CN102796935B - High-strength gray cast iron modifier and modification treatment process thereof - Google Patents
High-strength gray cast iron modifier and modification treatment process thereof Download PDFInfo
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- CN102796935B CN102796935B CN 201210330657 CN201210330657A CN102796935B CN 102796935 B CN102796935 B CN 102796935B CN 201210330657 CN201210330657 CN 201210330657 CN 201210330657 A CN201210330657 A CN 201210330657A CN 102796935 B CN102796935 B CN 102796935B
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Abstract
The invention relates to a high-strength gray cast iron modifier and a modification treatment process thereof. The modifier mainly comprises the following chemical components in percentage by weight: 30-50 percent of V, 5-10 percent of N, 5-10 percent of RE, 5-10 percent of Ca and the balance of Si. The modification treatment process comprises the following steps of: filling the modifier into the bottom of a gray cast iron casting ladle by using a cast iron casting ladle flush-in method; pouring into the casting ladle when temperature of molten gray cast iron reaches 1,480-1,550 DEG C; melting the modifier by the high-temperature molten iron; and feeding elements in the modifier into the molten iron to obtain high-strength gray cast iron. Primary austenite dendritic crystals are obtained from the gray cast iron and are fine, and the number of the primary austenite dendritic crystals is increased; the thickness of laminates of pearlite clusters is reduced, the space of the laminates is reduced, and the laminates are arranged in a staggered way; the number of graphite is increased, the graphite is fine and bent, and the tip is passivated; and thus, the strength of the gray cast iron is obviously improved, and the tensile strength of the standard test rod reaches 400 MPa.
Description
Technical field
Novel material-the present invention's " a kind of high-strength gray cast iron alterant " relates to a kind of graphitic cast iron and improves the used novel alterant of intensity, particularly relates to a kind of technology of preparing of high-strength gray cast iron.
Background technology
Graphitic cast iron is a kind of time-honored traditional structural materials.Global researcher and engineering technical personnel are making great efforts to improve the intensity of graphitic cast iron always.The mechanism of the raising strength of gray cast iron of generally acknowledging at present, has following four aspects: (1) increases the number of primary austenite dendrite; (2) refine pearlite sheet spacing; (3) refinement graphite, make graphite bending and passivation; (4) refining eutectic group.
In order to improve the intensity of graphitic cast iron, the cast iron scientific worker has carried out a large amount of research work at aspects such as graphitic cast iron Composition Design, micro alloying element compositions both at home and abroad, has obtained certain achievement.Mainly be to improve intensity by adding the alloying elements such as a certain amount of chromium, molybdenum, copper, nickel, vanadium and rare earth.Current, to water the tensile strength maximum of the standard coupon of 30 millimeters of diameters outpouring, 280 millimeters of length in the tide mould sand type be 395 MPas to the microalloying graphitic cast iron of report in the world, see patent of invention " the micro alloyed high strength grey cast iron " (patent No.: 2005100168785), also do not reach more than 400 MPas for details.The present invention forms by a kind of new alterant of design, the alterant that invention makes new advances joins alterant of the present invention in the graphitic cast iron molten iron, has obtained beyond thought result, make graphitic cast iron obtain the primary austenite dendrite of network frame structure, and dendrite is little, number increases; Synusia thin thickness and the sheet spacing of perlite cluster are little, and simultaneously, the perlite cluster is staggered; The graphite number increases, tiny, crooked, wedge angle passivation; Eutectic cell obtains the tissue of refinement, makes the intensity of high graphitic cast iron obtain very significant raising, and the tensile strength of standard coupon has reached 400 MPas.
Summary of the invention
The objective of the invention is: invent a kind of new alterant and form, alterant of the present invention is joined in the molten iron of graphitic cast iron, make the primary austenite dendrite of graphitic cast iron acquisition network frame structure, and dendrite is tiny, number increases; The synusia thickness attenuation of perlite cluster, sheet spacing reduce, and staggered; The graphite number increases, tiny, crooked, wedge angle passivation; The tissue that eutectic mass size reduces is significantly improved the intensity of graphitic cast iron, and the tensile strength of standard coupon has reached 400 MPas.
Above-mentioned purpose of the present invention is achieved in that a kind of weight percent chemical ingredients of invention is: V:30-50; N:5-10; RE:5-10; Ca:5-10; All the other are the high-strength gray cast iron alterant of Si.Alterant of the present invention is joined in the graphitic cast iron molten iron that contains C, Si, Mn, P, S, Cr, Cu, Sn, and the element in the alterant enters into the molten iron of graphitic cast iron, has obtained a kind of high-strength gray cast iron.
Adopt the as-cast structure of the high graphitic cast iron of high strength that alterant of the present invention processes to compare with the Mo alloying high-strength gray cast iron (containing C, Si, Mn, P, S, Cr, Cu, Sn element) that adds of the mainstream technology in the present world-employing ferrosilicon inoculation, primary austenite the axle network frame structure dendrite such as changes into by common thick, non-equiaxed dendrite (consulting shown in Fig. 1 (a)), and the dendrite number increases (consulting shown in Fig. 1 (b)); Perlite changes small pieces spacing, thin ferrite and cementite synusia (consulting shown in Fig. 2 (b)) into by large stretch of spacing, thick ferrite and cementite synusia (consulting shown in Fig. 2 (a)), and the synusia of two pearlite colony bunch grain boundaries changes little angle arrange (consulting shown in Fig. 2 (b)) into by arrange by the big angle (consulting shown in Fig. 2 (a)); Graphite is few, thick, straight by number, wedge angle sharp-pointed (consulting shown in Fig. 3 (a)) changes that number increases, tiny, crooked, wedge angle passivation (consulting shown in Fig. 3 (b)) into; Eutectic cell is few by number, size large (consulting shown in Fig. 4 (a)) changes that number is many, size is little (consulting shown in Fig. 4 (b)) into.The transformation of tissue makes the intensity of graphitic cast iron obtain unexpected effect, and the tensile strength of standard coupon has reached 400 MPas.
The major technique advantage that alterant of the present invention has is: make the tissue of graphitic cast iron that beyond thought transformation occur, primary austenite the axle network frame structure dendrite such as changes into by common thick, non-equiaxed dendrite, and dendrite is tiny, number increases; Perlite changes small pieces spacing, thin ferrite and cementite synusia into by large stretch of spacing, thick ferrite and cementite synusia, and the synusia of two pearlite colony bunch grain boundaries changes the big angle into by arranging by little angle and arranges; Graphite is few, thick, straight by number, wedge angle changes sharply that number increases, tiny, crooked, wedge angle passivation into; Eutectic cell is few by number, the size big change is that number is many, size is little.
The effect of being brought by the major technique advantage is: the transformation of tissue is significantly improved the intensity of graphitic cast iron, the tensile strength of standard coupon has reached 400 MPas, only is 350 MPas and adopt the maximum pulling strength of the standard coupon that adds Mo alloying high-strength gray cast iron of ferrosilicon inoculation.Simultaneously, the economic benefit advantage of bringing is: adopt the material cost per ton that adds Mo alloying high-strength gray cast iron of ferrosilicon inoculation approximately than the high 200-400 RMB￥ of high-strength gray cast iron that adopts alterant of the present invention to process, economic benefit will be very remarkable.
Marginal data
Fig. 1 is the primary austenite dendritic morphology, wherein:
Fig. 1 (a) is the axle network frame structure austenite dendrites such as common, thick, non-that adds Mo alloying high-strength gray cast iron of ferrosilicon inoculation;
Fig. 1 (b) is that the austenite dendrites of the rotten high-strength gray cast iron of processing of this alterant is tiny for structure such as network frame such as axle such as grade, secondary dendrite.
Fig. 2 is Morphology of pearlite, wherein:
Fig. 2 (a) is that the pearlitic synusia thickness and the spacing that add Mo alloying high-strength gray cast iron of ferrosilicon inoculation is large, simultaneously, and perlite cluster parallel arrangement;
Fig. 2 (b) is that pearlitic synusia thickness and the sheet spacing of the rotten high-strength gray cast iron of processing of this alterant is tiny, and the perlite cluster is staggered.
Fig. 3 is graphite form, wherein:
Fig. 3 (a) is that the graphite that adds Mo alloying high-strength gray cast iron of ferrosilicon inoculation is straight, thick, number is few, skewness;
Fig. 3 (b) is that the graphite of the rotten high-strength gray cast iron of processing of this alterant is crooked, tiny, number is many, is evenly distributed.
Fig. 4 is the eutectic cell form, wherein:
Fig. 4 (a) is that the eutectic mass size that adds Mo alloying high-strength gray cast iron of ferrosilicon inoculation is large, number is few;
Fig. 4 (b) is that the eutectic mass size of the rotten high-strength gray cast iron of processing of this alterant is little, number is many.
Embodiment
Below in conjunction with the accompanying drawing illustrated embodiment, further specify particular content of the present invention.
Embodiment one
The modification process of alterant of the present invention adopts and pours method in the cast iron casting ladle: alterant is put into the bottom of graphitic cast iron casting ladle, the graphitic cast iron that melts (C:2.92～3.48 in cupola furnace or electric furnace; Si:1.52～2.46; Mn:0.22～0.78; P:0.011～0.048; S:0.03～0.15; Cr:0.15～0.5; Cu:0.3～0.78; When Sn:0.011～0.098) molten iron temperature reached 1480-1550 and spends, molten iron was poured in the graphitic cast iron casting ladle, and high temperature liquid iron melts alterant, and the element in the alterant enters in the graphitic cast iron molten iron, obtains high-strength gray cast iron.
The positively effect of the composition of optimization design alterant of the present invention is to improve primary austenite dendrite, perlite, graphite and the eutectic cell structure of graphitic cast iron, thereby improve the tensile strength of graphitic cast iron, its result has obtained beyond thought unusual effect, and the tensile strength of standard coupon of watering the graphitic cast iron of 30 millimeters of diameters outpouring, 280 millimeters of length in the tide mould sand type has reached 400 MPas.
Alterant of the present invention forms the mechanism of action that primary austenite dendrite, perlite, graphite and eutectic cell structure to graphitic cast iron improve.
(1) primary austenite the axle network frame structure dendrite such as changes into by common thick, non-equiaxed dendrite, and dendrite is tiny, number increases.
1. the V in the alterant and N, in the iron liquid (temperature is greater than 1600 ℃) of high temperature, VN and VC have been formed, their fusing point is respectively 2340 ℃ and 2800 ℃, the lattice misfit degree of (110) crystal face of their (001) crystal face and austenite (Fe-r) all less than 15% (VN (001) //Fe-r (110)=14%, VC (001) //Fe-r (110)=13.9%.)。Therefore, VN and VC all can be used as the non-spontaneous core of primary austenite crystallization, make the axle network frame structures such as primary austenite dendrite number in the graphitic cast iron increases, dendrite refinement, formation.
2. N can make that the primary austenite Models For Secondary Dendrite Arm attenuates, secondary arm spacing reduces, consult Fig. 1 (a) and (b) shown in.
(2) perlite changes small pieces spacing, thin ferrite and cementite synusia into by large stretch of spacing, thick ferrite and cementite synusia, and the synusia of two pearlite colony bunch grain boundaries changes little angle into by arranging by the big angle and arranges.
1. V can form alloyed cementite, form the required carbon amount of alloyed cementite and be lower than the required carbon amount of formation cementite, accelerated the speed of growth of cementite interalloy cementite, reduced the thickness of ferrite synusia, accelerated the speed of eutectoid transformation, the result causes reducing of pearlitic spacing.
2. the VN that separates out at the interface at ferritic phase, VC or V (C, N) phase have stoped growing up of ferrite crystal grain effectively, make the perlite in the matrix thin.
3. V is the element that dwindles the austenitic area, makes the A of austenitic area
1And A
3Point rises, A
4Point descends, and has increased the condensate depression of perlitic transformation, refinement perlite sheet spacing.
4. N content increases, and the eutectoid transformation temperature of graphitic cast iron is reduced, and the eutectoid transformation district broadens, and condensate depression increases, thus refinement perlite.Above-mentioned V, N effect reduce the attenuation of pearlitic synusia thickness, sheet spacing, and the perlite cluster is staggered, consult Fig. 2 (a) and (b) shown in.
(3) graphite, wedge angle few, thick, straight by number changes sharply that number increases, tiny, crooked, wedge angle passivation into.
1. secondary dendrite refinement, the number of primary austenite dendrite reach reducing of Secondary Dendrite Arm Spacing more, caused the amount of space that waits axle network frame structure of austenite dendrites to increase, size decreases, cause the graphite nucleation rate to increase, growth of graphite is restricted, and become more tiny, crooked, number of graphite is increased.
2. N constantly is adsorbed on growth of graphite forward position and graphite flake both sides in the eutectic solidification process, be enriched in the border of graphite or eutectic cell with unbound state, cause graphite in crystallisation process, N Enrichment around it, especially stretch to tip in the molten iron at graphite, thereby affect the growth of graphite on the solid-liquid interface, make that graphite shortens, chap.Simultaneously, because the N atomic adsorption at the defective locations of growth graphite, produces branch when making growth of graphite, the increase of graphite branch is the Another reason that graphite shortens.
3. Si promotes graphite element, increases the graphite number.
4. S, the O in RE, Ca and iron liquid reaction generates rare-earth sulfide, oxide compound and CaS, CaO, and these compounds can be used as the non-spontaneous core of the forming core of graphite, have increased the core amounts of graphite forming core, makes that graphite increases, size reduction; The adsorption of RE reduces graphite size, and shape is crooked, the wedge angle passivation.The effect of above-mentioned V, N, RE, Ca, Si makes that the graphite number increases, tiny, crooked, wedge angle passivation, consult Fig. 3 (a) and (b) shown in.
(4) eutectic cell, size big change few by number is that number is many, size is little.
1. S, the O in RE, Ca and iron liquid reaction generates rare-earth sulfide, oxide compound and CaS, CaO, and these compounds can be used as the non-spontaneous core of graphite forming core, refinement eutectic cell;
2. secondary dendrite refinement, the number of primary austenite dendrite reach reducing of Secondary Dendrite Arm Spacing more, caused the amount of space that waits axle network frame structure of austenite dendrites to increase, size decreases, the graphite nucleation rate is increased, and growth is restricted, and causes eutectic mass size to reduce;
3. V can increase eutectic cell quantity, makes that eutectic mass size reduces, number increases, consult Fig. 4 (a) and (b) shown in.
Primary austenite is to wait axle network frame structure dendrite, and dendrite is tiny, number increases; The sheet spacing of pearlitic ferrite and cementite synusia reduces, the attenuation of synusia thickness, and the synusia of two pearlite colony bunch grain boundaries is arranged by little angle; The stone number increases, tiny, crooked, wedge angle passivation; The strengthening mechanism that the eutectic cell number is many, size is little:
Constantly change direction when 1. a large amount of graphite crooked, tiny, the wedge angle passivation make crackle be difficult for germinating, expansion;
2. the eutectic cell number is many, the little crack propagation path that makes of size is more tortuous, and resistance increases;
3. must be subject to the serious obstruction of the tiny perlite cluster (this cluster is staggered) of the numerous size, synusia thickness and the sheet spacing that wait axle network frame structure distribution during crack propagation, the perlite that causes crackle must pass the skeleton construction distribution could be expanded, consume larger energy, simultaneously, the perlite cluster is staggered, further consumed energy.Above-mentioned three kinds of mechanism that hinder crack propagation significantly improve the intensity of graphitic cast iron.
The present invention's's " a kind of high-strength gray cast iron alterant " composition and mechanical property are as shown in table 1, are shown by table 1, and the tensile strength that adopts the different alterants of the present invention to form the standard coupon of the high-strength gray cast iron of processing has reached 400 MPas.
Table 1 the present invention's " a kind of high-strength gray cast iron alterant " composition and mechanical property
Annotate: the preparation of sample adopts 150 kilograms of medium-frequency induction furnaces to carry out melting.Graphitic cast iron molten iron tapping temperature is 1480～1530 ℃, adds the alterant of the present invention processing of go bad in casting ladle, pours into a mould φ 30 * 280mm round bar shape coupon in sand mold, produces standard tensile strength coupon and Analysis on Microstructure sample from this coupon.
Embodiment two
The JMC Light-duty Vehicle engine that the discharging of Jiangling Motor Co., Ltd.'s independent research reaches state's four standards has the characteristics such as explosion pressure is large, consumption of lubricating oil is low, engine cylinder-body is lightweight.Therefore, require engine cylinder-body intensity high, cylinder deck body tensile strength 〉=250MPa.Employing adds Mo alloying high-strength gray cast iron casting JMC Light-duty Vehicle engine cylinder-body and exists cylinder body body intensity not reach great, a crucial difficult problem that requires and produce the casting flaws such as shrinkage crack, recessed contracting.Simultaneously, production cost is high.Adopt the rotten micro alloyed high strength grey cast iron casting JMC Light-duty Vehicle engine cylinder-body of processing of the present invention's " a kind of high-strength gray cast iron alterant ", successfully solved to adopt and added great, the crucial difficult problem that Mo alloying high-strength gray cast iron exists cylinder body body intensity not reach requirement and produces the casting flaws such as shrinkage crack, recessed contracting, simultaneously, reduced production cost, molten iron material cost per ton approximately joint is propped up 200 yuan.
Claims (8)
1. a high-strength gray cast iron alterant is characterized in that, described alterant is elementary composition by V, N, RE, Ca, Si, and its weight percent chemical ingredients is: V:30-50; N:5-10; RE:5-10; Ca:5-10; All the other are Si.
2. a kind of high-strength gray cast iron alterant as claimed in claim 1 is characterized in that, the weight percent chemical ingredients of described alterant is: V:30; N:5; RE:6; Ca:7; All the other are Si.
3. a kind of high-strength gray cast iron alterant as claimed in claim 1 is characterized in that, the weight percent chemical ingredients of described alterant is: V:35; N:7; RE:5; Ca:6; All the other are Si.
4. a kind of high-strength gray cast iron alterant as claimed in claim 1 is characterized in that, the weight percent chemical ingredients of described alterant is: V:40; N:10; RE:10; Ca:5; All the other are Si.
5. a kind of high-strength gray cast iron alterant as claimed in claim 1 is characterized in that, the weight percent chemical ingredients of described alterant is: V:45; N:8; RE:7; Ca:8; All the other are Si.
6. a kind of high-strength gray cast iron alterant as claimed in claim 1 is characterized in that, the weight percent chemical ingredients of described alterant is: V:50; N:6; RE:9; Ca:10; All the other are Si.
7. such as the rotten treatment process of each described a kind of high-strength gray cast iron alterant of claim 1～6, it is characterized in that, adopt and pour method in the cast iron casting ladle: the bottom of alterant being put into the graphitic cast iron casting ladle, when the Gray Iron water temp that melts in cupola furnace or the electric furnace reaches 1480-1550 and spends, molten iron is poured in the graphitic cast iron casting ladle, high temperature liquid iron melts alterant, and the element in the alterant enters in the graphitic cast iron molten iron, obtains high-strength gray cast iron; Its tissue: the axle network frame structures such as primary austenite dendrite formation.
8. rotten treatment process as claimed in claim 7 is characterized in that, described graphitic cast iron molten iron contains by weight percentage: C:2.92～3.48; Si:1.52～2.46; Mn:0.22～0.78; P:0.011～0.048; S:0.03～0.15; Cr:0.15～0.5; Cu:0.3～0.78; Sn:0.011～0.098.
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| US4769063A (en) * | 1986-03-06 | 1988-09-06 | Sumitomo Special Metals Co., Ltd. | Method for producing rare earth alloy |
| CN1105613A (en) * | 1993-06-24 | 1995-07-26 | 北京科技大学 | Compound inoculation modificator |
| CN1718822A (en) * | 2005-08-09 | 2006-01-11 | 赣州龙钇稀土材料有限公司 | Yttrium base heavy rare earth wear resistant alloy cast iron alterant |
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|---|---|---|---|---|
| US4769063A (en) * | 1986-03-06 | 1988-09-06 | Sumitomo Special Metals Co., Ltd. | Method for producing rare earth alloy |
| CN1105613A (en) * | 1993-06-24 | 1995-07-26 | 北京科技大学 | Compound inoculation modificator |
| CN1718822A (en) * | 2005-08-09 | 2006-01-11 | 赣州龙钇稀土材料有限公司 | Yttrium base heavy rare earth wear resistant alloy cast iron alterant |
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| 李润勤.稀土高强度灰铸铁生产工艺.《金属铸锻焊技术》.2008,第37卷(第19期),142-143页. |
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