CN117305682A

CN117305682A - Vermicular graphite cast iron and preparation process and application thereof

Info

Publication number: CN117305682A
Application number: CN202311239431.9A
Authority: CN
Inventors: 请求不公布姓名; 唐武魁; 覃明; 张康; 律刚; 何武鹏
Original assignee: Anhui Meizhi Precision Manufacturing Co Ltd
Current assignee: Anhui Meizhi Precision Manufacturing Co Ltd
Priority date: 2023-09-22
Filing date: 2023-09-22
Publication date: 2023-12-29

Abstract

The invention discloses vermicular cast iron and a preparation process and application thereof. The vermicular cast iron is prepared from Fe, rare earth-containing vermiculizer, rare earth-containing inoculant, C, si, mn, cu, sn and other elements. Based on the component collocation of the preparation raw materials, the vermicular cast iron has the characteristics of small hardness fluctuation, good thermal conductivity, good wear resistance and high tensile strength, can better meet the use requirements of high-temperature and high-pressure working conditions, and prolongs the service life; meanwhile, the vermicular cast iron has low manufacturing cost. The invention also provides a preparation process and application of the vermicular graphite cast iron.

Description

Vermicular graphite cast iron and preparation process and application thereof

Technical Field

The invention relates to the technical field of cast iron materials, in particular to vermicular graphite cast iron and a preparation process and application thereof.

Background

Cast iron can be classified into the following categories according to graphite morphology: gray cast iron, ductile iron, malleable cast iron, and vermicular cast iron. Wherein, graphite in the gray cast iron is independently dispersed in a matrix in a flake shape, and the graphite is separated from each other; graphite in the spheroidal graphite cast iron is spherically distributed; graphite in the malleable cast iron is in flocculent distribution; graphite in vermicular cast iron is distributed in a worm shape. The metallographic structures of gray cast iron, ball cast iron and vermicular cast iron are shown in figures 1-3. In comparison, gray cast iron contains a large amount of flaky graphite, has a large cutting effect on a matrix, and has low strength and wear resistance; the ball-milled cast iron has higher strength but poor thermal conductivity and machinability.

Currently, gray cast iron or spheroidal graphite cast iron is a common material for manufacturing transmission parts or braking parts such as scroll plates. The main structure of the scroll compressor is shown in fig. 4, and includes an orbiting scroll 110, a fixed scroll 120, an upper bracket 130, an oldham ring 140, an eccentric crankshaft 150, an intake port 160, and an exhaust port 170. The working principle is as follows: the motor drives the eccentric crankshaft 150 to rotate, the movable scroll 110 makes circumferential translation around the fixed scroll 120 under the limit of the upper bracket 130 and the cross slip ring 140, the movable scroll 110 is meshed with the fixed scroll 120 to form a plurality of crescent compression cavities, the volume of the compression cavities is gradually reduced along with the circumferential translation, the gas pressure is gradually increased, and finally high-pressure gas is discharged from an axial hole in the center of the fixed scroll 120. Because the gray cast iron has insufficient strength and wear resistance, the vortex plate is easy to break or wear, and the service life is short; ductile iron is limited by thermal conductivity and workability, as well as application limitations.

The combination property of the vermicular cast iron is between that of gray cast iron and spheroidal graphite cast iron, and the vermicular cast iron is one of potential materials for manufacturing parts such as vortex plates and the like. However, the existing vermicular cast iron also has the problems of insufficient strength, large hardness fluctuation, poor thermal conductivity and the like, has limited performances in the aspects of wear resistance, thermal fatigue resistance and the like, and can not well meet the application requirements of high-temperature-difference and high-pressure-difference working environments. Therefore, there is a need to develop a new high-performance cast iron material.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides the vermicular cast iron, which has the characteristics of controllable microscopic morphology, small hardness fluctuation, good thermal conductivity, good wear resistance and high tensile strength.

The invention also provides a preparation process of the vermicular graphite cast iron.

The invention also provides application of the vermicular cast iron.

In particular, a first aspect of the invention relates to a vermicular cast iron comprising Fe, a rare earth-containing vermiculizer, a rare earth-containing inoculant and the following preparation raw materials in mass percent:

C:3.5％～3.8％，Si:1.8％～2.6％，Mn:0.2％～0.5％，Cu:0.2％～0.5％，Sn:0.03％～0.06％，Cr:0％～0.05％，Sb:0％～0.01％。

the vermicular cast iron according to the embodiment of the first aspect of the present invention has at least the following advantageous effects:

in this embodiment, the preparation of the raw material formulation has a significant impact on the microstructure morphology and the physical mechanical properties of the vermicular cast iron, wherein:

c is a basic element forming a graphite structure, the content of C has a large influence on the microscopic morphology and mechanical properties of cast iron, the content of carbon is controlled in a proper range, the contents of ferrite and graphite can be regulated, and the strength and hardness are ensured.

The molten iron contains a trace amount of O, si reacts with O in the molten iron to generate silicon dioxide crystals, and the silicon dioxide crystals serve as external crystal nuclei of graphite crystals to promote graphitization, and the proper Si content is also beneficial to the morphological stability of the vermicular graphite cast iron.

Mn plays roles in reducing eutectic cell number, stabilizing carbide, austenite and the like, and in the eutectoid transformation process, mn plays roles in refining and stabilizing pearlite, but the Mn content is not excessively high, so that supercooling is avoided.

Cu plays a role in increasing and stabilizing pearlite in the matrix, and proper Cu content plays an important role in ensuring mechanical properties such as strength, elongation and the like.

Cr is a strong pearlite promoting element, but in the solidification of cast iron, chromium has a strong effect of promoting cementite, and the tendency of the cast iron to white is enhanced, so that the Cr content is not excessively high. The pearlite content is regulated by matching two elements of Cr and Cu, so that the mechanical property and the wear resistance are ensured.

Sn plays a role in increasing pearlite, and the content of Sn is not excessively high, so that hard brittleness is avoided.

Sb has the effect of refining graphite, but an excessively high content adversely affects the cast iron properties.

The rare earth-containing vermicular agent and the rare earth-containing inoculant can control the morphology of graphite and the morphology of cast iron tissue to form a mixed structure of pearlite, ferrite and graphite, the vermicular rate, the pearlite ratio and the graphite ratio are regulated and controlled in proper ranges in an auxiliary mode, the tissue uniformity is improved, and further the wear resistance and the heat conductivity are improved on the basis of ensuring the mechanical property.

The microstructure form and the distribution uniformity of the whole cast iron matrix structure are regulated by reasonably controlling the content of C, si and the mass percentages of pearlite forming elements Mn, cu and Sn and matching with a rare earth-containing vermiculizer and a rare earth-containing inoculant, so that the fluctuation range of the hardness of the cast iron is reduced, the abrasion resistance and the machinability of the cast iron are prevented from being influenced due to the existence of hard particles which are too hard, and the manufacturing cost is reduced; the creep rate and the graphite duty ratio are controlled in a proper range, so that the thermal conductivity is improved, the boundary friction generated by high-temperature thermal deformation is reduced, the antifriction and wear-resistant characteristics are enhanced, the use requirements of high-temperature and high-pressure working conditions can be better met, and the service life is prolonged. Further, by adding a proper amount of the segregation facilitating element Sb and the carbide forming element Cr, a better modifying effect can be achieved.

The vermicular cast iron of the embodiment of the invention has the tensile strength more than or equal to 450MPa, the yield strength more than or equal to 335MPa, the hardness value reaching HB 160-230, small hardness fluctuation, the hardness fluctuation range being as low as below 10HB, and the overall mechanical property, the wear resistance and the thermal conductivity being obviously improved compared with the existing vermicular cast iron.

According to some embodiments of the first aspect of the invention, the rare earth element is selected from Ce, zr, or a combination thereof.

According to some embodiments of the first aspect of the present invention, the rare earth-containing vermiculizer further comprises Si, mg, ca and Fe.

According to some embodiments of the first aspect of the invention, the rare earth-containing vermiculizer comprises Fe and the following elements in mass percent: 4-6% of Mg, 43-47% of Si, 1-2% of Ca and 2-4% of Re, wherein Re is selected from Ce, zr or a combination thereof. The balance being Fe without taking into account the content of impurity elements.

According to some embodiments of the first aspect of the present invention, the rare earth-containing vermiculizer is 0.2% -0.5% by mass of the total mass of the preparation raw materials except for the rare earth-containing vermiculizer and the rare earth-containing inoculant.

According to some embodiments of the first aspect of the invention, the rare earth element in the rare earth-containing inoculant is selected from Ce, zr, or a combination thereof.

According to some embodiments of the first aspect of the present invention, the rare earth-containing inoculant further comprises Si, ca, ba and Fe, or the rare earth-containing inoculant further comprises Si, ca, ba, al and Fe.

According to some embodiments of the first aspect of the invention, the rare earth element of the rare earth-containing inoculant is selected from Ce.

According to some embodiments of the first aspect of the invention, the rare earth-containing inoculant comprises Fe and the following elements in mass percent: 70-80% of Si, 0.75-2% of Ca, 1-3% of Ba, 0.3-1% of Ce and 0-1.5% of Al. The balance being Fe without taking into account the content of impurity elements.

According to some embodiments of the first aspect of the present invention, the rare earth-containing inoculant comprises a rare earth ferrosilicon alloy and a barium-calcium-iron alloy, the rare earth ferrosilicon alloy comprising Fe and the following elements in mass percent: 70-76% of Si, 0.75-1.25% of Ca, 0.75-1.25% of Al and 1.5-2.0% of Ce; the silicon-barium-calcium-iron alloy comprises Fe and the following elements in percentage by mass: 72-78% of Si, 1.0-2.0% of Ca, 2.0-3.0% of Ba and 0-1.25% of Al, wherein the mass ratio of the rare earth ferrosilicon alloy to the ferrosilicon barium calcium alloy is 1:1-4. The rare earth ferrosilicon or the ferrosilicon is Fe in balance without considering the content of impurity elements.

The two alloys are adopted for compound inoculation, so that the limit of the traditional vermicular cast iron smelting on the addition amount of inoculant is relaxed, the limitation of single inoculant is avoided, the inoculant composition is favorably regulated, the microstructure morphology and uniformity of the inside of cast iron are ensured, and the integral performance of the cast iron is improved.

According to some embodiments of the first aspect of the present invention, the weight percentage of the rare earth ferrosilicon alloy is 0.1% -0.2% and the weight percentage of the ferrosilicon alloy is 0.2% -0.4% based on the total mass of the preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant.

According to some embodiments of the first aspect of the present invention, the mass percentage of the rare earth-containing inoculant is 0.3% -0.6% based on the total mass of the remaining preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant.

The selection of inoculant or vermiculizer has influence on grain refinement, and the selection of proper inoculant or vermiculizer system can play roles in reducing white mouths, promoting graphitization and the like. This is because the molten iron contains trace amounts of dissolved O and N and possibly also the accompanying impurities S, which can combine with elements in the rare earth inoculant to improve the inoculant and creep effect. Specifically, ca, al, ce can form sulfides, si, mg, ca, al, ba can form oxides, si, al, ca, ba can form carbides, si, al, zr, ce can form nitrides, ce can form intermetallic compounds with Sb, sn, and adverse effects of trace interfering elements are suppressed. The generated sulfides, oxides, carbides, nitrides, rare earth compounds and the like can be used as crystal nuclei, play a role in promoting graphitization and refining grains, can adjust the morphology and uniformity of a matrix structure, avoid cementite formation and prevent the tendency of white mouth.

By selecting the matching of the vermiculizer and the inoculant and introducing a plurality of nucleation elements, the dosage of rare earth elements can be reduced on the basis of ensuring the integral performance of cast iron.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a carbon equivalent c.e. value of 4.3-4.6. The carbon equivalent range is controlled, so that the carbon equivalent of molten iron in the solidification process is ensured to be close to that of eutectic components, near-eutectic solidification can be realized, the graphite size is thinned, shrinkage porosity in cast iron is reduced, and meanwhile, graphite floatation caused by overlarge carbon equivalent is avoided.

According to some embodiments of the first aspect of the present invention, the mass percentage of C is 3.7% to 3.8%.

According to some embodiments of the first aspect of the present invention, the Si is 1.8% to 2.2% by mass.

According to some embodiments of the first aspect of the invention, the Mn is 0.25% to 0.4% by mass.

According to some embodiments of the first aspect of the present invention, the Cu is 0.3% to 0.4% by mass.

According to some embodiments of the first aspect of the present invention, the Sn is 0.04% to 0.06% by mass.

According to some embodiments of the first aspect of the present invention, the Cr is 0.02% to 0.04% by mass.

According to some embodiments of the first aspect of the invention, the mass percentage of Sb is not more than 0.001%.

According to some embodiments of the first aspect of the invention, the raw materials for preparing the vermicular cast iron further comprise an impurity element. The common accompanying impurity elements are P, S and other elements, generally harmful impurity elements, but trace phosphorus can increase the fluidity of molten iron. The S content can be controlled below 0.01% and the P content can be controlled below 0.02%.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a vermicular rate of 50% to 80% as measured in GB/T26656-2023.

The graphite has certain self-lubricating effect, the end of the vermicular graphite is round and blunt, shorter and thicker than the flaky graphite, the matrix cracking effect is smaller than that of the flaky graphite, and the matrix crack is not easy to expand. The lower the creep rate, the higher the strength or hardness, and the more abrasion resistant the matrix microstructure ratio, carbon equivalent, and graphite ratio are.

The creep rate is controlled in a proper range so as to better consider the heat conductivity, the thermal fatigue resistance and the mechanical property. When the vermicular rate in the vermicular cast iron structure is less than 50%, the thermal conductivity and the thermal fatigue resistance are reduced, and the abrasion resistance is not improved, and particularly the abrasion resistance under the high temperature condition is greatly influenced. When the vermicular rate is more than 80%, the thermal conductivity and the thermal fatigue resistance of the vermicular iron tend to be stable, but the excessive vermicular rate can increase the cutting effect on the matrix and influence the toughness.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a vermicular rate of 55% to 75%.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a pearlite content of 50% to 80% as tested by GB/T26656-2023. In the content range, the tissue morphology with high dispersity and uniform distribution is obtained, and the hardness uniformity and the wear resistance are improved. When the pearlite content is less than 50%, the abrasion resistance is greatly reduced, and when the pearlite content is more than 80%, the machining is made difficult.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a pearlite content of 50% to 60%.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a pearlite content of 55% to 60%.

According to some embodiments of the first aspect of the invention, the graphite content of the vermicular cast iron is between 10% and 15%. The graphite ratio range directly affects lubricity, wear resistance, and thermal conductivity: too low a graphite ratio affects thermal conductivity, is detrimental to lubrication and resistance to adhesive wear, and causes low surface strength and reduced wear resistance.

According to some embodiments of the first aspect of the invention, the graphite fraction of the vermicular cast iron is 11% -13%.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a tensile strength of 450MPa or more, a yield strength of 335MPa or more, and the test standard is GB/T228.1-2021.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a brinell hardness number HB of 160-230.

According to some embodiments of the first aspect of the invention, the vermicular cast iron has a Brinell hardness number HB of 10 or less. By adjusting the shape and the distribution uniformity of the microstructure of the matrix, the hard phase is dispersed in the matrix as uniformly as possible, and the fluctuation range of the hardness is reduced.

An embodiment of the second aspect of the invention relates to a process for preparing the vermicular cast iron, comprising the following steps:

smelting preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant, adding the rare earth-containing vermiculizer for vermiculization treatment, adding the rare earth-containing inoculant for inoculation treatment, discharging the obtained molten iron, and casting to obtain the vermicular cast iron.

The preparation process of the vermicular cast iron according to the second aspect of the present invention has at least the following advantages:

after smelting the preparation raw materials, performing vermiculizer and inoculation before discharging soup, so that the addition amount and the dispersibility of the vermiculizer and the inoculant can be controlled more accurately, a more uniform vermiculizer and inoculation effect can be obtained, and the graphite morphology and the precipitation amount thereof, and the microstructure morphology and the uniformity of the interior of the vermicular cast iron are ensured.

One common inoculation process for industrially preparing vermicular cast iron is: meanwhile, ladle inoculation and stream inoculation technology are adopted, wherein ladle inoculation refers to adding part of inoculant when pouring molten iron into a transfer ladle, stream inoculation refers to adding part of inoculant in the process of casting molten iron, and casting defects can be eliminated by adopting two-stage inoculation treatment. In comparison, the embodiment adopts a section of inoculation process, inoculation operation is completed before casting ladle, the requirements on equipment and process control are low, industrial production is easy to realize, and production cost is reduced.

The vermicular cast iron prepared by the embodiment has uniform mixed structure of pearlite, ferrite and graphite, the vermicular rate, the pearlite ratio and the graphite ratio range are easy to regulate and control, the hardness fluctuation range is reduced, and the wear resistance and the heat conductivity are improved, and meanwhile, the excellent mechanical property is ensured.

According to some embodiments of the second aspect of the invention, the smelting temperature is 1450-1500 ℃. The smelting temperature control is favorable for improving the purity of molten iron and eliminating the inheritance of graphite so as to obtain fine and uniform graphite morphology through inoculation.

According to some embodiments of the second aspect of the invention, the temperature of the vermiculizing process is 1500 to 1550 ℃.

According to some embodiments of the second aspect of the invention, the vermiculizing process is for a time of 20 to 40 seconds.

According to some embodiments of the second aspect of the invention, the inoculation temperature is 1500-1550 ℃.

According to some embodiments of the second aspect of the invention, the incubation time is 20 to 40 seconds.

If the temperature of the vermiculizer or inoculant is too low, the vermiculizer or inoculant is not easy to open; if the temperature is too high, burning loss may increase. The treatment time of the vermiculizer or inoculant stage is controlled, so that the vermiculizer or inoculant is ensured to be dissolved in melted molten iron, and a certain concentration difference is formed in microcosmic, so that enough crystallization cores are formed in the later cooling and solidification process of the molten iron, and the microstructure form of the vermicular cast iron is better regulated and controlled.

According to some embodiments of the second aspect of the present invention, the hot metal tapping temperature is 1500-1550 ℃.

According to some embodiments of the second aspect of the present invention, the casting time is not more than 15min, so as to avoid affecting the fluidity of molten iron and ensure casting quality.

According to some embodiments of the second aspect of the present invention, the unpacking time after the casting is completed is greater than or equal to 75min, so as to better control the matrix structure morphology and improve the overall properties such as hardness.

According to some embodiments of the second aspect of the present invention, the composition analysis is performed on the molten iron after smelting and/or the molten iron before casting. The composition analysis is used for determining whether the actual composition of the obtained molten iron meets the requirement of the embodiment of the vermicular cast iron after the corresponding procedure treatment, preparing the element proportioning range (namely the target element composition) of the raw materials, and supplementing the materials according to the analysis result as required to ensure that the molten iron composition is consistent with the feeding proportioning.

According to some embodiments of the second aspect of the invention, the component analysis is performed using a silicon-carbon meter and a spectroscopic spectrometer. The carbon-silicon meter is used for detecting the carbon content of the corresponding molten iron, and the spectroscope is used for detecting the Si, mn, P, S, cu, sn, cr content of the corresponding molten iron.

According to some embodiments of the second aspect of the invention, deslagging is performed after the component analysis.

According to some embodiments of the second aspect of the invention, the preparation raw material may be selected from scrap steel and return charge to enable reuse of resources.

An embodiment of the third aspect of the invention relates to the use of the vermicular cast iron described above for the manufacture of a transmission component or a brake component.

Because the vermicular cast iron has excellent physical and mechanical properties, thermal conductivity and wear resistance, the industrial production is easy, the integral performance of the transmission part or the brake part prepared by the vermicular cast iron is improved, the service life is prolonged, and the production cost is reduced.

According to some embodiments of the third aspect of the present invention, the driving component is selected from an automatic scroll, a fixed scroll, a scroll compressor, an engine block, an engine head, or an engine.

According to some embodiments of the third aspect of the invention, the brake component is selected from a brake disc or a brake device.

A fourth aspect of the present invention is directed to a scroll compressor comprising an orbiting scroll and a non-orbiting scroll, the orbiting and/or non-orbiting scrolls being made of the vermicular cast iron.

In view of the obvious improvement of the comprehensive performance of the vermicular cast iron of the embodiment of the invention, the comprehensive performance of the movable vortex plate or the fixed vortex plate is improved, so that the vortex compressor has obvious advantages in terms of service life and production cost.

A fifth aspect of the present invention relates to a refrigeration device provided with the scroll compressor.

The scroll compressor has the performance characteristics of high efficiency, silence, stable operation and wide compression ratio range, is widely applied to household or commercial refrigeration devices such as air conditioners, refrigerators, freezers and the like, and can meet the compression requirements of different types of refrigeration devices. In view of the performance advantages of the scroll compressor, the refrigeration apparatus, which is in turn equipped with the scroll compressor, is also advantageous in terms of service life and production costs.

According to some embodiments of the fifth aspect of the invention, the refrigeration device is selected from an air conditioner, a refrigerator or a freezer.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 shows a metallographic structure of a conventional gray cast iron.

FIG. 2 is a metallographic structure of a conventional cast iron mill.

FIG. 3 is a metallurgical structure of a conventional vermicular cast iron.

Fig. 4 is a schematic structural view of the scroll compressor.

FIG. 5 shows the metallographic structure of example 1.

FIG. 6 shows the metallographic structure of example 2.

FIG. 7 shows the metallographic structure of example 3.

FIG. 8 shows the metallographic structure of comparative example 1.

FIG. 9 is a plot of block sizes for the hardness test.

Detailed Description

The following detailed description of embodiments of the invention is exemplary and is provided merely to illustrate the invention and is not to be construed as limiting the invention.

The embodiment of the first aspect of the invention relates to vermicular cast iron, which comprises Fe, a rare earth-containing vermiculizer, a rare earth-containing inoculant and the following preparation raw materials in percentage by mass:

the C content has great influence on the microscopic morphology and mechanical properties of cast iron, the carbon content is controlled in a proper range, the ferrite and graphite content can be regulated, and the strength and hardness are ensured. Si is an element for promoting graphitization, and proper Si content is favorable for the morphological stability of vermicular graphite cast iron. Mn plays roles in reducing eutectic cell number, stabilizing carbide, refining and stabilizing pearlite, but the Mn content is not too high, so that supercooling is avoided. Cu plays a role in increasing and stabilizing pearlite in the matrix, and proper Cu content is beneficial to ensuring mechanical properties such as strength, elongation and the like. Cr is a very strong pearlite promoting element, and the content of pearlite is regulated by matching two elements of Cr and Cu, so that the mechanical property and the wear resistance are ensured. Sn is used for increasing pearlite, and Sb has the function of refining graphite, so that the content of the Sn and the Sb is not excessively high, and adverse effects on the performance of cast iron are avoided.

The content of C, si is reasonably controlled, the mass percentages of pearlite forming elements Mn, cu and Sn are matched with a rare earth-containing vermiculizer and a rare earth-containing inoculant, so that the microstructure form and the distribution uniformity of the whole cast iron matrix structure are regulated, the fluctuation range of the cast iron hardness is reduced, the wear resistance, the heat conductivity and the machinability are improved, and the manufacturing cost is reduced. Further, by adding a proper amount of the segregation facilitating element Sb and the carbide forming element Cr, a better modifying effect can be achieved.

The vermicular cast iron has the tensile strength more than or equal to 450MPa, the yield strength more than or equal to 335MPa, the hardness value reaching HB 160-230, the fluctuation range of the hardness being as low as below 10HB, and the integral physical and mechanical properties being obviously superior to the existing vermicular cast iron.

In some embodiments, the rare earth-containing vermiculizer is selected from Ce, zr, or a combination thereof.

In some embodiments, the rare earth-containing vermiculizer also contains Si, mg, ca, and Fe.

In some embodiments, the rare earth-containing vermiculizer includes Fe and the following elements in mass percent: 4-6% of Mg, 43-47% of Si, 1-2% of Ca and 2-4% of Re, wherein Re is selected from Ce, zr or a combination thereof. It is understood that the balance is Fe without considering the content of the impurity element.

In some embodiments, the rare earth-containing vermiculizer is 0.2% -0.5% by mass of the total mass of the remaining preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant.

In some embodiments, the rare earth element in the rare earth-containing inoculant is selected from Ce, zr, or a combination thereof.

In some embodiments, the rare earth inoculant further comprises Si, ca, ba, and Fe, or the rare earth inoculant further comprises Si, ca, ba, al and Fe.

In some embodiments, the rare earth element in the rare earth-containing inoculant is selected from Ce.

In some embodiments, the rare earth-containing inoculant comprises Fe and the following elements in mass percent: 70-80% of Si, 0.75-2% of Ca, 1-3% of Ba, 0.3-1% of Ce and 0-1.5% of Al. It is understood that the balance is Fe without considering the content of the impurity element.

In some embodiments, the rare earth-containing inoculant comprises a rare earth ferrosilicon alloy and a ferrobarium calcium ferrosilicon alloy, the rare earth ferrosilicon alloy comprising Fe and the following elements in mass percent: 70-76% of Si, 0.75-1.25% of Ca, 0.75-1.25% of Al and 1.5-2.0% of Ce; the silicon-barium-calcium-iron alloy comprises Fe and the following elements in percentage by mass: 72 to 78 percent of Si, 1.0 to 2.0 percent of Ca, 2.0 to 3.0 percent of Ba, 0 to 1.25 percent of Al, and the mass ratio of the rare earth ferrosilicon alloy to the silicon barium calcium iron alloy is 1:1 to 4. It is understood that the balance of Fe is rare earth ferrosilicon or ferrosilicon without considering the content of impurity elements.

The two alloys are matched, so that the inoculant composition is adjusted, the microstructure morphology and uniformity of the cast iron are ensured, and the overall performance of the cast iron is improved.

As one implementation mode, the mass ratio of the rare earth ferrosilicon alloy to the silicon barium calcium ferrosilicon alloy is 1:2-3.

In some embodiments, the rare earth ferrosilicon alloy is 0.1-0.2% by mass and the barium-calcium-iron alloy is 0.2-0.4% by mass based on the total mass of the rest of the preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant.

In some embodiments, the rare earth inoculant comprises 0.3-0.6% by mass of the total mass of the remaining preparation materials excluding the rare earth vermiculizer and the rare earth inoculant.

In some embodiments, the vermicular cast iron has a carbon equivalent c.e. value of 4.3-4.6.

The amounts of the elements are calculated as an increase or decrease in the amount of carbon, i.e., the equivalent of carbon, based on the effect of the elements on the actual amount of carbon at the eutectic point, expressed as c.e. values (%). The formula for calculating the carbon equivalent is: C.E =c++1/3 (si+p)% +1/6 mn++1/5 cr++1/15 Cu) in mass percent (%).

The carbon equivalent range is controlled, so that the carbon equivalent of molten iron in the solidification process is ensured to be close to that of eutectic components, near-eutectic solidification can be realized, the graphite size is thinned, shrinkage porosity in cast iron is reduced, and meanwhile, graphite floatation caused by overlarge carbon equivalent is avoided.

In some embodiments, the mass percent of C is 3.7% to 3.8%.

In some embodiments, the mass percentage of Si is 1.8% to 2.2%.

In some embodiments, the mass percent of Mn is 0.25% to 0.4%.

In some embodiments, the mass percent of Cu is 0.3% to 0.4%.

In some embodiments, the mass percentage of Sn is 0.04% to 0.06%.

In some embodiments, the mass percentage of Cr is 0.02% to 0.04%.

In some embodiments, the mass percent of Sb is no more than 0.001%.

In some embodiments, the raw materials for preparing the vermicular cast iron further comprise impurity elements, such as P, S, etc., the content of S can be controlled below 0.01%, and the content of P can be controlled below 0.02%.

In some embodiments, the vermicular cast iron has a vermicular rate of 50% to 80% as measured in GB/T26656-2023. The creep rate is controlled in a proper range so as to better consider the heat conductivity, the thermal fatigue resistance and the mechanical property.

In some embodiments, the vermicular cast iron has a vermicular rate of 55% to 75%.

In some embodiments, the vermicular cast iron has a pearlite content of 50% to 80% as tested by GB/T26656-2023. In the content range, the tissue morphology with high dispersity and uniform distribution is obtained, and the hardness uniformity and the wear resistance are improved. And when the pearlite is more than 80%, it may cause great difficulty in machining.

In some embodiments, the vermicular cast iron has a pearlite content of 50% to 60%.

In some embodiments, the pearlite content of the vermicular cast iron is 55% -60%.

In some embodiments, the graphite fraction of the vermicular cast iron is 10% -15%.

In some embodiments, the graphite fraction of the vermicular cast iron is 11% -13%.

The graphite ratio can be calculated according to the area ratio of the graphite in the field of view by referring to a test method of the vermicular rate related to GB/T26656-2023.

In some embodiments, the vermicular cast iron has a tensile strength of 450MPa or more, a yield strength of 335MPa or more, and a test standard of GB/T228.1-2021.

In some embodiments, the vermicular cast iron has a brinell hardness number HB of 160-230.

In some embodiments, the fluctuation range of the Brinell hardness number HB of the vermicular cast iron is less than or equal to 10.

The embodiment of the second aspect of the invention relates to a preparation process of vermicular cast iron, which comprises the following steps:

smelting the preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant, adding the rare earth-containing vermiculizer for vermiculization treatment, adding the rare earth-containing inoculant for inoculation treatment, discharging the obtained molten iron, and casting to obtain the vermicular cast iron.

After smelting the preparation raw materials, performing vermiculizer and inoculation before discharging soup, so that the addition amount and the dispersibility of the vermiculizer and the inoculant can be controlled more accurately, a more uniform vermiculizer and inoculation effect can be obtained, and the graphite morphology and the precipitation amount thereof, and the microstructure morphology and the uniformity of the interior of the vermicular cast iron are ensured. Inoculant is added in the same section of procedure to perform inoculation treatment, inoculation operation is completed before casting ladle, requirements on equipment and process control are low, industrial production is easy to realize, and production cost is reduced. The prepared vermicular cast iron has uniform mixed structure of pearlite, ferrite and graphite, the vermicular rate, the pearlite ratio and the graphite ratio range are easy to regulate and control, the hardness fluctuation range is reduced, and the wear resistance and the heat conductivity are improved while the excellent mechanical property is ensured.

In some embodiments, the smelting temperature is 1450-1500 ℃. The smelting temperature control is favorable for improving the purity of molten iron and eliminating the inheritance of graphite so as to obtain fine and uniform graphite morphology through inoculation.

In some embodiments, the temperature of the creep treatment is 1500-1550 ℃.

In some embodiments, the vermiculizer process is for a period of 20 to 40 seconds.

In some embodiments, the temperature of the inoculation is 1500 to 1550 ℃.

In some embodiments, the incubation time is 20 to 40 seconds.

In some embodiments, the hot metal tapping temperature is 1500-1550 ℃.

In some embodiments, the casting time does not exceed 15 minutes. The casting time is too long, so that the fluidity of molten iron is easily influenced, and the casting quality is further influenced.

In some embodiments, the unpacking time after casting is more than or equal to 75 minutes, so that the matrix structure form is better controlled, and the overall performances such as hardness and the like are improved.

In some embodiments, composition analysis is performed on molten iron after smelting and/or molten iron before casting.

In some embodiments, the component analysis is performed using a silicon-carbon instrument and a spectroscopic instrument.

In some embodiments, deslagging is performed after the composition analysis.

In some embodiments, the preparation feedstock may be selected from scrap steel and return charge to enable reuse of the resource.

Specifically, the mass percentage of the scrap steel can be controlled to be 40% -60%, and the mass percentage of the furnace return material can be controlled to be 60% -40%. Depending on the target elemental composition, the appropriate type of scrap and scrap material and the respective duty ratio are easily selected.

The driving component may be, for example, an orbiting scroll, a fixed scroll, or a scroll compressor including at least one of them, or may be an engine block, an engine head, or an engine including at least one of them. The braking component is, for example, selected from a brake disc or a brake device comprising the same.

A fourth aspect of the present invention is directed to a scroll compressor including an orbiting scroll and a non-orbiting scroll, the orbiting and/or non-orbiting scrolls being made of vermicular cast iron.

In view of the obvious improvement of the comprehensive performance of the vermicular cast iron provided by the embodiment of the invention, the comprehensive performance of the movable scroll or the fixed scroll is improved, and the scroll compressor provided with the movable scroll or the fixed scroll has obvious advantages in terms of service life and production cost.

A fifth aspect of the present invention is directed to a refrigeration device provided with a scroll compressor.

In view of the performance advantages of the scroll compressor, the refrigeration apparatus, which is in turn equipped with the scroll compressor, is also advantageous in terms of service life and production costs.

The present invention will be described in detail with reference to the following examples. Wherein, the related raw materials are as follows:

vermiculizer, ankenThe concrete composition comprises the following components in percentage by mass: 4-6% of Mg, 43-47% of Si, 1-2% of Ca, 2-4% of Re, ce and Zr, and the balance of Fe.

Inoculant: rare earth ferrosilicon alloy, rankineThe concrete composition comprises the following components in percentage by mass: 70-76% of Si, 0.75-1.25% of Ca, 0.75-1.25% of Al, 1.5-2.0% of Ce and the balance of iron; silicon barium calcium iron alloy, elken->The concrete composition comprises the following components in percentage by mass: 72-78% of Si, 1.0-2.0% of Ca, 2.0-3.0% of Ba, 0-1.25% of Al and the balance of iron.

Unless otherwise indicated, all starting materials used were conventional commercially available.

Example 1

The vermicular cast iron is prepared in the embodiment, and comprises the following preparation steps:

s1, melting: the scrap steel and the furnace return materials are put into an intermediate frequency induction furnace according to a certain proportion, the total element composition of the scrap steel and the furnace return materials meets the element composition shown in table 1 (or called target value, the rest main element is Fe except the elements shown in table 1), the temperature in the furnace is raised to 1450-1500 ℃ to be smelted, so that the molten iron is melted into molten iron, the carbon content of the molten iron is detected by a carbosilicate meter, the content of Si, mn, P, S, cu, sn, cr is detected by a spectroscope, and the alloy ingredients are added according to the difference between the actual measurement value and the target value to adjust the relative element composition to meet the element composition shown in table 1.

S2, vermiculizing: stabilizing the temperature of molten iron at 1525 ℃, adding a vermiculizer into the heated molten iron by a wire feeding process, and performing vermiculizing treatment, wherein the dosage of the vermiculizer is 0.4% of the mass of the molten iron, and the vermiculizing treatment time is 30s.

S3, inoculation: and (3) sequentially adding the silicon-barium-calcium-iron alloy and the rare earth silicon-iron alloy into the ladle at constant temperature for inoculation treatment, wherein the treatment time is 25s, the dosage of the silicon-barium-calcium-iron alloy is 0.35% of the mass of molten iron, and the dosage of the rare earth silicon-iron alloy is 0.15% of the mass of molten iron.

S4, casting: transferring the ladle to the front of a furnace for tapping operation, controlling the tapping temperature to be 1525 ℃, pouring the molten iron of the ladle into a transfer ladle, sampling the molten iron before casting for component analysis, determining that the components meet the element proportioning requirements of table 1, finishing casting within 12min, and opening the ladle 80min after finishing casting to obtain the vermicular cast iron.

Example 2

This example produced a vermicular cast iron, which differs from example 1 in that:

(1) The main elements of the vermicular cast iron have different compositions, and the specific differences are shown in table 1.

(2) In step S4, the unpacking time is prolonged from 80min to 100min.

Example 3

(2) In step S4, the unpacking time is prolonged from 80min to 110min.

Comparative example 1

The main element composition of the conventional RuT450 vermicular cast iron is shown in Table 1.

TABLE 1

Test case

The vermicular cast irons prepared in examples 1 to 3 and comparative example 1 were tested for metallographic structure and physical mechanical properties, the golden phase diagrams are shown in fig. 5 to 8, and the performance indexes are shown in table 2, which represent examples 1 to 3 and comparative example 1 in order.

Test sample:

the test method is as follows:

(1) Metallographic structure: adopting a metallographic microscope for detection, and branding: leica, model: DM6000M, magnification: 200X.

(2) Mechanical properties: national standard GB/T228.1-2021 section 1 of Metal tensile test: room temperature test methods, test instruments: universal tensile testing machine detects, brand: MTS, model: BHTMS-002.

(3) Hardness: the test sample was tested using a brinell hardness tester: 1) And (3) test block: the dimensions of the cylinder are shown in fig. 9, and the measurement surface is tested in parallel three times to obtain an average value; 2) Parts: the movable vortex plate is used for testing the fluctuation range of hardness, 7 test points are uniformly selected on the part, and the distribution range of hardness values is recorded.

(4) Thermal conductivity coefficient: national standard GB/T3651-2008 "method for measuring high-temperature coefficient of thermal conductivity of metals".

(5) Abrasion resistance: the abrasion loss after 20 minutes was recorded by using a conventional friction tester to test, applying a force of 100N at a rotation speed of 500 rpm.

TABLE 2

As shown by test results, in the vermicular cast iron of the embodiments 1 to 3, graphite morphology is obviously changed, the vermicular rate is obviously higher, meanwhile, the graphite ratio and the pearlite content are higher, and the distribution of graphite and microstructure is uniformGood in property. The integral physical and mechanical properties of the vermicular graphite cast iron are improved to a certain extent, and the tensile strength is more than or equal to 450N/mm ² Yield strength is more than or equal to 335N/mm ² The elongation is less than or equal to 6 percent, the hardness range is HB 170-230, the fluctuation range of the hardness is small and is not more than 10HB, and the wear resistance and the heat conduction performance are obviously improved.

In comparison, example 3 had a higher graphite ratio but a lower vermiculizer rate, indicating that more non-vermicular graphite was present in example 3. As can be seen from fig. 7, the cast iron of example 3 has more spheroidal graphite structure inside, which has less cutting effect on the matrix, and thus has higher strength, hardness and toughness. The range of hardness fluctuation of example 3 is equivalent to other examples, but the overall hardness of example 3 is higher, and the abrasion resistance is higher. However, example 3 increases the content of the spherical graphite, which is disadvantageous in improving the thermal conductivity. It can be seen that the difference of the microstructure morphology of the matrix has a significant effect on the cast iron performance. The difference in matrix structure in example 3 may be related to the long time of unpacking, which affects the growth morphology of the matrix structure, or may be related to the difference in nucleation induced in the matrix structure due to the difference in element collocation such as Cu.

From the golden phase diagrams and the physical and mechanical property data of comparative example 1 and examples 1 to 3, it can be found that the conventional RuT450 vermicular cast iron of comparative example 1 has low vermicular rate, graphite ratio and pearlite content and uneven microstructure distribution. The difference among graphite morphology, graphite duty ratio and microstructure morphology leads to obvious reduction of thermal conductivity of comparative example 1, larger fluctuation range of hardness, uneven temperature distribution in cast iron under the working conditions of heating and the like, increased internal temperature difference can increase thermal stress, low strength of cast iron, uneven hardness, obvious insufficient wear resistance and obvious increase of wear resistance under the same test conditions. It will be appreciated that the vermicular cast iron prepared in comparative example 1 is less prone to cracking under stress or heat conditions, and has significantly lower thermal fatigue resistance than the vermicular cast iron of examples 1-3 of the present invention.

The vermicular cast iron disclosed by the embodiment of the invention has the performance advantages of high strength, high hardness, high wear resistance, high thermal conductivity, small hardness fluctuation and the like, can be used for manufacturing transmission parts or braking parts with high mechanical strength requirements, such as parts of a compressor core part scroll, an engine cylinder body or an engine cylinder cover and the like, and can be used for prolonging the service life of the parts or equipment provided with the parts. Meanwhile, the vermicular cast iron disclosed by the embodiment of the invention is easy for industrial production, can reduce the production cost of parts or equipment using the vermicular cast iron, and has obvious application advantages.

As an example, the component or the device may be a scroll compressor or an engine, and may be a household or commercial refrigeration device such as an air conditioner, a refrigerator, a freezer, or the like.

The present invention has been described in detail with reference to the embodiments, but the present invention is not limited to the embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention.

Claims

1. The vermicular cast iron is characterized by comprising Fe, a rare earth-containing vermiculizer, a rare earth-containing inoculant and the following preparation raw materials in percentage by mass:

2. the vermicular cast iron of claim 1, wherein the rare earth-containing vermiculizer and the rare earth-containing inoculant are independently selected from Ce, zr, or a combination thereof; and/or the rare earth-containing vermiculizer also contains Si, mg, ca and Fe; and/or the rare earth inoculant also contains Si, ca, ba and Fe, or further contains Si, ca, ba, al and Fe.

3. The vermicular cast iron of claim 2, wherein the rare earth-containing vermiculizer comprises Fe and the following elements in mass percent: 4-6% of Mg, 43-47% of Si, 1-2% of Ca and 2-4% of Re; wherein Re is selected from Ce, zr or a combination thereof.

4. The vermicular cast iron of claim 2, wherein the rare earth-containing inoculant comprises a rare earth ferrosilicon alloy and a barium-calcium-iron alloy, the rare earth ferrosilicon alloy comprising Fe and the following elements in mass percent: 70-76% of Si, 0.75-1.25% of Ca, 0.75-1.25% of Al and 1.5-2.0% of Ce; the silicon-barium-calcium-iron alloy comprises Fe and the following elements in percentage by mass: 72 to 78 percent of Si, 1.0 to 2.0 percent of Ca, 2.0 to 3.0 percent of Ba, 0 to 1.25 percent of Al, and the mass ratio of the rare earth ferrosilicon alloy to the silicon barium calcium iron alloy is 1:1 to 4.

5. The vermicular cast iron of claim 4, wherein the rare earth ferrosilicon alloy is 0.1-0.2% by mass and the barium-calcium-iron alloy is 0.2-0.4% by mass based on the total mass of the rest of the preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant.

6. The vermicular cast iron according to any one of claims 1 to 5, wherein the mass percentage of the rare earth-containing vermicular agent is 0.2% to 0.5% based on the total mass of the remaining preparation raw materials except the rare earth-containing vermicular agent and the rare earth-containing inoculant; and/or the mass percentage of the rare earth-containing inoculant is 0.3-0.6%.

7. The vermicular cast iron of any one of claims 1-5, wherein the vermicular cast iron has a carbon equivalent c.e. value of 4.3-4.6; and/or the vermicular rate of the vermicular cast iron is 50% -80%; and/or, the pearlite content of the vermicular cast iron is 50% -80%; and/or the graphite ratio of the vermicular graphite cast iron is 10% -15%.

8. The vermicular cast iron of any one of claims 1-5, wherein the vermicular cast iron has a tensile strength of 450MPa or more, a yield strength of 335MPa or more, and a test standard of GB/T228.1-2021; and/or the Brinell hardness value HB of the vermicular graphite cast iron is 160-230, and the fluctuation range of the hardness value HB is less than or equal to 10.

9. The process for preparing vermicular cast iron according to any one of claims 1 to 8, comprising the steps of: smelting preparation raw materials except the rare earth-containing vermiculizer and the rare earth-containing inoculant, adding the rare earth-containing vermiculizer for vermiculization treatment, adding the rare earth-containing inoculant for inoculation treatment, discharging the obtained molten iron, and casting to obtain the vermicular cast iron.

10. The process according to claim 9, wherein the smelting temperature is 1450-1500 ℃; and/or the temperature of the vermiculizer is 1500-1550 ℃, and the vermiculizer time is 20-40 s; and/or the inoculation temperature is 1500-1550 ℃, and the inoculation time is 20-40 s; and/or the temperature of the molten iron soup outlet is 1500-1550 ℃; and/or, the casting is for no more than 15 minutes; and/or, the unpacking time after casting is more than or equal to 75min.

11. The process according to claim 9 or 10, further comprising the step of: and carrying out component analysis on the melted molten iron and/or the molten iron before casting, and deslagging after the component analysis.

12. Use of the vermicular cast iron of any one of claims 1-8 for manufacturing a transmission component or a brake component.

13. A scroll compressor comprising an orbiting scroll and a non-orbiting scroll, the orbiting and/or non-orbiting scrolls being made of the vermicular cast iron of any one of claims 1-8.

14. A refrigeration device provided with a scroll compressor as claimed in claim 13.

15. The refrigeration unit of claim 14, wherein the refrigeration unit is selected from an air conditioner, a refrigerator, or a freezer.