than 1 percent (see fig. 3.1 and 3.2).
Example 4:
the integrated creeping cored wire adopted by the embodiment is as follows: the diameter was 13mm, the thread weight was 450g/m and the core dose was 300g/m. The components and the weight percentage of the alloy powder are 10wt% of Mg; 58wt% of Si;
4wt% of Ba; 1.20wt% of AL; 3wt% of C; and the balance of Fe.
The molten iron in the step S2 is adjusted to have the following components: 3.82wt% of C, 2.16wt% of Si, 0.18wt% of Mn, 0.015wt% of S, 0.015wt% of P and 0.008wt% of Ti.
In step S3 — alloying treatment, 12Kg of Cu and 1.2Kg of Sn were added to a 2-ton melting ladle having a height-diameter ratio of 1.5.
Step S4, in the vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in a 2-ton smelting ladle by adopting the integrated vermicular cored wire of the embodiment; wherein the temperature of the vermicular wire feeding treatment is 1450 ℃, the wire feeding speed is 25m/min, and the adding amount of the integrated vermicular cored wire is 12m according to the sulfur content in the molten iron obtained in the step S2.
The thin-wall vermicular iron casting obtained by final pouring comprises the following chemical element components in percentage by weight:
C:3.85wt％，S:0.014wt％，Si:2.23wt％，Mn:0.18wt％，P:0.015wt％，Ti:0.007wt％，Mg:0.017wt％，Cu:0.61wt％，Sn:0.065wt％。
the thin-wall vermicular iron casting prepared by the method by adopting the integrated vermicular cored wire and the preparation method has the tensile strength of more than 496MPa, the elongation of 2 percent, the vermicular rate of 85 percent, the hardness of 220HBW, pearlite 85 percent and carbide less than 1 percent (see fig. 4.1 and 4.2).
Example 5:
the integrated creeping cored wire adopted by the embodiment is as follows: the diameter was 13mm, the thread weight was 500g/m and the core dose was 350g/m. The components and the weight percentage of the alloy powder are that Mg accounts for 12wt%; 55wt% of Si;
4wt% of Ba; 1.20wt% of AL; 3wt% of C; the balance of Fe.
The molten iron in the step S2 is adjusted to have the following components: 3.82wt% of C, 2.20wt% of Si, 0.27wt% of Mn, 0.015wt% of S, 0.018wt% of P and 0.006wt% of Ti.
In step S3 — alloying treatment, 12Kg of Cu and 1.2Kg of Sn were added to a 2-ton melting ladle having a height-diameter ratio of 1.5.
Step S4, in the vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in a 2-ton smelting ladle by adopting the integrated vermicular cored wire of the embodiment; wherein the temperature of the vermicular wire feeding treatment is 1458 ℃, the wire feeding speed is 25m/min, and the adding amount of the integrated vermicular cored wire is 8.5m according to the sulfur content in the molten iron obtained in the step S2.
The thin-wall vermicular iron casting obtained by final pouring comprises the following chemical element components in percentage by weight:
C:3.79wt％，S:0.013wt％，Si:2.27wt％，Mn:0.24wt％，P:0.018wt％，Ti:0.006wt％，Mg:0.017wt％，Cu:0.66wt％，Sn:0.065wt％。
the thin-wall vermicular iron casting prepared by the method and prepared by the integrated vermicular cored wire has the tensile strength of more than 502MPa, the elongation of 2 percent, the vermicular rate of 85 percent, the hardness of 224HBW, pearlite 85 percent and carbide less than 1 percent (see fig. 5.1 and 5.2).
Example 6:
the integrated creeping cored wire adopted by the embodiment is as follows: the diameter was 13mm, the thread weight was 530g/m and the core dose was 380g/m. The components and the weight percentage of the alloy powder are 15wt% of Mg; 62wt% of Si;
4wt% of Ba; 1.0wt% of AL; 3wt% of C; and the balance of Fe.
The molten iron in the step S2 is adjusted to have the following components: 3.77wt% of C, 2.16wt% of Si, 0.24wt% of Mn, 0.015wt% of S, 0.016wt% of P and 0.008wt% of Ti.
In step S3 — alloying treatment, 12Kg of Cu and 1.2Kg of Sn were added to a 2-ton melting ladle having a height-diameter ratio of 1.5.
Step S4, in the vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in a 2-ton smelting ladle by adopting the integrated vermicular cored wire of the embodiment; wherein the temperature of the vermicular wire feeding treatment is 1460 ℃, the wire feeding speed is 25m/min, and the adding amount of the integrated vermicular cored wire is 6.5m according to the sulfur content in the molten iron obtained in the step S2.
The thin-wall vermicular iron casting obtained by final pouring comprises the following chemical element components in percentage by weight:
C:3.82wt％，S:0.013wt％，Si:2.21wt％，Mn:0.24wt％，P:0.015wt％，Ti:0.008wt％，Mg:0.018wt％，Cu:0.66wt％，Sn:0.063wt％。
the thin-wall vermicular iron casting prepared by the method and prepared by the integrated vermicular cored wire has the tensile strength of more than 512MPa, the elongation of 2%, the vermicular rate of 80%, the hardness of 226HBW, pearlite of 85% and carbide of less than 1% (see fig. 6.1 and 6.2).
The integrated vermicular cored wire is prepared by a mechanical mixing method, does not contain rare earth elements, and contains a certain amount of carburant and barium elements. Compared with the vermiculizer prepared by smelting, the vermiculizer can reduce the generation of magnesium oxide, thereby reducing the probability of slag holes; the burning loss of carbon elements in the molten iron in the vermicular treatment process can be compensated, and the carbon equivalent and the liquidus temperature of the molten iron are stabilized; the existence of the silicon-barium component can also play a role in inoculation, and in addition, the silicon-barium component does not contain rare earth elements, so that the graphite precipitation is promoted to be added to reduce the chilling tendency; the thin-wall vermicular cast iron casting preparation method adopting the integrated vermicular cored wires omits the step of inoculating the cored wires, simplifies the preparation process of the thin-wall vermicular cast iron casting and reduces the production cost.
In conclusion, the magnesium oxide can be reduced, the probability of slag holes can be reduced, the burning loss of carbon elements can be supplemented, the carbon equivalent and the liquidus temperature of molten iron can be stabilized, and the graphite precipitation can be promoted and the white cast tendency can be reduced; the preparation process of the thin-wall vermicular cast iron can be simplified, and the production cost is reduced.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. An integrated vermicular core-spun yarn is characterized by comprising an outer skin and alloy powder wrapped in the outer skin;
wherein the alloy powder comprises the following components in percentage by weight:
Mg:10wt％～15wt％；
Si:55wt％～65wt％；
Ba:3wt％～5wt％；
Al:0.8wt％～1.5wt％；
C:2wt％～4wt％；
the balance of Fe.
2. The integrated vermicular cored wire according to claim 1, wherein the alloy powder is formed by mixing magnesium powder, silicon-barium alloy powder and graphitized carburant which have the grain sizes of 12-18 meshes.
3. The integrated vermicular cored wire of claim 1, wherein the sheath is made of a 08AL steel strip.
4. The integrated vermicular cored wire of claim 1, wherein the integrated vermicular cored wire has a diameter of 10mm to 13mm, a wire weight of 450g/m to 600g/m, and a core dose of 300g/m to 450g/m.
5. A preparation method of a thin-wall vermicular iron casting is characterized by comprising the following steps:
s1, smelting: adding a mixture of pig iron, vermicular iron return stock, scrap steel and a graphitizing carburant into an electric furnace to be melted into molten iron;
s2, adjusting the content of the molten iron components: and (3) regulating the weight percentage of each chemical element component in the molten iron obtained in the step (S1) to the following range through stokehole analysis: 3.7 to 3.85 percent of C, 2.1 to 2.2 percent of Si, 0 to 0.3 percent of Mn, 0.008 to 0.015 percent of S, 0 to 0.03 percent of P and 0 to 0.01 percent of Ti;
s3, alloying treatment: adding alloy elements into a 2-ton smelting ladle with the height-diameter ratio of 1.5;
s4, vermicular wire feeding treatment: carrying out vermicular wire feeding treatment on the molten iron obtained in the step S3 in the 2-ton smelting ladle by adopting the integrated vermicular cored wire of any one of claims 1 to 4;
s5, pouring: transferring the molten iron obtained in the step S4 into a casting cavity for pouring, and naturally cooling after pouring to obtain the thin-wall vermicular iron casting.
6. The method for preparing the thin-wall vermicular iron casting according to claim 5, wherein in the step S4, the vermicular wire feeding treatment temperature is 1440-1460 ℃, the wire feeding speed is 20-30 m/min, and the addition amount of the integrated vermicular cored wire is 6-12 m according to the sulfur content in the molten iron obtained in the step S2.
7. The method for preparing the thin-wall vermicular iron casting according to claim 6, wherein in the step S1, the ratio of pig iron to scrap steel to vermicular iron returns is 2;
and the alloy elements added in the step S3 are Cu or/and Sn.
8. The method for preparing the thin-wall vermicular iron casting according to claim 7, wherein the weight percentage of each chemical element component in the thin-wall vermicular iron casting obtained in the step S5 is as follows:
C:3.7wt％～3.85wt％，S:0.008wt％～0.015wt％，Si:2.2wt％～2.3wt％，Mn:0wt％～0.3wt％，P:0～0.03wt％，Ti:0wt％～0.01wt％，Mg:0.014wt％～0.018wt％,Cu:0.5wt％～0.7wt％，Sn:0.05wt％～0.07wt％。
9. the method of making a thin-walled vermicular cast iron casting of claim 5, further comprising the steps performed between step S4 and step S5 of: the slag skimming, temperature measurement and component detection are sequentially carried out.
10. The method for preparing the thin-wall vermicular iron casting according to the claim 8, wherein the thin-wall vermicular iron casting obtained in the step S5 has the tensile strength of more than 450MPa, the elongation of more than 1.5%, the vermicular rate of 80-95%, the hardness of 200-250 HBW, the pearlite of more than 75% and the carbide of less than 1%.
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