CN114000043B - Ductile cast iron with high plastic toughness and fatigue resistance and manufacturing method thereof - Google Patents
Ductile cast iron with high plastic toughness and fatigue resistance and manufacturing method thereof Download PDFInfo
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- CN114000043B CN114000043B CN202111252050.5A CN202111252050A CN114000043B CN 114000043 B CN114000043 B CN 114000043B CN 202111252050 A CN202111252050 A CN 202111252050A CN 114000043 B CN114000043 B CN 114000043B
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- 229910001141 Ductile iron Inorganic materials 0.000 title claims abstract description 97
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- 229910052796 boron Inorganic materials 0.000 claims abstract description 16
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000000126 substance Substances 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000003723 Smelting Methods 0.000 claims abstract description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 35
- 239000010439 graphite Substances 0.000 claims description 28
- 229910002804 graphite Inorganic materials 0.000 claims description 28
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 30
- 229910052580 B4C Inorganic materials 0.000 description 24
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 description 24
- 230000000694 effects Effects 0.000 description 19
- 230000002829 reductive effect Effects 0.000 description 14
- 238000005728 strengthening Methods 0.000 description 12
- 229910052717 sulfur Inorganic materials 0.000 description 9
- 238000012360 testing method Methods 0.000 description 8
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 7
- 230000007423 decrease Effects 0.000 description 7
- 239000011572 manganese Substances 0.000 description 7
- 239000010949 copper Substances 0.000 description 6
- 238000005087 graphitization Methods 0.000 description 6
- 238000007670 refining Methods 0.000 description 6
- 238000013461 design Methods 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 5
- 239000011777 magnesium Substances 0.000 description 5
- 230000001737 promoting effect Effects 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- -1 boron carbides Chemical class 0.000 description 3
- 230000001965 increasing effect Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 150000002910 rare earth metals Chemical class 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000005204 segregation Methods 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910000805 Pig iron Inorganic materials 0.000 description 1
- MKPXGEVFQSIKGE-UHFFFAOYSA-N [Mg].[Si] Chemical compound [Mg].[Si] MKPXGEVFQSIKGE-UHFFFAOYSA-N 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000011081 inoculation Methods 0.000 description 1
- 239000002054 inoculum Substances 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/04—Cast-iron alloys containing spheroidal graphite
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/08—Making cast-iron alloys
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
The invention relates to high-ductility and fatigue-resistant spheroidal graphite cast iron and a manufacturing method thereof, wherein the high-ductility and fatigue-resistant spheroidal graphite cast iron comprises the following chemical components: c:3.5-4.2%, si:1.8-2.5%, mn:0.2-0.4%, cu:0.4-0.8%, B:10-50ppm, mg:0.01-0.08%, RE:0.01-0.05%, sn:0.01-0.06%, the balance being Fe and unavoidable impurities, and C/10b=80-360, si/10b=44-200; the manufacturing method of the ductile cast iron with high plastic toughness and fatigue resistance comprises the steps of smelting, spheroidizing, inoculating and pouring.
Description
Technical Field
The invention relates to a high-plasticity and fatigue-resistant spheroidal graphite cast iron and a manufacturing method thereof, wherein the spheroidal graphite cast iron has excellent fatigue characteristics, higher strength, plasticity and toughness, wide application range, high long-period working reliability and low cost, and is particularly suitable for working conditions bearing alternating loads for a long time.
Background
Spheroidal graphite cast iron is iron in nature, but has similar properties to steel and obvious cost advantages, and therefore, the spheroidal graphite cast iron is widely applied to various mechanical parts, particularly parts which are frequently used for high-load and alternating-load bearing. Therefore, the spheroidal graphite cast iron is required to have excellent fatigue strength and mechanical properties, and the plasticity and toughness also meet certain requirements.
The common spheroidal graphite cast iron in the prior art cannot generally achieve the fatigue performance, strength, plasticity and toughness, so that a plurality of elements are often adopted to be added into the spheroidal graphite cast iron in a compounding way to improve the corresponding performance, the spheroidal graphite cast iron has high production cost, and because the components are complex, the elements are mutually influenced, the influence of' the length is easily brought to the spheroidal graphite cast iron performance, namely the strength is often improved to bring about the reduction of the plasticity and the toughness, and the strength is difficult to ensure when the toughness and the plasticity are improved, so that the development of the spheroidal graphite cast iron with various mechanical properties has great technical difficulty.
Based on the knowledge, the invention provides the spheroidal graphite cast iron which has simple element design, obvious cost advantage and excellent strength, plasticity, toughness and fatigue property.
Disclosure of Invention
The invention provides a ductile cast iron which has the advantages of strength, plasticity, toughness and fatigue property, has simple component design, can ensure excellent strength, plasticity, toughness and fatigue property at low cost, and can be suitable for components such as axle housing, crankshaft, connecting rod and the like.
The technical purpose of the invention is realized by the following means.
The invention provides high-plasticity and high-toughness fatigue-resistant spheroidal graphite cast iron, which comprises the following chemical components: c:3.5-4.2%, si:1.8-2.5%, mn:0.2-0.4%, cu:0.4-0.8%, B:10-50ppm, mg:0.01-0.08%, RE:0.01-0.05%, sn:0.01-0.06%, the balance being Fe and unavoidable impurities, and C/10b=80-360, si/10b=44-200.
The design principle of the composition, content and proportion relation of the invention is described below.
C: carbon is an element constituting a graphite structure, which is advantageous for improving molten iron fluidity of spheroidal graphite cast iron. The strength of the ductile iron is improved, the strength, toughness, elongation and other properties are reduced simultaneously due to graphite segregation when the carbon is too high, the strength of the ductile iron is not ensured when the carbon is too low, the fluidity of molten iron is poor, casting defects are increased, and various mechanical properties are reduced. The C content suitable for the present invention is 3.5-4.2%, preferably 3.6-4.0%, more preferably 3.7-3.9%.
Si: silicon is a graphitization promoting element and a solid solution strengthening element, the Si content has a larger influence on the fluidity of molten iron, and the Si can also improve the high-temperature oxidation resistance. If the Si content is too low, the graphitization effect and the strengthening effect of the spheroidal graphite cast iron are insufficient, if the Si content is too high, the plasticity and the elongation of the spheroidal graphite cast iron are remarkably reduced, and the toughness is remarkably deteriorated, and the Si content in the invention is limited to 1.8-2.5%, preferably 1.9-2.4%, more preferably 2.0-2.3%.
Mn: manganese can be combined with sulfur to generate MnS so as to reduce the deterioration of impurity sulfur on the performance of the spheroidal graphite cast iron, and a proper amount of Mn is beneficial to ensuring the strength of the spheroidal graphite cast iron, and too high Mn can lead to the reduction of the plasticity and toughness of the spheroidal graphite cast iron, and too low Mn causes insufficient desulfurization effect and strengthening effect. The Mn content in the present invention is set to 0.2 to 0.4%, preferably 0.25 to 0.35%.
Cu: copper is a strengthening element of the ductile iron axle housing, but may deteriorate elongation properties. Too low Cu does not have obvious strengthening effect, and too high Cu does seriously deteriorate elongation performance. The Cu content in the present invention is limited to 0.4 to 0.8%, preferably 0.45 to 0.75%, more preferably 0.55 to 0.65%.
Mg: magnesium is an element that promotes spheroidization, O and S are impurities that hinder spheroidization of graphite, and Mg can react with O and S to promote spherulitic ink. The Mg content is too high, and inclusions are easily formed or precipitated during crystallization, resulting in embrittlement of the spheroidal graphite cast iron and reduction of plasticity and toughness. The Mg content in the present invention is set to 0.01 to 0.08%, preferably 0.012 to 0.06%, more preferably 0.015 to 0.04%.
RE: rare earth is an element that promotes spheroidization, which can react with O, S, ensures the spheroidization effect of graphite, and contributes to refinement of spherical graphite. Excessive costs rise and increase the cost of the manufacturing process. The rare earth content in the present invention is set to 0.01 to 0.05%, preferably 0.015 to 0.04%, more preferably 0.02 to 0.035%.
Sn: sn is an element for increasing the number of graphite grains, so that the spheroidization rate of the spheroidal graphite cast iron can be improved, and a proper Sn content is important for ensuring the strength, toughness and elongation of the spheroidal graphite cast iron. Too low an addition amount results in insignificant spheroidization promoting effect, while too high an addition amount results in segregation, which seriously affects various mechanical properties of the spheroidal graphite cast iron. The Sn addition amount of the present invention is 0.01 to 0.06%, preferably 0.012 to 0.04%.
B. C/10B and Si/10B: the trace amount of boron can promote the existence of free carbon and reduce the generation amount of carbide, thereby promoting graphitization and refining graphite. Although a trace amount of boron is advantageous for improving the toughness, strength, fatigue strength and the like of the spheroidal graphite cast iron, and a trace amount of boron can form boron carbide which can effectively prevent the propagation of fatigue cracks so as to greatly improve the fatigue performance of the material, the boron carbide usually presents a continuous network structure, and the network structure can cause the mechanical properties such as the strength, toughness, plasticity, fatigue strength and the like of the spheroidal graphite cast iron to be deteriorated. The inventor of the present invention has found that by controlling the ratio of C to B within a certain range, it is possible to ensure the presence of sufficient amount of free carbon to graphitize and refine graphite and to form a certain amount of boron carbide, while by controlling the reasonable ratio of Si to B, it is possible to make the boron carbide exist in a discontinuous network form, avoiding its negative effects on strength, toughness, fatigue strength, plasticity. On the basis of adding trace boron and controlling the proportion of carbon, silicon and boron, the strength, toughness, plasticity and fatigue performance of the spheroidal graphite cast iron are considered, the graphite size grade reaches 6-7, and the spheroidization grade reaches 1-2. In order to obtain the above-mentioned effects, the B content of the present invention is set to 10 to 50ppm, preferably 25 to 45ppm, more preferably 30 to 40ppm; C/10B is defined as 80-360, preferably 85-150, and Si/10B is defined as 44-200, preferably 50-90.
In the present invention, as an unavoidable impurity element, P, S is not exhaustive, and the contents of both are defined as P: less than 0.05%, S: the lower the content of impurities is below 0.03%, the better, but the higher the requirements on raw materials and smelting are, the higher the cost is, and the comprehensive consideration is that P is preferable: less than 0.03%, S: less than 0.02%.
The spheroidal graphite cast iron of the invention can further comprise V and/or Mo on the basis of containing the elements: v and Mo are elements capable of enhancing tensile strength, yield strength and fatigue characteristics of spheroidal graphite cast iron by forming carbides, but too high content of V or Mo causes excessive carbide formation to affect spheroidization effect of graphite, and increase of carbide drastically deteriorates toughness and plasticity of spheroidal graphite cast iron. Thus, the addition amount of V and/or Mo is controlled to be 0.01 to 1%, preferably 0.05 to 0.95%, more preferably 0.1 to 0.9%, still more preferably 0.2 to 0.8%, and most preferably 0.3 to 0.7%.
The microstructure matrix of the high-plasticity and fatigue-resistant spheroidal graphite cast iron is pearlite and ferrite, the spheroidization grade of the high-plasticity and fatigue-resistant spheroidal graphite cast iron is 1-2, and the graphite size grade is 6-7.
Through optimization of components, content and proportion relation, the high-plasticity ductile cast iron has tensile strength of more than 700MPa, elongation of more than 11%, yield strength of more than 480MPa and room-temperature impact toughness of 50J/cm 2 Above, in fatigue life cycle N f ＝10 7 The fatigue limit strength under the condition is 450MPa or more.
In addition, as another aspect of the invention, the invention also provides a manufacturing method of the high-ductility and fatigue-resistant spheroidal graphite cast iron, which comprises the steps of smelting, spheroidizing, inoculating and pouring.
The beneficial effects of the invention are as follows.
The high-ductility and fatigue-resistant spheroidal graphite cast iron has simple component design, is reinforced by low-cost common elements Si, mn and Cu, and is further added with trace amount of B to further improve the mechanical property of the spheroidal graphite cast iron. By controlling the content proportion relation of the elements C and B, a certain amount of boron carbide is generated while the graphitization promotion and graphite refinement actions of B are fully exerted, and by limiting the relation of Si and B, the generation of boron carbide in a continuous net form is avoided, the boron carbide in a discontinuous net form does not have negative influence on various mechanical properties of spheroidal graphite cast iron, so that the improvement action of trace boron on the strength and toughness of the spheroidal graphite cast iron is ensured, the non-continuous net boron carbide has an obstructing action on the expansion of fatigue cracks, the action of the boron carbide on improving the fatigue performance of the spheroidal graphite cast iron is effectively exerted, and in addition, the plasticity, toughness and strength of the spheroidal graphite cast iron can be ensured by adding trace Sn in a proper content. The high-ductility, high-toughness and fatigue-resistant spheroidal graphite cast iron provided by the invention has the advantages that the cost is effectively controlled, and meanwhile, excellent strength, toughness, plasticity and fatigue characteristics are obtained.
Detailed Description
In order to enable those skilled in the art to fully understand the technical scheme and the beneficial effects of the present invention, the following description is made with reference to specific test examples.
And (3) manufacturing the spheroidal graphite cast iron according to the design components, wherein all P elements are controlled to be 0.025+/-0.002 percent, namely the spheroidal graphite cast iron is qualified, and all S elements are controlled to be 0.02+/-0.002 percent, namely the spheroidal graphite cast iron is qualified. The specific manufacturing method is as follows.
Firstly, designing chemical components: selecting pig iron, scrap steel, furnace return materials and the like with low sulfur, phosphorus and manganese contents as raw materials according to target chemical components, and calculating the consumption of each raw material.
Secondly, smelting in an intermediate frequency furnace: and smelting each component into molten iron by adopting a medium-frequency induction furnace.
Thirdly, spheroidizing: the spheroidizing agent adopts rare earth magnesium silicon spheroidizing agent, and the spheroidizing method adopts a flushing method to carry out spheroidizing treatment.
Fourth, inoculation treatment and pouring: inoculating by adopting a ferrosilicon inoculant in a ladle; and (3) casting by adopting a sand mold, and pouring to obtain a high-ductility and fatigue-resistant spheroidal graphite cast iron test sample.
And (3) carrying out chemical component analysis on the cast high-plasticity and fatigue-resistant spheroidal graphite cast iron, and simultaneously carrying out microstructure observation and analysis on the detection of strength, elongation (plasticity), toughness and fatigue characteristics. The analysis of chemical components, the test of strength, elongation (plasticity) and toughness performance and the observation and analysis of microstructure are all carried out according to the national standard GB/T1348-2009 and the cited standard requirements, the fatigue characteristics are carried out according to the national standard GB/T37306-2019 and the cited standard requirements, and the fatigue life cycle is 10 7 And twice. The analysis results of the chemical components of the spheroidal graphite cast iron of test numbers 1 to 28 are recorded in table 1, and the results of each mechanical property test and tissue observation are shown in table 2.
Table 1 (the components are mass percent, the balance is Fe)
In the above test examples, the components numbered 1 to 14 and the element proportion elements all meet the requirements of the present invention, and are examples of the present invention. 15-28, at least one of the components or element proportions thereof does not meet the requirements of the present invention, and thus, test example numbers 15-28 are comparative examples of the present invention.
Table 2 shows the mechanical properties and microstructure of test numbers 15-28.
TABLE 2
Further analysis is described below in connection with the chemical composition of Table 1 and the mechanical properties and microstructure of Table 2.
The numbers 1 to 14 in Table 1 are all inventive examples of the present invention, which satisfy the requirements of the present invention for the content and the ratio of each element. The mechanical properties of each inventive example in Table 2 can meet the requirements of tensile strength of more than 700MPa, elongation of more than 11%, yield strength of more than 480MPa and room temperature impact toughness of 50J/cm 2 The above-mentioned examples of the invention in Table 2 were rated for spheroidization of 1 to 2 and for graphite of 6 to 7 in terms of microstructure with fatigue strength of 450MPa or more. In particular, the fatigue strength of the invention examples 2-3, 6-7, 9, 11, 14 satisfying both C/10b=85-150 and Si/10b=50-90 can be 500MPa or more, and it is demonstrated that the reasonable control of C/10B, si/10B in the preferable range is particularly significant for obtaining excellent fatigue performance.
The comparative examples of the present invention are analyzed one by one in the following with reference to tables 1 and 2.
Comparative example 15 is a comparative example of inventive example 13, which decreases the B content in inventive example 13, resulting in C/10B higher than the requirements of the present invention, however, since C/10B is too high, the amount of boron carbide produced is too small, the effect of improving mechanical properties is insufficient, and the effect of boron on promoting graphitization and refining graphite is weakened, resulting in eventually that the tensile strength, yield strength, toughness, elongation, fatigue strength of spheroidal graphite cast iron cannot meet the requirements of the present invention, and the spheroidization grade and graphite size grade cannot meet the requirements of the present invention. Illustrating that suitable C/10B is important to ensure tensile strength, yield strength, elongation, toughness, fatigue characteristics, spheroidization, graphite size grade of spheroidal graphite cast iron.
Comparative example 16 is a comparative example of inventive example 13, which increases the B content in inventive example 13, resulting in Si/10B lower than the requirements of the present invention, however, although an increase in B content is advantageous for refining graphite to increase the graphite size grade, an increase in B content means the presence of more boron carbide of network structure, si has limited ability to hinder boron carbide of continuous network structure, the presence of continuous network boron carbide counteracts the strengthening effect brought by B and further deteriorates mechanical properties, resulting in failure of the yield strength, toughness, elongation, fatigue strength of spheroidal graphite cast iron to meet the requirements of the present invention, and the tensile strength is drastically decreased. Illustrating that suitable Si/10B is important for ensuring tensile strength, yield strength, elongation, toughness, fatigue properties of spheroidal graphite cast iron.
Comparative example 17 is a comparative example of inventive example 1, which reduced the B content in inventive example 1, resulting in Si/10B higher than the requirements of the present invention, however, since Si/10B is too high, the Si has a limited effect of preventing the formation of continuous network boron carbide, resulting in failure to satisfy the requirements of the present invention in terms of yield strength, toughness, elongation, fatigue strength of spheroidal graphite cast iron, and also a significant decrease in tensile strength. Illustrating that suitable Si/10B is important for ensuring tensile strength, yield strength, elongation, toughness, fatigue properties of spheroidal graphite cast iron.
Comparative example 18 is a comparative example of inventive example 1, which increases the B content in inventive example 1, resulting in C/10B lower than the requirements of the present invention, however, although an increase in B content is advantageous for refining graphite to increase the graphite size grade, an increase in B content means the presence of more boron carbide of network structure, si has limited ability to hinder boron carbide of continuous network structure, the presence of continuous network boron carbide counteracts the strengthening effect brought by B and further deteriorates mechanical properties, resulting in failure of the ductile iron to meet the requirements of the present invention in terms of yield strength, toughness, elongation, fatigue strength, and also a great decrease in tensile strength. Illustrating that suitable C/10B is important to ensure tensile strength, yield strength, elongation, toughness, fatigue properties of the spheroidal graphite cast iron.
Comparative example 19 is a comparative example of invention example 4, which reduces the C content in invention example 4, and although C/10B is still within the scope of the present invention, C is an important strengthening element because the C content is lower than the requirement of the present invention, and too low a C content results in failure of the tensile strength, yield strength and fatigue strength of the spheroidal graphite cast iron to meet the requirement of the present invention, indicating that controlling the appropriate C content is important for ensuring the tensile strength, yield strength and fatigue characteristics of the spheroidal graphite cast iron.
Comparative example 20 is a comparative example of inventive example 4, which increases the content of C in inventive example 4, and although C/10B is still within the scope of the present invention, C decreases the toughness and elongation of spheroidal graphite cast iron while strengthening because the content of C is higher than the requirements of the present invention, C content is too high to satisfy the requirements of the invention because of the excessively high elongation and toughness of spheroidal graphite cast iron, and spheroidization grade and graphite size grade are also decreased relative to inventive example 4 although within the requirements of the present invention because of the increased content of C, indicating that controlling the proper content of C is important for ensuring the elongation, toughness, spheroidization grade, and graphite size grade of spheroidal graphite cast iron.
Comparative example 21 is a comparative example of invention example 9, which reduces the Si content in invention example 9, and although Si/10B is still within the scope of the present invention, since the Si content is lower than the requirement of the present invention, si content is too low to cause the yield strength, fatigue strength, failure to meet the requirement of the invention, and tensile strength is also greatly reduced, indicating that controlling the appropriate Si content is important for ensuring the tensile strength, yield strength, fatigue strength of the spheroidal graphite cast iron.
Comparative example 22 is a comparative example of inventive example 9, which increases the Si content in inventive example 9, and although Si/10B is still within the scope of the present invention, si decreases the toughness and elongation of spheroidal graphite cast iron while strengthening because the Si content is higher than the requirement of the present invention, and too high Si content results in failure of the elongation and toughness of spheroidal graphite cast iron to meet the requirement of the invention, indicating that controlling the appropriate Si content is important for ensuring the elongation and toughness of spheroidal graphite cast iron.
Comparative example 23 is a comparative example of inventive example 10, which reduced the Si content of inventive example 10, while Si was still within the scope of the present invention, si/10B was lower than the requirements of the present invention, however, too low Si/10B (i.e., higher relative content of B) had limited ability to block boron carbide of continuous network structure, the presence of continuous network boron carbide deteriorated mechanical properties, resulting in failure to meet the requirements of the present invention for ductile iron in terms of yield strength, toughness, elongation, fatigue strength, and a drastic decrease in tensile strength. Illustrating that suitable Si/10B is important for ensuring tensile strength, yield strength, elongation, toughness, fatigue properties of spheroidal graphite cast iron.
Comparative example 24 is a comparative example of inventive example 10, which reduced the C content of inventive example 10, although C was still within the scope of the present invention, C/10B was lower than the requirements of the present invention, whereas, while lower C/10B (i.e., higher relative content of B) was advantageous for refining graphite to increase graphite size grade, the increase in relative content of B meant the presence of more network boron carbide, limited ability of Si to block continuous network boron carbide, the presence of continuous network boron carbide deteriorated mechanical properties, resulting in failure of the tensile strength, yield strength, toughness, elongation, fatigue strength of the spheroidal graphite cast iron to meet the requirements of the present invention. Illustrating that suitable C/10B is important to ensure tensile strength, yield strength, elongation, toughness, fatigue properties of the spheroidal graphite cast iron.
Comparative example 25 is a comparative example of inventive example 3, which reduced the B content in inventive example 3, resulted in B lower than the requirements of the present invention and C/10B, si/10B higher than the requirements of the present invention, too low B resulted in C/10B too high, reduced B formation of boron carbide, reduced strengthening effect and reduced graphitization and graphite refining effect, too low B resulted in Si/10B too high, resulted in limited effect of Si inhibiting the ability of formation of continuous network boron carbide, resulted in failure of tensile strength, yield strength, toughness, elongation, fatigue strength of spheroidal graphite cast iron to meet the requirements of the present invention, and failed in spheroidization grade and graphite size grade to meet the requirements of the present invention. Illustrating that suitable B, si/10B, C/10B is important for ensuring tensile strength, yield strength, elongation, toughness, fatigue characteristics, spheroidization, graphite size grade of spheroidal graphite cast iron.
Comparative example 26 is a comparative example of invention example 3, which increases the B content in invention example 3, resulting in B higher than the requirement of the present invention and C/10B, si/10B lower than the requirement of the present invention; too high a B content results in too low a C/10B and Si/10B content, an increase in B content means the presence of more boron carbides of network structure, si has limited ability to hinder boron carbides of continuous network structure, the presence of continuous network boron carbides counteracts the strengthening effect brought by B and further worsens the mechanical properties, resulting in failure to meet the requirements of the invention for the yield strength, toughness, elongation and fatigue strength of the spheroidal graphite cast iron, and a great decrease in tensile strength. Illustrating that suitable B, C/10B, si/10B is important for ensuring tensile strength, yield strength, elongation, toughness, fatigue properties of spheroidal graphite cast iron.
Comparative example 27 is a comparative example of inventive example 2, which reduced the Sn content in inventive example 2, and the effect of promoting graphite spheroidization was reduced due to the excessively low Sn content, so that the toughness and elongation of spheroidal graphite cast iron could not meet the requirements of the present invention, but the tensile strength, yield strength, fatigue strength, spheroidization grade could be reduced, though they could meet the requirements of the invention. Indicating that the proper Sn content is important for ensuring tensile strength, yield strength, elongation, toughness, fatigue characteristics, spheroidization grade of the spheroidal graphite cast iron.
Comparative example 28 is a comparative example of inventive example 8, which increases the Sn content in inventive example 8, and since the Sn content is too high, segregation occurs during the solidification of spheroidal graphite cast iron, which seriously affects various mechanical properties of spheroidal graphite cast iron, resulting in failure to meet the requirements of the present invention in terms of tensile strength, yield strength, toughness, elongation, and fatigue strength. It is explained that a suitable Sn content is important to ensure tensile strength, yield strength, elongation, toughness, and fatigue characteristics of the spheroidal graphite cast iron.
The above description of the embodiments is only for aiding in the understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. The ductile iron with high plastic toughness and fatigue resistance is characterized by comprising the following chemical components in percentage by mass: c:3.5-4.2%, si:1.8-2.5%, mn:0.2-0.4%, cu:0.4-0.72%, B:25-50ppm, mg:0.01-0.08%, RE:0.01-0.05%, sn:0.026-0.06%, the balance being Fe and unavoidable impurities, and C/10b=80-158.5, si/10b=44-90.
2. The ductile and fatigue-resistant ductile iron according to claim 1 further comprising 0.01-1% V and/or Mo.
3. A high plasticity ductile iron with fatigue resistance according to any one of claims 1 to 2, characterized in that the Sn content is 0.026-0.035%.
4. A high plasticity ductile iron according to any one of claims 1 to 2 characterized in that said C content is 3.6-4.0%.
5. A high plasticity ductile iron with fatigue resistance according to any of claims 1-2, characterized in that the Si content is 2.0-2.4%.
6. A high plasticity ductile iron with fatigue resistance according to any of claims 1-2 characterized in that the B content is 25-45ppm.
7. A high plasticity ductile iron according to any one of claims 1 to 2 characterized in that said C/10b=85-150 and si/10b=50-90.
8. The ductile and fatigue-resistant ductile iron according to any one of claims 1 to 2 characterized in that it has a tensile strength of 700-900MPa, an elongation of 11% or more, a yield strength of 480-620MPa, and a room temperature impact toughness of 50J/cm 2 Above, in fatigue life cycle N f ＝10 7 The fatigue limit strength under the condition is 450MPa or more.
9. A high plasticity ductile iron according to any one of claims 1 to 2 characterized in that said fatigue resistant ductile iron has a graphite size grade of 6 to 7 and a spheroidization grade of 1 to 2.
10. A method of manufacturing a high ductile iron, fatigue resistant ductile iron according to any one of claims 1 to 9, characterized in that: the manufacturing method of the ductile cast iron with high plastic toughness and fatigue resistance comprises the steps of smelting, spheroidizing, inoculating and pouring.
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| JP2003221638A (en) * | 2002-01-29 | 2003-08-08 | Hino Motors Ltd | Globular graphite cast iron |
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| KR101409877B1 (en) * | 2011-11-14 | 2014-06-20 | 엘지전자 주식회사 | Alloy cast iron and manufacturing method of vane using the same |
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| JP2003221638A (en) * | 2002-01-29 | 2003-08-08 | Hino Motors Ltd | Globular graphite cast iron |
| CN103834854A (en) * | 2014-03-20 | 2014-06-04 | 上海宝华威热处理设备有限公司 | Isothermal quenching nodular cast iron roller for push-pull vehicle on heat treatment production line and production method thereof |
| CN111004965A (en) * | 2019-12-27 | 2020-04-14 | 宁国东方碾磨材料股份有限公司 | High-compression-resistance nodular cast iron pump body for fire fighting and preparation method thereof |
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