CN116638060A - Production method of centrifugal spheroidal graphite cast iron pipe - Google Patents
Production method of centrifugal spheroidal graphite cast iron pipe Download PDFInfo
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- CN116638060A CN116638060A CN202310571913.8A CN202310571913A CN116638060A CN 116638060 A CN116638060 A CN 116638060A CN 202310571913 A CN202310571913 A CN 202310571913A CN 116638060 A CN116638060 A CN 116638060A
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- 229910001141 Ductile iron Inorganic materials 0.000 title claims abstract description 84
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 claims abstract description 33
- 230000008569 process Effects 0.000 claims abstract description 27
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 468
- 229910052742 iron Inorganic materials 0.000 claims description 225
- 238000011081 inoculation Methods 0.000 claims description 93
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 71
- 229910052799 carbon Inorganic materials 0.000 claims description 68
- 239000002054 inoculum Substances 0.000 claims description 67
- 238000011282 treatment Methods 0.000 claims description 46
- 229910052710 silicon Inorganic materials 0.000 claims description 45
- 239000011777 magnesium Substances 0.000 claims description 41
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 39
- 239000010703 silicon Substances 0.000 claims description 39
- 229910052749 magnesium Inorganic materials 0.000 claims description 38
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 34
- 229910052751 metal Inorganic materials 0.000 claims description 32
- 239000002184 metal Substances 0.000 claims description 32
- 239000012535 impurity Substances 0.000 claims description 28
- 238000001816 cooling Methods 0.000 claims description 25
- 230000009467 reduction Effects 0.000 claims description 25
- 238000005266 casting Methods 0.000 claims description 22
- 239000011248 coating agent Substances 0.000 claims description 22
- 238000000576 coating method Methods 0.000 claims description 22
- 239000003973 paint Substances 0.000 claims description 16
- 238000009413 insulation Methods 0.000 claims description 13
- 229910052714 tellurium Inorganic materials 0.000 claims description 12
- 229910000975 Carbon steel Inorganic materials 0.000 claims description 8
- 229910052684 Cerium Inorganic materials 0.000 claims description 8
- 238000003723 Smelting Methods 0.000 claims description 8
- 239000010962 carbon steel Substances 0.000 claims description 8
- 238000000465 moulding Methods 0.000 claims description 8
- 229910052796 boron Inorganic materials 0.000 claims description 6
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 6
- 229910052720 vanadium Inorganic materials 0.000 claims description 6
- 229910000636 Ce alloy Inorganic materials 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- 229910052787 antimony Inorganic materials 0.000 claims description 4
- 229910052785 arsenic Inorganic materials 0.000 claims description 4
- 229910052797 bismuth Inorganic materials 0.000 claims description 4
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052745 lead Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052718 tin Inorganic materials 0.000 claims description 4
- 238000005119 centrifugation Methods 0.000 claims description 2
- 239000003795 chemical substances by application Substances 0.000 claims 1
- 239000000203 mixture Substances 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 abstract description 35
- 229910000859 α-Fe Inorganic materials 0.000 abstract description 6
- 238000005265 energy consumption Methods 0.000 abstract description 5
- 238000009750 centrifugal casting Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 13
- 229910002804 graphite Inorganic materials 0.000 description 10
- 239000010439 graphite Substances 0.000 description 10
- 229910001562 pearlite Inorganic materials 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 229910000805 Pig iron Inorganic materials 0.000 description 6
- 229910001567 cementite Inorganic materials 0.000 description 6
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000000137 annealing Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000005087 graphitization Methods 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 238000007599 discharging Methods 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 1
- 239000005909 Kieselgur Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical group [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D13/00—Centrifugal casting; Casting by using centrifugal force
- B22D13/02—Centrifugal casting; Casting by using centrifugal force of elongated solid or hollow bodies, e.g. pipes, in moulds rotating around their longitudinal axis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
- B22D1/007—Treatment of the fused masses in the supply runners
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D13/00—Centrifugal casting; Casting by using centrifugal force
- B22D13/12—Controlling, supervising, specially adapted to centrifugal casting, e.g. for safety reasons
-
- 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
- C22C37/00—Cast-iron alloys
- C22C37/06—Cast-iron alloys containing chromium
- C22C37/08—Cast-iron alloys containing chromium with nickel
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention relates to the technical field of centrifugal casting, and particularly discloses a production method of a centrifugal spheroidal graphite cast iron pipe. The production method of the centrifugal spheroidal graphite cast iron pipe can directly obtain the ferrite-based spheroidal graphite cast iron pipe in an as-cast state without heat treatment procedures in the traditional process, thereby effectively reducing energy consumption and production cost, improving production efficiency, avoiding the problems that the traditional heat treatment process easily causes inconsistent product size and quality of the spheroidal graphite cast iron pipe, and the like, and more importantly, on the premise of omitting the traditional heat treatment process, the production method also obviously improves the performance of the spheroidal graphite cast iron pipe, wherein the tensile strength of the prepared spheroidal graphite cast iron pipe is 600-650 MPa, the yield strength is 440-525 MPa, the extensibility is more than 12 percent, and the requirement of GB/T13295 standard is obviously higher.
Description
Technical Field
The invention relates to the technical field of centrifugal casting, in particular to a production method of a centrifugal spheroidal graphite cast iron pipe.
Background
The ductile cast iron pipe is mainly prepared by adopting a metal model through a centrifugal casting method. In actual production, in order to accelerate production efficiency and protect the service life of the metal model, a circulating water cooling system is generally additionally arranged on the outer wall of the metal model so as to accelerate cooling and protecting the metal model and improve production efficiency. However, there is a problem that carbide structures such as cementite and pearlite often appear in the base structure of the spheroidal graphite cast iron pipe obtained in an as-cast state, and if a later heat treatment link for eliminating cementite or pearlite is not performed, the plasticity and toughness of the spheroidal graphite cast iron pipe cannot meet the use requirements of products, so that the heat treatment link for eliminating cementite or pearlite at high temperature is required in the production process of the existing centrifugal spheroidal graphite cast iron pipe at present.
Adverse effects caused by heat treatment are: (1) energy waste is caused; (2) The free expansion of graphitization of the spheroidal graphite cast iron pipe can cause larger change of the size of the spheroidal graphite cast iron pipe due to carbide decomposition in the heat treatment process; (3) The heat treatment process can produce tracks or riding wheel marks on the surface of the nodular cast iron pipe, and the consistency of appearance quality is affected; (4) In the high-temperature annealing stage for eliminating cementite, the ductile cast iron pipe can be scrapped due to ellipse caused by overhigh temperature; (5) The high temperature is long in cementite elimination time and low in production efficiency. Therefore, it is necessary to provide a new process which has high production efficiency and low energy consumption and can further improve the performance of the spheroidal graphite cast iron pipe.
Disclosure of Invention
Aiming at the problems of high production cost, high energy consumption and influence on the performance and the product percent of pass of the spheroidal graphite cast iron pipe caused by the fact that the conventional production process of the spheroidal graphite cast iron pipe is subjected to heat treatment, the invention provides a production method of the spheroidal graphite cast iron pipe.
In order to solve the technical problems, the technical scheme provided by the embodiment of the invention is as follows:
the production method of the centrifugal spheroidal graphite cast iron pipe comprises the following steps:
s1, smelting in an electric furnace to obtain molten iron with components meeting requirements;
s2, according to pearlescent factor P x Determining the carbon equivalent Ceq in the molten iron after carbon reduction, and then determining the carbon equivalent Ceq= [ C]+1/3(n+[P]) The +m determines the carbon content in the molten iron after carbon reduction, and carbon steel is added into the molten iron according to the requirement of the carbon content to obtain carbon-reduced molten iron; m=0.15 to 0.25;
wherein P is x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]；
If the metal inner wall of the centrifugal machine is not sprayed with heat insulation paint before casting, n=3.4-3.6, and a=3; if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting, n=2.6-2.8, and a=2;
if the metal inner wall of the centrifugal machine is not sprayed with heat-insulating paint before casting:
if P x When the carbon equivalent Ceq in the molten iron after the carbon reduction is controlled to be 4.5-4.65 percent; if 2.0 < P x When the Ceq is less than or equal to 3.0, controlling the Ceq in the molten iron after the carbon reduction to be 4.7-4.9%;
if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting:
if P x Controlling Ceq in the molten iron after carbon reduction to be 4.1-4.25% when the content is less than or equal to 2.0; if 2.0 < P x Controlling Ceq in the molten iron after carbon reduction to be 4.3-4.4% when the content is less than or equal to 2.5;
s3, according to the anti-spheroidization factor K 1 Determining the magnesium content in the spheroidized molten iron, and then adding a magnesium spheroidizer into the carbon-reduced molten iron according to the requirement of the magnesium content in the molten iron for spheroidization;
if K 1 The content of magnesium in the molten iron after spheroidization is controlled to be 0.05 to 0.06 percent and is less than or equal to 1.0; if 1.0 < K 1 When the magnesium content in the molten iron after spheroidization is controlled to be less than or equal to 2.0, the magnesium content in the molten iron after spheroidization is controlled to be 0.035-0.045%;
s4, adding a silicon-containing inoculant into the spheroidized molten iron, and performing primary inoculation treatment;
s5, adding a silicon-containing inoculant into the fan-shaped package, pouring the molten iron subjected to primary inoculation into the fan-shaped package, and performing secondary inoculation;
s6, pouring the molten iron subjected to the secondary inoculation treatment into a launder, adding a silicon-containing inoculant along with the flow in the pouring process, and performing tertiary inoculation treatment;
s7, coating a silicon-containing inoculant on the inner wall of the pipe die, feeding molten iron flowing into the launder into the pipe die, performing four-time inoculation treatment, and performing rotary centrifugation and cooling forming to obtain the centrifugal spheroidal graphite cast iron pipe.
In the production method of the centrifugal spheroidal graphite cast iron pipe, primary inoculation is carried out after spheroidization, so that fluctuation of components in molten iron is aggravated, a silicon-rich region exists in the molten iron, the activity of carbon elements is increased, and the formation of graphite is promoted; the secondary inoculation is carried out on the fan-shaped ladle, so that a carbon atom group and a larger carbon molecular chain Cn can be formed in molten iron, the component fluctuation of the molten iron is further increased, the nucleation supercooling degree of the molten iron is reduced, and the formation of carbide is inhibited; in the molten iron pouring process, adopting stream inoculation, increasing the external core of graphite nucleation, and improving the graphite tissue morphology and quantity; in-mold inoculation is carried out in the mold tube, so that the sensitivity to larger cooling speed in the solidification process can be reduced, and carbide on the outer surface of the nodular cast iron tube is prevented from being formed; further, the magnesium content in the molten iron after spheroidization is precisely controlled by the anti-spheroidization factor, the roundness of graphite spheres in the spheroidal graphite cast iron is improved, meanwhile, the C content in the molten iron is precisely controlled by the pearlescence factor, the generation of ferrite is promoted, the generation of pearlite and carbide is inhibited, thereby obtaining ferrite and graphite tissues, obviously improving the strength and plasticity of the spheroidal graphite cast iron, further, the spheroidal graphite cast iron with high strength and high plasticity can be prepared without a heat treatment procedure of the traditional process, the process is simple, the energy consumption is lower, the production efficiency of the spheroidal graphite cast iron can be effectively improved, the production cost is reduced, the market competitiveness of enterprises is obviously improved, and the spheroidal graphite cast iron has higher popularization and application values.
In a specific embodiment of the present invention, in S1, the chemical components of the molten iron are: 4.2 to 4.6 percent of C, 0.6 to 1.2 percent of Si, 0.2 to 0.4 percent of Mn, less than or equal to 0.08 percent of P, less than or equal to 0.03 percent of S, and the balance of Fe and unavoidable impurities.
Carbon is the element with the strongest graphitization capability and can strongly promote the formation of graphite, but excessive carbon easily causes defects such as floating of graphite, slag inclusion and the like; si is also an element with strong graphite capability, and at the same time, the increase of the silicon content can enlarge the temperature interval between two phases, and the formation of a large amount of carbide is easily caused by the excessively low Si content.
By controlling the C, si content within the above range, carbide formation can be reduced as much as possible, which is advantageous for obtaining a ferrite matrix and provides conditions for omitting the heat treatment process in the subsequent step.
It should be noted that the heat-insulating coating according to the present invention is a conventional heat-insulating coating in the art, such as diatomaceous earth.
Further, in S1, the content of other impurity elements in the molten iron is required to be: cr is less than or equal to 0.035%, ni is less than or equal to 0.035%, mo is less than or equal to 0.001%, cu is less than or equal to 0.03%, al is less than or equal to 0.03%, ti is less than or equal to 0.06%, V is less than or equal to 0.008%, B is less than or equal to 0.001%, sb is less than or equal to 0.005%, as is less than or equal to 0.007%, sn is less than or equal to 0.007%, pb is less than or equal to 0.001%, ce is less than or equal to 0.003%, bi is less than or equal to 0.002% and Te is less than or equal to 0.001%.
By controlling the content of each impurity element, the sphericity of graphite spheres in the spheroidal graphite cast iron can be ensured, and the generation of carbide can be inhibited, so that the strength and plasticity of the spheroidal graphite cast iron are improved.
In S3, the temperature of the molten iron is controlled to be 1480-1500 ℃ when the magnesium nodulizer is added.
The preferable molten iron temperature can improve the spheroidization effect, promote the uniform mixing of molten iron components and reduce the content of impurity elements.
As one embodiment of the present invention, in S3, if the inverse spheroidization factor 1.0 < K 1 And when the content of cerium in the carbon-reduced molten iron is less than or equal to 2.0, adding cerium alloy into the carbon-reduced molten iron during spheroidizing, and controlling the cerium content in the carbon-reduced molten iron to be 0.001-0.003%.
It should be noted that, the calculation formula of the anti-spheroidization factor in the invention is as follows:
anti-spheroidization factor K 1 ＝4.4×[Ti]+2.0×[As]+2.3×[Sn]+5.0×[Sb]+290×[Pb]+370×[Bi]+1.6×[Al]。
Preferably, in S4, if the metal inner wall of the centrifugal machine is not sprayed with heat insulation coating before casting, the silicon content after one inoculation treatment is controlled to be 3.4-3.6%; if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting, the silicon content after one inoculation treatment is controlled to be 2.6-2.8%.
By controlling the above silicon content, the generation of pearlite can be effectively suppressed, and the structure and the number of ferrite can be improved.
Preferably, in S5, the silicon-containing inoculant is silicon carbide or ferrosilicon inoculant, the granularity is 2-3mm, and the adding amount of the silicon-containing inoculant is 0.3-0.5% of the mass of molten iron after primary inoculation treatment.
Preferably, in S5, the temperature of molten iron after primary inoculation treatment is controlled to be 1350-1380 ℃.
Preferably, in S6, the granularity of the silicon-containing inoculant is 1 mm-3 mm, and if the metal inner wall of the centrifugal machine is not sprayed with heat insulation coating before casting, the adding amount of the silicon-containing inoculant is 0.2-0.4% of the mass of molten iron after secondary inoculation treatment; if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting, the adding amount of the silicon-containing inoculant is 0.5-0.75% of the mass of molten iron after secondary inoculation treatment.
Preferably, in S6, the temperature of molten iron after secondary inoculation is controlled to be 1310-1350 ℃.
Preferably, in S7, before molten iron enters the pipe die, the rotating speed of the pipe die is controlled to be 700-1200 r/min.
Preferably, in S7, the addition amount of the silicon-containing inoculant is 0.08-0.12% of the mass of molten iron.
If the heat-insulating coating is not sprayed on the metal inner wall of the centrifugal machine before casting, in S7, before molten iron enters the pipe die, the rotating speed of the pipe die is controlled to be 1000-1200 r/min; if the metal inner wall of the centrifugal machine is sprayed with the heat-insulating coating before casting, in S7, before molten iron enters the pipe die, the rotating speed of the pipe die is controlled to be 700-900 r/min.
Preferably, in S7, after cooling and molding, the pipe die continues to rotate for 1 to 5 minutes, and is cooled to 600 to 700 ℃ for demoulding.
Preferably, in S7, the granularity of the silicon-containing inoculant is 0.3 mm-1 mm.
Preferably, in S7, the temperature of molten iron after three inoculation treatments is controlled to be 1250-1320 ℃.
Through specific four inoculation treatment, specific carbon reduction treatment and magnesium content control in the spheroidization process, the graphitization of the spheroidal graphite cast iron can be effectively promoted, carbide generation in the spheroidal graphite cast iron is restrained, meanwhile, the eutectic cell number in the spheroidal graphite cast iron is improved, crystal grains are refined, graphite morphology is improved, sensitivity to larger cooling speed in the molten iron solidification process is further reduced, carbide generation on the surface of a spheroidal graphite cast iron pipe is further reduced, the mechanical performance of the spheroidal graphite cast iron is obviously improved, a process of eliminating cementite or pearlite at high temperature in the traditional process is not required, the product quality and performance of the spheroidal graphite cast iron pipe are obviously improved, and the spheroidal graphite cast iron pipe has higher practical value.
Preferably, if the metal inner wall of the centrifugal machine is not sprayed with heat insulation coating before casting, the centrifugal spheroidal graphite cast iron pipe comprises the following chemical components: 3.3 to 3.8 percent of C, 3.8 to 4.4 percent of Si, 0.2 to 0.4 percent of Mn, 0.035 to 0.060 percent of Mg, less than or equal to 0.08 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.035 percent of Cr, less than or equal to 0.035 percent of Ni, less than or equal to 0.001 percent of Mo, less than or equal to 0.03 percent of Cu, less than or equal to 0.03 percent of Al, less than or equal to 0.06 percent of Ti, less than or equal to 0.008 percent of V, less than or equal to 0.001 percent of B, less than or equal to 0.005 percent of Sb, less than or equal to 0.007 percent of As, less than or equal to 0.007 percent of Sn, less than or equal to 0.001 percent of Pb, less than or equal to 0.003 percent of Ce, less than or equal to 0.002 percent of Bi, less than or equal to 0.001 percent of Te. The balance being Fe and unavoidable impurities.
If the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting, the centrifugal spheroidal graphite cast iron pipe comprises the following chemical components: 3.1 to 3.4 percent of C, 3.2 to 3.8 percent of Si, 0.2 to 0.4 percent of Mn, 0.035 to 0.060 percent of Mg, less than or equal to 0.08 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.035 percent of Cr, less than or equal to 0.035 percent of Ni, less than or equal to 0.001 percent of Mo, less than or equal to 0.03 percent of Cu, less than or equal to 0.03 percent of Al, less than or equal to 0.06 percent of Ti, less than or equal to 0.008 percent of V, less than or equal to 0.001 percent of B, less than or equal to 0.005 percent of Sb, less than or equal to 0.007 percent of As, less than or equal to 0.007 percent of Sn, less than or equal to 0.001 percent of Pb, less than or equal to 0.003 percent of Ce, less than or equal to 0.002 percent of Bi, less than or equal to 0.001 percent of Te. The balance being Fe and unavoidable impurities.
The production method of the centrifugal spheroidal graphite cast iron pipe can directly obtain the ferrite-based spheroidal graphite cast iron pipe in an as-cast state without heat treatment procedures in the traditional process, thereby effectively reducing energy consumption and production cost, improving production efficiency, avoiding the problems that the traditional heat treatment process easily causes inconsistent product size and quality of the spheroidal graphite cast iron pipe, and the like, and more importantly, on the premise of omitting the traditional heat treatment process, the performance of the spheroidal graphite cast iron pipe is obviously improved, the tensile strength of the prepared spheroidal graphite cast iron pipe is 600-650 MPa, the yield strength is 440-525 MPa, the extensibility is more than 12 percent, and the requirements of GB/T13295 standard are obviously higher.
Drawings
FIG. 1 is a metallographic structure chart (100) of spheroidal graphite cast iron prepared in example 1 of the present invention;
FIG. 2 is a metallographic structure chart (. Times.100) of spheroidal graphite cast iron prepared in comparative example 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In order to better illustrate the present invention, the following examples are provided for further illustration.
Example 1
The embodiment of the invention provides a production method of a centrifugal spheroidal graphite cast iron pipe DN800 (the inside of a metal mould of a centrifugal machine is not sprayed with heat insulation coating), which comprises the following steps:
s1, smelting pig iron by a medium frequency electric furnace to obtain molten iron with the components of C4.2%, si 0.6%, mn0.2%, P0.02%, S0.02%, cr 0.021%, ni 0.018%, mo 0.0008%, cu0.025%, al0.021%, ti0.04%, V0.007%, B0.0007%, sb 0.002%, as0.004%, sn0.004%, pb 0.001%, bi 0.001% and Te 0.0008%;
s2, calculating P according to the molten iron components of the intermediate frequency electric furnace x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]，n＝3.4，a＝3Calculating pearlescent impact factor P x =1.209, i.e. P x Less than or equal to 2.0, therefore, ceq takes a value of 4.5% according to Ceq= [ C ]]+1/3([n]+[P]) C content is 3.53% after carbon reduction is calculated by +0.2, carbon steel is added into molten iron according to the requirement of carbon content, and the carbon-reduced molten iron of the medium frequency furnace is obtained;
the molten iron after the intermediate frequency furnace is subjected to carbon reduction comprises the following components: 3.53% of C, 0.6% of Si, 0.2% of Mn, 0.02% of P, 0.02% of S, 0.021% of Cr, 0.018% of Ni, 0.0008% of Mo, 0.025% of Cu, 0.021% of Al, 0.04% of Ti, 0.007% of V, 0.0007% of B, 0.002% of Sb, 0.004% of As, 0.004% of Sn, 0.001% of Pb, 0.001% of Bi, 0.0008% of Te and the balance of iron and unavoidable impurity elements;
s3, heating the molten iron in the intermediate frequency electric furnace to 1480 ℃, pouring the molten iron into a balling bag, transporting to a balling station, and according to K 1 ＝4.4×[Ti]+2.0×[As]+2.3×[Sn]+5.0×[Sb]+290×[Pb]+370×[Bi]+1.6×[Al]Calculation of the inverse spheroidization factor K 1 =0.897, determining the magnesium content in the spheroidized molten iron to be 0.05%, and then adding a magnesium spheroidizer into the molten iron according to the requirement of the magnesium content for spheroidization;
s4, adding 75SiFe inoculant into the spheroidized molten iron according to the Si content requirement, performing primary inoculation treatment, and controlling the Si content after the primary inoculation treatment to be 3.4%;
the components of the molten iron after primary inoculation are as follows: c:3.33%, si:3.4%, mn:0.2%, mg 0.05%, P0.02%, S0.02%, cr 0.021%, ni 0.018%, mo 0.0008%, cu0.025%, al0.021%, ti0.04%, V0.007%, B0.0007%, sb 0.002%, as0.004%, sn0.004%, pb 0.001%, bi 0.001%, te 0.0008%, and the balance of Fe and impurity elements;
s5, adding 75SiFe inoculant with the mass of 0.3% of the molten iron into the bottom of the fan-shaped ladle, heating the molten iron subjected to primary inoculation to 1350 ℃, pouring the molten iron into the centrifuge fan-shaped ladle, and performing secondary inoculation; the granularity of the 75SiFe inoculant is 2-3mm;
s6, heating the molten iron subjected to secondary inoculation to 1310 ℃, pouring the heated molten iron into a launder, adding a 75SiFe inoculant with the mass of 0.2% of the molten iron along with the flow in the pouring process, and performing tertiary inoculation; the granularity of the 75SiFe inoculant is 1-3mm;
s7, coating 75SiFe inoculant with the mass of 0.1% of the molten iron on the inner wall of the pipe die, and then conveying the molten iron flowing into the launder into the pipe die for four times of inoculation treatment; the granularity of the 75SiFe inoculant is 0.3-1mm;
the components of the molten iron after four times of inoculation are as follows: c:3.33%, si:3.85%, mn:0.2%, mg:0.050%, P0.02%, S0.02%, cr 0.021%, ni 0.018%, mo 0.0008%, cu0.025%, al0.021%, ti0.04%, V0.007%, B0.0007%, sb 0.002%, as0.004%, sn0.004%, pb 0.001%, bi 0.001%, te 0.0008%, and the balance of Fe and impurity elements;
and S8, before molten iron enters the die pipe, controlling the rotating speed of the die pipe to be 1000r/min, carrying out circulating water cooling on the outer wall after the molten iron is poured into the die pipe, continuously keeping the die pipe rotating for 3min after cooling and molding, reducing the temperature of the cast pipe to 600 ℃, and demoulding to obtain the centrifugal spheroidal graphite cast iron pipe.
Example 2
The embodiment of the invention provides a production method of a centrifugal spheroidal graphite cast iron pipe DN800 (the inside of a metal mould of a centrifugal machine is not sprayed with heat insulation coating), which comprises the following steps:
s1, smelting pig iron by a medium frequency electric furnace to obtain molten iron with the components of C4.4%, si 1.0%, mn0.3%, P0.05%, S0.01%, cr 0.035%, ni 0.035%, mo 0.001%, cu0.015%, al0.03%, ti 0.05%, V0.005%, B0.0005%, sb 0.004%, as0.007%, sn0.006%, pb 0.0008%, bi 0.0012% and Te 0.001%;
s2, calculating P according to the molten iron components of the intermediate frequency electric furnace x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]N=3.5, a=3, and the pearlescent impact factor P is calculated x = 1.679, i.e. P x Less than or equal to 2.0, therefore, ceq takes a value of 4.6% according to Ceq= [ C ]]+1/3([n]+[P]) C content is 3.62% after carbon reduction is calculated by +0.2, and carbon steel is added into molten iron according to the requirement of carbon content to obtain carbon-reduced molten iron;
the molten iron after the intermediate frequency furnace is subjected to carbon reduction comprises the following components: 3.62% of C, 1.0% of Si, 0.3% of Mn, 0.05% of P, 0.01% of S, 0.035% of Cr, 0.035% of Ni, 0.001% of Mo, 0.015% of Cu, 0.03% of Al, 0.05% of Ti, 0.005% of V, 0.0005% of B, 0.004% of Sb, 0.007% of As, 0.006% of Sn, 0.0008% of Pb, 0.0012% of Bi, 0.001% of Te, and the balance of iron and unavoidable impurity elements;
s3, heating the molten iron in the intermediate frequency electric furnace to 1490 ℃, pouring the molten iron into a spheroidizing ladle, transporting to a spheroidizing station, and according to K 1 ＝4.4×[Ti]+2.0×[As]+2.3×[Sn]+5.0×[Sb]+290×[Pb]+370×[Bi]+1.6×[Al]Calculation of the inverse spheroidization factor K 1 =0.992, determining the magnesium content in the spheroidized molten iron to be 0.06%, and then adding a magnesium spheroidizer into the molten iron according to the requirement of the magnesium content for spheroidization;
s4, adding 75SiFe inoculant into the spheroidized molten iron, performing primary inoculation treatment, and controlling the Si content in the primary inoculated molten iron to be 3.5%;
the components of the molten iron after primary inoculation are as follows: c:3.42%, si:3.5%, mn:0.3%, mg 0.06%, P0.05%, S0.01%, cr 0.035%, ni 0.035%, mo 0.001%, cu0.015%, al0.03%, ti 0.05%, V0.005%, B0.0005%, sb 0.004%, as0.007%, sn0.006%, pb 0.0008%, bi 0.0012%, te 0.001%, and the balance of Fe and impurity elements;
s5, adding 75SiFe inoculant with the mass of 0.4% of the molten iron into the bottom of the fan-shaped ladle, heating the molten iron subjected to primary inoculation to 1360 ℃, pouring the molten iron into the centrifuge fan-shaped ladle, and performing secondary inoculation; the granularity of the 75SiFe inoculant is 2-3mm;
s6, heating the molten iron subjected to secondary inoculation to 1330 ℃, pouring the heated molten iron into a launder, adding a 75SiFe inoculant with the mass of 0.3% of the molten iron along with the flow in the pouring process, and performing tertiary inoculation; the granularity of the 75SiFe inoculant is 1-3mm;
s7, coating 75SiFe inoculant with the mass of 0.1% of the molten iron on the inner wall of the pipe die, and then conveying the molten iron flowing into the launder into the pipe die for four times of inoculation treatment; the granularity of the 75SiFe inoculant is 0.3-1mm;
the components of the molten iron after four times of inoculation are as follows: c:3.42%, si:4.1%, mn:0.3%, mg:0.060%, P0.05%, S0.01%, cr 0.035%, ni 0.035%, mo 0.001%, cu0.015%, al0.03%, ti 0.05%, V0.005%, B0.0005%, sb 0.004%, as0.007%, sn0.006%, pb 0.0008%, bi 0.0012%, te 0.001%, and the balance of Fe and impurity elements;
and S8, before molten iron enters the die pipe, controlling the rotating speed of the die pipe to be 1100r/min, carrying out circulating water cooling on the outer wall after the molten iron is poured into the die pipe, continuously keeping the die pipe to rotate for 2min after cooling and molding, reducing the temperature of the cast pipe to 650 ℃, and demoulding to obtain the centrifugal spheroidal graphite cast iron pipe.
Example 3
The embodiment of the invention provides a production method of a centrifugal spheroidal graphite cast iron pipe DN800 (the inside of a metal mould of a centrifugal machine is not sprayed with heat insulation coating), which comprises the following steps:
s1, smelting pig iron by a medium frequency electric furnace to obtain molten iron with the components of C4.6%, si 1.2%, mn0.4%, P0.08%, S0.03%, cr 0.031%, ni 0.028%, mo 0.0009%, cu0.03%, al0.025%, ti 0.06%, V0.004%, B0.001%, sb 0.005%, as0.005%, sn0.007%, pb 0.001%, ce 0.001%, bi 0.002% and Te 0.0007%;
s2, calculating P according to the molten iron components of the intermediate frequency electric furnace x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]N=3.6, a=3, and the pearlescent impact factor P is calculated x =2.252, i.e. 2.0<P x Less than or equal to 3.0, therefore, ceq takes a value of 4.8% according to Ceq= [ C ]]+1/3([n]+[P]) C content is 3.81% after carbon reduction is calculated by +0.2, and carbon steel is added into molten iron according to the requirement of carbon content to obtain carbon-reduced molten iron;
the molten iron after the intermediate frequency furnace is subjected to carbon reduction comprises the following components: 3.81% of C, 1.2% of Si, 0.4% of Mn, 0.08% of P, 0.03% of S, 0.031% of Cr, 0.028% of Ni, 0.0009% of Mo, 0.03% of Cu, 0.025% of Al, 0.06% of Ti, 0.004% of V, 0.001% of B, 0.005% of Sb, 0.005% of As, 0.007% of Sn, 0.001% of Pb, 0.002% of Bi, 0.0007% of Te, and the balance of iron and unavoidable impurity elements;
s3, after the temperature of the molten iron in the intermediate frequency electric furnace is raised to 1500 ℃, pouring the molten iron into a balling bag,in-transit spheroidization station according to K 1 ＝4.4×[Ti]+2.0×[As]+2.3×[Sn]+5.0×[Sb]+290×[Pb]+370×[Bi]+1.6×[Al]Calculation of the inverse spheroidization factor K 1 =1.385, determining the magnesium content in the spheroidized molten iron to be 0.04%, adding a magnesium spheroidizer and cerium alloy into the molten iron according to the requirement of the magnesium content for spheroidization, and controlling the Ce content in the molten iron to be 0.001%;
s4, adding 75SiFe inoculant into the spheroidized molten iron, performing primary inoculation treatment, and controlling the Si content after primary inoculation treatment to be 3.6%;
the components of the molten iron after primary inoculation are as follows: c:3.61%, si:3.6%, mn:0.4%, mg:0.040%, P0.08%, S0.03%, cr 0.031%, ni 0.028%, mo 0.0009%, cu0.03%, al0.025%, ti 0.06%, V0.004%, B0.001%, sb 0.005%, as0.005%, sn0.007%, pb 0.001%, ce 0.001%, bi 0.002%, te 0.0007%, and the balance of Fe and impurity elements;
s5, adding 75SiFe inoculant with the mass of 0.5% of the molten iron into the bottom of the fan-shaped ladle, heating the molten iron subjected to primary inoculation to 1380 ℃, pouring the molten iron into the fan-shaped ladle of the centrifugal machine, and performing secondary inoculation; the granularity of the 75SiFe inoculant is 2-3mm;
s6, heating the molten iron subjected to the secondary inoculation to 1350 ℃, pouring the heated molten iron into a launder, adding a 75SiFe inoculant accounting for 0.4% of the mass of the molten iron along with the flow in the pouring process, and performing tertiary inoculation; the granularity of the 75SiFe inoculant is 1-3mm;
s7, coating 75SiFe inoculant with the mass of 0.1% of the molten iron on the inner wall of the pipe die, and then conveying the molten iron flowing into the launder into the pipe die for four times of inoculation treatment; the granularity of the 75SiFe inoculant is 0.3-1mm;
the components of the molten iron after four times of inoculation are as follows: c:3.61%, si:4.35%, mn:0.4%, mg:0.04%, P0.08%, S0.03%, cr 0.031%, ni 0.028%, mo 0.0009%, cu0.03%, al0.025%, ti 0.06%, V0.004%, B0.001%, sb 0.005%, as0.005%, sn0.007%, pb 0.001%, bi 0.0018%, te 0.0007%, and the balance of Fe and impurity elements;
and S8, before molten iron enters the die pipe, controlling the rotating speed of the die pipe to be 1200r/min, carrying out circulating water cooling on the outer wall after the molten iron is poured into the die pipe, continuously keeping the die pipe rotating for 5min after cooling and molding, reducing the temperature of the cast pipe to 700 ℃, and demoulding to obtain the centrifugal spheroidal graphite cast iron pipe.
Example 4
The embodiment of the invention provides a production method of a centrifugal spheroidal graphite cast iron pipe DN1400 (spraying heat insulation coating inside a metal mold of a centrifugal machine), which comprises the following steps:
s1, smelting pig iron by a medium frequency electric furnace to obtain molten iron with the components of C4.2%, si 0.6%, mn0.2%, P0.02%, S0.02%, cr 0.021%, ni 0.018%, mo 0.0008%, cu0.025%, al0.021%, ti0.04%, V0.007%, B0.0007%, sb 0.002%, as0.004%, sn0.004%, pb 0.001%, bi 0.001% and Te 0.0008%;
s2, calculating P according to the molten iron components of the intermediate frequency electric furnace x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]N=2.7, a=2, and the pearlescent impact factor P is calculated x =0.414, i.e. P x Less than or equal to 2.0, therefore, ceq takes a value of 4.2% according to Ceq= [ C ]]+1/3([n]+[P]) C content is 3.49% after carbon reduction is calculated by +0.2, and carbon steel is added into molten iron according to the requirement of carbon content to obtain carbon-reduced molten iron;
the molten iron after the intermediate frequency furnace is subjected to carbon reduction comprises the following components: 3.49% of C, 0.6% of Si, 0.2% of Mn, 0.02% of P, 0.02% of S, 0.021% of Cr, 0.018% of Ni, 0.0008% of Mo, 0.025% of Cu, 0.021% of Al, 0.04% of Ti, 0.007% of V, 0.0007% of B, 0.002% of Sb, 0.004% of As, 0.004% of Sn, 0.001% of Pb, 0.001% of Bi, 0.0008% of Te and the balance of iron and unavoidable impurity elements;
s3, heating the molten iron in the intermediate frequency electric furnace to 1480 ℃, pouring the molten iron into a balling bag, transporting to a balling station, and according to K 1 ＝4.4×[Ti]+2.0×[As]+2.3×[Sn]+5.0×[Sb]+290×[Pb]+370×[Bi]+1.6×[Al]Calculation of the inverse spheroidization factor K 1 =0.897, determining the magnesium content in the spheroidized molten iron to be 0.05%, and then adding a magnesium spheroidizer into the molten iron according to the requirement of the magnesium content for spheroidization;
s4, adding 75SiFe inoculant into the spheroidized molten iron, performing primary inoculation treatment, and controlling the Si content in the inoculated molten iron to be 2.7%;
the components of the molten iron after primary inoculation are as follows: c:3.29%, si:2.7%, mn0.2%, mg:0.05%, P0.02%, S0.02%, cr 0.021%, ni 0.018%, mo 0.0008%, cu0.025%, al0.021%, ti0.04%, V0.007%, B0.0007%, sb 0.002%, as0.004%, sn0.004%, pb 0.001%, bi 0.001%, te 0.0008%, and the balance of Fe and impurity elements;
s5, adding 75SiFe inoculant with the mass of 0.4% of the molten iron into the bottom of the fan-shaped ladle, heating the molten iron subjected to primary inoculation to 1350 ℃, pouring the molten iron into the centrifuge fan-shaped ladle, and performing secondary inoculation; the granularity of the 75SiFe inoculant is 2-3mm;
s6, heating the molten iron subjected to secondary inoculation to 1310 ℃, pouring the heated molten iron into a launder, adding a 75SiFe inoculant with the mass of 0.6% of the molten iron along with the flow in the pouring process, and performing tertiary inoculation; the granularity of the 75SiFe inoculant is 1-3mm;
s7, coating 75SiFe inoculant with the mass of 0.1% of the molten iron on the inner wall of the pipe die, and then conveying the molten iron flowing into the launder into the pipe die for four times of inoculation treatment; the granularity of the 75SiFe inoculant is 0.3-1mm;
the components of the molten iron after four times of inoculation are as follows: 3.3% of C, 3.5% of Si, 0.2% of Mn, 0.050% of Mg, 0.02% of P, 0.02% of S, 0.021% of Cr, 0.018% of Ni, 0.0008% of Mo, 0.025% of Cu, 0.021% of Al, 0.04% of Ti, 0.007% of V, 0.0007% of B, 0.002% of Sb, 0.004% of As, 0.004% of Sn, 0.001% of Pb, 0.002% of Bi and 0.001% of Te; the balance of Fe and unavoidable impurities;
and S8, before molten iron enters the die pipe, controlling the rotating speed of the die pipe to be 700r/min, carrying out circulating water cooling on the outer wall after the molten iron is poured into the die pipe, continuously keeping the die pipe to rotate for 5min after cooling and molding, reducing the temperature of the cast pipe to 600 ℃, and demoulding to obtain the centrifugal spheroidal graphite cast iron pipe.
Example 5
The embodiment of the invention provides a production method of a centrifugal spheroidal graphite cast iron pipe DN1400 (spraying heat insulation coating inside a metal mold of a centrifugal machine), which comprises the following steps:
s1, smelting pig iron by a medium frequency electric furnace to obtain molten iron with the components of C4.4%, si 1.0%, mn0.3%, P0.05%, S0.01%, cr 0.035%, ni 0.035%, mo 0.001%, cu0.015%, al0.03%, ti 0.05%, V0.005%, B0.0005%, sb 0.004%, as0.007%, sn0.006%, pb 0.0008%, bi 0.0012% and Te 0.001%;
s2, calculating P according to the molten iron components of the intermediate frequency electric furnace x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]N=2.8, a=2, and the pearlescent impact factor P is calculated x =0.885, i.e. P x Less than or equal to 2.0, therefore, ceq takes a value of 4.1% according to Ceq= [ C ]]+1/3([n]+[P]) C content is 3.39% after carbon reduction is calculated by +0.2, and carbon steel is added into molten iron according to the requirement of carbon content to obtain carbon-reduced molten iron;
the molten iron after the intermediate frequency furnace is subjected to carbon reduction comprises the following components: 3.39% of C, 1.0% of Si, 0.3% of Mn, 0.05% of P, 0.01% of S, 0.035% of Cr, 0.035% of Ni, 0.001% of Mo, 0.015% of Cu, 0.03% of Al, 0.05% of Ti, 0.005% of V, 0.0005% of B, 0.004% of Sb, 0.007% of As, 0.006% of Sn, 0.0008% of Pb, 0.0012% of Bi, 0.001% of Te, and the balance of iron and unavoidable impurity elements;
s3, heating the molten iron in the intermediate frequency electric furnace to 1490 ℃, pouring the molten iron into a spheroidizing ladle, transporting to a spheroidizing station, and according to K 1 ＝4.4×[Ti]+2.0×[As]+2.3×[Sn]+5.0×[Sb]+290×[Pb]+370×[Bi]+1.6×[Al]Calculation of the inverse spheroidization factor K 1 =0.99, determining the magnesium content in the spheroidized molten iron to be 0.06%, and then adding a magnesium spheroidizer into the molten iron according to the requirement of the magnesium content for spheroidization;
s4, adding 75SiFe inoculant into the spheroidized molten iron, performing primary inoculation treatment, and controlling the Si content in the molten iron after the primary inoculation treatment to be 2.8%;
the components of the molten iron after primary inoculation are as follows: c:3.19%, si:2.8%, mn:0.3%, mg:0.060%, P0.05%, S0.01%, cr 0.035%, ni 0.035%, mo 0.001%, cu0.015%, al0.03%, ti 0.05%, V0.005%, B0.0005%, sb 0.004%, as0.007%, sn0.006%, pb 0.0008%, bi 0.0012%, te 0.001%, and the balance of Fe and impurity elements;
s5, adding 75SiFe inoculant with the mass of 0.5% of the molten iron into the bottom of the fan-shaped ladle, heating the molten iron subjected to primary inoculation to 1360 ℃, pouring the molten iron into the centrifuge fan-shaped ladle, and performing secondary inoculation; the granularity of the 75SiFe inoculant is 2-3mm;
s6, heating the molten iron subjected to secondary inoculation to 1330 ℃, pouring the heated molten iron into a launder, adding a 75SiFe inoculant with the mass of 0.75% of the molten iron along with the flow in the pouring process, and performing tertiary inoculation; the granularity of the 75SiFe inoculant is 1-3mm;
s7, coating 75SiFe inoculant with the mass of 0.1% of the molten iron on the inner wall of the pipe die, and then conveying the molten iron flowing into the launder into the pipe die for four times of inoculation treatment; the granularity of the 75SiFe inoculant is 0.3-1mm;
the components of the molten iron after four times of inoculation are as follows: 3.2% of C, 3.8% of Si, 0.3% of Mn, 0.060% of Mg, 0.05% of P, 0.01% of S, 0.035% of Cr, 0.035% of Ni, 0.001% of Mo, 0.015% of Cu, 0.03% of Al, 0.05% of Ti, 0.005% of V, 0.0005% of B, 0.004% of Sb, 0.007% of As, 0.006% of Sn, 0.0008% of Pb, 0.0012% of Bi and 0.001% of Te; the balance of Fe and unavoidable impurities;
and S8, before molten iron enters the die pipe, controlling the rotating speed of the die pipe to be 800r/min, carrying out circulating water cooling on the outer wall after the molten iron is poured into the die pipe, continuously keeping the die pipe rotating for 4min after cooling and molding, reducing the temperature of the cast pipe to 680 ℃, and demoulding to obtain the centrifugal spheroidal graphite cast iron pipe.
Example 6
The embodiment of the invention provides a production method of a centrifugal spheroidal graphite cast iron pipe DN1400 (spraying heat insulation coating inside a metal mold of a centrifugal machine), which comprises the following steps:
s1, smelting pig iron by a medium frequency electric furnace to obtain molten iron with the components of C4.6%, si 1.2%, mn0.4%, P0.08%, S0.03%, cr 0.031%, ni 0.028%, mo 0.0009%, cu0.03%, al0.025%, ti 0.06%, V0.004%, B0.001%, sb 0.005%, as0.005%, sn0.007%, pb 0.001%, ce 0.001%, bi 0.002% and Te 0.0007%;
s2, calculating P according to the molten iron components of the intermediate frequency electric furnace x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]N=2.6, a=2, and calculating the pearlescent impact factor P x =2.25, i.e. 2.0<P x Less than or equal to 2.5, therefore, ceq takes a value of 4.3% according to Ceq= [ C ]]+1/3([n]+[P]) C content is 3.57% after carbon reduction is calculated by +0.2, and carbon steel is added into molten iron according to the requirement of carbon content to obtain carbon-reduced molten iron;
the molten iron after the intermediate frequency furnace is subjected to carbon reduction comprises the following components: 3.57% of C, 1.2% of Si, 0.4% of Mn, 0.08% of P, 0.03% of S, 0.031% of Cr, 0.028% of Ni, 0.0009% of Mo, 0.03% of Cu, 0.025% of Al, 0.06% of Ti, 0.004% of V, 0.001% of B, 0.005% of Sb, 0.005% of As, 0.007% of Sn, 0.001% of Pb, 0.001% of Ce, 0.002% of Bi, 0.0007% of Te, and the balance of iron and unavoidable impurity elements;
s3, heating the molten iron in the intermediate frequency electric furnace to 1500 ℃, pouring the molten iron into a spheroidizing ladle, conveying to a spheroidizing station, and carrying out the process according to K 1 ＝4.4×[Ti]+2.0×[As]+2.3×[Sn]+5.0×[Sb]+290×[Pb]+370×[Bi]+1.6×[Al]Calculation of the inverse spheroidization factor K 1 =1.38, determining the magnesium content in the spheroidized molten iron to be 0.04%, adding a magnesium spheroidizer and cerium alloy into the molten iron according to the requirement of the magnesium content for spheroidization, and controlling the Ce content in the molten iron to be 0.001%;
s4, adding 75SiFe inoculant into the spheroidized molten iron, performing primary inoculation treatment, and controlling the Si content in the molten iron after the primary inoculation treatment to be 2.6%;
the components of the molten iron after primary inoculation are as follows: c:3.37%, si:2.6%, mn: mn0.4%, mg:0.040%, P0.08%, S0.03%, cr 0.031%, ni 0.028%, mo 0.0009%, cu0.03%, al0.025%, ti 0.06%, V0.004%, B0.001%, sb 0.005%, as0.005%, sn0.007%, pb 0.001%, ce 0.001%, bi 0.002%, te 0.0007%, and the balance of Fe and impurity elements;
s5, adding 75SiFe inoculant with the mass of 0.3% of the molten iron into the bottom of the fan-shaped ladle, heating the molten iron subjected to primary inoculation to 1380 ℃, pouring the molten iron into the fan-shaped ladle of the centrifugal machine, and performing secondary inoculation; the granularity of the 75SiFe inoculant is 2-3mm;
s6, heating the molten iron subjected to the secondary inoculation to 1350 ℃, pouring the heated molten iron into a launder, adding a 75SiFe inoculant accounting for 0.5% of the mass of the molten iron along with the flow in the pouring process, and performing tertiary inoculation; the granularity of the 75SiFe inoculant is 1-3mm;
s7, coating 75SiFe inoculant with the mass of 0.1% of the molten iron on the inner wall of the pipe die, and then conveying the molten iron flowing into the launder into the pipe die for four times of inoculation treatment; the granularity of the 75SiFe inoculant is 0.3-1mm;
the components of the molten iron after four times of inoculation are as follows: 3.37% of C, 3.3% of Si, 0.4% of Mn, 0.040% of Mg, 0.08% of P, 0.03% of S, 0.031% of Cr, 0.028% of Ni, 0.0009% of Mo, 0.03% of Cu, 0.025% of Al, 0.06% of Ti, 0.004% of V, 0.001% of B, 0.005% of Sb, 0.005% of As, 0.007% of Sn, 0.001% of Pb, 0.001% of Ce, 0.002% of Bi and 0.0007% of Te; the balance of Fe and unavoidable impurities;
and S8, before molten iron enters the die pipe, controlling the rotating speed of the die pipe to be 900r/min, carrying out circulating water cooling on the outer wall after the molten iron is poured into the die pipe, continuously keeping the die pipe to rotate for 1min after cooling and molding, reducing the temperature of the cast pipe to 600 ℃, and demoulding to obtain the centrifugal spheroidal graphite cast iron pipe.
Comparative examples 1 to 3
This comparative example provides a method for preparing a ductile iron pipe, which is exactly the same as the corresponding examples 1-3, except that: (1) The sequence of the step S2 and the step S3 is exchanged, namely, primary inoculation treatment is carried out firstly and then spheroidization treatment is carried out, and the silicon content in molten iron after primary inoculation is 1.8% -2.3% (the silicon content of comparative example 1 is 1.8%, the silicon content of comparative example 2 is 2.0%, and the silicon content of comparative example 3 is 2.3%); (2) The inoculation in the sector-shaped package is not carried out, namely, the sector-shaped package is not added with silicon inoculant and is not subjected to secondary inoculation treatment; (3) annealing the demoulded spheroidal graphite cast iron pipe; the rest of the operations are exactly the same.
The specific annealing treatment steps are as follows:
and heating the demoulded nodular cast iron pipe to 960 ℃, preserving heat for 18min, performing high-temperature carburization elimination heat treatment, and then cooling to below 650 ℃ along with a furnace, discharging and air cooling.
Comparative examples 4 to 6
This comparative example provides a method for preparing a ductile iron pipe, which is exactly the same as the corresponding examples 4-6, except that: (1) The sequence of the step S2 and the step S3 is exchanged, namely, primary inoculation treatment is carried out firstly and then spheroidization treatment is carried out, and the silicon content in molten iron after primary inoculation is 1.8% -2.3% (the silicon content of comparative example 1 is 1.8%, the silicon content of comparative example 2 is 2.0%, and the silicon content of comparative example 3 is 2.3%); (2) The inoculation in the sector-shaped package is not carried out, namely, the sector-shaped package is not added with silicon inoculant and is not subjected to secondary inoculation treatment; (3) annealing the demoulded spheroidal graphite cast iron pipe; the rest of the operations are exactly the same.
And heating the demoulded nodular cast iron pipe to 760 ℃, preserving heat for 8min, performing heat treatment for eliminating pearlite, and then cooling to below 650 ℃ along with a furnace, discharging and air cooling.
The ductile cast iron pipes prepared in examples 1 to 6 and comparative examples 1 to 6 were processed into standard test bars according to the national standard of ductile cast iron pipes, tensile tests were performed on a universal tester, performance indexes were measured, and the results are shown in Table 1 with reference to standard GB/T228.1-2021. The cast-state centrifugal spheroidal graphite cast-iron pipe was subjected to metallographic examination according to the spheroidal graphite cast-iron metallographic examination standard, and the metallographic structures of spheroidal graphite cast-iron pipes prepared in example 1 and comparative example 1 are shown in fig. 1 and 2 with reference to standard GB/T9441-2021.
TABLE 1
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, or alternatives falling within the spirit and principles of the invention.
Claims (10)
1. The production method of the centrifugal spheroidal graphite cast iron pipe is characterized by comprising the following steps of:
s1, smelting in an electric furnace to obtain molten iron with components meeting requirements;
s2, according to pearlescent factor P x Determining the carbon equivalent Ceq in the molten iron after carbon reduction, and then determining the carbon equivalent Ceq= [ C]+1/3(n+[P]) The +m determines the carbon content in the molten iron after carbon reduction, and carbon steel is added into the molten iron according to the requirement of the carbon content to obtain carbon-reduced molten iron; m=0.15 to 0.25;
wherein P is x ＝3.0×[Mn]-2.65×(n-a)+7.75×[Cu]+90×[Sn]+357×[Pb]+333×[Bi]+20.1×[As]+9.6×[Cr]+71.7×[Sb]；
If the metal inner wall of the centrifugal machine is not sprayed with heat insulation paint before casting, n=3.4-3.6, and a=3; if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting, n=2.6-2.8, and a=2;
if the metal inner wall of the centrifugal machine is not sprayed with heat-insulating paint before casting:
if P x When the carbon equivalent Ceq in the molten iron after the carbon reduction is controlled to be 4.5-4.65 percent; if 2.0 < P x When the Ceq is less than or equal to 3.0, controlling the Ceq in the molten iron after the carbon reduction to be 4.7-4.9%;
if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting:
if P x Controlling Ceq in the molten iron after carbon reduction to be 4.1-4.25% when the content is less than or equal to 2.0; if 2.0 < P x Controlling Ceq in the molten iron after carbon reduction to be 4.3-4.4% when the content is less than or equal to 2.5;
s3, according to the anti-spheroidization factor K 1 Determining the magnesium content in the spheroidized molten iron, and then adding a magnesium spheroidizer into the carbon-reduced molten iron according to the requirement of the magnesium content in the molten iron for spheroidization;
if K 1 The content of magnesium in the molten iron after spheroidization is controlled to be 0.05 to 0.06 percent and is less than or equal to 1.0; if 1.0 < K 1 When the magnesium content in the molten iron after spheroidization is controlled to be less than or equal to 2.0, the magnesium content in the molten iron after spheroidization is controlled to be 0.035-0.045%;
s4, adding a silicon-containing inoculant into the spheroidized molten iron, and performing primary inoculation treatment;
s5, adding a silicon-containing inoculant into the fan-shaped package, pouring the molten iron subjected to primary inoculation into the fan-shaped package, and performing secondary inoculation;
s6, pouring the molten iron subjected to the secondary inoculation treatment into a launder, adding a silicon-containing inoculant along with the flow in the pouring process, and performing tertiary inoculation treatment;
s7, coating a silicon-containing inoculant on the inner wall of the pipe die, feeding molten iron flowing into the launder into the pipe die, performing four-time inoculation treatment, and performing rotary centrifugation and cooling forming to obtain the centrifugal spheroidal graphite cast iron pipe.
2. The method for producing centrifugal spheroidal graphite cast iron pipe according to claim 1, wherein in S1, the chemical components of the molten iron are: 4.2 to 4.6 percent of C, 0.6 to 1.2 percent of Si, 0.2 to 0.4 percent of Mn, less than or equal to 0.08 percent of P, less than or equal to 0.03 percent of S, and the balance of Fe and unavoidable impurities.
3. The method for producing centrifugal spheroidal graphite cast iron pipe according to claim 2, wherein in S1, the content of other impurity elements in the molten iron is as follows: cr is less than or equal to 0.035%, ni is less than or equal to 0.035%, mo is less than or equal to 0.001%, cu is less than or equal to 0.03%, al is less than or equal to 0.03%, ti is less than or equal to 0.06%, V is less than or equal to 0.008%, B is less than or equal to 0.001%, sb is less than or equal to 0.005%, as is less than or equal to 0.007%, sn is less than or equal to 0.007%, pb is less than or equal to 0.001%, ce is less than or equal to 0.003%, bi is less than or equal to 0.002% and Te is less than or equal to 0.001%.
4. The production method of the centrifugal spheroidal graphite cast iron pipe according to claim 1, wherein in S3, the temperature of the carbon-reducing molten iron is controlled to 1480 ℃ to 1500 ℃ when the magnesium spheroidizing agent is added; and/or
In S3, if the inverse spheroidization factor is 1.0 < K 1 And when the content of cerium in the carbon-reduced molten iron is less than or equal to 2.0, adding cerium alloy into the carbon-reduced molten iron during spheroidizing, and controlling the cerium content in the carbon-reduced molten iron to be 0.001-0.003%.
5. The production method of the centrifugal spheroidal graphite cast iron pipe according to claim 1, wherein in S4, if the metal inner wall of the centrifugal machine is not sprayed with heat insulating paint before casting, the silicon content after one inoculation treatment is controlled to be 3.4% -3.6%; if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting, controlling the silicon content after primary inoculation to be 2.6-2.8%; and/or
In S5, the granularity of the silicon-containing inoculant is 2-3mm, and the adding amount of the silicon-containing inoculant is 0.3-0.5% of the mass of molten iron after primary inoculation treatment.
6. The method for producing centrifugal spheroidal graphite cast iron pipe according to claim 1, wherein in S5, the temperature of molten iron after one inoculation treatment is controlled to 1350 ℃ -1380 ℃.
7. The method for producing centrifugal spheroidal graphite cast iron pipe according to claim 1, wherein in S6, the granularity of the silicon-containing inoculant is 1 mm-3 mm; if the metal inner wall of the centrifugal machine is not sprayed with heat insulation paint before casting, the adding amount of the silicon-containing inoculant is 0.2-0.4% of the mass of molten iron after secondary inoculation treatment; if the metal inner wall of the centrifugal machine is sprayed with heat insulation paint before casting, the adding amount of the silicon-containing inoculant is 0.5-0.75% of the mass of molten iron after secondary inoculation; and/or
And S6, controlling the temperature of the molten iron after the secondary inoculation treatment to be 1310-1350 ℃.
8. The production method of the centrifugal ductile iron pipe according to claim 1 wherein in S7, the adding amount of the silicon-containing inoculant is 0.08% to 0.12% of the mass of molten iron; and/or
S7, before molten iron enters the pipe die, controlling the rotating speed of the pipe die to be 700-1200 r/min; and/or
And S7, after cooling and molding, continuously rotating the pipe die for 1-5 min, cooling to 600-700 ℃ and demolding.
9. The method for producing centrifugal spheroidal graphite cast iron pipe according to claim 1, wherein in S7, the granularity of the silicon-containing inoculant is 0.3 mm-1 mm; and/or
And S7, controlling the temperature of the molten iron after the three inoculation treatments to be 1250-1320 ℃.
10. The method for producing centrifugal spheroidal graphite cast iron pipe according to claim 1, wherein if the inner wall of the metal of the centrifugal machine is not sprayed with heat-insulating coating before casting, the obtained centrifugal spheroidal graphite cast iron pipe has the chemical composition: 3.3 to 3.8 percent of C, 3.8 to 4.4 percent of Si, 0.2 to 0.4 percent of Mn, 0.035 to 0.060 percent of Mg, less than or equal to 0.08 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.035 percent of Cr, less than or equal to 0.035 percent of Ni, less than or equal to 0.001 percent of Mo, less than or equal to 0.03 percent of Cu, less than or equal to 0.03 percent of Al, less than or equal to 0.06 percent of Ti, less than or equal to 0.008 percent of V, less than or equal to 0.001 percent of B, less than or equal to 0.005 percent of Sb, less than or equal to 0.007 percent of As, less than or equal to 0.007 percent of Sn, less than or equal to 0.001 percent of Pb, less than or equal to 0.003 percent of Ce, less than or equal to 0.002 percent of Bi, less than or equal to 0.001 percent of Te. The balance of Fe and unavoidable impurities;
if the metal inner wall of the centrifugal machine is sprayed with heat-insulating paint before casting, the centrifugal spheroidal graphite cast iron pipe comprises the following chemical components: 3.1 to 3.4 percent of C, 3.2 to 3.8 percent of Si, 0.2 to 0.4 percent of Mn, 0.035 to 0.060 percent of Mg, less than or equal to 0.08 percent of P, less than or equal to 0.03 percent of S, less than or equal to 0.035 percent of Cr, less than or equal to 0.035 percent of Ni, less than or equal to 0.001 percent of Mo, less than or equal to 0.03 percent of Cu, less than or equal to 0.03 percent of Al, less than or equal to 0.06 percent of Ti, less than or equal to 0.008 percent of V, less than or equal to 0.001 percent of B, less than or equal to 0.005 percent of Sb, less than or equal to 0.007 percent of As, less than or equal to 0.007 percent of Sn, less than or equal to 0.001 percent of Pb, less than or equal to 0.003 percent of Ce, less than or equal to 0.002 percent of Bi, less than or equal to 0.001 percent of Te. The balance being Fe and unavoidable impurities.
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