CN107326257A - A kind of hi-strength nodular iron section bar and preparation method thereof - Google Patents

Abstract

The invention discloses a high-strength ductile iron profile, which is composed of: C: 3.0-3.3%, Si: 2.2-3.0%, Mn: 0.1-0.3%, P≤0.15%, S≤0.06%, according to the weight percentage, Sb: 0.01-0.015%, _{residual Mg ≥ 0.05%, residual RE} : 0.015-0.018%, the rest is Fe, and the sum of the above weight percentages is 100%. The invention also discloses a preparation method of the above-mentioned high-strength ductile iron profile. The high-strength ductile iron profile of the invention has a tensile strength greater than 600 MPa, uniform hardness, good surface quality, high dimensional accuracy, no casting defects such as sand inclusions, slag inclusions, pores, shrinkage cavities, etc., and good cutting performance. The number of graphite balls in the core of ductile iron profiles is more than 20% higher than that of ordinary ductile iron profiles. The diameter of graphite balls is about 6-7 grades, and there is no obvious 4-5 grades of large-diameter graphite.

Description

A kind of high-strength ductile iron profile and its preparation method

technical field

The invention belongs to the technical field of cast iron material casting, and relates to a high-strength ductile iron profile, and also relates to a preparation method of the ductile iron profile.

Background technique

Ductile iron profiles are high-quality ductile iron blank materials produced by horizontal continuous casting. Due to the advantages of compact structure, good product quality, excellent comprehensive mechanical properties, and excellent processing performance, horizontal continuous casting ductile iron profiles have been widely used in Mechanical, hydraulic, metallurgy, textile, printing and many other fields or industries.

At present, it is difficult to directly adopt the horizontal continuous casting method to produce ductile iron profiles with a tensile strength above 600MPa. The general method is to obtain high-performance ductile iron profiles through ADI austempering. Although ductile iron profiles with high tensile properties above 1000MPa or even 1500MPa can be obtained through ADI treatment, the window of heat treatment is narrow, it is very difficult to control stability, and the cost is high. In addition, the hardness of ductile iron profiles treated by ADI is relatively high, and the machining performance is poor, which also causes some difficulties for subsequent processing.

However, with the rapid development of machining technology, the requirements for the mechanical properties of ductile iron profiles are getting higher and higher, and in order to control production costs, users do not want to add precious metals such as Cu, Ni, Mo or Cr and heat treatment to achieve high Performance, and at the same time, it is hoped that the hardness of the material will not be too high, and it can be processed by subsequent machining. This requires strict control of each link in the horizontal continuous casting production process of cast iron profiles, in order to achieve the requirements of low cost and high performance.

Contents of the invention

The object of the present invention is to provide a high-strength ductile iron profile, which solves the problem of low mechanical properties of the existing ductile iron profile.

Another object of the present invention is to provide a method for preparing the above-mentioned high-strength ductile iron profile.

The technical solution adopted in the present invention is a high-strength ductile iron profile, which is composed of: C: 3.0-3.3%, Si: 2.2-3.0%, Mn: 0.1-0.3%, P≤0.15%, S≤0.06%, Sb: 0.01～0.015%, _residual Mg≥0.05%, _residual RE: 0.015～0.018%, and the rest is Fe.

Another technical solution adopted in the present invention is a preparation method of high-strength nodular iron profiles, specifically implemented according to the following steps:

Step 1, molten iron smelting:

According to the set weight percentage, the amount of silicon brought in by the inoculant is deducted, and the cast ductile iron pig iron, scrap steel, recycled materials, 75% ferrosilicon and SiC required for the original molten iron are weighed, melted into molten iron in an induction furnace, and taken Rapid analysis of the composition of the original molten iron before the furnace to adjust the content of each element in the original molten iron, of which C: 3.0-3.3%, Si: 1.1-1.8%, Mn: 0.1%-0.3%, P≤0.15%, S≤0.06% , the rest is Fe, the sum of the weight percentages of the above components is 100%, and iron is tapped;

In step 2, the molten iron obtained in step 1 is spheroidized and inoculated using a dam type nodular iron ladle;

Step 3, pouring the molten iron obtained in step 2 into the holding furnace, and performing horizontal continuous casting to obtain high-strength ductile iron profiles.

The present invention is also characterized in that,

The order of melting and feeding in step 1 is as follows: first put a part of cast ductile iron pig iron to cover the bottom of the furnace, add SiC after the batch of pig iron is melted, then add the remaining pig iron, scrap steel and returned materials, and press it on SiC above.

The amount of SiC used in step 1 is 0.8-1.1% of the weight of molten iron, and the particle size is 3-10mm.

The melting temperature is 1550-1580°C, the tapping temperature is 1500-1550°C, and the pouring temperature is 1360-1420°C.

Inoculation in step 2 is two inoculations, the first inoculation and spheroidization treatment are carried out at the same time, the second inoculation is carried out after the spheroidization treatment is completed, and the slag is removed. The inoculant is placed on the upper surface of the molten iron in the ladle and waits to Pour into the holding furnace.

The spheroidizing treatment in step 2 is as follows: pour molten iron into the pre-baked ladle, add the Sb-containing nodulizer into the embankment, and cover the nodulizer with the inoculant used for the first inoculation, and then use low Sulfur iron filings are covered on the nodulizer. After compaction, the thickness of the iron filings covering layer is not less than 2-3cm. After tapping the iron, quickly cover the ladle cover. After the nodularization reaction is completed, remove the ladle cover and remove the slag.

The particle size of the primary inoculant is 3-5mm, and the amount of the primary inoculant is 0.3-0.4% of the total weight of the molten iron; the particle size of the secondary inoculant is 1-3mm, and the amount of the secondary inoculant is 0.4-0.5% of the total weight of the molten iron. %.

In step 2, the dosage of the nodulizer is 1.1-1.6%, and the particle size is 15-30mm; the dosage of the inoculant is 0.7-0.9% of the weight of the molten iron.

In step 3, the horizontal continuous casting adopts the "pull-stop-pull" processing method. During the casting process, the rotation speed of the traction motor is 800-1200rpm, the drawing time is 0.2-2.0s, the residence time is 1-35s, and the mold length is 200 ~600mm, the inlet water temperature is room temperature, the outlet water temperature is 50~70°C, and the outlet temperature of the profile crystallizer is controlled at 900~1050°C.

The beneficial effect of the present invention is that the high-strength ductile iron profile material of the present invention has a tensile strength greater than 550 MPa, uniform hardness, good surface quality, high dimensional accuracy, and no casting defects such as sand inclusions, slag inclusions, pores, and shrinkage cavities. The number of graphite balls in the center of the ductile iron profile material is more than 20% higher than that of ordinary ductile iron profiles. The diameter of the graphite balls is about 6-7 grades, and there is no obvious 4-5 grades of large-diameter graphite; the hardness of the ductile iron profiles of the present invention is HB200 ~260, the cutting performance of ductile iron profiles is good, the cutting resistance is small, it can be finished at high speed, and the smoothness of the machined surface is relatively small.

detailed description

The present invention will be described in detail below in combination with specific embodiments.

The invention provides a high-strength ductile iron profile, which is composed of: C: 3.0-3.3%, Si: 2.2-3.0%, Mn: 0.1-0.3%, P≤0.15%, S≤0.06%, Sb: 0.01-0.015%, _{residual Mg ≥ 0.05%, residual RE} : 0.015-0.018%, the rest is Fe, and the sum of the above weight percentages is 100%.

The preparation method of the above-mentioned high-strength ductile iron profile is specifically implemented in the following steps:

Step 1, molten iron smelting:

The molten iron is melted in an intermediate frequency induction furnace. According to the set weight percentage, the amount of silicon brought in by the long-term ferrosilicon inoculant during inoculation is deducted, and the low manganese cast ductile iron pig iron, scrap steel, and recycled materials required for weighing the original molten iron are calculated and weighed. 75% The amount of ferrosilicon and SiC, etc., for molten iron smelting. The order of melting and feeding is as follows: first put in a part of low-manganese cast ductile iron pig iron to cover the bottom of the furnace, and after this batch of pig iron is melted, add SiC with a particle size of 3-10mm at one time, and its weight is 1/2 of the weight of molten iron per furnace. 0.8-1.1% calculation, then add the remaining pig iron, scrap steel and returned materials, and press them on the SiC, until all the materials in the furnace are completely melted; the ferroalloys added in the intermediate frequency induction furnace are calculated according to the burning loss of 10%; After all the ferroalloys are melted, take the original molten iron for rapid analysis of the composition before the furnace, determine and supplement 75% ferrosilicon or recarburizer, and adjust the content of each element in the original molten iron according to the diameter of the nodular iron profile to be produced. Among them, C: 3.0-3.3%, Si: 1.1-1.8%, Mn: 0.1-0.3%, P≤0.15%, S≤0.06%, and the rest is Fe, ready to be baked. The melting temperature is 1550-1580°C, and the tapping temperature is 1500-1550°C.

Step 2, spheroidization and primary incubation:

Choose embankment-type nodular iron ladle for spheroidization treatment, and the ladle requires height/diameter ≥ 1.6. Before the spheroidizing treatment, the hot ladle treatment is carried out, the molten iron is poured into the pre-baked ladle, and then the molten iron is poured back into the electric furnace, and the process is repeated three times. Then, add Sb-containing nodulizers with a total weight of molten iron of 1.1-1.6% and a particle size of 15-30mm into the embankment, and cover the nodulizers with the inoculant used for the first inoculation, with an amount of 0.3-0.4% of the total amount of molten iron Then use low-sulfur iron filings to cover the nodulizer, and the thickness of the covering layer of iron filings after compaction is not less than 2-3cm. Wherein, the particle size of the primary inoculant is 3-5mm. Quickly cover the lid with a special ladle after tapping to ensure the absorption rate of Mg and RE, and indirectly control the _residual Mg ≥ 0.05%, and the _residual RE to 0.015-0.018%. After the spheroidizing reaction is completed, remove the special ladle cover, and then remove the slag for the second inoculation and pouring.

Step 3, Second Breeding:

Weigh the long-acting ferrosilicon inoculant containing Sr and Ba according to the weight of each ladle of molten iron and the amount of Si to be supplemented. The total amount of the primary and secondary inoculants is 0.7-0.9% of the total weight of the molten iron in the ladle. After the spheroidized molten iron is slag removed, the amount of the primary inoculant is deducted, and the amount of the remaining secondary inoculant is 0.4-0.5% of the total amount of molten iron. The particle size of the inoculant is 1-3mm, and it is placed in the iron ladle The upper surface of the water is to be poured into the holding furnace with the flow.

Step 4, Pouring:

Before pouring, use an atomized diesel nozzle to bake the inner wall of the holding furnace for 30-40 minutes until it is bright red, insert a dummy head into the crystallizer, connect the dummy head to the dummy rod, and pull it out by a tractor. The treated molten iron is poured into the holding furnace through the gate of the holding furnace.

Step 5, horizontal continuous casting:

The molten iron is poured into the holding furnace and stays for 1 to 4 minutes, so that the molten iron entering the crystallizer wraps the dummy head, and the dummy is drawn after the crystallization is solidified, and the continuous casting is produced with the "pull-stop-pull" process level. Among them, the rotation speed of the traction motor in the horizontal continuous casting process is 800-1200rpm, the drawing time is 0.2-2.0s, the residence time is 1-35s, the mold length is 200-600mm, the inlet water temperature is room temperature, and the outlet water temperature is 50 ~70°C, the outlet temperature of the profile crystallizer is controlled at 900-1050°C, and the ductile iron profile material is obtained.

Control the drawing speed and profile outlet temperature to prevent furnace leaks, and control the pouring interval of molten iron to no more than 10 minutes to prevent graphite morphology variation and carbides from spheroidizing and incubating recession.

The tensile performance index of the ductile iron profile material of the present invention exceeds the requirements of the LZQT600-3 standard (JB/T 10854-2008 horizontal continuous casting cast iron profile, China Machinery Industry Standard).

The high-strength ductile iron profile material of the invention has a tensile strength greater than 550 MPa, uniform hardness, good surface quality, high dimensional accuracy, and no casting defects such as sand inclusions, slag inclusions, pores, shrinkage cavities, and the like. The number of graphite balls in the center of the ductile iron profile material is more than 20% higher than that of common ductile iron profiles, and the diameter of the graphite balls is about 6 to 7 grades, without obvious 4 to 5 grades of large-diameter graphite; the hardness of the ductile iron profiles of the present invention is HB200～260, the cutting performance of ductile iron profiles is good, the cutting resistance is small, it can be finished at high speed, and the smoothness of the machined surface is relatively small.

The main feature of the preparation method of the ductile iron profile material of the present invention is that SiC is added to the electric furnace during the molten iron smelting process, which is beneficial to increase the content of Si and C. At the same time, the addition of SiC can be used as the core of heterogeneous nucleation, and can also improve The number of nucleated nuclei and, therefore, the number of graphite nodules can be increased. At the same time, due to the increase in the number of graphite spheres, it is beneficial to avoid excessive growth of primary graphite spheres and the appearance of large-diameter primary graphite spheres. This is beneficial to reduce the difference between the internal and external structures of the profile, increase the hardness of the core of the profile, reduce the hardness of the surface layer, and improve the machining performance of the profile. In addition, since the melting point of SiC is 2800°C and its density is much lower than that of iron, its addition method is very critical. If it is added directly into molten iron, it cannot be melted, and the absorption rate of SiC is extremely low, so it cannot be used as the core of heterogeneous nucleation, and It may be removed when it becomes an inclusion or slag. Therefore, the present invention adopts a unique preparation method.

Low magnesium and low rare earth nodulizers containing 1% Sb are used in the spheroidization. After spheroidization, the Sb content in the casting is guaranteed to be about 0.01-0.015%, Mg _residue ≥ 0.05%, and RE _residue 0.015-0.018%, which can improve graphite The roundness of the ball is beneficial to improve performance.

Increase the amount of long-acting ferrosilicon inoculants containing Sr and Ba during the inoculation process, and adopt the secondary inoculation method, which can improve the inoculation effect and prolong the inoculation time, and avoid the long solidification time of large-diameter ductile iron profiles in the production process. Caused by the recession and the emergence of carbides.

In the production process, no precious metals such as Cu, Ni, Mo or Cr are added, so the production cost has no obvious change compared with ordinary ductile iron profiles. In addition, because these precious metal alloy elements are not used, the hardenability of the ductile iron profile of the present invention is basically the same as that of the ordinary ductile iron profile, and there are no complex carbides and acicular austenite in the structure, so the hardness of the material is much lower than that of ADI The hardness of the treatment, and the cutting performance of the material is excellent.

Example 1

Φ35mm ductile iron profile material and its preparation.

Its composition by weight percentage is C: 3.3%, Si: 3.0%, Mn: 0.1%, P: 0.10%, S: 0.06%, Sb: 0.01%, Mg _residual : 0.05%, RE _residual : 0.015%, and the rest is Fe.

Use a 2T medium frequency induction furnace to melt molten iron. According to the above weight percentage composition, deduct the amount of silicon brought in by the long-term ferrosilicon inoculant, calculate the amount of casting pig iron, scrap steel, recycled material and 75% ferrosilicon required for the original molten iron, and the melting and feeding sequence Put in a part of low-manganese cast ductile iron pig iron in order to cover the bottom of the furnace. After this batch of pig iron is melted, add SiC with a particle size of 3mm at one time. The weight is calculated according to 0.8% of the weight of molten iron in each furnace, and then Add the remaining pig iron, scrap steel and returned materials, and press them on the SiC until all the materials in the furnace are completely melted; the ferroalloys added in the intermediate frequency induction furnace are calculated according to the burning loss of 10%; after all the ferroalloys are melted, take Carry out rapid analysis of the composition of the original molten iron before the furnace, determine and supplement 75% ferrosilicon or recarburizer, and produce the diameter of ductile iron profiles according to the needs, adjust the composition of C, Si, Mn, P, S in the original molten iron to achieve Request, ready to bake. The melting temperature is 1550°C, and the tapping temperature is 1520°C. Carry out a quick pre-furnace analysis and composition adjustment before each furnace release, and recarburizers need to be added when appropriate.

Before tapping, the embankment-type nodular iron ladle with a tapping capacity of 300kg and a height/diameter ratio of 1.6 is pre-baked, and then scalded; nodularizers containing Sb are selected for nodularization, and the dosage is 1.1% of the total weight of molten iron. %, particle size is 15mm. Add the nodulizer into the embankment, and cover the nodulizer with the inoculant used in the first inoculation, the dosage is 0.3% of the total weight of molten iron, and then cover the nodulizer with low-sulfur iron filings, and the iron filings after compaction The thickness of the covering layer is not less than 2cm. Wherein, the particle size of the primary inoculant is 3mm. Quickly cover the lid with a special ladle after tapping to ensure the absorption rate of Mg and RE, and indirectly control the _residual Mg to 0.05-0.06%, and the _residual RE to 0.016-0.018%. After the spheroidizing reaction is completed, remove the special ladle cover, remove the slag, and prepare for pouring.

According to the weight of each ladle of molten iron, weigh the long-acting ferrosilicon inoculant containing Sr and Ba according to the amount of Si to be added, the total amount of the primary and secondary inoculants is 0.7% of the total amount of molten iron in the ladle, and the secondary The particle size of the inoculant is 1mm. After the spheroidized molten iron is slag removed, the amount of the primary inoculant is deducted, and the remaining 0.4% inoculant is placed on the upper surface of the molten iron in the ladle. Bake the holding furnace with an atomized diesel nozzle for 30 minutes, insert the dummy head into the crystallizer, pour the treated molten iron into the holding furnace through the gate of the holding furnace, and the pouring temperature is 1420°C.

The molten iron is poured into the holding furnace and stays for 1 minute, so that the molten iron entering the crystallizer wraps the dummy head, and the dummy is drawn after the crystallization is solidified, and the continuous casting is produced with the "pull-stop-pull" process level. Among them, the rotation speed of the traction motor in the horizontal continuous casting process is 800rpm, the drawing time is 0.2s, the residence time is 1s, the mold length is 200mm, the inlet water temperature is room temperature, the outlet water temperature is 50-70°C, and the profile crystallizer outlet temperature Controlled at 900°C, the ductile iron profile material can be obtained.

Control the drawing speed and profile outlet temperature to prevent furnace leaks, and control the pouring interval of molten iron to no more than 10 minutes to prevent graphite morphology variation and carbides from spheroidizing and incubating recession.

The Φ35mm ductile iron profile material prepared in Example 1 is sampled at the center, the tensile strength is 620MPa, the elongation is 3.5%, the hardness is HB225～245, and the tensile performance index exceeds the LZQT600-3 standard (JB/T 10854 -2008 horizontal continuous casting cast iron profiles, China Machinery Industry Standard) requirements.

Example 2

Φ145mm ductile iron profile material and its preparation.

Its composition by weight percentage is: C: 3.2%, Si: 2.6%, Mn: 0.2%, P: 0.13%, S: 0.04%, Sb: 0.012%, Mg _residual : 0.06%, RE _residual : 0.016%, and the rest For Fe.

Use a 3T intermediate frequency induction furnace to melt molten iron. According to the above weight percentage composition, deduct the amount of silicon brought in by the long-term ferrosilicon inoculant, calculate the amount of casting pig iron, scrap steel, recycled material and 75% ferrosilicon required for the original molten iron, and the order of melting and feeding Put in a part of low-manganese cast ductile iron pig iron in order to cover the bottom of the furnace. After the batch of pig iron is melted, add SiC with a particle size of 10mm at one time. The weight is calculated according to 0.9% of the weight of molten iron in each furnace, and then Add the remaining pig iron, scrap steel and returned materials, and press them on the SiC until all the materials in the furnace are completely melted; the ferroalloys added in the intermediate frequency induction furnace are calculated according to the burning loss of 10%; after all the ferroalloys are melted, take Carry out rapid analysis of the composition of the original molten iron before the furnace, determine and supplement 75% ferrosilicon or recarburizer, and adjust the composition of C, Si, Mn, P, and S in the original molten iron according to the diameter of the ductile iron profile to be produced. Meet the requirements, ready to bake. The melting temperature is 1550°C-1580°C, and the tapping temperature is 1500-1530°C. Carry out a quick pre-furnace composition analysis and composition adjustment before each furnace release, and recarburizers need to be added when appropriate.

Before tapping, the dike-type nodular iron ladle with a tapping capacity of 600kg and a height/diameter ratio of 1.6 is pre-baked, and then scalded; nodularizers containing Sb are selected for nodularization, and the dosage is 1.6% of the total weight of molten iron. %, the particle size is 20mm. Add the nodulizer into the embankment, and cover the nodulizer with the inoculant used in the first inoculation, the dosage is 0.4% of the total weight of molten iron, and then cover the nodulizer with low-sulfur iron filings, and cover the iron filings after compaction The thickness of the layer is not less than 2cm. Wherein, the particle size of the primary inoculant is 5mm. Cover the ladle with a special ladle lid quickly after tapping during spheroidization, so as to ensure the absorption rate of Mg and RE, and indirectly control the _residual Mg to 0.05-0.06%, and the _residual RE to 0.016-0.018%. After the spheroidizing reaction is completed, remove the special ladle cover, remove the slag, and prepare for pouring.

According to the weight of each ladle of molten iron, weigh the long-acting ferrosilicon inoculant containing Sr and Ba according to the amount of Si to be added, the total amount of the primary and secondary inoculants is 0.9% of the amount of molten iron in the ladle, and the particle size of the inoculant is 5mm. After the spheroidized molten iron is slag removed, the amount of the primary inoculant is deducted, and the remaining 0.5% inoculant is placed on the upper surface of the molten iron in the ladle. Bake the holding furnace with an atomized diesel nozzle for 40 minutes, insert the dummy head into the crystallizer, pour the treated molten iron into the holding furnace through the gate of the holding furnace, and the pouring temperature is 1400°C.

The molten iron is poured into the holding furnace and stays for 4 minutes, so that the molten iron entering the crystallizer wraps the dummy head, and the dummy is drawn after the crystallization is solidified, and the continuous casting is produced with the "pull-stop-pull" process level. Among them, the rotation speed of the traction motor in the horizontal continuous casting process is 900rpm, the drawing time is 2.0s, the residence time is 35s, the crystallizer length is 350mm, the inlet water temperature is room temperature, the outlet water temperature is 70°C, and the outlet temperature of the profile crystallizer is controlled at 1050°C, the ductile iron profile material is obtained.

Control the drawing speed and profile outlet temperature to prevent furnace leaks, and control the pouring interval of molten iron to no more than 10 minutes to prevent graphite morphology variation and carbides from spheroidizing and incubating recession.

The Φ145mm ductile iron profile material prepared in Example 2 is sampled at 1/2 radius, the tensile strength is 600MPa, the elongation is 4%, the hardness is HB225～250, and the tensile performance index exceeds the LZQT600-3 standard (JB /T10854-2008 horizontal continuous casting cast iron profiles, China Machinery Industry Standard) requirements.

Example 3

Φ320mm ductile iron profile material and its preparation.

Its composition by weight percentage is: C: 3.0%, Si: 2.3%, Mn: 0.3%, P: 0.10%, S: 0.03%, Sb: 0.015%, Mg _residue : 0.07%, RE _residue : 0.018%, and the rest For Fe.

Use a 5T intermediate frequency induction furnace to melt molten iron. According to the above weight percentage composition, deduct the amount of silicon brought in by the long-term ferrosilicon inoculant, calculate the amount of casting pig iron, scrap steel, recycled material and 75% ferrosilicon required for the original molten iron, and the order of melting and feeding Put in a part of low-manganese cast ductile iron pig iron in order to cover the bottom of the furnace. After the batch of pig iron is melted, add SiC with a particle size of 7mm at one time. The weight is calculated as 0.9% of the weight of molten iron in each furnace, and then Add the remaining pig iron, scrap steel and returned materials, and press them on the SiC until all the materials in the furnace are completely melted; the ferroalloys added in the intermediate frequency induction furnace are calculated according to the burning loss of 10%; after all the ferroalloys are melted, take Carry out rapid analysis of the composition of the original molten iron before the furnace, determine and supplement 75% ferrosilicon or recarburizer, and adjust the composition of C, Si, Mn, P, and S in the original molten iron according to the diameter of the ductile iron profile to be produced. Meet the requirements, ready to bake. The melting temperature is 1565°C, and the tapping temperature is 1515°C. Carry out a quick pre-furnace composition analysis and composition adjustment before each furnace release, and recarburizers need to be added when appropriate.

Before tapping, the embankment-type nodular iron ladle with a tapping capacity of 1000kg and a height/diameter ratio of 1.6 is pre-baked, and then scalded; nodularizers containing Sb are used for nodularization, and the dosage is 1.3% of the total weight of molten iron. %, particle size is 23mm. Add the nodulizer into the embankment, and cover the nodulizer with the primary inoculant, the amount is 0.35% of the total weight of molten iron, and then cover the nodulizer with low-sulfur iron filings, and the iron filings cover the layer after compaction The thickness is not less than 2.5cm. Wherein, the particle size of the primary inoculant is 4 mm. Cover the ladle with a special ladle lid quickly after tapping during spheroidization to ensure the absorption rate of Mg and RE, and indirectly control the _residual Mg to 0.05-0.06% and the _residual RE to 0.016-0.018%. After the spheroidizing reaction is completed, remove the special ladle cover, remove the slag, and prepare for pouring.

According to the weight of each ladle of molten iron, weigh the long-acting ferrosilicon inoculant containing Sr and Ba according to the amount of Si to be added, the total amount of the primary and secondary inoculants is 0.8% of the amount of molten iron in the ladle, and the secondary inoculant The particle size is 2mm. After the spheroidized molten iron is slag removed, the amount of the primary inoculant is deducted, and the remaining 0.45% inoculant is placed on the upper surface of the molten iron in the ladle. Bake the holding furnace with an atomized diesel nozzle for 35 minutes, insert the dummy head into the crystallizer, pour the treated molten iron into the holding furnace through the gate of the holding furnace, and the pouring temperature is 1380°C.

The molten iron is poured into the holding furnace and stays for 2 minutes, so that the molten iron entering the crystallizer wraps the dummy head, and the dummy is drawn after the crystallization is solidified, and the continuous casting is produced with the "pull-stop-pull" process level. Among them, the rotation speed of the traction motor in the horizontal continuous casting process is 1200rpm, the drawing time is 1.6s, the residence time is 18s, the crystallizer length is 600mm, the inlet water temperature is room temperature, the outlet water temperature is 60°C, and the profile crystallizer outlet temperature is controlled at 975°C, the ductile iron profile material is obtained.

Control the drawing speed and profile outlet temperature to prevent furnace leaks, and control the pouring interval of molten iron to no more than 10 minutes to prevent graphite morphology variation and carbides from spheroidizing and incubating recession.

The Φ320mm ductile iron profile material prepared in Example 3 is sampled at 1/2 radius, the tensile strength is 600MPa, the elongation is 3.5%, the hardness is HB215～260, and the tensile performance index exceeds the LZQT600-3 standard (JB /T10854-2008 horizontal continuous casting cast iron profiles, China Machinery Industry Standard) requirements.

Claims (10)

1. A high-strength ductile iron profile, characterized in that, by weight percentage, it is composed of: C: 3.0-3.3%, Si: 2.2-3.0%, Mn: 0.1-0.3%, P≤0.15%, S≤0.06 %, Sb: 0.01-0.015%, _{residual Mg ≥ 0.05%, residual RE} : 0.015-0.018%, the rest is Fe, and the sum of the above composition weight percentages is 100%. 2. A preparation method for high-strength nodular iron profiles, characterized in that, it is specifically implemented in the following steps: Step 1, molten iron smelting: According to the set weight percentage, the amount of silicon brought in by the inoculant is deducted, and the cast ductile iron pig iron, scrap steel, recycled materials, 75% ferrosilicon and SiC required for the original molten iron are weighed, melted into molten iron in an induction furnace, and taken Rapid analysis of the composition of the original molten iron before the furnace to adjust the content of each element in the original molten iron, of which C: 3.0-3.3%, Si: 1.1-1.8%, Mn: 0.1%-0.3%, P≤0.15%, S≤0.06% , the rest is Fe, the sum of the weight percentages of the above components is 100%, and iron is tapped; In step 2, the molten iron obtained in step 1 is spheroidized and inoculated using a dam type nodular iron ladle; Step 3, pouring the molten iron obtained in step 2 into the holding furnace, and performing horizontal continuous casting to obtain high-strength ductile iron profiles. 3. the preparation method of a kind of high-strength nodular iron profile according to claim 2, is characterized in that, in described step 1, melting and charging order is successively: first put into a part of cast nodular iron pig iron, to cover the bottom of the furnace It is advisable to add SiC after the batch of pig iron is melted, and then add the remaining pig iron, scrap steel and furnace charge, and press it on top of SiC. 4. A method for preparing a high-strength ductile iron profile according to claim 2, characterized in that the amount of SiC in the step 1 is 0.8-1.1% of the weight of molten iron, and the particle size is 3-10mm. 5. A method for preparing high-strength ductile iron profiles according to claim 2, characterized in that the melting temperature is 1550-1580°C, the tapping temperature is 1500-1550°C, and the pouring temperature is 1360-1420°C . 6. The preparation method of a kind of high-strength nodular iron profile according to claim 2, characterized in that, inoculation in said step 2 is two inoculations, the first inoculation and nodularization treatment are carried out simultaneously, and the second inoculation After the spheroidization treatment is completed and the slag is removed, the inoculant is placed on the upper surface of the molten iron in the ladle and poured into the holding furnace with the flow. 7. The preparation method of a kind of high-strength nodular iron profile according to claim 6, characterized in that, the spheroidizing treatment in the step 2 is specifically: pouring molten iron into a pre-baked ladle, adding Add Sb nodulizer into the embankment, cover the nodulizer with the inoculant used for the first inoculation, and then cover the nodulizer with low-sulfur iron filings. After compaction, the thickness of the iron filings covering layer is not less than 2-3cm , After the iron is tapped, quickly cover the ladle cover. After the spheroidization reaction is completed, remove the ladle cover and remove the slag. 8. A method for preparing high-strength ductile iron profiles according to claim 6, characterized in that the particle size of the primary inoculant is 3-5mm, and the amount of the primary inoculant is 0.3-0.4% of the total weight of molten iron The particle size of the secondary inoculant is 1-3mm, and the consumption of the secondary inoculant is 0.4-0.5% of the total weight of molten iron. 9. A method for preparing high-strength nodular iron profiles according to claim 2, characterized in that, in the step 2, the dosage of the nodularizing agent is 1.1 to 1.6%, and the particle size is 15 to 30 mm; the dosage of the inoculant is 0.7-0.9% of the weight of molten iron. 10. The preparation method of a high-strength ductile iron profile according to claim 2, characterized in that, in the step 3, the horizontal continuous casting adopts the processing method of "pull-stop-pull", and the rotation speed of the traction motor during the casting process is 800~1200rpm, drawing time 0.2~2.0s, residence time 1~35s, crystallizer length 200~600mm, inlet water temperature 50~70℃, profile crystallizer outlet temperature controlled at 900～1050℃.