Control method for increasing number of graphite nodule by solid solution strengthening ferrite nodular cast iron with thick and large cross section

Abstract

The invention discloses a control method for increasing the number of graphite nodules by solid solution strengthening ferrite nodular cast iron with a thick and large cross section, which comprises the following steps: selecting materials: 50-70 percent of pig iron and 30-50 percent of scrap steel; smelting: adding the materials into an electric furnace for smelting, wherein the tapping temperature of the molten iron is 1420-1450 DEG C; spheroidizing: adding a spheroidizing agent, adding a covering agent on the spheroidizing agent, and then spheroidizing, wherein the spheroidizing temperatureis 1420-1450 DEG C; inoculating: adding a silicon-aluminum-calcium-barium type inoculant during a primary inoculation, and respectively adding the inoculant on the surface of the covering agent and the other side of a ladle dam before tapping, wherein the distribution proportion is 50 percent; adding a trace amount of alloy Sb along with the flow of the molten iron during casting, wherein the adding amount of the alloy Sb is 0.003-0.005% of the total amount of the molten iron, molding, casting and cooling: ensuring that the casting opening temperature is controlled to be <= 300 DEG C, and thecasting is obtained by air cooling after the casting is opened. The control method has the advantages of obtaining higher number of the graphite nodules, ensuring a metallographic structure and goodconsistency of performance indexes, thereby improving the quality of the castings and prolonging the service life.

Description

technical field

[0001] The invention relates to the technical field of casting metals, in particular to a control method for increasing the number of graphite balls in solid-solution strengthened ferritic nodular cast iron with thick and large sections. Background technique

[0002] In the current national standard "GB / T1348-2009 Ductile Iron Castings", 7.5.1 graphite form requires that the graphite is mainly spherical, and the nodularization level is not lower than the nodularization level 4 stipulated in GB / T9441. If there are special requirements, nodularization The level is agreed upon by both parties. Spheroidization level 4 refers to the spheroidization rate ≥ 70%. In Appendix F, the spheroidization rate is defined as the percentage of spherical graphite and flocculent graphite. At the same time, it is mentioned in the appendix that the spheroidization level is not only related to the measurement method, but also related to The material grade of the casting is related...

Examples

Embodiment 1

[0044] A control method for increasing the number of graphite nodules in solid-solution strengthened ferritic nodular cast iron with thick and large sections, the steps of the method include:

[0045] (1) Material selection: pig iron, scrap steel; low rare earth magnesium ferrosilicon alloy nodulizer, covering agent with component content C≤0.3%, Mn≤0.30%, P≤0.035%, S:≤0.03%, and the balance is Fe Silicon steel sheet, the primary inoculant chooses silicon aluminum calcium barium inoculant, and the flow inoculant uses silicon aluminum inoculant;

[0046] (2) Smelting: pig iron and scrap steel are put into electric furnace for smelting to obtain molten iron, and the temperature of molten iron is 1420-1450°C;

[0047] (3) Spheroidizing treatment: Add low rare earth magnesium ferrosilicon alloy spheroidizing agent into the ladle, wherein the composition of the spheroidizing agent is: Mg 5.5-6.2%, Si 40-50%, RE 0.15-0.40%, and the rest is Iron, the addition of nodulizer is 1.0% of...

Embodiment 2

[0059] Guaranteed to obtain the element composition of molten iron with fixed composition as follows: C: 3.65%, Si: 3.70%, Mn: 0.18%, P: ≤0.030%, S: 0.012%, Sb: 0.004%, Mg: 0.04%, RE≤0.010 %, the rest is Fe. In addition, the cooling conditions of the present embodiment are molded according to the graphite chilled iron mode, and the metallographic photo of the casting obtained is as attached Figure 5-6 Shown: After the test block is chilled by the graphite cold iron, the shape of the graphite balls, the number of graphite balls and the distribution of graphite at the edge and the center are more uniform, and the properties of the edge and the center are closer. This is because the cold iron makes the whole test block The cooling capacity is improved synchronously, the synchronization of austenite phase transformation becomes better, and the phase transformation proceeds in the direction that is conducive to the formation of graphite and ferrite. The castings use 250 square tes...

Embodiment 3

[0062] Guaranteed to obtain the elemental composition of molten iron with a fixed composition as follows: C: 3.50%, Si: 3.80%, Mn: 0.15%, P: ≤0.030%, S: 0.015%, Sb: 0.004%, Mg: 0.035%, RE≤0.010 %, the rest is Fe.

[0063] In addition, the cooling conditions of the present embodiment are molded according to the cast iron chill (material is QT400-18AL), and the metallographic photo of the casting obtained is as attached Figure 7-8 As shown: the chilling effect of cast iron chills is better than that of graphite chills. When the test block is solidified, the austenite phase changes into graphite and ferrite with better synchronization, so the number of graphite balls is more, and the mechanical properties of the material change. better.

[0064] as attached Figure 1-2 , the specific casting adopts 250 square test blocks (the length, width and height of the test block size are 250×250×250mm), the chill iron size is 100×100×80mm, and the chill iron spacing is 30mm; a 400 square...

technical field

[0001] The invention relates to the technical field of casting metals, in particular to a control method for increasing the number of graphite balls in solid-solution strengthened ferritic nodular cast iron with thick and large sections. Background technique

[0002] In the current national standard "GB / T1348-2009 Ductile Iron Castings", 7.5.1 graphite form requires that the graphite is mainly spherical, and the nodularization level is not lower than the nodularization level 4 stipulated in GB / T9441. If there are special requirements, nodularization The level is agreed upon by both parties. Spheroidization level 4 refers to the spheroidization rate ≥ 70%. In Appendix F, the spheroidization rate is defined as the percentage of spherical graphite and flocculent graphite. At the same time, it is mentioned in the appendix that the spheroidization level is not only related to the measurement method, but also related to The material grade of the casting is related...

Examples

Embodiment 1

[0044] A control method for increasing the number of graphite nodules in solid-solution strengthened ferritic nodular cast iron with thick and large sections, the steps of the method include:

[0045] (1) Material selection: pig iron, scrap steel; low rare earth magnesium ferrosilicon alloy nodulizer, covering agent with component content C≤0.3%, Mn≤0.30%, P≤0.035%, S:≤0.03%, and the balance is Fe Silicon steel sheet, the primary inoculant chooses silicon aluminum calcium barium inoculant, and the flow inoculant uses silicon aluminum inoculant;

[0046] (2) Smelting: pig iron and scrap steel are put into electric furnace for smelting to obtain molten iron, and the temperature of molten iron is 1420-1450°C;

[0047] (3) Spheroidizing treatment: Add low rare earth magnesium ferrosilicon alloy spheroidizing agent into the ladle, wherein the composition of the spheroidizing agent is: Mg 5.5-6.2%, Si 40-50%, RE 0.15-0.40%, and the rest is Iron, the addition of nodulizer is 1.0% of...

Embodiment 2

[0059] Guaranteed to obtain the element composition of molten iron with fixed composition as follows: C: 3.65%, Si: 3.70%, Mn: 0.18%, P: ≤0.030%, S: 0.012%, Sb: 0.004%, Mg: 0.04%, RE≤0.010 %, the rest is Fe. In addition, the cooling conditions of the present embodiment are molded according to the graphite chilled iron mode, and the metallographic photo of the casting obtained is as attached Figure 5-6 Shown: After the test block is chilled by the graphite cold iron, the shape of the graphite balls, the number of graphite balls and the distribution of graphite at the edge and the center are more uniform, and the properties of the edge and the center are closer. This is because the cold iron makes the whole test block The cooling capacity is improved synchronously, the synchronization of austenite phase transformation becomes better, and the phase transformation proceeds in the direction that is conducive to the formation of graphite and ferrite. The castings use 250 square tes...

Embodiment 3

[0062] Guaranteed to obtain the elemental composition of molten iron with a fixed composition as follows: C: 3.50%, Si: 3.80%, Mn: 0.15%, P: ≤0.030%, S: 0.015%, Sb: 0.004%, Mg: 0.035%, RE≤0.010 %, the rest is Fe.

[0063] In addition, the cooling conditions of the present embodiment are molded according to the cast iron chill (material is QT400-18AL), and the metallographic photo of the casting obtained is as attached Figure 7-8 As shown: the chilling effect of cast iron chills is better than that of graphite chills. When the test block is solidified, the austenite phase changes into graphite and ferrite with better synchronization, so the number of graphite balls is more, and the mechanical properties of the material change. better.

[0064] as attached Figure 1-2 , the specific casting adopts 250 square test blocks (the length, width and height of the test block size are 250×250×250mm), the chill iron size is 100×100×80mm, and the chill iron spacing is 30mm; a 400 square...

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