CN111519088A - Iron casting, composite part comprising an iron casting, and method for producing an iron casting - Google Patents
Iron casting, composite part comprising an iron casting, and method for producing an iron casting Download PDFInfo
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- CN111519088A CN111519088A CN201910247711.1A CN201910247711A CN111519088A CN 111519088 A CN111519088 A CN 111519088A CN 201910247711 A CN201910247711 A CN 201910247711A CN 111519088 A CN111519088 A CN 111519088A
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- iron casting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J10/00—Engine or like cylinders; Features of hollow, e.g. cylindrical, bodies in general
- F16J10/02—Cylinders designed to receive moving pistons or plungers
- F16J10/04—Running faces; Liners
Abstract
The present invention provides an iron casting, which aims to improve corrosion resistance to corrosion caused by sulfuric acid and other acids occurring in an EGR system. The iron casting contains 2.9-3.7 mass% of carbon, 1.8-2.8 mass% of silicon, 0.5-1.0 mass% of manganese, 0.05-0.4 mass% of phosphorus, less than 0.12 mass% of sulfur and 0.5-3.0 mass% of copper, and contains A-type graphite, and the proportion of the A-type graphite in the total graphite is less than 65%, so that the purpose can be achieved by using the iron casting.
Description
Technical Field
The present invention relates to an iron casting having improved corrosion resistance suitable for a cylinder liner of an internal combustion engine and a method for manufacturing the same.
Background
In order to reduce the concentration of NOx in the exhaust gas from an internal combustion engine according to environmental requirements, an EGR system may be employed. Since the EGR gas of the EGR system contains sulfur components in the fuel, the condensed water of the EGR gas contains sulfuric acid, and corrosion of the inner wall of the cast iron cylinder liner may be caused.
A technique of reducing the distance between the ferrite phase and the cementite phase in the pearlite phase in order to cope with the corrosion caused by the EGR gas is disclosed (see patent documents 1 and 2).
On the other hand, since the cylinder liner slides at a high speed in the internal combustion engine, abrasion resistance is required not only to wear resistance but also to abrasion resistance that does not cause scratches due to sliding of the piston ring. Therefore, a cast iron containing a-type graphite is disclosed as a cast iron used for a cylinder liner having improved wear resistance and scuff resistance (see patent documents 3 and 4).
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 5757755
Patent document 2: japanese laid-open patent publication No. 2015-196897
Patent document 3: japanese examined patent publication No. 58-036664
Patent document 4: japanese patent laid-open No. 2008-106357
Disclosure of Invention
Problems to be solved by the invention
The present invention addresses the problem of providing an iron casting having improved corrosion resistance to corrosion caused by an acid such as sulfuric acid occurring in an EGR system.
Means for solving the problems
The present inventors have made extensive studies to solve the above problems and found that corrosion resistance can be improved by containing a fixed amount of copper in an iron casting and then reducing the ratio of a-type graphite, thereby completing the present invention.
The invention relates to an iron casting containing 2.9-3.7 mass% of carbon, 1.8-2.8 mass% of silicon, 0.5-1.0 mass% of manganese, 0.05-0.4 mass% of phosphorus, less than 0.12 mass% of sulfur, and 0.5-3.0 mass% of copper,
the iron casting comprises A-type graphite, and the proportion of the A-type graphite in the total graphite is less than 65%.
In the iron casting, the ferrite phase and the cementite are alternately precipitated to form a pearlite phase, and the lamella spacing (lamellar spacing) of the pearlite phase is preferably 0.5 μm or more and 2.5 μm or less, and the carbon equivalent C.E value is preferably 2.6 or more and 3.8 or less.
The present invention also relates, as another aspect, to a composite member including the above-described iron casting and a piston including a piston ring whose outer peripheral surface slides on an inner wall of the iron casting,
the outer peripheral surface of the piston ring is covered with a coating film selected from PVD and DLC.
The present invention also relates to a method for producing an iron casting, which includes a pouring step of pouring a cast iron material into a mold, and a cooling step of cooling the cast iron material poured into the mold to obtain an iron casting,
the iron casting contains a type a graphite,
the temperature of the cast iron material injected in the injection step is adjusted, and the temperature of the mold and/or the cooling rate in the cooling step is/are adjusted so that the ratio of the a-type graphite in the total graphite is 65% or less.
Effects of the invention
According to the present invention, there can be provided an iron casting which is less corroded by an acid and is excellent in corrosion resistance.
Drawings
FIG. 1 is a graph showing the results of the corrosion test in examples 1 to 4 and comparative example 1.
Detailed Description
One embodiment of the present invention is an iron casting containing 2.9 to 3.7 mass% of carbon, 1.8 to 2.8 mass% of silicon, 0.5 to 1.0 mass% of manganese, 0.05 to 0.4 mass% of phosphorus, 0.12 mass% or less of sulfur, and 0.5 to 3.0 mass% of copper. The iron casting contains A-type graphite, and the proportion of A-type graphite in the total graphite is 65% or less. The iron casting of the present embodiment may contain elements other than those described above, such as boron, chromium, nickel, molybdenum, and the like. When boron is contained, the content thereof may be 0.03 to 0.08% by mass, and the wear resistance can be improved by containing boron.
The iron casting in this embodiment contains a fixed amount of copper to improve corrosion resistance. Further, the iron casting contains copper and also contains a-type graphite, and the ratio of the a-type graphite in the total graphite is 65% or less, whereby the corrosion resistance to acid can be improved.
The iron casting of the present embodiment can improve the corrosion resistance to acid by containing a fixed amount of copper, and the content thereof is usually 0.5 mass% or more, may be 0.6 mass% or more, may be 0.8 mass% or more, and may be 1.0 mass% or more. In addition, the content is usually 3.0 mass% or less, may be 2.5 mass% or less, and may be 2.0 mass% or less.
In the case of an iron casting containing a type a graphite, the graphite in the iron casting is present in a non-directional, disorderly and uniformly distributed manner. In the present embodiment, the ratio of the a-type graphite in the total graphite is set to 65% or less, and corrosion resistance against corrosion by acid can be improved. The ratio of the a-type graphite in the total graphite may be 60% or less, 55% or less, 50% or less, 45% or less, or 40% or less. The lower limit is not limited, and may be more than 0%, 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, and 30% or more. In addition, when the ratio of a-type graphite is too high, ferrite precipitates, and thus corrosion resistance is lowered. Therefore, in the present embodiment, ferrite is preferably not precipitated.
In addition, when the proportion of the a-type graphite in the total graphite is too small, the wear resistance tends to be insufficient. Therefore, when the total graphite content of the iron casting is relatively low, it is preferable that the film covering the outer peripheral surface of the piston ring slidable on the inner wall of the iron casting be covered with a film having excellent wear resistance and low attack by other substances, such as PVD and DLC.
The iron casting may contain graphite other than A-type graphite, for example, B-type graphite, D-type graphite, and E-type graphite in fixed amounts, but generally the proportion of E-type graphite is large. The content of E-type graphite is usually 50% or less, but may be 40% or less, or may be 30% or less. The content of other graphite is usually not more than 30%, may not more than 20%, and may not more than 10%.
In the iron casting, the value of carbon equivalent C.E is usually not more than 3.8, but may be not more than 3.6, but may be not more than 3.5, and usually not less than 2.6, but may be not less than 3.2.
The carbon equivalent C.E is represented by (carbon amount + silicon amount/3.2), and the smaller the value, the more likely it is to be a hard and brittle iron casting.
The iron casting has pearlite as a lamellar structure of ferrite and cementite, and the lamellar spacing of the pearlite is usually 0.5 μm or more, but may be 0.7 μm or more, and is usually 2.5 μm or less, or may be 2.3 μm or less, or may be 2.0 μm or less, or may be 1.0 μm or less. By setting the above range, the corrosion resistance is improved.
The ratio of the a-type graphite in the total graphite can be determined by visual inspection. Specifically, the ratio (area ratio) of a-type graphite was measured based on astm a 247. The determination of the ratio of type a graphite is preferably carried out by a person skilled in the art and is preferably carried out at a plurality of places in the iron casting, for example at 2 or more, preferably at 4 or more, and the average value thereof is calculated.
Further, the lamellar spacing of pearlite was calculated by observing a plurality of places in the iron casting through a metal microscope and calculating the average lamellar spacing in the range of 20 μm. With regard to the lamella spacing, it is preferred that the measurement is carried out at a plurality of places in the iron casting, for example at 2 or more, preferably at 4 or more, and the average value thereof is calculated.
In the present embodiment, setting the ratio of the a-type graphite in the total graphite within the above range can be achieved by adjusting the temperature of the mold into which the cast iron material (melt) is injected; adjusting the temperature of the injected melt; adjusting a cooling rate of a cast iron material injected into a mold during a manufacturing process of the iron casting; adjusting the thickness of a mold agent layer coated on the mold; an element that inhibits graphitization and an element that promotes graphitization are introduced into a cast iron material.
Further, the lamellar spacing of pearlite can be achieved by adjusting the temperature of the mold into which the cast iron material is injected; accelerating the cooling rate of the cast iron material injected into the mold during the manufacturing process of the iron casting; the Cu content in the cast iron material is adjusted.
Hereinafter, a method for manufacturing a cast iron article according to the present embodiment will be described.
Another embodiment of the present invention is a method for manufacturing an iron casting, including an injection step of injecting a cast iron material into a mold, and a cooling step of cooling the cast iron material injected into the mold to obtain the iron casting,
in the method for manufacturing the iron casting, the iron casting contains A-type graphite, and the injection step and/or the cooling step are/is adjusted so that the proportion of the A-type graphite in the total graphite is 65% or less. The specific method for making the ratio of a-type graphite 65% or less in the injecting step and/or the cooling step is as described above.
The iron castings are generally manufactured by centrifugal casting, but may be manufactured by gravity casting.
In the injection step, a mold for forming an iron casting is prepared, and the molten cast iron material (melt) is injected into the mold. In this case, the temperature of the mold is usually 250 ℃ to 300 ℃ and preferably 260 ℃ to 290 ℃. The injected melt is a substance satisfying the composition of the cast iron material. The temperature of the melt injected into the mold is not particularly limited and may be appropriately set, but the cooling rate in the cooling step may be adjusted by the temperature of the melt.
The casting mold is internally coated with a casting coating containing a refractory, a binder, water, a surfactant, and the like. The thickness of the casting paint layer is not particularly limited and may be appropriately set, but the cooling rate in the cooling step may be adjusted by the thickness of the casting paint layer.
In the cooling process, the cast iron material injected into the mold is cooled, thereby obtaining an iron casting. In this case, the cooling temperature rate of the cast iron material is not particularly limited, and may be adjusted by an air cooling system or by adjusting an air conditioner. In addition, the cooling speed of the cast iron material can be adjusted by adjusting the type of the casting coating and the thickness of the casting coating layer.
The obtained iron casting is obtained by taking it out of the casting mould and removing the layer of cast coating on the surface from the iron casting by means of sand blasting.
In the iron casting of the present embodiment, the corrosion resistance against corrosion by acid is improved by setting the ratio of the a-type graphite to 65% or less of the total graphite, while the wear resistance may be insufficient by setting the ratio of the a-type graphite to a relatively low value. Therefore, when the cylinder liner is used in an engine together with a piston, it is preferable that a film covering the outer peripheral surface of a piston ring slidable on the inner wall of the iron casting is covered with a film having excellent wear resistance and low attack by other substances, such as PVD and DLC.
That is, another aspect of the present invention is a composite part including the above-described iron casting and a piston including a piston ring having an outer peripheral surface sliding on an inner wall of the iron casting, wherein the outer peripheral surface of the piston ring is covered with a film selected from PVD and DLC.
The coating film for covering the piston ring selected from PVD and DLC is more preferably DLC.
[ examples ] A method for producing a compound
The present invention will be described in more detail below with reference to examples, but the present invention is not limited to only the following examples.
< example 1: 0.5 mass% Cu >
Iron castings having the following composition were manufactured.
Carbon: 3.4% by mass
Silicon: 2.4% by mass
Manganese: 0.63% by mass
Phosphorus: 0.12% by mass
Sulfur: 0.035% by mass
Copper: 0.5% by mass
Boron: 0.06% by mass
Chromium: 0.10% by mass
Specifically, the cast iron material having the above composition after heating at 1400 ℃ was poured into a mold at 280 ℃ and then air-cooled, thereby obtaining an iron casting. The physical properties of the obtained iron castings were measured and the results are shown in table 1. In addition, the iron castings obtained by the examples were of diameter
The "distance from the outer periphery" in the cylindrical shape having a height of 13.5cm and a wall thickness of 0.6cm means the distance from the outer peripheral surface of the iron casting.
[ TABLE 1 ]
TABLE 1
< example 2: 1.0 mass% Cu >
An iron casting having the same composition as in example 1 was produced, except that the Cu content was set to 1.0 mass%.
The physical properties of the obtained iron castings were measured and the results are shown in table 2.
[ TABLE 2 ]
TABLE 2
< example 3: 1.5% by mass of Cu >
An iron casting having the same composition as in example 1 was produced, except that the Cu content was set to 1.5 mass%.
The physical properties of the obtained iron castings were measured and the results are shown in table 3.
[ TABLE 3 ]
TABLE 3
< example 4: 2.0 mass% Cu >
An iron casting having the same composition as in example 1 was produced, except that the Cu content was set to 2.0 mass%.
The physical properties of the obtained iron castings were measured and the results are shown in table 4.
[ TABLE 4 ]
TABLE 4
< comparative example 1: 0.2 mass% Cu >
An iron casting having the same composition as in example 1 was produced, except that the Cu content was set to 0.2 mass% and the boron content was set to zero.
The physical properties of the obtained iron castings were measured and the results are shown in table 5.
[ TABLE 5 ]
TABLE 5
The iron castings obtained above were subjected to corrosion tests. The corrosion test was conducted by exposing a test piece having a plane for measuring the above a-type graphite ratio and pearlite interlamellar spacing and having a thickness of 10mm × 10mm as a surface to 2.5% sulfuric acid at 65 ℃ for 15 hours, and measuring the weight difference between the test piece before and after the exposure to sulfuric acid. The results are shown in FIG. 1.
As can be understood from fig. 1: by containing a specific amount of Cu and setting the a-type graphite ratio to 65% or less, high corrosion resistance to acid is exhibited.
Claims (5)
1. An iron casting comprising 2.9 to 3.7 mass% of carbon, 1.8 to 2.8 mass% of silicon, 0.5 to 1.0 mass% of manganese, 0.05 to 0.4 mass% of phosphorus, 0.12 mass% or less of sulfur, and 0.5 to 3.0 mass% of copper,
the iron casting contains A-type graphite, and the proportion of the A-type graphite in the total graphite is less than 65%.
2. The iron casting of claim 1,
ferrite phases and cementite phases are alternately precipitated to constitute a pearlite phase, and the lamellar spacing of the pearlite phase is 0.5 to 2.5 [ mu ] m.
3. The iron casting according to claim 1 or 2,
the carbon equivalent C.E value of the iron casting is more than 2.6 and less than 3.8.
4. A composite part comprising the iron casting according to any one of claims 1 to 3 and a piston having a piston ring whose outer peripheral surface slides on the inner wall of the iron casting,
the outer peripheral surface of the piston ring is covered with a coating film selected from PVD and DLC.
5. A method for manufacturing iron castings comprises the following steps: an injection step of injecting a cast iron material into a mold, and a cooling step of cooling the cast iron material injected into the mold to obtain an iron casting,
the iron casting contains a type a graphite,
the temperature of the cast iron material injected in the injection step is adjusted, and the temperature of the mold and/or the cooling rate in the cooling step is/are adjusted so that the ratio of the a-type graphite in the total graphite becomes 65% or less.
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| JP2019-016638 | 2019-02-01 | ||
| JP2019016638A JP6963576B2 (en) | 2019-02-01 | 2019-02-01 | Cast iron member, method for manufacturing composite member including cast iron member and cast iron member |
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| CN111519088A true CN111519088A (en) | 2020-08-11 |
| CN111519088B CN111519088B (en) | 2022-11-01 |
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0718368A (en) * | 1993-06-30 | 1995-01-20 | Teikoku Piston Ring Co Ltd | Cast iron having excellent corrosion resistance and wear resistance and cylinder liner formed by the same cast iron |
| JP2012188719A (en) * | 2011-03-14 | 2012-10-04 | Hino Motors Ltd | Cast iron and cylinder liner produced from the cast iron |
| US20130118651A1 (en) * | 2011-11-14 | 2013-05-16 | Lg Electronics Inc. | Alloy cast iron and manufacturing method of vane using the same |
| CN103122432A (en) * | 2007-06-26 | 2013-05-29 | 国立大学法人岩手大学 | Flaky graphite cast iron, and method for production thereof |
| CN104011239A (en) * | 2011-12-23 | 2014-08-27 | 斗山英维高株式会社 | Method for manufacturing high strength flake graphite cast iron, flake graphite cast iron manufactured by the method, and engine body comprising the cast iron for internal combustion engine |
| JP2015196897A (en) * | 2014-04-03 | 2015-11-09 | 日野自動車株式会社 | Cast iron member and method of manufacturing cast iron member |
| CN106521308A (en) * | 2016-12-09 | 2017-03-22 | 大连锦航新能源设备有限公司 | Bottom ring material DPR-D5 of piston rings of marine diesel engine and casting method thereof |
| CN107345285A (en) * | 2016-05-05 | 2017-11-14 | 通富热处理(昆山)有限公司 | Automobile brake disc alloy gray cast-iron material, automobile brake disc and preparation method thereof |
-
2019
- 2019-02-01 JP JP2019016638A patent/JP6963576B2/en active Active
- 2019-03-29 CN CN201910247711.1A patent/CN111519088B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0718368A (en) * | 1993-06-30 | 1995-01-20 | Teikoku Piston Ring Co Ltd | Cast iron having excellent corrosion resistance and wear resistance and cylinder liner formed by the same cast iron |
| CN103122432A (en) * | 2007-06-26 | 2013-05-29 | 国立大学法人岩手大学 | Flaky graphite cast iron, and method for production thereof |
| JP2012188719A (en) * | 2011-03-14 | 2012-10-04 | Hino Motors Ltd | Cast iron and cylinder liner produced from the cast iron |
| US20130118651A1 (en) * | 2011-11-14 | 2013-05-16 | Lg Electronics Inc. | Alloy cast iron and manufacturing method of vane using the same |
| CN104011239A (en) * | 2011-12-23 | 2014-08-27 | 斗山英维高株式会社 | Method for manufacturing high strength flake graphite cast iron, flake graphite cast iron manufactured by the method, and engine body comprising the cast iron for internal combustion engine |
| JP2015196897A (en) * | 2014-04-03 | 2015-11-09 | 日野自動車株式会社 | Cast iron member and method of manufacturing cast iron member |
| CN107345285A (en) * | 2016-05-05 | 2017-11-14 | 通富热处理(昆山)有限公司 | Automobile brake disc alloy gray cast-iron material, automobile brake disc and preparation method thereof |
| CN106521308A (en) * | 2016-12-09 | 2017-03-22 | 大连锦航新能源设备有限公司 | Bottom ring material DPR-D5 of piston rings of marine diesel engine and casting method thereof |
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| Publication number | Publication date |
|---|---|
| JP2020125505A (en) | 2020-08-20 |
| JP6963576B2 (en) | 2021-11-10 |
| CN111519088B (en) | 2022-11-01 |
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