KR101409877B1 - Alloy cast iron and manufacturing method of vane using the same - Google Patents

Abstract

According to one aspect of the present invention, there is provided a method of manufacturing a vane for a rotary compressor using alloy cast iron and an alloy cast iron, and a vane for a rotary compressor using the same, wherein the weight ratio of C: 3.2 to 3.8%, Si: 2.0 to 2.6 0.1 to 0.6% of Cr, 0.1 to 0.6% of Mo, 0.04 to 0.15% of Ti, 0.3% or less of P, 0.1% or less of S and the balance of Fe and impurities , Martensite matrix structure, and graphite having a flake structure and an alloy cast iron containing 15 to 30% of carbide by volume ratio

Description

TECHNICAL FIELD [0001] The present invention relates to an alloy cast iron and a method of manufacturing a vane for a rotary compressor using the alloy cast iron.

The present invention relates to an alloy cast iron and a method of manufacturing a vane for a rotary compressor using the same.

2. Description of the Related Art Generally, a compressor includes a driving motor for generating a driving force in an internal space of a shell, and a compression unit for being coupled to the driving motor to compress the refrigerant. For example, in the case of a rotary compressor, the compression unit includes a cylinder defining a compression space, a vane separating the compression space of the cylinder into a suction chamber and a discharge chamber, A plurality of bearing members for supporting the vane and forming a compression space together with the cylinder, and a rolling piston rotatably mounted in the cylinder.

The vane is inserted into the vane slot formed in the cylinder and the end portion is fixed to the outer circumferential portion of the rolling piston to divide the compression space into two parts and slide continuously in the vane slot during the compression process. In this process, the vane has to have high strength and wear resistance because it must be kept in constant contact with the high temperature and high pressure refrigerant and kept in close contact with the rolling piston and the bearing to prevent the refrigerant from leaking.

In particular, new refrigerants such as HFC, which replace CFCs that have been discontinued due to ozone depletion, have low lubricating performance compared to CFCs, and wear resistance required for vanes due to the use of inverters to reduce energy consumption .

In order to satisfy such a condition, the present vane is manufactured by processing a high-speed steel or a stainless steel into a predetermined shape and then finishing the surface treatment or the like. However, these vanes have a problem that the content of Gr, W, Mo, V, Co and the like, which are expensive rare earth metals, are too high and are processed into a predetermined shape by forging, resulting in low productivity and high price. Particularly, in order to improve the abrasion resistance as described above, it has a high hardness, which is a factor that makes the machining process through forging difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an alloy cast iron which can meet the requirements for strength and abrasion resistance as a vane, .

Another object of the present invention is to provide a manufacturing method for manufacturing a vane as described above.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device, the method comprising: providing a semiconductor device including a semiconductor substrate having a composition of C: 3.2 to 3.8%, Si: 2.0 to 2.6%, Mn: 0.5 to 1.0% The balance being Fe and impurities, and having a martensite matrix structure and a graphite structure having a cubic structure in a volume ratio of 15 to 30% Is provided.

In addition, the alloy cast iron may be added with the inoculant in the molten state drawn out from the melting furnace. Here, the inoculant may be a barium base inoculant (Fe-Si-Ba). The inoculant may be added by 0.4 to 1.0% of the mass of the molten metal.

On the other hand, the alloy cast iron may be obtained by cooling the molten metal in a mold and transforming it into a martensite base structure through quenching and tempering. The quenching may be performed by maintaining the alloy cast iron at a temperature of 860 to 950 ° C for 0.5 to 1.5 hours and then oil-cooling the alloy cast iron to a normal temperature. The tempering may be performed by heating the quenched alloy cast iron at a temperature of 180 to 220 ° C, And then air-cooled to room temperature.

On the other hand, it may further include 0.005 to 0.0015 mm of a precipitate layer formed by ion-oxygenating the alloy cast iron transformed into the martensite matrix structure.

Further, Nb may be added in an amount of 0.01 to 0.5% by weight.

In addition, V of 0.1 to 0.5% by weight can be additionally included.

Further, B of 0.06 to 0.1% by weight can be additionally contained.

In addition, Cu of 0.2 to 0.4% by weight can be additionally contained.

According to still another aspect of the present invention, there is provided a method for manufacturing a steel sheet, comprising: preparing a steel sheet having a composition comprising 3.2 to 3.8% of C, 2.0 to 2.6% of Si, 0.5 to 1.0% of Mn, 0.2 to 0.6% of Cr, 0.1 to 0.6% of Mo, 0.15%, P: not more than 0.3%, S: not more than 0.1%, and the remainder being Fe and impurities; A casting step of injecting the molten metal into a mold and cooling the molten product to obtain a semi-finished product containing graphite and a carbide of 15 to 30% in a volumetric ratio of the flake structure; A polishing step of polishing the cooled semi-finished product into a predetermined shape; And heat treating the polished product to transform it into a martensite matrix structure.

Here, it is possible to additionally include an inoculating step of taking out the molten metal and administering the inoculating agent to the molten metal.

The annealing step may include a quenching step of maintaining the polished semi-product at 860 to 950 ° C for 0.5 to 1.5 hours, followed by oil-cooling to room temperature; And a tempering step of maintaining the quenched semi-finished product at 180 to 220 ° C for 0.5 to 1.5 hours, followed by air cooling to room temperature.

Further, it may further include a precision polishing step of precision polishing the semi-finished product after the heat treatment.

Further, it may further include an ionizing step of forming a precipitated layer having a thickness of 0.005 to 0.0015 mm on the surface of the semi-finished product after the heat treatment.

In addition, Nb may be added in an amount of 0.01 to 0.5% by weight.

In addition, V of 0.1 to 0.5% by weight can be additionally included.

Further, B of 0.06 to 0.1% by weight can be additionally contained.

In addition, Cu of 0.2 to 0.4% by weight can be additionally contained.

According to another aspect of the present invention, there is provided a vane for a compressor manufactured using the alloy cast iron described above.

According to aspects of the present invention having the above-described structure, an alloy cast iron is provided that can simultaneously improve abrasion resistance and tensile strength through combination of components mixed in a proper amount, martensite matrix structure, flake graphite structure and carbide Therefore, it is possible to manufacture a member used in a high-temperature high-pressure atmosphere such as a vane for a compressor inexpensively and easily.

In addition, since it is possible to produce the rare earth metal instead of the expensive rare earth metal, which is conventionally added to satisfy the requirements of the vane for a compressor, by using relatively inexpensive elements, the raw material cost can be reduced.

According to another aspect of the present invention, since a vane for a compressor can be manufactured through a casting process rather than a conventional forging process, the post-processing process can be greatly reduced and a plurality of vanes can be manufactured at the same time, do. In addition, instead of expensive high-speed steel used in the forging process, it can be manufactured using relatively inexpensive alloy cast iron, thereby greatly reducing raw material costs.

1 is a front view schematically showing a specimen for testing a tensile strength of an embodiment of an alloy cast iron according to the present invention.
Figs. 2 to 12 are enlarged photographs of the surface structure of the first to eleventh embodiments of the alloy cast iron according to the present invention. Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Generally, cast iron has high abrasion resistance and good cutting properties because of its high hardness, but has low tensile strength and strong brittleness and is not well used as a member exposed to a high-pressure atmosphere. In particular, in the case of the vane of the compressor described above, since it is slid in close contact with the adjacent components in order not to leak the compressed refrigerant as well as the high pressure atmosphere, higher abrasion resistance is required compared with the conventional one. The present invention provides an alloy cast iron which can be used for various purposes by mixing various elements contained in cast iron in an appropriate amount and having high tensile strength and wear resistance. Hereinafter, each element will be described. Here, unless otherwise indicated, the respective contents are by weight.

(1) Carbon (C): 3.2 to 3.8%

The carbon present in the cast iron exists as graphite or in the form of carbide (or carbide) denoted Fe ₃ C. Therefore, when the content of carbon is small, most of the carbon exists in the form of carbide, so that the flaky graphite structure does not appear well. Specifically, when the C content is 1.7 to 2.0%, the graphite is distributed in the form of a network. When the C content is 2.0 to 2.6%, graphite appears between the crystals. When the C content is 2.6 to 3.5%, the graphite exhibits a normal thin flake When the C content is more than 3.5%, rough and thick graphite with flake structure appears. When the content of carbon in the alloy cast iron is limited to 2.7 to 3.8%, the carbon is mainly present as graphite in a flake-like structure, the metal structure of the high-carbon alloy cast iron includes graphite in a coarse-grained structure with ferrite, It has strength and hardness, but excessive performance deteriorates the mechanical performance.

Therefore, it is added in an amount of 3.2% or more so as to obtain a homogeneous flaky graphite structure as a whole. On the other hand, the higher the content of carbon, the lower the freezing point, which is helpful to improve the casting, but the excess amount of graphite precipitation increases the brittleness and adversely affects the tensile strength. That is, since the maximum tensile strength can be obtained when the degree of carbon saturation (Sc) is approximately 0.8 to 0.9, a maximum tensile strength can be set to 3.8% to obtain a good tensile strength.

(2) Silicon (Si): 2.0 to 2.6%

Silicon acts as a graphitization accelerating element to decompose carbides and precipitate them as graphite. That is, the addition of silicon provides the same effect as increasing the amount of carbon. In addition, silicon plays a role in causing the fine graphite structure existing in the cast iron to grow into a piece-shaped graphite structure. Generally, when Si-C content is low, relatively high mechanical strength and hardness can be obtained, but fluidity is relatively low. Conversely, when Si-C content is high, fluidity is good, but mechanical strength and hardness are low

However, when a large amount of silicon is added, it also strengthens the base structure of the cast iron and also increases the tensile strength. That is, when Si / C is large, the amount of graphite is small and the tensile strength can be improved due to the reinforcing effect of the matrix due to high silicon, which is more apparent when the molten metal is inoculated. From this point of view, the silicon content was determined to be 2.0 to 2.6%.

(3) manganese (Mn): 0.5 to 1.0%

Manganese plays a role in stabilizing carbon (ie, cementite) as a white iron promoting element that prevents graphitization of carbon. In addition, manganese inhibits the precipitation of ferrite and makes the pelletite finer, which is useful when pelletizing the base structure of cast iron. In particular, manganese bonds with sulfur in cast iron to form manganese sulphide. The manganese sulphide floats on the surface of the molten metal and is removed as slag or solidified, and then remains in cast iron as a nonmetallic inclusion to prevent the formation of iron sulfide. In other words, manganese acts as an element that neutralizes the solution of sulfur.

As described above, manganese stabilizes and refines pearlite, but in this case, as the content of manganese increases, the strength and hardness of the cast iron increase, and the firing and toughness become low. In addition, manganese can remarkably lower the starting point (Ms) of transition of martensite state, but when added in large amounts, carbides are formed to increase the vulnerability and affect the mechanical performance of the alloy cast iron.

In addition, when silicon is sufficiently contained, manganese does not greatly affect the texture of the cast iron. Therefore, the manganese content is 0.5 to 1.0% for promotion of pelleting and removal of sulfur components.

(4) Cr (Cr): 0.2 to 0.6%

Chromium accelerates the formation of carbides, and when a large amount of graphite is added as an element to interfere with the graphitization of carbon, it becomes white iron, which causes excessive hardness and deteriorates workability. On the other hand, it acts to stabilize the carbide and also helps improve the heat resistance. In addition, chromium is an element that inhibits ferrite formation in cast iron, reduces the distance between the pillared lamellae, and promotes pearlite formation. In addition, chrome not only enhances and stabilizes the amount of pale light, it also serves to subdivide the pale light organization. However, if the content of chromium is excessive, excess cementite may form and chilled tissue may be formed.

Therefore, it is added in an amount of 0.2 to 0.6% to improve mechanical performance and heat resistance. And more preferably 0.1 to 0.3%.

(5) molybdenum (Mo): 0.1 to 0.6%

When the content of molybdenum is 0.6% or less, it stabilizes the carbide and serves to subdivide pearlite and graphite. The amount of phosphorus (P) should be low when adding molybdenum. Otherwise, the P-Mo 4-dimensional process (eutectic) is formed to increase the vulnerability. On the other hand, molybdenum improves the uniformity of the cross-sectional structure and improves the strength, hardness, impact strength, fatigue strength, high temperature (less than 550 ° C) performance, reduces shrinkage, improves heat treatment and improves quenchability . Considering these points, the content of molybdenum is set to 0.1 to 0.6%. And more preferably 0.4 to 0.6%.

(6) Vanadium (V): 0.1 to 0.5%

Vanadium also plays a role of refining pearlite structure and graphite, and it plays a role of allowing carbide and nitride to form well in cast iron, and to make carbide and nitride to be in a particle state so that it spreads widely evenly. Thus, uniform physical properties can be obtained over the entire cast iron. In addition, vanadium does not deteriorate machinability while improving hardness and tensile strength of cast iron. In addition, although it has a particularly good effect on abrasion resistance, it contains 0.1 to 0.5% because it causes the cast iron to be hardened when it is contained excessively. It is preferably 0.2 to 0.4%.

(7) Boron (B): 0.06 to 0.1%

Boron serves to refine graphite, but also to reduce the amount of graphite and promote the formation of carbides. Particularly, when a small amount of boron is added, it precipitates in a boron carbide state, and this boron carbide significantly increases the hardness and abrasion resistance of the cast iron. Particularly, the boron carbide is formed in a net shape. If the content of boron is small, the net shape has an interrupted shape, but in case of excess, a continuous net is formed to decrease the mechanical performance.

When adding boron to cast iron, the relationship between Si and B should be considered. In general, boron carbide can be precipitated in cast iron when Si / B < 80, and a small amount of boron carbide can be precipitated when 80 < Si / B < 130. When Si / B> 130, boron carbide precipitates It does not. In one embodiment of the present invention, when Si / B = 36.6, a relatively large amount of boron carbide was present, and in this case, it was confirmed that the boron carbide had a very strong abrasion resistance.

When the boron-containing alloy cast iron is worn, the boron carbide having a high hardness forms a first sliding surface to support the load, and a relatively low hardness pearlite or the like is worn and a concave second sliding surface is formed. The slot between the second sliding surface and the first sliding surface has an oil storing action so that the boron carbide is continuously supplied with the lubricating oil to reduce the rolling shape and improve the abrasion resistance of the boron cast iron. At the same time, when the boron content is increased, the boron carbide is increased, thereby increasing the supporting action of the boron carbide, thereby reducing the pressure applied to the unit area on the first sliding surface, thereby reducing the degree of wear, thereby improving the wear resistance.

However, if the boron content is too high, the particle size of the boron carbide becomes large, and the bonding force with the base structure is lowered. Therefore, when the frictional force is applied, the boron carbide easily detaches, and the boron carbide thus removed acts as the hard abrasive grains on the friction surface, which causes the abrasion of the cast iron to become severe. Further, in this case, the hardness of the cast iron is too high, and the workability is deteriorated. As a result, the content of boron is determined to be 0.06% to 0.1%.

(8) Titanium (Ti): 0.04 to 0.15%

Titanium granulates graphite, promotes pearlite formation, and improves the high temperature stability of pearlite. When the content of titanium is relatively low, it promotes graphitization and improves the distribution and morphology of graphite in cast iron. However, as the content is increased, the compound is precipitated around the interface of the crystal in the form of TIN, TIC, This results in an increase in the cast iron hardness and a deterioration in the processing performance. When the Ti content is relatively low, Ti accelerates the graphitization formation and increases the ferrite content of the gray iron structure to lower the hardness. On the contrary, when the Ti content is increased, Ti refines the cast iron crystal and strengthens the alloy structure TIC ₂ precipitates at the interface of the crystals, so that the hardness of the gray cast iron becomes higher.

Ti is one of the alloying elements for making D type graphite cast iron. D type graphite cast iron has higher strength than A type graphite cast iron and has better abrasion resistance. When the content of Ti is 0.1% or less, Ti is partially dissolved in ferrite and precipitated mostly in the form of TiC ₂ or TiN. As a result, titanium has a strong deoxidizing and denitrating effect on the molten metal. When the hinge, TiC ₂ , and TiN are supercooled, D-type graphite appears while finishing the A-type graphite. And the graphite content and ferrite content are relatively large, so that mixed structure of A and D is formed and the strength and hardness of the gray cast iron are lowered.

When the Ti content is larger than 0.1%, Ti causes the strength of the D-type graphite to increase and the amount of the D-type graphite to exceed 95%. In addition, the amount of graphite and ferrite is relatively small and dissolves in the ferrite As the amount of added Ti is increased and the ferrite is strengthened, the strength and hardness of the gray cast iron are increased.

Therefore, it is contained in an amount of 0.04 to 0.15% in order to secure the amount of the D-type graphite and to improve the processing performance.

(9) Niobium (Nb): 0.01 to 0.5%

The niobium further refines the metal crystal and serves to uniformize the texture. Particularly, when it is contained at 0.5% or less, it forms a band-shaped niobium enriched phase to further subdivide graphite, increase the high temperature stability of the alloy, and increase the hardness of the phosphorus process (P eutectic). However, when it exceeds 0.5%, a cubic niobium dense phase is formed, which causes a deterioration of mechanical performance, so it is contained by 0.01 to 0.5%.

(10) Copper (Cu): 0.2 to 0.4%

Copper is an element which promotes the graphite A to a large size and shortens the shape of graphite, reduces the superconducting graphite of type D and E, and accelerates the graphite type A graphite. Copper also plays a very good role in improving the morphology of graphite, inhibiting graphitization during vacant conversion and alleviating the tendency to cast iron. In addition, it improves the distribution of carbides, forms pearlite, and subdivides the tissue.

In addition, the distance between the pellights is reduced while facilitating formation of the pellights, and the pellights are subdivided. In addition, there is an effect that the fluidity of the molten metal is increased to increase the casting composition and thereby reduce the residual stress.

In addition, copper makes the structure more dense and improves the tensile strength and hardness of the cast iron. This effect is conspicuous in the case of containing about 3.0% of carbon, and when 0.3 to 0.5% of chrome is added together, a better effect can be obtained. Therefore, copper contains 0.2 to 0.4% as described above.

(11) phosphorus (P): not more than 0.3%

Phosphorus forms a compound of iron (Fe ₃ P) and is present as a three-way process stepite with ferrite and iron carbide. The iron phosphide tends to be subcooled and segregates well in the casting. As the content of phosphorus increases, the brittleness increases and the tensile strength rapidly decreases. Therefore, the content of phosphorus should be 0.3% or less.

(12) Sulfur (S): not more than 0.1%

As the sulfur is added in large amounts, the flowability of the molten metal is lowered, the amount of shrinkage is increased, and the shrinkage cavity and cracks are generated. Therefore, it is preferable that the content is as low as possible. However, when the content is 0.1% or less, such adverse effects are not largely revealed.

The elements having the above-mentioned characteristics can be mixed to produce the alloy cast iron according to the present invention, which can be used for producing the vane of the compressor. Now, a manufacturing process for producing a vane for a compressor made of the alloy cast iron will be described.

(1) smelting

The raw materials are prepared by selecting the above-mentioned elements at an appropriate ratio, and the raw materials are put into a middle frequency induction furnace, and the raw materials are heated and melted. At this time, the temperature at which the molten metal is taken out from the furnace is approximately 1500 to 1550 ° C.

(2) Inoculation

The inoculating agent is inoculated into the molten metal smelted in the smelting step. Inoculation promotes graphitization by generating a lot of graphite nuclei, and it helps to increase the strength by homogenizing the distribution of graphite. At this time, a barium silicon iron alloy (FeSi72Ba ₂ ) is used as the inoculation agent, and the addition amount is 0.4 to 1.0% of the mass of the molten metal.

(3) casting

The molten metal is injected into a mold previously prepared so as to have a desired shape of the molten metal inoculated in the seeding step. At this time, casting is performed using a shell mold process or an investment mold process using a resin-coated sand. The cooled vane semi-finished product will contain graphite and carbide of a flake structure and the content of carbide is 15% to 30% of the total vane volume. Here, the carbide means a form in which the added component is bonded to carbon, and includes, for example, Fe ₃ C, which is so-called iron carbide.

(4) grinding

The vane semi-finished product obtained in the casting step is polished and processed to have an intended shape.

(5) Heat treatment

The heat treatment process may consist of quenching and tempering.

- quenching: semi-finished product of the polished vane is heated to 860 ~ 950 ℃ for 0.5 ~ 1.5 hours by using electric resistance furnace which can control the air temperature, And cooled to room temperature. Through such quenching, the pearlite base structure is transformed into the martensite base structure, which can greatly improve the hardness. That is, when the quenching treatment is completed, a vane containing martensite matrix structure and carbide and slab graphite is obtained.

Tempering: The bain of the martensite cast iron containing the carbide obtained by the quenching treatment and the graphite of the flat structure was heated to 180 to 220 ° C using an electric resistance furnace capable of controlling the air temperature, and then heated for 0.5 to 1.5 hours And air cooling is performed to the next room temperature so that the ductility is lowered by lowering the strength and hardness slightly lowered by the quenching treatment.

(6) Fine grinding and polishing

The carbide alloy cast iron vane obtained by the quenching and tempering treatment in the heat treatment step is processed through precision polishing and polishing to have a final shape and a required surface quality.

(7) Sulphurizing

A sulphurizing process is performed on the vane of the alloy cast iron of the carbide obtained in the precision polishing and polishing step to form a sulphurizing layer having a thickness of 0.005-0.015 mm on the surface of the vane. The precipitate layer acts together with the flake graphite present in the vane, thereby further enhancing the lubricating and abrasion resistance of the vane itself.

Example 1

The above Example 1 was produced through the following process.

The composition of the present invention is as follows: Elemental mass Percentage: C: 3.4%, Si: 2.2%, Mn: 0.7%, Cr: 0.4%, Mo: 0.4%, V: 0.3%, B: 0.06% : 0.25%, P < 0.3%, S < 0.1% and the remainder being Fe. The prepared raw materials are put into a medium induction furnace and the temperature is raised so that the raw materials are completely dissolved, The temperature to be taken out is 1525 ° C.

In the above step, the inoculating treatment is carried out on the molten alloy cast iron from the furnace, wherein the inoculating agent is FeSi72Ba2 as the barium silicon iron alloy, and the addition amount thereof is 0.7% of the molten mass.

The molten alloy cast iron subjected to the inoculating treatment in the above step is cast by a cell molding method or an embedding casting method to obtain a pearlitic cast iron vane containing graphite and a carbide of a flaky structure, wherein the content of the carbide is 25 %to be.

The vanes obtained in the above step are polished and processed to have an intended shape.

Thereafter, the vane is heated to 910 占 폚 and maintained at the temperature for 0.7 hours, then put in an oil having a temperature of 20 占 폚 and cooled to room temperature to transform the base structure into martensite. Then, the vane obtained from the quenching is heated to 210 DEG C, held for 0.7 hours, and then air-cooled to room temperature.

The obtained vane semi-finished product was precision polished and polished, and then subjected to an ionization treatment to form a 0.008 mm thick emulsion sublimation layer on the surface of the vane.

Example 2

In the case of Example 2, the percentage of elemental mass: C: 3.2%, Si: 2.0%, Mn: 0.5%, Cr: 0.2%, Mo: 0.1%, Ti: 0.04%, P <0.3%, S < The remainder is Fe. After the raw material is dissolved, the melt is withdrawn at 1,500 ° C in warmth, and FeSi 72 Ba ₂ is added as the inoculant by 0.4% of the mass of the molten metal. Thereafter, the casted molten metal is cast by a cell molding method or an embedding casting method to obtain a semi-finished product of a vane having a carbide content of 15% by volume.

The mixture was heated to 860 ° C., maintained at a temperature of 0.5 hours, put in an oil having a temperature of 10 ° C., cooled to room temperature, martensized, heated to 180 ° C., held for 0.5 hours, Precision polishing and polishing, and subjected to an ionization treatment to form a 0.005 mm thick emulsion precipitate layer on the surface of the vane.

Example 3

Example 3 was prepared in the same manner as in Example 3 except that the elemental mass percentage was 3.8% C, 2.6% Si, 1.0% Mn, 0.6% Cr, 0.6% Mo, 0.5% V, 0.1% 0.5% of Cu, 0.5% of P, 0.3% of S, 0.1% of S and the balance of Fe is dissolved and taken out at 1550 ° C, and FeSi72Ba ₂ is added by 1.0% of the mass of the melt. The inoculated molten metal is cast by the cell molding method or the embedding casting method, cast to a volume ratio of 30% of the carbide corresponding to 30% of the vane, and polished in a predetermined shape.

The polished vane was heated to 950 DEG C and held for 1.5 hours, then put in an oil having a temperature of 30 DEG C and cooled to room temperature to obtain a vane containing martensite matrix structure and carbide and slab graphite, Keep for 1.5 hours and then cool to room temperature to reduce embrittlement. After completing the final shape through precision polishing and polishing, a 0.015 mm thick emulsion precipitate layer was formed on the surface of the vane through ionic oxidation treatment.

Example 4

Example 4 was prepared in the same manner as in Example 4, except that the elemental mass percentage was 3.3%, C: 2.1%, Mn: 0.6%, Cr: 0.3%, Mo: 0.2%, V: 0.2% 0.3%, S <0.1% and the remainder Fe is melted and the molten metal is taken out at a temperature of 1515 ° C. The remaining steps are the same as those in the first embodiment.

Example 5

Example 5 was prepared in the same manner as in Example 5 except that the elemental mass percentage was 3.3%, C: 2.2%, Mn: 0.7%, Cr: 0.4%, Mo: 0.3%, V: 0.2%, Ti: 0.04-0.15% P <0.3%, S <0.1% and the remainder Fe is melted and the molten metal is taken out at a temperature of 1510 ° C. The remaining steps are the same as those in the first embodiment.

Example 6

Example 6 was prepared in the same manner as in Example 6 except that the elemental mass percentage was 3.4%, Si: 2.3%, Mn: 0.8%, Cr: 0.4%, Mo: 0.3%, V: 0.3%, Ti: 0.06% 0.3%, S <0.1% and the remainder Fe is melted and the molten metal is taken out at a temperature of 1520 ° C. The remaining steps are the same as those in the first embodiment.

Example 7

Example 7 was prepared in the same manner as in Example 7 except that the element mass percentages were 3.6%, 2.4%, 0.9%, 0.5%, 0.5%, 0.05%, 0.12% <0.3%, S <0.1% and the remainder Fe is melted and the molten metal is taken out at a temperature of 1530 ° C. The remaining steps are the same as those in the first embodiment.

Example 8

Example 8 was prepared in the same manner as in Example 8 except that the element mass percentages were as follows: C: 3.3%, Si: 2.2%, Mn: 0.7%, Cr: 0.4%, Mo: 0.3%, Ti: 0.04-0.15% S <0.1% and the remainder Fe is melted and the melt is taken out at a temperature of 1510 ° C. The remaining steps are the same as those in the second embodiment.

Example 9

Example 9 was prepared in the same manner as in Example 9, except that the elemental mass percentage was 3.4%, Si: 2.3%, Mn: 0.8%, Cr: 0.4%, Mo: 0.3%, Ti: 0.06%, Cu: 0.2% 0.1% and the remainder is Fe, and then the molten metal is taken out at a temperature of 1520 ° C. The remaining steps are the same as those in the second embodiment.

Example 10

Example 10 was prepared in the same manner as in Example 10 except that the elemental mass percentage was 3.4%, C: 2.2%, Mn: 0.7%, Cr: 0.4%, Mo: 0.4%, V: 0.3%, B: 0.25%, P < 0.3%, S < 0.1% and the remainder Fe is melted and the melt is taken out at a temperature of 1535 캜. The remaining steps are the same as those in the third embodiment.

Example 11

Example 11 was prepared in the same manner as in Example 11 except that the elemental mass percentage was 3.8% C, 2.6% Si, 1.0% Mn, 0.6% Cr, 0.6% Mo, 0.1% B, 0.15% 0.5%, P < 0.3%, S < 0.1% and the remainder Fe is melted and the molten metal is taken out at a temperature of 1545 ° C. The remaining steps are the same as those in the third embodiment.

The above examples are summarized in Table 1 below.

C Si Mn Cr Mo V B Ti Nb Cu P S One 3.4 2.2 0.7 0.4 0.4 0.3 0.06 0.1 0.25 0.25 <0.3 &Lt; 0.1 2 3.2 2.0 0.5 0.2 0.1 0.04 <0.3 &Lt; 0.1 3 3.8 2.6 1.0 0.6 0.6 0.5 0.1 0.15 0.5 0.5 <0.3 &Lt; 0.1 4 3.3 2.1 0.6 0.3 0.2 0.2 0.02 0.05 <0.3 &Lt; 0.1 5 3.3 2.2 0.7 0.4 0.3 0.2 0.04 0.1 <0.3 &Lt; 0.1 6 3.4 2.3 0.8 0.4 0.3 0.3 0.06 0.2 <0.3 &Lt; 0.1 7 3.6 2.4 0.9 0.5 0.5 0.05 0.12 0.3 <0.3 &Lt; 0.1 8 3.3 2.2 0.7 0.4 0.3 0.04 0.1 <0.3 &Lt; 0.1 9 3.4 2.3 0.8 0.4 0.3 0.06 0.2 <0.3 &Lt; 0.1 10 3.4 2.2 0.7 0.4 0.4 0.3 0.06 0.1 0.25 <0.3 &Lt; 0.1 11 3.8 2.6 1.0 0.6 0.6 0.1 0.15 0.5 0.5 <0.3 &Lt; 0.1

For the above embodiments, a cast sample was taken, its surface was polished, the hardness test was performed on five points for each of the examples using the HB-3000 type hardness meter, The diameter of the groove formed was measured, and the hardness was calculated on the basis of the diameter. The average value of the five points was taken as the hardness of the sample.

In addition, the hardness test was carried out using a HR-150A type Rockwell hardometer for the samples after the heat treatment. The test locations were two points vertically near the casting fluid injection port, two vertically at the point away from the casting fluid injection port, and one point between them.

Further, test specimens of the type shown in Fig. 1 were produced from the same materials as those of the respective examples, and tensile strengths were measured. The test results are shown in Table 2 below.

One 2 3 4 5 6 7 8 9 10 11 Hardness (HRC) 60.8 55.2 52.2 60.7 54.4 60.3 60.0 59.5 57.2 58.5 59.0 Tensile Strength (MPa) 394.2 385.9 408.1 385.2 377.3 389.5 387.4 387.7 399.2 372.7 388.0

As shown in Table 2 above, it can be seen that the embodiment of the present application has a hardness of about 52 to 60 on the basis of the Rockwell hardness, and therefore has sufficient hardness as a vane of the compressor.

Table 3 below summarizes the test results for the cutting workability and the abrasive workability of the above embodiments.

Detail Examples of the present invention High speed steel Cutting workability
Load factor 75% 100% Tool life (parts) 200 100 Abrasive processability
Load factor 75% 100% Grinding stone dressing cycle 800 pieces / 1 time 500 pieces / 1 time

From the viewpoint of cutting workability, the alloy cast iron according to the present invention shows a cutting load corresponding to 75% when the conventional high speed steel is taken as 100%, and it can be understood that the cutting can be performed more easily than the high speed steel. In addition, in the case of the alloy cast iron according to the present invention, 200 vanes, which are twice as high as those in the case of the alloy cast iron according to the present invention, can be cut. Therefore, it is possible not only to prevent frequent replacement of the tool, but also to reduce the time required for the cutting operation, thereby improving the productivity.

In the case of the alloy cast iron according to the present invention, the abrasive load corresponds to 75% of the high-speed steel, and 800 vanes can be polished per dressing of the abrasive stone, thereby remarkably increasing the abrasive performance compared to the high-speed steel .

In addition, the conventional vane using a high-speed steel has a problem of low productivity because it is required to use a forging method instead of a casting method. However, in this case, since the casting method has relatively good abrasion resistance, And the processing cost can be greatly reduced.

Claims (20)

The steel sheet according to any one of claims 1 to 3, wherein the steel sheet has a composition of 3.2 to 3.8% by weight of C, 2.0 to 2.6% of Si, 0.5 to 1.0% of Mn, 0.2 to 0.6% of Cr, 0.1 to 0.6% of Mo, 0.04 to 0.15% , P: not more than 0.3%, S: not more than 0.1%, and the balance of Fe and impurities,
Alloy cast iron containing martensite base structure and graphite of flake structure and 15 to 30% of carbide by volume ratio. The steel sheet according to any one of claims 1 to 3, wherein the steel sheet comprises, in terms of weight ratio, 3.2 to 3.8% of C, 2.0 to 2.6% of Si, 0.5 to 1.0% of Mn, 0.2 to 0.6% of Cr, 0.1 to 0.6% of Mo, 0.04 to 0.15% , P: not more than 0.3%, S: not more than 0.1%, and the balance of Fe and impurities,
Alloy cast iron containing martensite base structure and graphite of flake structure and 15 to 30% of carbide by volume ratio. The steel sheet according to any one of claims 1 to 3, wherein the steel sheet has a weight ratio of C: 3.2 to 3.8%, Si: 2.0 to 2.6%, Mn: 0.5 to 1.0%, Cr: 0.2 to 0.6%, Mo: 0.1 to 0.6%, Ti: 0.04 to 0.15% , P: not more than 0.3%, S: not more than 0.1%, and the balance of Fe and impurities,
Alloy cast iron containing martensite base structure and graphite of flake structure and 15 to 30% of carbide by volume ratio. 4. The method according to any one of claims 1 to 3,
Wherein the alloy cast iron is added with an inoculant in a molten state drawn out from a melting furnace. 5. The method of claim 4,
Wherein the inoculant is added by 0.4 to 1.0% of the mass of the molten metal. 4. The method according to any one of claims 1 to 3,
Wherein the alloy cast iron is formed by quenching and tempering the molten metal in a mold to transform it into a martensite base structure. The method according to claim 6,
The quenching
Wherein the alloy cast iron is maintained at 860 to 950 ° C for 0.5 to 1.5 hours and then oil-cooled to room temperature. The method according to claim 6,
The tempering
Characterized in that the alloy cast iron after quenching is maintained at 180 to 220 ° C for 0.5 to 1.5 hours and then cooled to room temperature. The method according to claim 6,
Wherein the alloy cast iron further comprises 0.005 to 0.0015 mm of a precipitate layer formed by ion-oxygenating the alloy cast iron transformed into the martensite base structure. delete 4. The method according to any one of claims 1 to 3,
Further comprising Cu in an amount of 0.2 to 0.4% by weight. The steel sheet according to any one of claims 1 to 3, wherein the steel sheet has a composition of 3.2 to 3.8% by weight of C, 2.0 to 2.6% of Si, 0.5 to 1.0% of Mn, 0.2 to 0.6% of Cr, 0.1 to 0.6% of Mo, 0.04 to 0.15% , P: not more than 0.3%, S: not more than 0.1%, and the remainder being Fe and impurities;
A casting step of injecting the molten metal into a mold and cooling the molten product to obtain a semi-finished product containing graphite and a carbide of 15 to 30% in a volumetric ratio of the flake structure;
A polishing step of polishing the cooled semi-finished product into a predetermined shape; And
And heat treating the polished product to transform it into a martensite matrix structure. The steel sheet according to any one of claims 1 to 3, wherein the steel sheet comprises, in terms of weight ratio, 3.2 to 3.8% of C, 2.0 to 2.6% of Si, 0.5 to 1.0% of Mn, 0.2 to 0.6% of Cr, 0.1 to 0.6% of Mo, 0.04 to 0.15% , P: not more than 0.3%, S: not more than 0.1%, and the remainder being Fe and impurities;
A casting step of injecting the molten metal into a mold and cooling the molten product to obtain a semi-finished product containing graphite and a carbide of 15 to 30% in a volumetric ratio of the flake structure;
A polishing step of polishing the cooled semi-finished product into a predetermined shape; And
And heat treating the polished product to transform it into a martensite matrix structure. The steel sheet according to any one of claims 1 to 3, wherein the steel sheet has a weight ratio of C: 3.2 to 3.8%, Si: 2.0 to 2.6%, Mn: 0.5 to 1.0%, Cr: 0.2 to 0.6%, Mo: 0.1 to 0.6%, Ti: 0.04 to 0.15% , P: not more than 0.3%, S: not more than 0.1%, and the remainder being Fe and impurities;
A casting step of injecting the molten metal into a mold and cooling the molten product to obtain a semi-finished product containing graphite and a carbide of 15 to 30% in a volumetric ratio of the flake structure;
A polishing step of polishing the cooled semi-finished product into a predetermined shape; And
And heat treating the polished product to transform it into a martensite matrix structure. 15. The method according to any one of claims 12 to 14,
Further comprising the step of taking out the molten metal and administering the inoculant to the molten metal. 15. The method according to any one of claims 12 to 14,
The heat treatment step
A quenching step of holding the polished semi-finished product at 860 to 950 캜 for 0.5 to 1.5 hours, followed by oil-cooling to room temperature; And
And a tempering step of maintaining the quenched semi-finished product at 180 to 220 DEG C for 0.5 to 1.5 hours, followed by air cooling to room temperature. 15. The method according to any one of claims 12 to 14,
Further comprising a precision polishing step of accurately polishing the semi-finished product after the heat treatment. 15. The method according to any one of claims 12 to 14,
Further comprising an ionizing step of forming a precipitated layer having a thickness of 0.005 to 0.0015 mm on the surface of the semi-finished article which has been heat-treated. delete 15. The method according to any one of claims 12 to 14,
0.2 to 0.4% Cu. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;

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