A method for producing a ductile cast iron cylinder block

Abstract

The application discloses a production method of a nodular cast iron cylinder body and belongs to the technical field of nodular cast iron. In the application, spheroidizing agents are added into molten iron to form spherical graphite morphology of carbon separated out in the solidification process of the molten iron. The graphite nucleation and spheroidization recession can be promoted and the spheroidization effect can be improved through twice inoculation and stream inoculation treatment processes. Silicon has two important functions, i.e. solid solution strengthening and matrix ferritization. Through high-concentration solid solution strengthening, silicon can enhance the strength of the alloy, improve the uniformity of the alloy and reduce the weight. Solid solution strengthening can change the crystal structure, and the solute atoms dissolved in the solid can cause lattice distortion, which increases the resistance of dislocation movement, makes the sliding difficult, and thus the strength and hardness of the nodular cast iron are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nodular cast iron, and particularly relates to a production method of a nodular cast iron cylinder body. BACKGROUND

[0002] Nodular cast iron is composed of basic elements such as iron, carbon and silicon. After adding nodularizing agent, carbon is precipitated from the iron liquid in the form of spheroidal graphite and solidified into nodular cast iron. The traditional production process is to add a small amount of magnesium to low-sulfur iron liquid, and magnesium can promote the formation of carbide, so silicon also needs to be added to offset the effect of magnesium promoting the formation of carbide. The addition of magnesium makes the graphite form spheroids. In order to improve the strength, the pearlite content is usually increased by adding elements such as Mn, Cu and Sn. However, this method of enhancing strength is achieved by increasing the content of hard phases (pearlite and cementite), which leads to a decrease in elongation with the increase of strength. Unlike traditional nodular cast iron, the strengthening mechanism of high-silicon nodular cast iron is achieved by increasing the silicon content, which can dissolve in ferrite to form a substitutional solid solution and achieve solid solution strengthening effect through lattice distortion. Compared with traditional ferrite-pearlite mixed matrix nodular cast iron, increasing the Si content in nodular cast iron can not only improve the uniformity of its performance and processing performance, but also have better breaking elongation under the condition of equal tensile strength. Nodular cast iron material itself has many advantages, such as low price, good casting performance, good machinability and higher specific strength and fatigue strength. Therefore, the technical personnel in the field urgently need to develop a production method of a nodular cast iron cylinder body to meet the existing use requirements and performance requirements. SUMMARY

[0003] The purpose of the application is to provide a production method of a nodular cast iron cylinder body to solve the existing problems.

[0004] A production method of a nodular cast iron cylinder body, characterized in that it comprises the following steps:

[0005] (1) the mass ratio of 35% to 50% pig iron, 35% to 50% scrap steel, 15% to 25% return material in the smelting furnace for smelting, after smelting, first in the temperature of 1450 to 1470 ℃ liquid iron liquid weight 0.4 to 0.5% of FeMn68C7.0, low frequency stirring uniform; (2) using the dike treatment package into the method, set the dam, dam side first flat iron liquid weight 0.9 to 1.3% of spheroidizing agent, on the spheroidizing agent flat iron liquid weight 0.1 to 0.3% of the first inoculant, on the first inoculant layer of broken ball iron or broken silicon steel sheet, alloy nickel uniform placed package bottom spheroidizing agent opposite concave pit, gap covered with perlite slag collector, spheroidizing agent according to the 1.30% to 1.60% of the iron output, spheroidizing reaction time control 1.5 to 5 min; (3) after spheroidizing treatment into the perlite slag collector repeatedly, after the slag into 0.35 to 0.6% secondary inoculant, one-time into the molten iron; (4) measure the temperature of molten iron, molten iron chemical composition: C3.14 to 3.28%, Si3.4% to 3.8%, Mn0.5%, P0.05%, S0.012%, Mg0.044% to 0.046%, Ni0.5 to 1.0%, pouring temperature in 1300 to 1360 ℃, pouring start synchronous with stream inoculation, according to the process requirements ahead of time to measure the stream inoculant, when pouring, iron liquid weight 0.05% to 0.15% of the stream inoculant into the funnel for pouring stream inoculation, stream inoculant funnel port should be aimed at the pouring of molten iron flow, out of the pit box, box cleaning.

[0006] Further, the step (2) spheroidizing agent is FeSiMg8Re3 or FeSiMg6Re4, particle size is 5 to 20 mm. Graphite spheroidizing treatment: adding spheroidizing agent in the molten iron, so that the carbon precipitated in the solidification process of the molten iron forms the process of mainly spherical graphite. Solid solution strengthening: solid solution atoms enter the interstitial space of the matrix lattice or replace the lattice atoms, causing the lattice to be distorted, resulting in an increase in the resistance to dislocation slip, thereby improving the strength and hardness of the material. This phenomenon is called solid solution strengthening.

[0007] Further, the step (3) secondary inoculant is chemical composition mass fraction Si55 to 60%, Ca0.5 to 3%, Ba4 to 6%, Mn≤0.5%, Cr≤0.5%, P≤0.04%, S≤0.02%. Solid solution strengthening ferritic spheroidal graphite cast iron, mainly through the silicon solid solution strengthening of ferrite matrix of spheroidal graphite cast iron.

[0008] Further, the step (2) first inoculant is 75SiFe, particle size is 0.5 to 1 mm.

[0009] Further, the step (4) stream inoculant particle size is 0.1 to 0.5 mm, chemical composition mass fraction Si72 to 80%, Ca1.0 to 1.5, Al≤2%.

[0010] Further, the step (4) is below 300℃.

[0011] The beneficial effects of the present application are:

[0012] The present application adopts adding spheroidizing agent in the molten iron to form spherical graphite morphology of carbon precipitated during the solidification process of the molten iron. Through twice inoculation and stream inoculation process, the graphite nucleation and spheroidization recession can be promoted, so as to refine the graphite and improve the spheroidization effect. Silicon has two important effects: solid solution strengthening effect and matrix ferritization effect. Through high concentration solid solution strengthening, silicon can enhance the strength of the alloy, improve its uniformity, and reduce the weight. Solid solution strengthening can change the crystal structure, and the solute atoms dissolved in the solid can cause lattice distortion, which increases the resistance of dislocation movement, making sliding difficult, thereby improving the strength and hardness of the ductile cast iron. DETAILED DESCRIPTION

[0013] The present application will be described in detail below with specific examples, but is not limited to the present application. Example 1

[0014] Raw materials and equipment: Zhicheng ZCR91 pouring machine; steel shell electric furnace 1t; new pig iron meets the requirements of GB / T1412-2005, wherein Mn≤0.20, P≤0.020, Ti≤0.050. Scrap steel meets the requirements of GB / T4223-2004, the block size shall not be greater than 240*240mm. The recycled material is limited to ductile cast iron recycled material, and the shot blasting cleaning removes the silt. The silicon iron grade FeSi75 meets the requirements of GB / T2272-2009. The manganese iron grade FeMn68C7.0 meets the requirements of GB / T3795-2014. The rare earth magnesium silicon iron alloy spheroidizing agent grade is Jianke FeSiMg8Re3, the particle size is 5mm, and meets the requirements of GB / T4138-2015; the spheroidizing package adopts 1000kg special spheroidizing package, and the spheroidizing package should be baked to dark red before spheroidizing treatment. The BS-1Al secondary inoculant has a chemical composition of Si60%, Ca3%, Ba6%, Mn≤0.5%, Cr≤0.5%, P≤0.04%, and S≤0.02%. The primary inoculant is 75SiFe, and the particle size is 0.5-1mm. The Hongguan mechanical stream inoculant has a particle size of 0.5mm, and a chemical composition of Si80%, Ca1.5%, and Al≤2%.

[0015] The production method of the ductile cast iron cylinder body comprises the following steps:

[0016] (1) The mass ratio of 50% pig iron, 35% scrap steel, 15% recycled material is smelted in a smelting furnace, and after smelting, 0.5% of FeMn68C7.0 by weight of the molten iron is added to the molten iron at a temperature of 1470°C, and low-frequency stirring is uniform; (2) The dam treatment bag is poured into the method, the dam is set, and 0.9% of the spheroidizing agent by weight of the molten iron is first laid flat on one side of the dam, 0.3% of the primary inoculant by weight of the molten iron is laid flat on the spheroidizing agent, a layer of crushed ball iron scrap is laid on the primary inoculant, the alloy nickel is uniformly placed in the concave pit opposite the spheroidizing agent, the gap is covered with perlite slag collector, the spheroidizing agent is added at 1.6% of the iron output, and the spheroidizing reaction time is controlled for 1.5 min; (3) After spheroidizing treatment, put into perlite slag collector and repeatedly scrape slag, after scraping slag, put into 0.6% secondary inoculant, pour into molten iron at one time; (4) Measure the temperature of the molten iron, the chemical composition of the molten iron: C 3.28%, Si 3.8%, Mn 0.5%, P 0.05%, S 0.012%, Mg 0.044%, Ni 1.0%, pouring temperature is 1360°C, and synchronous stream inoculation is performed at the beginning of pouring, stream inoculant is weighed in advance according to the process requirements, and stream inoculant is poured into the funnel at a rate of 0.15% by weight of the molten iron for stream inoculation. The stream inoculant funnel port should be aligned with the pouring direction of the molten iron, the pit is tapped, and the tapping and cleaning are completed to obtain the product. The pouring is completed safely, smoothly and quickly within the specified time, and three packages are poured at the same time. Each package of molten iron is composed of three people, the main pouring hand is responsible for opening the crane and the pouring object, and the pouring speed control principle is: slow at both ends, fast in the middle, and keep the pouring cup full. High-temperature fast pouring is adopted for thin-walled parts, and low-temperature fast pouring is adopted for thick-walled parts. After the overflow of the water pile, stop for 10 seconds to perform three times of water backfilling. One person pours, one person ignites and blocks slag, and the time from the end of spheroidizing of each package of molten iron to the end of pouring is 15 minutes; before pouring, the slag blocking personnel pushes the slag away from the pot wall, so that it floats with the water, the pot opening insulation cotton is pressed well, and is used for blocking slag. Example 2

[0017] Raw materials and equipment: Y32-500T pouring machine; steel shell electric furnace 1 t; new pig iron meets the requirements of GB / T1412-2005, wherein Mn≤0.20, P≤0.020, Ti≤0.050. Scrap steel meets the requirements of GB / T4223-2004, the block size shall not be greater than 240*240mm. The re-melted material is limited to nodular cast iron re-melted material, and the shot blasting cleaning removes the silt. The ferrosilicon grade FeSi75 meets the requirements of GB / T2272-2009. The ferromanganese grade FeMn68C7.0 meets the requirements of GB / T3795-2014. The rare earth magnesium ferrosilicon inoculant grade is Huatuo FeSiMg6Re4, the particle size is 20mm, and meets the requirements of GB / T4138-2015; the spheroidizing ladle is baked to dark red before spheroidizing treatment. The secondary inoculant is chemical composition mass fraction Si 55%, Ca 0.5%, Ba 4%, Mn≤0.5%, Cr≤0.5%, P≤0.04%, S≤0.02%, and the primary inoculant is 75SiFe with a particle size of 0.5mm. The stream inoculant has a particle size of 0.1mm, and the chemical composition mass fraction is Si 72%, Ca 1.0%, Al≤2%.

[0018] A method for producing a nodular cast iron cylinder block, characterized in that it comprises the following steps:

[0019] (1) In the smelting furnace, smelt 35% pig iron, 50% scrap steel and 25% recycled materials by mass ratio, and then add FeMn68C7.0 with a weight of 0.4% of the molten iron at a temperature of 1450℃, and stir uniformly at low frequency; (2) Use the dike treatment ladle pouring method, set up a dike, first lay 1.3% of the molten iron weight of the spheroidizing agent on one side of the dike, then lay 0.1% of the molten iron weight of the primary inoculant on the spheroidizing agent, and then lay a layer of crushed ball iron scrap on the primary inoculant, place the alloy nickel uniformly in the opposite concave pit of the spheroidizing agent, cover the gap with perlite slag collector, add the spheroidizing agent at 1.30%-1.60% of the iron output, and control the spheroidizing reaction time for 5 minutes; (3) After spheroidizing treatment, put into the perlite slag collector and repeatedly rake the slag, then put in 0.35% of the secondary inoculant and pour it into the molten iron at one time; (4) Measure the temperature of the molten iron, the chemical composition of the molten iron is C 3.14%, Si 3.4%, Mn 0.5%, P 0.05%, S 0.012%, Mg 0.046%, and Ni 0.5%, the pouring temperature is 1300℃, and the synchronous stream inoculation is performed at the beginning of pouring, the stream inoculant is weighed in advance according to the process requirements, the stream inoculant with a weight of 0.05% of the molten iron is put into the funnel for pouring stream inoculation, the stream inoculant funnel port should be aligned with the pouring molten iron stream, the pit is tapped, the tapping and cleaning are completed, and the pouring is safely, smoothly and quickly completed within the specified time, three ladles are poured at the same time, and each ladle of molten iron is composed of three people, the main pouring hand is responsible for opening the crane and the pouring object, and the control principle of the pouring speed is: slow at both ends, fast in the middle, and keep the pouring cup full; high-temperature fast pouring is adopted for thin-walled parts, and low-temperature fast pouring is adopted for thick-walled parts, and the pouring iron water pile overflows for 5 seconds after stopping for secondary water replenishment. One person pours, one person ignites and blocks the slag, and the time from the end of spheroidizing of each ladle of molten iron to the end of pouring is 10 minutes; before pouring, the slag blocking personnel pushes the slag collector away from the wall of the ladle, so that it floats with the water, the ladle port is well pressed with heat preservation cotton, and is used for blocking the slag.

[0020]

[0021] Note: GB / T231.3 Metal Brinell Hardness Test Part 3: Calibration of Standard Hardness Blocks; Tensile Test is performed according to GB / T228.1-2021 Metal Materials Tensile Test Part 1: Room Temperature Test Method; Hardness Test is performed according to GB / T231.1-2018 Metal Materials Brinell Hardness Test Part 1: Test Method.

Claims

1. A method of producing a ductile iron cylinder block, characterized by, The method comprises the following steps: (1) smelting 35-50% pig iron, 35-50% scrap steel and 15-25% return materials in a smelting furnace, and then adding FeMn68C7.0 with a weight of 0.4-0.5% of the molten iron at a temperature of 1450-1470 ℃, and uniformly stirring at low frequency; (2) adopting the dam treatment ladle pouring method, setting a dam, first laying 0.9-1.3% of the molten iron by weight of spheroidizing agent on one side of the dam, laying 0.1-0.3% of the molten iron by weight of primary inoculant on the spheroidizing agent, laying a layer of crushed scrap iron on the primary inoculant, uniformly placing the alloy nickel in the concave surface opposite to the spheroidizing agent, covering the gap with perlite slag collector, adding the spheroidizing agent at 1.30-1.60% of the iron output, and controlling the spheroidizing reaction time to be 1.5-5 min; (3) after the spheroidizing treatment, repeatedly scraping the slag with the perlite slag collector, and then adding 0.35-0.6% of the secondary inoculant to the molten iron; (4) measuring the temperature of the molten iron, and the chemical composition of the molten iron is C 3.14-3.28%, Si 3.4-3.8%, Mn 0.5%, P 0.05%, S 0.012%, Mg 0.044-0.046% and Ni 0.5-1.0%, the pouring temperature is 1300-1360 ℃, and the on-stream inoculation is simultaneously performed at the beginning of pouring, the on-stream inoculant is weighed in advance according to the process requirements, the on-stream inoculant with a weight of 0.05-0.15% of the molten iron is placed in a funnel for on-stream inoculation during pouring, the port of the on-stream inoculant funnel should be aligned with the molten iron flow, the pit is tapped, and the castings are obtained after cleaning; the spheroidizing agent in step (2) is FeSiMg8Re3 or FeSiMg6Re4, and the particle size is 5-20 mm; the secondary inoculant is composed of Si 55-60%, Ca 0.5-3%, Ba 4-6%, Mn≤0.5%, Cr≤0.5%, P≤0.04% and S≤0.02% by mass fraction; and the primary inoculant is 75SiFe, and the particle size is 0.5-1 mm.

2. The method of producing a nodular cast-iron cylinder block according to claim 1, characterized by, The particle size of the on-stream inoculant in step (4) is 0.1-0.5 mm, and the chemical composition of the on-stream inoculant is composed of Si 72-80%, Ca 1.0-1.5% and Al≤2% by mass fraction.

3. The method of producing a nodular cast-iron cylinder block according to claim 1, characterized by, The temperature of the pit tapping and the box is below 300 ℃.

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