Efficient and Long-lasting Compound Inoculant for Cast Iron
Release time:
2012-09-28 15:05
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(I) in modern cast iron production, inoculation treatment is an extremely important process link. The purpose of inoculation treatment is to eliminate white mouth, improve processing performance, refine eutectic group, promote A- type graphite, make graphite thicker and shorter, end blunt, shape deformation and bending, uniform distribution of graphite, improve body structure, improve mechanical properties, reduce section sensitivity, etc. For ductile iron, it is to refine the graphite ball while refining the eutectic group, the number of balls increases, the ball diameter becomes smaller, the roundness is improved, the spheroidization level is improved, the body organization is improved, and the comprehensive performance of the ductile iron is improved.
Improper handling of cast iron inoculation will also produce some side effects:
1. Inoculation may increase the tendency of shrinkage.
The Al in the inoculant increases the possibility of pinholes in the casting.
The inoculation treatment of iron temperature is low, or inoculant particle size is not appropriate, often make the casting to produce inclusions.
4. If the carbon equivalent of the original molten iron is relatively high, excessive inoculation will make graphite coarse and reduce its mechanical properties.
Therefore, the breeding must be strictly controlled. For possible side effects, preventive measures should be taken in advance, and excessive breeding should be prevented in actual production.
(II) different inoculation elements are C, Si, Ca, Ba, Sr, Al, Zr, RE, Mn, etc., which have different behaviors in the inoculation process. They show their own characteristics in eliminating white mouth, refining eutectic group, improving matrix structure and inoculation recession speed, and the side effects and influence on casting quality are also obviously different. Therefore, to develop a variety of inoculant, according to their different production process conditions on the casting material of different requirements to choose a more suitable inoculant.
(3) The inoculation effect of a compound inoculant composed of several inoculation elements matched with each other is not equal to the simple superposition of the inoculation effect of the individual action of the inoculation elements. The combination of certain inoculation elements can greatly enhance the inoculation effect, such as Si and Ca, Si and Ba, Si and Ca, Ba, Mn,Si and RE,Si and Al,Si and Sr, etc. The combination of some inoculation elements weakens the inoculation effect, such as Sr and Al, Ca,Sr and RE,Ti and RE, etc. Therefore, when developing a new compound inoculant and determining its organization and ratio, it is necessary to consider that the compound may greatly increase the inoculation effect and may also weaken the inoculation effect.
(4) Do not overemphasize the refinement of the cocrystalline group. Generally speaking, reducing the carbon equivalent of the original iron can significantly refine the eutectic group, thereby improving the mechanical properties of cast iron. However, the finer the eutectic group, the greater the tendency of intercrystalline shrinkage, when the mold rigidity is insufficient, it will cause the wall to move, and will produce shrinkage or shrinkage inside the casting. Most inoculants have the ability to refine the cocrystalline group, so we should pay attention to control the amount of inoculation, on the one hand, to ensure that the casting does not produce white mouth and obtain good A- type graphite, and at the same time to prevent excessive inoculation of the cocrystalline group caused by excessive refinement of the casting shrinkage.
(v) Generally speaking, the stronger the gestation effect of the inoculant, the faster its decline. For most inoculant, the inoculation effect has disappeared more than half in 5 minutes after inoculation, so the molten iron is required to be poured as soon as possible after inoculation. The decline of inoculation is manifested by the recovery of white mouth tendency, coarsening of eutectic group, coarse graphite sheet, and the appearance of supercooled graphite (D, E-type graphite), which reduces the quality of castings. The decay rate of the same inoculant may vary greatly, such as the RE-containing inoculant for the inoculation of ductile iron, showing a very outstanding anti-recession ability, and for ordinary gray cast iron inoculation, this anti-recession ability is not very obvious.
(6) The sulfur content of gray iron molten iron plays a very important role in inoculation. The appropriate amount of S in gray cast iron (S≥ 0.06, ≤ 0.12) can improve the mechanical properties of gray cast iron and improve the cutting performance. It is the result of S in hot metal improving and enhancing the inoculation effect, improving the graphite morphology and refining the eutectic group. As the amount of S increases, the graphite becomes shorter, the ends become blunt, and the form becomes curved, so that the performance of gray iron can be improved. If S≤ 0.025%, for most inoculants, the gestation effect is very poor, and the gestation effect disappears quickly after a short maintenance time. Cast iron melted by electric furnace contains about 0.03% S. In order to improve the inoculation effect, it is best to add FeS to the furnace charge to increase the sulfur content of molten iron to 0.06-0.12%. The inoculant containing RE or Ca and Ba can get better inoculation effect on cupola molten iron with high S content and electric furnace molten iron with low S content.
YJ-1 of high-efficiency and long-lasting compound inoculant for cast iron
YJ-1 inoculant chemical composition: Si 60-70%,Ba 2.0-4.0%,Ca 0.5-2.0%,RE 0-5%,Al 1-2% and appropriate amount of Bi and other elements. RE, Ba, Ca and oxygen, nitrogen, sulfur has a strong binding force, there is a certain role in promoting the ball. The formation of oxides, nitrides, sulfides, oxysulfides part of the floating on the surface of the molten iron is excluded, so that the molten iron purification; the other part in the molten iron as the core of graphite particles. In addition, at high temperatures, barium vapor pressure is small, in the molten iron is not easy to lose, it also protects the calcium is not easy to lose, so that the breeding recession slows down.
Bi is a strong surface active element, which is easily adsorbed around the graphite-austenite eutectic group, hindering the diffusion of carbon atoms in molten iron to graphite, thus limiting the growth of eutectic group and graphite, and thus improving the anti-recession ability of spheroidization and inoculation. Due to the core role of RE, Ca, Ba, Si, etc. and the "interfacial activity" of Bi, not only the anti-recession ability of ductile iron is improved, but also the nucleation ability of graphite is improved.
The biggest feature of YJ-1 inoculant is strong anti-recession ability, significantly increase the number of graphite balls, refine the graphite balls, improve the roundness, uniform distribution, and improve the spheroidization level 1-1.5. Purify iron water, eliminate carburizing, reduce and disperse phosphorus eutectic, and inhibit the effect of anti-white mouth, casting section sensitivity is small, the matrix ferrite content is high (F≥ 90%), the production of high strength, toughness cast ferrite ball iron stability is good.
This inoculant is also suitable for high phosphorus (0.12-0.13 P) and common phosphorus content of ductile iron.
YJ-1 inoculant, cupola, electric furnace smelting hot metal inoculation are applicable. The particle size of 3-15mm is used for flushing the iron outlet in front of the furnace, and the dosage is 0.6-0.8. Fine-grained inoculant with particle size of 0.1-0.6mm or 0.2-0.85mm is used for pouring in-flow inoculation or inverted inoculation (pouring into small bags with a quantitative spoon and then flushing into molten iron), I .e. the so-called secondary inoculation, with the dosage of 0.10-0.25%.
YJ-2 of High Efficiency and Long Lasting Compound Inoculant for Cast Iron
YJ-2 inoculant chemical composition: Si 55-65%,Ca 3-7%,Ba right amount, RE right amount, Al 1-2%, balance Fe, is a very versatile inoculant, can be used for gray iron inoculation, can also be used for ferrite or pearlite ductile iron inoculation.
YJ-2 inoculant is a graphitization inoculant, which has a strong ability to reduce the white mouth, and is particularly effective for thin-walled castings containing residual elements such as Cr, Mo and V.
It has good dissolution characteristics in molten iron, so it can make RE evenly distributed in molten iron. RE, Ba and Ca are important nucleating elements. They form a large number of crystalline cores with oxides, sulfides, nitrides and salt compounds of O, S and N remaining in molten iron, and have a strong effect of refining eutectic groups. It can neutralize the interference of harmful trace elements, such as Pb, Sb, Bi, etc., on the deterioration of graphite morphology. It can reduce the sensitivity of casting section, because it is not obvious to increase the number of eutectic groups, so it can reduce the tendency of casting shrinkage, and 75FeSi ratio can improve the tensile strength of 15-35N/mm2, improve the hardness of 10-25HB. The anti-recession ability is strong, and the effective time of incubation can reach about 15min.
The use of YJ-2 inoculant, the amount of addition, hot metal composition, temperature sensitivity is small, production stability is good, whether it is cupola, induction furnace or with or without alloying elements can obtain good breeding effect. It is most suitable for the inoculation of thin-walled, high-strength gray iron castings, with a particle size of 1-5mm or 3-8mm, an addition of about 0.3%, and a processing temperature of 1380-1450 ℃.
YJ-3 and YJ-4 of high-efficiency and long-lasting compound inoculant for cast iron
Chemical composition of YJ-3 inoculant: Si 60-70%,Ca 0.5-2.0, Al 1-2%,Ba, Mn appropriate amount, Fe balance.
YJ-4 inoculant contains Si 55-65%,Ca 0.5-2.0%,Al 1-2%, appropriate amount of Ba and Mn, and balance of Fe.
These two inoculants are strong graphitization inoculants, and their ability to inhibit white mouth is significantly higher than that of 75FeSi. In the early stage of inoculation, the width of white mouth is not much different, but the difference is nearly doubled after 15min, so YJ-3 and YJ-4 are long-acting inoculants.
Ba and Ca in YJ-3 and YJ-4 inoculants can promote the decomposition of carburizing body and play the role of deoxidation and denitrification. Barium vapor pressure is small at high temperatures, and it is not easy to lose in molten iron. It also protects calcium from loss, thus slowing down the breeding decline.
The supercooling degree of the inoculant is smaller than that of 75FeSi, which is beneficial to obtain uniform A- type graphite and pearlite structure, and can improve the strength and wear resistance of cast iron. The sensitivity of cast iron section is smaller than that of 75FeSi, which can improve the uniformity of the microstructure of different sections of the casting, reduce the hardness difference of the thick and thin sections of the casting, improve the quality of the casting and improve the cutting performance.
These two inoculants are also good inoculants for ductile iron, which can increase the number of graphite balls, improve roundness, eliminate cementite, disperse or reduce phosphorus cocrystals. YJ-3,YJ-4 inoculant can be widely used in various grades of gray cast iron and ductile iron, especially for large thick-walled parts, thick-walled uneven parts. It is suitable for occasions with long pouring time or long transportation distance. Can also be used for creeping cast iron inoculation, with auxiliary creeping effect.
The dosage of these two inoculants is half of that of 75FeSi, and the particle sizes are 0.1-0.6mm,0.2-0.85mm (pouring or inverted bag inoculation) and 3-8mm,5-15mm (iron outlet inoculation before furnace).
YJ-5 of High Efficiency and Long Lasting Compound Inoculant for Cast Iron
Chemical composition of YJ-5 inoculant: Si 55-65%,Ca 0.8-3.0%,RE 0-10%,Al 1-2.5%, proper amount of Sb or Sn,Fe balance.
RE, Ca, Ba and oxygen, nitrogen, sulfur has a strong binding force, they and oxygen, nitrogen, sulfur compounds part of the slag together with stripped, so that the molten iron purification, part of the foreign crystal nucleus. Sb is a strong surface active element, which reduces the surface tension of molten iron and the interfacial energy of graphite/molten iron and increases the nucleation rate. As a result of the combined effect of the core effect formed by the above-mentioned elements and the surface activity of Sb, the anti-recession ability and nucleation ability of the inoculation are further improved.
YJ-5 inoculant is mainly used for as-cast pearlite ductile iron furnace inoculation and pouring flow inoculation, its main feature is to have a strong ability to promote the formation of pearlite and graphitization, significantly increase the amount of as-cast pearlite (P≥ 90%), improve the spheroidization level level, increase the number of balls, ball diameter smaller, roundness improved, uniform distribution.
Adding 0.35-0.45%Cu in molten iron, ZZ-1 or ZZ-1D with special spheroidizing agent (for electric furnace), spheroidizing treatment with ZZ-2 or ZZ-2D (for cupola), and inoculating with YJ-5 inoculants in front of furnace and pouring flow can stably produce QT600-3, QT700-2 and QT800-2 cast ductile iron. If the molten iron in the furnace is pretreated first and then spheroidized, 0.4-0.6% purple Cu plate is added to the bag to stably produce special grades of QT600-0, QT700-4 and QT850-4 as-cast pearlite ductile iron.
YJ-5 inoculant cupola and electric furnace molten iron are suitable. The particle size is 1-3mm for inoculation when tapping iron in front of the furnace. The dosage is about 0.3, and the particle size is 0.1-0.6mm or 0.2-0.85mm. It is used for pouring with flow inoculation or inverted bag inoculation. The dosage is generally 0.10-0.25%.
YJ-5 inoculant can be used for the inoculation of high strength gray cast iron HT250, HT300 and HT350 with proper adjustment of ingredients.
YJ-6 of efficient and long-lasting compound inoculant for cast iron
Chemical composition of YJ-6 inoculant: Si 30-45%,Ca 3-7%,C 25-45%,Al 0.5-1%, proper amount of Ba or Zr,Fe balance. YJ-6 inoculant is composed of crystal graphite and other alloy elements. After crystal graphite with particle sizes of 0.1-1.0mm and 1-3mm enters high-temperature molten iron, dispersed particles form to play an external core role and delay inoculation recession. This graphite carbon has good adsorption effect on oxygen, nitrogen, sulfur and other trace elements, can eliminate impurities and improve the purity of molten iron. In addition, Si, Ba, Ca, Zr, etc. can also deoxidize, denitrogenate, and desulfurize. Some of their oxides, nitrides, sulfides and oxysulfides float to the surface of molten iron and are removed together with slag, and some form graphite foreign crystal nuclei in molten iron. Their combined effects can not only reduce the sensitivity of wall thickness and delay the recession, but also increase the activity of carbon, improve the graphitization ability of inoculant, eliminate the pores of castings, improve the fluidity of molten iron, reduce the tendency of white mouth, help to obtain fine and uniform type A graphite and refine pearlite, increase the strength of cast iron 20-40N/mm2.
The biggest characteristic of YJ-6 inoculant is that its ability to inhibit white mouth is stronger than that of other inoculants, and it is suitable for inoculating high-temperature molten iron with high sulfur content (S 0.6-0.12%). Under the same conditions, 75FeSi has completely declined within 4min, while YJ-6 inoculant can be maintained for 20min, so it is a very good efficient and long-lasting inoculant.
YJ-6 inoculant melting point is higher, the treatment temperature should be above 1430 degrees C, the use of the bag into the method, that is, in the iron out with the iron flow evenly inoculated, the amount of about 0.3%.
YJ-6 inoculant is mainly used for high-strength gray cast iron with high sulfur content, such as machine tool bed, internal combustion engine cylinder block, cylinder head and pressure-resistant dense castings, etc., and is not applicable to ductile iron castings.
YJ-7 of high efficiency and long lasting compound inoculant for cast iron
YJ-7 inoculant, chemical composition: Si 72-76%,Al ≤ 0.5%,Ca ≤ 0.1, proper amount of Sr, balance of Fe. Under the same inoculation conditions, compared with 75FeSi, the eutectic group refining effect is weaker than 75FeSi and the graphitization ability is about twice as high. Therefore, the YJ-7 inoculant can prevent casting shrinkage and shrinkage defects caused by the increase of cast iron crystal nuclei, and has better resistance to inoculation recession.
YJ-7 inoculant is especially suitable for the inoculation of high-grade thin-walled gray cast iron parts and engine cylinder blocks, cylinder heads and other castings that are sensitive to shrinkage and porosity. Its section sensitivity is small and its hardness is uniform, which is beneficial to improve the uniformity of different sections and the quality of castings.
The dosage of YJ-7 inoculant is about 30% less than that of 75FeSi, the dosage is generally 0.2-0.3, and the inoculation temperature is 1360-1460 ℃.
YJ-7 inoculant can be well dissolved in molten iron, and the amount of slag produced is small.
YJ-7 inoculants cannot be used for inoculation of rare earth cast iron because RE counteracts the inoculation effect of Sr.
YJ-8 of High Efficiency and Long Lasting Compound Inoculant for Cast Iron
Chemical composition of YJ-8 inoculant: Si 60-72%,Ca 1-2%,Mn 5-7%,Al 1-2%,Zr, Ba appropriate amount, Fe balance.
Zr, Ca and Ba in inoculant have strong deoxidation, denitrification and desulfurization ability, especially Zr has strong binding ability with N in molten iron, so it has strong nitrogen fixation and desulfurization ability, which is beneficial to eliminate pores in castings and improve the fluidity of molten iron. The oxides, sulfides, nitrides and ZrC compounds formed by them with O, S, C and N further improve the graphitization ability and nucleation ability of inoculant, the ability to resist breeding recession and reduce the tendency of white mouth, improve the sensitivity of cast iron section, and obtain uniform and fine A- type graphite.
YJ-8 inoculant melts quickly in molten iron and has a wide range of applicable temperatures. It is suitable for inoculation of gray cast iron and ductile iron of various grades. It is especially suitable for electric furnace smelting. Iron with high N content, high smelting temperature and large white mouth tendency is also used for inoculation of molten iron with good effect.
YJ-9 of High Efficiency and Long Lasting Compound Inoculant for Cast Iron
Chemical composition of YJ-9 inoculant: Si 30-40%,Cr 15-20%,Mn 6-10%,Ca 3-6%,Al 1-3%,Ba, RE appropriate amount, Fe balance. RE, Ca and Ba have strong deoxidation, desulfurization and degassing capabilities. They form sulfides, nitrides, oxides and oxysulfides in molten iron. Some of these compounds are stripped into slag to purify the molten iron, while others form foreign crystal nuclei. Therefore, the inoculation effect of molten iron is improved and the quenching tendency of cast iron is reduced. In addition to the appropriate amount of Cr and Mn can make eutectic group refinement and improve the dispersion of pearlite, Cr can also refine graphite, Mn can offset the harmful effect of sulfur, improve the melting characteristics of inoculant in molten iron, the inoculant is also a graphitization inoculant, with a moderate degree of graphitization ability and good anti-recession performance. Compared with 75FeSi, the tensile strength is improved by 25-35N/mm2, with high hardness, small sensitivity of casting section and good uniformity. In the early stage of pouring, the white mouth tendency is slightly greater than 75FeSi, but in the normal range of dosage, the thin wall of the casting will not appear white mouth, with good processing performance. The number of eutectic groups is less than 75FeSi, so the casting tends to shrink less.
The cast iron is poured in front of the furnace, the addition amount is 0.4-0.6, the particle size is 1-3mm,2-6mm, and the treatment temperature is 1420-1470 ℃.
The inoculant is suitable for molten iron melted by cupola and electric furnace to produce thin-walled high-strength gray cast iron castings. If the wall thickness is less than 5mm, it should be used with caution. High carbon equivalent molten iron (CE 3.95-4.3%) should be used, the silicon-carbon ratio is 0.55-0.75, the sulfur content is 0.03-0.11%, and the production cast iron grades are HT200 and HT250. The effective action time of inoculation in the bag is 10-15min.
YJ-10 of High Efficiency and Long Lasting Compound Inoculant for Cast Iron
Chemical composition of YJ-10 inoculant: Si 20-30%,Cr 20-40%,Ca 2-8%,Zr 0-5%,N amount, Al 1-2%, the rest is Fe.
N promotes the formation of cast iron pearlite, can strongly stabilize and refine the pearlite, Cr plays a role of micro-alloying to stabilize the pearlite, Si, Ca, Al, Zr and other elements play a role of graphitization, they and N, Cr mutually restrict each other, jointly promote the shape of the nucleus, inhibit the carburizing body.
Generally, the N content in molten iron is 40-70ppm. When the N content increases, the graphite becomes shorter and thicker, and the tip becomes dull. When the N content is increased to 300PPM, the graphite becomes compact graphite.
The effect of YJ-10 inoculant on cast iron with high carbon equivalent (about CE4.2%) and low C/Si ratio is particularly obvious. It can improve and refine A- type graphite, reduce D and E-type graphite, and remove ferrite in cast iron with high C and Si content.
The most prominent feature of YJ-10 inoculant is that under the condition of high carbon equivalent (CE 3.95-4.2%), it increases σb30-45N/mm2 and HB 30-40 compared with 75FeSi inoculation. Its graphitization ability is slightly lower than 75FeSi, and its graphitization effect is slightly lower than 75FeSi. Its graphitization effect declines faster, but its strength declines slowly, and there is no obvious change within 10-15min.
The YJ-10 inoculant, with a particle size of 0.5-3mm, is evenly inoculated with the iron flow when the iron is taken out in front of the furnace, with an addition amount of about 0.7, and the inoculation temperature should be higher than 1450 ℃.
YJ-10 inoculant is suitable for the production of high strength (HT250, HT300) castings and large complex thick wall wear-resistant and high stiffness gray cast iron with high carbon equivalent CE 3.95-4.2%.