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CN-121988704-A - High-toughness ductile cast iron pipe fitting and preparation method thereof

CN121988704ACN 121988704 ACN121988704 ACN 121988704ACN-121988704-A

Abstract

The invention relates to the technical field of metallurgical industry, and provides a high-toughness ductile cast iron pipe fitting and a preparation method thereof. A method for preparing high-toughness nodular cast iron pipe fitting includes such steps as smelting raw materials, regulating chemical components to obtain the first molten iron, pretreating silicon carbide, spheroidizing, inoculating the first inoculant for one time to obtain the fourth molten iron, pouring the fourth molten iron, adding the second inoculant, stream inoculation, cooling, demoulding to obtain semi-finished product, and heat treating. Through the technical scheme, the problem of insufficient toughness of the ductile cast iron pipe fitting in the related technology is solved.

Inventors

  • ZHANG YU
  • YUAN JINPING
  • YE LIANSHENG
  • Chang Baohai
  • Liu Shuangdong
  • ZHANG HONGWANG
  • GAO LIANG
  • HAN JUNLAI

Assignees

  • 沧州永欣铸造有限公司

Dates

Publication Date
20260508
Application Date
20260303

Claims (10)

  1. 1. The preparation method of the high-toughness ductile cast iron pipe fitting is characterized by comprising the following steps of: S1, after smelting raw materials, adjusting chemical components to obtain a first molten iron; s2, adding silicon carbide into the first molten iron, and performing pretreatment to obtain a second molten iron; s3, adding a nodulizer into the second molten iron, and performing nodulizing treatment to obtain a third molten iron; s4, adding a first inoculant into the third molten iron to perform first inoculation treatment, so as to obtain a fourth molten iron; s5, after pouring the fourth molten iron, cooling and demolding to obtain a high-toughness nodular cast iron pipe fitting semi-finished product; s6, performing heat treatment on the high-toughness nodular cast iron pipe fitting semi-finished product to obtain a high-toughness nodular cast iron pipe fitting; In the step S5, adding a second inoculant in the pouring process for stream inoculation; The first inoculant comprises, by weight, 71-72% of Si, 2.0-2.5% of Ca, 0.8-1.1% of Al, 1.2-1.4% of a composite element and the balance of Fe and unavoidable impurities, wherein the composite element comprises Mo, sr and V in a mass ratio of 5:1:1; the second inoculant comprises, by weight, 71-72% of Si, 1-1.3% of Ca, 2-2.5% of Ba, 0.3-0.4% of Ce and the balance of Fe and unavoidable impurities.
  2. 2. The preparation method of the high-toughness ductile iron pipe fitting according to claim 1 is characterized in that the first molten iron consists of the following elements, by weight, 3.5% -3.7% of C, 2.0% -2.5% of Si, 0.20% -0.30% of Mn, 0.7% -0.8% of Cu, 0.02% -0.03% of S, 0.01% -0.03% of P, and the balance of Fe and unavoidable impurities.
  3. 3. The method for preparing a ductile iron pipe fitting according to claim 1 wherein in step S4, the addition amount of the first inoculant is 0.2% -0.3% of the mass of the first iron liquid.
  4. 4. The method for preparing a ductile iron pipe fitting according to claim 1 wherein in step S2, the addition amount of the silicon carbide is 0.4% -0.5% of the mass of the first molten iron.
  5. 5. The method for preparing the high-toughness ductile iron pipe fitting according to claim 1, wherein the temperature of the first inoculation is 1360-1390 ℃, and the time of the first inoculation is 2-3 min.
  6. 6. The method for preparing a ductile iron pipe fitting according to claim 1 wherein in step S5, the addition amount of the second inoculant is 0.2% -0.3% of the mass of the first iron liquid.
  7. 7. The method for preparing a ductile iron pipe fitting according to claim 1, wherein in step S2, the pretreatment temperature is 1420-1460 ℃, and the pretreatment time is 8-10 min.
  8. 8. The method for preparing a high-toughness ductile iron pipe fitting according to claim 1, wherein in step S3, the adding amount of the spheroidizing agent is 1.2% -1.3% of the mass of the first molten iron, and the spheroidizing agent is rare earth magnesium alloy.
  9. 9. The method for preparing the high-toughness spheroidal graphite cast iron pipe fitting according to claim 1, wherein in the step S6, the heat treatment process specifically comprises the steps of heating a semi-finished product of the high-toughness spheroidal graphite cast iron pipe fitting to 650 ℃ at a heating rate of 20-30 ℃ per hour, heating to 950 ℃ at a heating rate of 50-60 ℃ per hour, preserving heat for 3.5 hours, cooling to 750 ℃ at a cooling rate of 30-40 ℃ per hour, preserving heat for 4.5 hours, and carrying out furnace-following cooling to obtain the high-toughness spheroidal graphite cast iron pipe fitting.
  10. 10. A high-toughness ductile iron pipe fitting prepared by the method for preparing the high-toughness ductile iron pipe fitting according to any one of claims 1 to 9.

Description

High-toughness ductile cast iron pipe fitting and preparation method thereof Technical Field The invention relates to the technical field of metallurgical industry, in particular to a high-toughness ductile cast iron pipe fitting and a preparation method thereof. Background The nodular cast iron pipe fitting is a core pipe fitting in the fields of municipal water and gas supply, industrial medium conveying, agricultural irrigation and special engineering, and the application scene of the nodular cast iron pipe fitting covers extreme working conditions from the conventional environment to deep sea, high and cold, high pressure and the like, so that the market demand is continuously growing. Compared with common cast iron pipes, plastic pipes and steel pipes, the spheroidal graphite cast iron pipe fitting precipitates graphite in a spheroidal form through spheroidization, so that the splitting effect of graphite on a matrix is greatly reduced, the ductility and fatigue resistance of the material are obviously improved, the service life can reach more than 50 years, and the maintenance cost is obviously lower than that of other pipes. Currently, in the process of preparing ductile iron pipe fittings, spheroidization is a fundamental link for determining the toughness of the pipe fittings. Although the existing products can meet the basic performance requirements of ductile cast iron pipe fittings, the problem of insufficient toughness still exists under the scene of high toughness requirement. Therefore, there is a need to provide a high-toughness ductile cast iron pipe fitting and a preparation method thereof. Disclosure of Invention The invention provides a high-toughness ductile cast iron pipe fitting and a preparation method thereof, which solve the problem of insufficient toughness of the ductile cast iron pipe fitting in the related art. The technical scheme of the invention is as follows: The invention provides a preparation method of a high-toughness ductile cast iron pipe fitting, which comprises the following steps: S1, after smelting raw materials, adjusting chemical components to obtain a first molten iron; s2, adding silicon carbide into the first molten iron, and performing pretreatment to obtain a second molten iron; s3, adding a nodulizer into the second molten iron, and performing nodulizing treatment to obtain a third molten iron; s4, adding a first inoculant into the third molten iron to perform first inoculation treatment, so as to obtain a fourth molten iron; s5, after pouring the fourth molten iron, cooling and demolding to obtain a high-toughness nodular cast iron pipe fitting semi-finished product; s6, performing heat treatment on the high-toughness nodular cast iron pipe fitting semi-finished product to obtain a high-toughness nodular cast iron pipe fitting; in the step S5, adding a second inoculant in the casting process for stream inoculation; The first inoculant comprises, by weight, 71-72% of Si, 2.0-2.5% of Ca, 0.8-1.1% of Al, 1.2-1.4% of a composite element and the balance of Fe and unavoidable impurities, wherein the composite element comprises Mo, sr and V in a mass ratio of 5:1:1; the second inoculant comprises, by weight, 71-72% of Si, 1-1.3% of Ca, 2-2.5% of Ba, 0.3-0.4% of Ce and the balance of Fe and unavoidable impurities. As a further technical scheme, the first molten iron comprises, by weight, 3.5% -3.7% of C, 2.0% -2.5% of Si, 0.20% -0.30% of Mn, 0.7% -0.8% of Cu, 0.02% -0.03% of S, 0.01% -0.03% of P, and the balance of Fe and unavoidable impurities. As a further technical scheme, in the step S2, the addition amount of the first inoculant is 0.2% -0.3% of the mass of the first molten iron. As a further technical scheme, in the step S2, the addition amount of the silicon carbide is 0.4% -0.5% of the mass of the first molten iron. As a further technical scheme, the temperature of the first inoculation treatment is 1360-1390 ℃, and the time of the first inoculation treatment is 2-3 min. As a further technical scheme, in the step S5, the addition amount of the second inoculant is 0.2% -0.3% of the mass of the first molten iron. As a further technical scheme, in the step S2, the pretreatment temperature is 1420-1460 ℃, and the pretreatment time is 8-10 min. As a further technical scheme, in the step S3, the adding amount of the nodulizer is 1.2% -1.3% of the mass of the first molten iron, and the nodulizer is rare earth magnesium alloy. In the step S6, the heat treatment process specifically comprises the steps of heating a semi-finished product of the high-toughness nodular cast iron pipe fitting to 650 ℃ at a heating rate of 20-30 ℃ per hour, heating to 950 ℃ at a heating rate of 50-60 ℃ per hour, preserving heat for 3.5 hours, cooling to 750 ℃ at a cooling rate of 30-40 ℃ per hour, preserving heat for 4.5 hours, and carrying out furnace-following cooling to obtain the high-toughness nodular cast iron pipe fitting. The invention limits different rates and different heat