A kind of vanadium titanium vermicular cast iron
Technical field
The invention belongs to material field of metallurgy, be specifically related to a kind of vanadium titanium vermicular cast iron and preparation method thereof.
Background technology
The material of producing automobile brake drum at present both at home and abroad mainly contains common grey iron, alloy ash foundry goods two class.Graphitic cast iron has certain hardness, but the physical and mechanical property of graphitic cast iron brake drum, physical strength, resistance to low temperature and thermal fatigue resistance are unsatisfactory in automotive practical process, and in use easily there is the phenomenon of thermal crack and quick abrasion, cause certain potential safety hazard.
In order to improve intensity and the thermotolerance of cast iron, avoid the decrepitation occurred in use procedure, countries in the world successively develop various cast alloy iron, and the alloying element added mainly contains Ni, Mo, Cu, Cr etc.Ni, Mo can the high temperature microstructure of stable material, can improving the impact of high heat on wear resistance that brake drum produces when rubbing further, extending the brake drum life-span.Cu, Cr can stablize and refine pearlite tissue, improve the intensity of material.As the states such as Great Britain and America mainly adopt high C low-alloy V, Mo graphitic cast iron, the states such as Russia mainly adopt Cr, Ni, Mo alloy gray cast-iron.
Graphite form in cast iron has sheet, vermiform and spherical.Quasiflake graphite is a kind of intermediary graphite between flake graphite and globular graphite.During optical microphotograph Microscopic observation, in visual field, major part is mutual discontinuous graphite short-movie.With scanning electron microscopic observation after deep erosions, can see that they are interconnection in eutectic cell inside.This point is similar with flake graphite, and the slenderness ratio unlike vermicular cast iron is less, and density is high.Meanwhile, can see that under scanning electron microscope the end of vermicular cast iron is comparatively round blunt, what have is just ball-like structure, and globular graphite is quite similar.
These characteristics determine vermicular cast iron and have excellent over-all properties.The tensile strength of vermicular cast iron, apparently higher than graphitic cast iron, a little less than spheroidal graphite cast iron, particularly at high temperature has higher intensity.In addition, vermicular cast iron has excellent wear resistance, heat conductivility, anti-oxidant, heat resistanceheat resistant growth property and thermal fatigue resistance characteristic.Excellent over-all properties makes vermicular cast iron become structural part and ideal material that is heat-resisting, wear part, now applies on automobile brake drum, automobile brake disc, engine cylinder-body cylinder cap and exhaust manifold.
Therefore, from operation cost and safety perspective, the type material of the high comprehensive performances such as to have physical strength high in exploitation, good heat conductivity, and thermal fatigue resistance is excellent, not easily occur thermal crack, low temperature resistant is worth and realistic meaning to replace gray cast iron material to have important engineer applied.
Summary of the invention
The object of the present invention is to provide a kind of vanadium titanium vermicular cast iron, the mechanical property of this vermicular cast iron, thermal fatigue property and wear resisting property are higher than graphitic cast iron, and thermal conductivity damping property is better than magnesium iron again, and the proportion of vermicular cast iron is less than graphitic cast iron.
In order to achieve the above object, the present invention adopts following technical scheme:
A kind of vanadium titanium vermicular cast iron, it is characterized in that, composition containing, for example lower weight percent meter: (rare earth is inherently containing various rare metal for carbon 3.4 ~ 3.8%, silicon 2.1 ~ 2.5%, manganese 0.3 ~ 0.7%, vanadium 0.10 ~ 0.30%, titanium 0.10 ~ 0.20%, antimony 0.03 ~ 0.07%, chromium 0.03 ~ 0.07%, magnesium 0.01 ~ 0.035%, 0.02 ~ 0.045% rare earth, define unclear herein), phosphorus 0.07-0.17%, sulphur 0-0.07%, surplus is iron; Wherein, be > 60% at the content of vanadium titanium vermicular cast iron Medium pearlite, nodulizing rate > 60%.
Vanadium titanium vermicular cast iron of the present invention described above, wherein, described carbon equivalent ce is 4.1 ~ 4.7%, wherein CE=C+1/3 (Si+P).
Vanadium titanium vermicular cast iron of the present invention described above can be used for preparing in the brake drum of automobile, automobile brake disc, engine cylinder-body cylinder cap, exhaust manifold any one or multiple.
Containing the V of about the 0.30% and Ti of about 0.20% during the present invention is raw materials used, this refinement effectively, stabilizing pearlite, V and Ti all has high avidity with carbon, nitrogen and forms the high sclerosis phase vanadium titanium carbon nitrogen compound of microhardness simultaneously, improves intensity, wear resisting property and heat-resistant anti-fatigue performance.In addition, V, Ti add chilling tendency, belong to interference element and tension-active element, can suitably widen compactedization scope, be conducive to creepage rate, and therefore in the present invention, the content of vanadium is 0.10 ~ 0.30%, and the content of titanium is 0.10 ~ 0.20%.If vanadium titanium content is lower than 0.10%, the carboritride of formation is little, does not have the effect improving intensity and wear resistance.When vanadium titanium content is prescribed a time limit higher than upper, the vanadium titanium carbon nitrogen compound of formation is too much, and intensity hardness value is too high, not easily processes, and anti-spheroidization is strong, is unfavorable for creepage rate.
Antimony is one and strongly promotes pearlitic metallic element, main plaing a part strengthens cast iron engine block tissue, crystal grain thinning, in order to improve hardness and the wear resistance of cast iron, but when the content of antimony is more than 0.07%, can there is metamorphosis in compacted ink, there will be decomposition, tiny branch around.The antimony element simultaneously added can also and phosphorus form the eutectic of low melting point, finally separate out between eutectic cell, form the iron phosphide eutectic tissue containing antimony.The perlite that antimony metal is formed, can stablize vanadium titanium particle and steadite, hardness and wear resistance are significantly improved, therefore suitably can improve the content of phosphorus for wearing piece.
Chromium no matter eutectic, eutectoid process all hinders greying, promote that perlite generates, because chromium element and ferro element are body-centered cubic structure, the atomic radius of Cr atomic radius and α-Fe closely, no matter under room temperature or comparatively high temps, the solubleness of Cr in α-Fe is all higher, makes Cr solid solution enter in iron-based body, displacement ferro element, plays solution strengthening effect; In addition, Cr also can form the Fe-Cr-C compound of high rigidity complexity, plays dispersion-strengthened action to matrix.
C and Si in vanadium titanium vermicular cast iron of the present invention promotes graphited element.C, Si content is higher, and in vermicular cast iron, graphitizing process more easily carries out, and in vermicular cast iron tissue, graphite is just many.Requiring higher brake drum for producing heat-resistant antifriction, requiring the graphite of some amount in tissue, namely requiring higher carbon equivalent CE, CE=C+1/3 (Si+P).Suitable carbon equivalent contributes to reducing chilling tendency, but the too high meeting of carbon equivalent ce causes graphite many and thick, pearlite fraction in matrix is not enough, ferrite content increases, mechanical property (intensity and hardness) is reduced, and the carbon equivalent ce content of vermicular cast iron of the present invention is: 4.1 ~ 4.7%.In the present invention, the content of carbon controls in the scope of 3.4 ~ 3.8%, and carbon content molten iron flow within the scope of this is good, and easy feeding is shunk little, can obtain excellent castability.
Silicone content is very remarkable to matrix effect, is mainly used to prevent spoken parts in traditional operas, controls high content of pearlite in matrix.Along with silicon amount increases, matrix Medium pearlite amount reduces gradually, and ferrite content increases gradually.In order to obtain higher performance requriements, and obtaining the vermicular cast iron of pearlite matrix, can suitably reduce silicon amount.The final content of silicon controls 2.1 ~ 2.5% by the present invention.Whole silicon amount lower than 2.1% time, high content of pearlite in matrix is too much, and much higher hard, affects as cast condition brake drum machinability.Whole silicon amount higher than 2.5% time, matrix Medium pearlite is very few, and intensity, hardness do not reach requirement.
Manganese plays stabilizing pearlite in vermicular cast iron, on the impact of graphite compactedization nothing in conventional content.In order to make vanadium titanium vermicular cast iron high content of pearlite in matrix more than 60%, it is 0.3 ~ 0.7% that the present invention controls Fe content.If Fe content is less than 0.3%, then easily obtain the vanadium titanium vermicular cast iron of ferrite matrix, because high content of pearlite in matrix is few, intensity and hardness do not reach requirement.If but Fe content is greater than 0.7%, then the either pearlite occurred in vanadium titanium vermicular cast iron matrix is higher, make its intensity and hardness value too high, processing difficulties, and plasticity is poor, reduces thermal fatigue property.
Sulphur and all compactedization elements (mainly comprising magnesium and rare earth element) have very large avidity, and compactedization element adds in iron liquid and is first consumed in desulfurization and deoxidation, is down to by sulphur in iron liquid and is less than 0.03%, remain compactedization element and just make graphite compactedization.Original iron melt sulfur-bearing is more, consumes vermiculizer also more.Vermiculizer add-on is more, and the sulfuration slag inclusion of formation is also more, both uneconomical, endangers again the performance of material, accelerates vermiculation.This is the aspect that sulphur is harmful to vermicular cast iron.But sulphur has the effect expanding vermiculizer add-on within the specific limits, and namely all can obtain vermicular cast iron within the scope of wider vermiculizer add-on, this is that sulphur produces favourable one side to vermicular cast iron.Therefore, the present invention controls sulphur content for being no more than 0.07%.
Rare earth and magnesium elements are all strong alterant elements for iron liquid.Magnesium is a kind of strong nodularization element, first allows the desulfurization of iron liquid in iron liquid, then allows spheroidization of graphite, residual magnesium amount is too low can only generate flake graphite, residual magnesium content is too high, generates globular graphite, and when containing interference element titanium and antimony, chromium in iron liquid, residual magnesium weight range is widened.Rare earth element have very strong in and the ability of interference element, rare earth to join in iron liquid first with the element reactions such as sulphur, iron liquid is purified, after the purification of iron liquid, residual rare earth plays metamorphism to graphite, when being used alone RE-treated Cast Iron Melts, rare-earth residual amount can obtain quasiflake graphite 0.045 ~ 0.075%, rare earth price is relatively high, general employing rare earth alloy carries out creepage rate, and adopt the alloy of rare earth and magnesium to carry out creepage rate, rare earth and magnesium, in wider ratio range, can obtain quasiflake graphite.
Present invention also offers a kind of preparation method of vanadium titanium vermicular cast iron, it is characterized in that comprising the following steps: (1) raw materials, raw materials by weight is configured to following component: the carbon of 3.4 ~ 3.8%, the silicon of 2.1 ~ 2.5%, 0.3 ~ 0.7% manganese, 0.10 ~ 0.30% vanadium, 0.10 ~ 0.20% titanium, 0.03 ~ 0.07% antimony, 0.03 ~ 0.07% chromium, 0.01 ~ 0.035% residual magnesium, 0.02 ~ 0.045% residual rare earth, 0.07-0.17% phosphorus, be no more than 0.07% sulphur, surplus is iron;
(2) 1320 DEG C ~ 1350 DEG C high temperature liquid irons obtained after vanadium titano-magnetite fusing are directly proceeded to intermediate frequency furnace and carry out melting, smelting temperature is greater than 1500 DEG C;
(3) before molten iron is come out of the stove, cast pack processing is toasted at 350 ~ 450 DEG C, then vermiculizer, nucleating agent and insulating covering agent and metallic antimony, chromium are placed in the bag end;
(4) before molten iron furnace components tests qualified after, come out of the stove in 1450 DEG C ~ 1480 DEG C, adopt pour method molten iron is poured into cast pack processing carry out creepage rate, inoculation, cast, obtain vanadium titanium vermicular cast iron of the present invention.
Wherein, vermiculizer described above is the mixture of rare earth ferrosilicomagnesium and rare earth ferrosilicon, and the add-on of described vermiculizer is 1.2% ~ 1.8% of weight of molten iron, and wherein the weight percent of rare earth ferrosilicon is 50% ~ 70%; Rare earth ferrosilicon and rare earth ferrosilicomagnesium add with fine particle shape, and the granularity of rare earth ferrosilicon particle is 5 ~ 10mm, and the granularity of rare earth ferrosilicomagnesium particle is 10 ~ 15mm.
Nucleating agent described above is 75SiFe, and the add-on of described nucleating agent is 0.6% ~ 1.5% of weight of molten iron.
Insulating covering agent described above is poly-slag insulating covering agent or plant ash.
The present invention can directly utilize the high temperature liquid iron after vanadium titano-magnetite melting (1320 DEG C ~ 1350 DEG C) to obtain vanadium titanium vermicular cast iron through electric furnace adjusting component, avoids secondary smelting process, has saved the energy.
Beneficial effect of the present invention: the present invention utilizes the raw material being rich in V, Ti element, add a small amount of antimony, Chrome metal powder element, make the intensity of vanadium titanium vermicular cast iron, wear resisting property and thermal fatigue resistance all be better than adding alloy gray cast-iron and the vanadium titanium graphitic cast iron of Ni, Mo alloying element, greatly reduce cost.
Embodiment
The present invention is further described by following embodiment.
the preparation of sample
Raw materials by weight is configured to following component: the carbon of 3.4 ~ 3.8%, the silicon of 2.1 ~ 2.5%, 0.3 ~ 0.7% manganese, 0.10 ~ 0.30% vanadium, 0.10 ~ 0.20% titanium, 0.03 ~ 0.07% antimony, 0.03 ~ 0.07% chromium, 0.01 ~ 0.035% residual magnesium, 0.02 ~ 0.045% residual rare earth, 0.07-0.17% phosphorus, be no more than 0.07% sulphur, surplus is iron and inevitable impurity.1320 DEG C ~ 1350 DEG C high temperature liquid irons obtained after vanadium titano-magnetite fusing are directly proceeded to intermediate frequency furnace and carries out melting, smelting temperature is greater than 1500 DEG C, before molten iron is come out of the stove, cast pack processing is toasted at 350 ~ 450 DEG C, then vermiculizer, nucleating agent and insulating covering agent and metallic antimony, chromium are placed in the bag end, before molten iron furnace components tests qualified after, come out of the stove in 1450 DEG C ~ 1480 DEG C, employing pour method molten iron is poured into cast pack processing carry out creepage rate and inoculation, first cast pack processing is poured into by 2/3 of molten iron in stove during creepage rate, remaining molten iron is poured into cast pack processing again after process to be mixed evenly, remaining 1/3 nucleating agent is added with stream simultaneously, add poly-slag insulating covering agent or plant ash afterwards in molten iron surface, compactedization dips molten iron after having bred rear standing 2-3 min and produces wedge test piece, the wide mouth of spoken parts in traditional operas of chill block is that 5-8mm is qualified for breeding, breed the coupon of qualified rear cast 30*300, in order to preparing tensile test piece, hardness specimens, heat conduction sample, wear-resisting sample and metallographic specimen.
Embodiment 1-3
According to the preparation method in the specific embodiment of the invention, prepare the vanadium titanium vermicular cast iron coupon (numbering 1,2,3) of 3 stoves heterogeneity combination within the scope of predetermined component of the present invention.
Contrast material:
Common vanadium titanium graphitic cast iron sample (numbering 4);
Vanadium titanium vermicular cast iron sample (numbering 5) prepared by patent CN 102080177.
Table 1, each material chemical composition (wt%):
Numbering |
C |
Si |
Mn |
P |
S |
V |
Ti |
Cr |
Sb |
1 |
3.53 |
2.23 |
0.56 |
0.08 |
0.052 |
0.20 |
0.15 |
0.03 |
0.05 |
2 |
3.66 |
2.31 |
0.49 |
0.12 |
0.049 |
0.22 |
0.16 |
0.04 |
0.06 |
3 |
3.55 |
2.28 |
0.63 |
0.11 |
0.062 |
0.26 |
0.15 |
0.05 |
0.05 |
4 |
3.54 |
1.88 |
0.77 |
0.12 |
0.061 |
0.35 |
0.30 |
0 |
0 |
5 |
3.58 |
2.25 |
0.64 |
0.09 |
0.07 |
0.20 |
0.15 |
0 |
0 |
Stretching experiment is at CMT5305A C300kN) type electronic universal material experiment-machine (Shenzhen new two think company limiteds produce) on carry out.The tensile strength of each sample of measuring and elongation, each stove measures three samples, finally gets its mean value; Brinell hardness is determined on HBRVU-187.5 type Michael Burawoy optics sclerometer carries out, and measures four samples altogether, and each sample measures 1 point, and finally get its mean value, result is as shown in table 2.
The each material mechanical performance test result of table 2.
Numbering |
Tensile strength (Mpa) |
Average tensile strength (Mpa) |
HBS |
Average HBS |
1 |
380-450 |
420 |
220-290 |
265 |
2 |
390-440 |
425 |
230-290 |
246 |
3 |
400-460 |
418 |
230-300 |
272 |
4 |
240-280 |
255 |
210-230 |
215 |
5 |
350-380 |
365 |
210-260 |
245 |
Thermal conductivity tester device is LASER HEAT constant instrument (Japanese vacuum science and engineering Co., Ltd.), model is TC-7000H, during test, test each sample at 25 DEG C, 180 DEG C, 300 DEG C, 500 DEG C, the thermal diffusivity of 600 DEG C of equitemperature points and specific heat, then the thermal conductivity of vanadium titanium vermicular cast iron and graphitic cast iron is asked according to following formula:
γ=α*Cp*ρ
In formula: γ-material thermal conductivity; α-material thermal diffusivity; Cp-material specific heat; ρ-density of material, wherein vanadium titanium vermicular cast iron is 7.25 g/cm
3, vanadium titanium graphitic cast iron is 7.35 g/cm
3.
By calculating, obtain each heat vanadium titanium vermicular cast iron and the graphitic cast iron thermal conductivity in different temperature points, result is as table 3.
Thermal conductivity under each material differing temps of table 3.
Numbering |
25℃ |
180℃ |
300℃ |
500℃ |
600℃ |
1 |
41.5208 |
42.3351 |
44.4734 |
45.9456 |
44.2836 |
2 |
44.4505 |
45.3692 |
47.3562 |
49.0081 |
48.2538 |
3 |
37.7308 |
40.4235 |
44.5052 |
46.9036 |
46.0145 |
4 |
47.1526 |
57.5836 |
50.0086 |
43.3624 |
27.8986 |
5 |
34.4405 |
36.8821 |
40.2282 |
41.1305 |
38.3451 |
Wear-resisting characteristic tester device is HSR-2M type reciprocating friction wear testing machine (the triumphant China Tech of section in Lanzhou
Skill development corporation, Ltd. produces).During test, operation scheme is reciprocating, load p=35N that sample applies, and motor travelling speed is 200rpm, and fraction time is t=6min, and the travelling speed of bistrique is V=l0mm/s, and bistrique material is GCr 15 steel, and experimental result is as shown in table 4
The abrasion resistance results of each material of table 4.
Numbering |
1 |
2 |
3 |
4 |
5 |
Wear resistance |
0.523mg/h |
0.541mg/h |
0.517mg/h |
0.913mg/h |
0.702mg/h |
From table 2-4 above, vanadium titanium vermicular cast iron property indices according to the present invention has exceeded by the performance index of contrast material.The mechanical property of vermicular cast iron of the present invention, thermal fatigue property and wear resisting property than graphitic cast iron and existing vanadium titanium vermicular cast iron high, performance is more superior.
On tension specimen, each material metallographic specimen is cut after tension test completes, sample is polished, polishing, do not need to corrode directly by XJP-6A type metallography microscope sem observation graphite form, magnification is 100 times, after observing graphite form, HNO with 4%: alcohol corrosion sample, and then with each matrix of samples tissue of XJP-6A type metallography microscope sem observation, observing multiple is 100 times, and result is as shown in table 5
Table 5. each material metallographic result (%)
Numbering |
Compacted ink |
Perlite |
Ferrite |
1 |
80 |
80 |
17 |
2 |
90 |
80 |
17 |
3 |
85 |
85 |
18 |
4 |
0 |
0 |
100 |
5 |
70 |
60 |
38 |
From the above analysis, antimony (Sb) and chromium (Cr) alloying element add the comprehensive mechanical property significantly improving material, show as the raising of room temperature strength, hardness, 500 DEG C and 600 DEG C time intensity there is higher conservation rate, this is mainly because the change of matrix Medium pearlite and ferrite content and various strengthening effect joint effect.Ferritic intensity, hardness are not high, but have good plasticity and toughness, and perlite is the mechanical mixture of ferrite and cementite, its intensity, hardness is higher, but plasticity is relative with toughness poor, therefore the increase of content of pearlite in alloy improves intensity, reduces plasticity, toughness.And the increase of content of pearlite in alloy increases the resistance of dislocation motion, and this is realized by solution strengthening, refined crystalline strengthening and anchoring of dislocation strengthening acting in conjunction, the ferrite in chromium (Cr) solution strengthening perlite; Antimony (Sb) can be stablized and refine pearlite, and cause the phase interface of ferrite and cementite to increase, during fracture, dislocation not easy glide, makes intensity increase; The antimony (Sb) being enriched in graphite-basal body interface has very strong sticking power to the two, plays the effect of pinning strengthening, reduces stress concentration effect, also improves intensity equally; Limit solid solution form is present in matrix simultaneously, improves transformation temperature by solution strengthening, improves hot strength, serves unexpected technique effect.
The preparation of embodiment 4 vanadium titanium vermicular cast iron brake drum
Raw materials by weight is configured to following component: the carbon of 3.4 ~ 3.8%, the silicon of 2.1 ~ 2.5%, 0.3 ~ 0.7% manganese, 0.10 ~ 0.30% vanadium, 0.10 ~ 0.20% titanium, 0.03 ~ 0.07% antimony, 0.03 ~ 0.07% chromium, 0.01 ~ 0.035% residual magnesium, 0.02 ~ 0.045% residual rare earth, 0.07-0.17% phosphorus, be no more than 0.07% sulphur, surplus is iron and inevitable impurity.1320 DEG C ~ 1350 DEG C high temperature liquid irons obtained after vanadium titano-magnetite fusing are directly proceeded to intermediate frequency furnace and carries out melting, smelting temperature is greater than 1500 DEG C; Before molten iron is come out of the stove, cast pack processing is toasted at 350 ~ 450 DEG C, then vermiculizer, nucleating agent and insulating covering agent and metallic antimony, chromium are placed in the bag end; Before molten iron furnace components tests qualified after, come out of the stove in 1450 DEG C ~ 1480 DEG C, employing pour method molten iron is poured into cast pack processing carry out creepage rate and inoculation, first cast pack processing is poured into by 2/3 of molten iron in stove during creepage rate, pour remaining molten iron into cast pack processing again after process to be mixed evenly, remaining 1/3 nucleating agent is added with stream simultaneously, add poly-slag insulating covering agent or plant ash afterwards in molten iron surface, can be used for cast after leaving standstill 2min, teeming temperature is 1340 DEG C.When carrying out casting Technology Design, shrinkage coefficient gets 0.9%, adopts bottom gating.Molten casting iron after compactedization breeds is poured in casting mould case, and pouring speed is 9Kg/s, and the duration of pouring of molten iron is 9min, obtains the foundry goods of regulation shape, the sand in foundry goods and the filler sand in sandbox is cleaned out, obtains brake drum of the present invention.
The invention is not restricted to above-described embodiment, without departing from the present invention, can various changes and modifications be carried out.