CN114317863A - Method for producing nodular cast iron with spheroidization rate of more than 90% by adopting wire feeding method - Google Patents

Abstract

The invention discloses a method for producing nodular cast iron with a spheroidization rate greater than 90% by using a wire feeding method. The method comprises the following steps: 1) adding pig iron, silicon carbide, recarburizer, scrap steel, alloy and remaining return material in sequence In the furnace; 2) the molten iron in the furnace to be charged is melted, and sampling is carried out when the temperature reaches the first preset value; 3) the composition of the sample is detected, and quenched and tempered according to the detection result, so that the molten iron meets the composition requirements; 4) Raise the temperature of the molten iron to the second preset value, carry out slag removal and tapping; 5) transfer the molten iron to the spheroidizing station, and when the temperature of the molten iron reaches the third preset value, add 75% silicon to the surface of the molten iron Iron, then add spheroidizing wire to carry out spheroidization; 6) after spheroidization is completed, carry out slag removal on the molten iron, and add silicon-barium inoculant on the surface of the molten iron after the spheroidization is completed; 7) introduce the molten iron into the pouring ladle, carry out Silicon barium inoculant is added during pouring. The method of the invention has simple operation and low cost.

Description

Method for producing nodular cast iron with spheroidization rate greater than 90% by wire feeding method

technical field

The invention belongs to the technical field of casting, and more particularly relates to a method for producing ductile iron with a spheroidization rate greater than 90% by using a wire feeding spheroidization method.

Background technique

Ductile cast iron is a kind of cast iron alloy with a silver-gray cross section. After spheroidization inoculation, the graphite is spherical or flocculent, and has a certain strength and a certain toughness. Ductile iron has excellent mechanical properties, chemical properties and physical properties, and is widely used in hydraulic and auto parts fields. In recent years, due to the influence of environmental protection factors, most manufacturers have changed to use the wire feeding spheroidization method to produce ductile iron. It can realize on-line control, and determine the length of the core wire according to the sulfur content in the original molten iron; but it also has certain shortcomings: the wire feeding method produces ductile iron, the number of graphite nuclei is small, and the production The casting shrinkage and white mouth tend to be larger. In order to solve the above problems, the wire feeding method is used to produce castings with a spheroidization rate greater than 90%, and an imported sulfur-oxygen inoculant is usually used to provide the oxygen element required for graphite nucleation, increase the amount of graphite, increase the spheroidization rate of the castings, and reduce the whiteness of the castings. tendency. However, using imported sulfur-oxygen inoculants, although the number of graphite increases and the spheroidization rate of castings increases, the procurement cost is high, the procurement cycle is long, and the smelting cost is high.

Therefore, it is expected to develop a method for producing ductile iron with a spheroidization rate greater than 90% by the wire feeding method, which can not only increase the number of graphite nuclei, reduce the shrinkage and whitening tendency of castings, but also reduce the cost.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for producing nodular cast iron with a spheroidization rate greater than 90% by using a wire feeding method, using silicon to react to generate silicon dioxide as a substrate for heterogeneous crystal nuclei, increasing the number of graphite crystal nuclei, and reducing castings. Shrinkage porosity, white mouth tendency, and reduce procurement costs and smelting costs, shorten the procurement cycle.

In order to achieve the above object, the present invention provides a method for producing ductile iron with a spheroidization rate greater than 90% by a wire feeding method, the method comprising the following steps:

1) Add pig iron, silicon carbide, recarburizer, scrap steel, alloy and remaining return charge into the furnace in turn;

2) Sampling when the molten iron in the furnace is melted and the temperature reaches the first preset value;

3) Detecting the composition of the sample, and quenching and tempering according to the detection result, so that the molten iron meets the composition requirements;

4) the temperature of the molten iron is raised to the second preset value, and slag removal and tapping are carried out;

5) transferring the molten iron to a spheroidizing station, when the temperature of the molten iron reaches the third preset value, add 75 ferrosilicon on the surface of the molten iron, and then add a spheroidizing line for spheroidization;

6) after the spheroidization finishes, carry out slag removal to the molten iron, and add a silicon-barium inoculant on the surface of the molten iron after completing the slag removal;

7) The molten iron is introduced into the pouring ladle, and a silicon-barium inoculant is added during pouring.

Optionally, in the step 1), the material ratio in the charging furnace is: pig iron 50% + scrap steel 10% + return charge 40% + silicon carbide + recarburizer + alloy.

Optionally, in the step 2), the first preset value is 1400°C-1420°C.

Optionally, in the step 3), the composition requirements of the molten iron are: C: 3.6-3.9, Si: 1.2-1.4, Mn: 0.2-0.4, P: ≤ 0.05, S: ≤ 0.02, Cr: ≤0.05.

Optionally, in the step 4), the second preset value is 1530°C-1550°C.

Optionally, in the step 5), the third preset value is 1490°C-1510°C.

Optionally, in the step 5), the particle size of the 75 ferrosilicon is 40mm-50mm, the added amount is 0.35%-0.45% of the weight of the molten iron, and the amount of the spheroidizing wire is 0.9% of the weight of the molten iron %-1%.

Optionally, in the step 6), the addition amount of the silicon-barium inoculant is 0.35%-0.45% by weight of the molten iron.

Optionally, in the step 7), the pouring temperature of the molten iron is 1360°C-1380°C, and the amount of the silicon-barium inoculant added during pouring is 0.1%-0.15% by weight of the molten iron.

Optionally, in the step 7), the composition control during the pouring of the molten iron is: C: 3.5-3.8, Si: 2.0-2.3, Mn: 0.2-0.4, P: ≤ 0.05, S: ≤ 0.015, Cr:≤0.05, Mg:0.04-0.055.

The beneficial effects of the present invention are as follows: the method of the present invention adds 75% ferrosilicon on the surface of the molten iron before the spheroidization treatment, and the silicon-barium inoculant added on the surface of the molten iron after the spheroidization is poured into the ladle for pouring. Silicon barium flow inoculant. Using silicon to react to generate silicon dioxide as the substrate of heterogeneous crystal nuclei increases the number of graphite crystal nuclei, reduces the tendency of casting shrinkage and white mouth, and reduces the cost, and the method of the invention is easy to operate and has high efficiency.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Description of drawings

The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of the exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the exemplary embodiments of the present invention. same parts.

Fig. 1 shows a schematic diagram of the metallographic structure of the obtained casting body according to an embodiment of the present invention

Detailed ways

Preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention are described below, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " Rear, Left, Right, Vertical, Horizontal, Top, Bottom, Inner, Outer, Clockwise, Counterclockwise, Axial, The orientations or positional relationships indicated by "radial direction", "circumferential direction", etc. are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the indicated devices or elements. It must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as a limitation of the present invention.

The invention discloses a method for producing nodular cast iron with a spheroidization rate greater than 90% by using a wire feeding method. The method comprises the following steps:

1) Add pig iron, silicon carbide, recarburizer, scrap steel, alloy and remaining return charge into the furnace in turn;

2) the molten iron in the furnace to be charged is clear, and sampling is carried out when the temperature reaches the first preset value;

3) Detect the composition of the sample, and adjust and temper according to the test results, so that the molten iron meets the composition requirements;

4) raising the temperature of molten iron to the second preset value, carrying out slag removal and tapping;

5) Transfer the molten iron to the spheroidizing station, and when the temperature of the molten iron reaches the third preset value, add 75% ferrosilicon on the surface of the molten iron, and then add a spheroidizing line for spheroidization;

6) after the spheroidization finishes, carry out slag removal to the molten iron, and add a silicon-barium inoculant on the surface of the molten iron after completing the slag removal;

7) The molten iron is introduced into the pouring ladle, and the silicon-barium inoculant is added during pouring.

Specifically, in this method, 75% ferrosilicon is added on the surface of the molten iron before the spheroidization, and the silicon-barium inoculant added on the surface of the molten iron after the spheroidization is poured into the pouring ladle to add the silicon-barium flow inoculant. . Using silicon to react to generate silicon dioxide as the substrate of heterogeneous crystal nuclei increases the number of graphite crystal nuclei, reduces the tendency of casting shrinkage and white mouth, and reduces the cost, and the method of the invention is easy to operate and has high efficiency.

As an optional solution, in step 1), the material ratio in the charging furnace is: 50% pig iron+10% scrap steel+40% return charge+silicon carbide+carburizer+alloy.

As an optional solution, in step 2), the first preset value is 1400°C-1420°C.

As an optional solution, in step 3), the composition requirements of the molten iron are: C: 3.6-3.9, Si: 1.2-1.4, Mn: 0.2-0.4, P: ≤ 0.05, S: ≤ 0.02, Cr: ≤ 0.05.

As an optional solution, in step 4), the second preset value is 1530°C-1550°C.

As an optional solution, in step 5), the third preset value is 1490°C-1510°C.

As an optional solution, in step 5), the particle size of 75 ferrosilicon is 40mm-50mm, the addition amount is 0.35%-0.45% by weight of molten iron, and the addition amount of spheroidizing wire is 0.9%-1% by weight of molten iron.

As an optional solution, in step 6), the addition amount of the silicon-barium inoculant is 0.35%-0.45% of the weight of the molten iron.

As an optional solution, in step 7), the pouring temperature of the molten iron is 1360°C-1380°C, and the amount of silicon-barium inoculant added during pouring is 0.1%-0.15% by weight of the molten iron.

As an optional solution, in step 7), the composition of molten iron is controlled as follows: C: 3.5-3.8, Si: 2.0-2.3, Mn: 0.2-0.4, P: ≤ 0.05, S: ≤ 0.015, Cr: ≤ 0.05, Mg: 0.04-0.055.

Example 1

1) Add pig iron, silicon carbide, recarburizer, scrap steel, alloy and remaining returning charge into the furnace in turn, and the material ratio is: pig iron 50% + scrap steel 10% + returning charge 40% + silicon carbide + carburizing agent + alloy ;

2) The molten iron in the furnace to be charged is clear, and sampling is carried out when the temperature reaches 1418°C;

3) Detect the composition of the sample, and conduct quenching and tempering according to the test results, so that the molten iron meets the composition requirements: C: 3.87, Si: 1.29, Mn: 0.26, P: 0.031, S: 0.018, Cr: 0.031;

4) the temperature of molten iron is raised to 1543 ℃, carry out slag removal, tap iron;

5) Transfer the molten iron to the spheroidizing station, and measure the temperature. When the temperature of the molten iron reaches 1509 ° C, add 0.4% of the molten iron weight and 75 ferrosilicon with a particle size of 40mm-50mm on the surface of the molten iron, and then spheroidize, The addition amount of the spheroidizing line is 0.9%-1% of the weight of the molten iron;

6) slagging the molten iron after the spheroidization finishes, and adding a silicon-barium inoculant of 0.4% by weight of the molten iron on the surface of the molten iron after the slagging is completed;

7) The molten iron is introduced into the pouring ladle, and the silicon-barium inoculant of 0.1% by weight of the molten iron is added during pouring, and the composition control during pouring is: C: 3.72, Si: 2.23, Mn: 0.27, P: 0.032, S : 0.013, Cr: 0.029, Mg: 0.048, and the controlled pouring temperature is 1377℃.

The metallographic test results are as follows: the graphite shape is spherical, the spheroidization rate is 93%, the graphite size is 6-7, the pearlite content is 5 beads, and the number of graphite is 338/mm ²

Example 2

1) Add pig iron, silicon carbide, recarburizer, scrap steel, alloy and remaining returning charge into the furnace in turn, and the material ratio is: pig iron 50% + scrap steel 10% + returning charge 40% + silicon carbide + carburizing agent + alloy ;

2) The molten iron in the furnace to be charged is clear, and sampling is carried out when the temperature reaches 1418°C;

3) Detect the composition of the sample, and quench and temper according to the test results, so that the molten iron meets the composition requirements: C: 3.81, Si: 1.32, Mn: 0.3, P: 0.029, S: 0.017, Cr: 0.03;

4) the temperature of molten iron is raised to 1539 ℃, carry out slag removal, tap iron;

5) Transfer the molten iron to the spheroidizing station, and measure the temperature. When the temperature of the molten iron reaches 1509 ° C, add 0.4% of the molten iron weight and 75 ferrosilicon with a particle size of 40mm-50mm on the surface of the molten iron, and then spheroidize, The addition amount of the spheroidizing line is 0.9%-1% of the weight of the molten iron;

6) slagging the molten iron after the spheroidization finishes, and adding a silicon-barium inoculant of 0.4% by weight of the molten iron on the surface of the molten iron after the slagging is completed;

7) The molten iron is introduced into the pouring ladle, and the silicon-barium inoculant of 0.1% by weight of the molten iron is added during pouring, and the composition control during pouring is: C: 3.70, Si: 2.23, Mn: 0.31, P: 0.030, S : 0.013, Cr: 0.029, Mg: 0.048, and the controlled pouring temperature is 1377℃.

The metallographic test results are as follows: the shape of graphite is spherical, the spheroidization rate is 95%, the size of graphite is 6-7, the pearlite content is 5 beads, and the number of graphite is 355 pieces/mm ²

Example 3

1) Add pig iron, silicon carbide, recarburizer, scrap steel, alloy and remaining returning charge into the furnace in turn, and the material ratio is: pig iron 50% + scrap steel 10% + returning charge 40% + silicon carbide + carburizing agent + alloy ;

2) The molten iron in the furnace to be charged is clear, and sampling is carried out when the temperature reaches 1418°C;

3) Detect the composition of the sample, and quench and temper according to the test results, so that the molten iron meets the composition requirements: C: 3.79, Si: 1.33, Mn: 0.32, P: 0.032, S: 0.018, Cr: 0.028;

4) the temperature of molten iron is raised to 1546 ℃, carry out slag removal, tap iron;

5) Transfer the molten iron to the spheroidizing station, and measure the temperature. When the temperature of the molten iron reaches 1501 ° C, add 0.4% of the molten iron weight and 75 ferrosilicon with a particle size of 40mm-50mm on the surface of the molten iron, and then spheroidize, The addition amount of the spheroidizing line is 0.9%-1% of the weight of the molten iron;

6) slagging the molten iron after the spheroidization finishes, and adding a silicon-barium inoculant of 0.4% by weight of the molten iron on the surface of the molten iron after the slagging is completed;

7) The molten iron is introduced into the pouring ladle, and the silicon-barium inoculant of 0.1% by weight of the molten iron is added during pouring, and the composition control during pouring is: C: 3.68, Si: 2.27, Mn: 0.33, P: 0.032, S : 0.013, Cr: 0.028, Mg: 0.047, and the pouring temperature was controlled to be 1377°C.

The metallographic test results are as follows: the shape of graphite is spherical, the spheroidization rate is 92%, the length of graphite is 6-7, the pearlite content is 5 beads, and the number of graphite is 342/mm ² . The metallographic structure of the casting is shown in Figure 1.

The method is simple, easy to operate and high in efficiency; before the spheroidization treatment, 75 ferrosilicon with a particle size of 40mm-50mm is added to the surface of the molten iron with 0.4% weight of the molten iron, and the spheroidization is carried out. After the spheroidization, the molten iron is added to the surface of the molten iron. The silicon-barium inoculant of 0.4% by weight is poured into the pouring ladle, which is suitable for the production of ductile iron castings with a spheroidization rate greater than 90% by the wire-feeding spheroidization method.

Various embodiments of the present invention have been described above, and the foregoing descriptions are exemplary, not exhaustive, and not limiting of the disclosed embodiments. Numerous modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (10)

1. a method for producing nodular cast iron with a spheroidization rate of more than 90% using a wire feeding method, is characterized in that, the method comprises the steps: 1) Add pig iron, silicon carbide, recarburizer, scrap steel, alloy and remaining return charge into the furnace in turn; 2) Sampling when the molten iron in the furnace is melted and the temperature reaches the first preset value; 3) Detecting the composition of the sample, and quenching and tempering according to the detection result, so that the molten iron meets the composition requirements; 4) the temperature of the molten iron is raised to the second preset value, and slag removal and tapping are carried out; 5) transferring the molten iron to a spheroidizing station, when the temperature of the molten iron reaches the third preset value, add 75 ferrosilicon on the surface of the molten iron, and then add a spheroidizing line for spheroidization; 6) after the spheroidization finishes, carry out slag removal to the molten iron, and add a silicon-barium inoculant on the surface of the molten iron after completing the slag removal; 7) The molten iron is introduced into the pouring ladle, and a silicon-barium inoculant is added during pouring. 2. The method for producing ductile iron with a spheroidization rate greater than 90% using a wire feeding method according to claim 1, wherein in the step 1), the material ratio in the feed furnace is: pig iron 50% +Scrap steel 10%+Return charge 40%+Silicon carbide+carburizer+alloy. 3. The method for producing ductile iron with a spheroidization rate greater than 90% by a wire feeding method according to claim 1, wherein in the step 2), the first preset value is 1400°C-1420°C . 4. the method for producing the nodular cast iron with a spheroidization rate greater than 90% according to claim 1, is characterized in that, in described step 3), the composition requirement of described molten iron is: C: 3.6- 3.9, Si: 1.2-1.4, Mn: 0.2-0.4, P: ≤ 0.05, S: ≤ 0.02, Cr: ≤ 0.05. 5. The method for producing ductile iron with a spheroidization rate greater than 90% by a wire feeding method according to claim 1, wherein in the step 4), the second preset value is 1530°C-1550°C . 6. The method for producing ductile iron with a spheroidization rate greater than 90% by a wire feeding method according to claim 1, wherein in step 5), the third preset value is 1490°C-1510°C . 7. the method for producing the nodular cast iron with a spheroidization rate greater than 90% using the wire feeding method according to claim 1, is characterized in that, in the step 5), the granularity of the 75 ferrosilicon is 40mm-50mm, adding The amount is 0.35%-0.45% of the weight of the molten iron, and the added amount of the spheroidizing wire is 0.9%-1% of the weight of the molten iron. 8. the method that adopts wire feeding method to produce the nodular cast iron of greater than 90% according to claim 1, is characterized in that, in described step 6), the add-on of described silicon-barium inoculant is molten iron weight 0.35%-0.45%. 9. The method for producing ductile iron with a spheroidization rate greater than 90% by using a wire feeding method according to claim 1, wherein in the step 7), the pouring temperature of the molten iron is 1360°C-1380°C , the added amount of the silicon-barium inoculant is 0.1%-0.15% of the weight of the molten iron when pouring. 10. the method according to claim 1 that adopts wire feeding method to produce the nodular cast iron with spheroidization rate greater than 90%, is characterized in that, in described step 7), the composition control during described molten iron casting is: C: 3.5-3.8, Si: 2.0-2.3, Mn: 0.2-0.4, P: ≤ 0.05, S: ≤ 0.015, Cr: ≤ 0.05, Mg: 0.04-0.055.

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