Inoculating agent for improving molten iron in heat preservation pouring ladle and preparation method of nucleating agent

Abstract

The invention relates to the technical field of inoculants, in particular to an inoculant for improving molten iron in a heat preservation pouring ladle and a preparation method of the inoculant, and the inoculant comprises the following components in parts by weight: 1-3 parts of Mg, 0.2-1.5 parts of rare earth elements, 0.2-1.2 parts of Sr, 60-70 parts of Si and the balance of iron and impurities difficult to remove. Magnesium ingots are weighed and put into an intermediate frequency furnace to be heated and smelted; ferrosilicon and rare earth are weighed, ferrosilicon nodulizing agents and rare earth nodulizing agents are sequentially added into a feeding barrel in advance, the feeding barrel is hoisted to the position over a hearth through a traveling crane, and a discharging opening is opened for feeding; after the materials in the furnace are molten, adding the weighed strontium, and after the rest materials are completely molten and the temperature meets the requirement, adding the strontium to smelt into a uniform inoculant; and adding strontium for 30 seconds, immediately tapping into an ingot mould, pouring into an alloy block, crushing the alloy block, screening according to the required granularity, and packaging according to the requirement after screening. The molten iron nucleation capacity can be effectively improved, the supercooling tendency, the chilling tendency, the shrinkage porosity tendency and the shrinkage cavity tendency are improved, and therefore the product quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of inoculants, in particular to an inoculant for improving the heat preservation of molten iron in a pouring ladle and a preparation method thereof. Background Art

[0002] With the considerable development of cast iron equipment in recent years, many advanced equipment have been replaced, reducing labor, improving efficiency, improving working conditions, and improving process requirements. On this basis, casting equipment has also developed greatly.

[0003] During pouring, the temperature of the molten iron in general pouring equipment decreases at a rate of about 10℃ / min. For example, after pouring for 7-8 minutes, the overall molten iron will drop by about 80℃. High-temperature molten iron at the head and low-temperature molten iron at the tail will cause different casting defects, which are difficult to solve perfectly at the technical level. In order to solve this problem, many foundries currently use a new type of insulation pouring ladle, which has an insulation effect while pouring molten iron, and can control the pouring temperature within the range of ±10℃. This greatly improves the impact of molten iron temperature on castings.

[0004] In order to keep the molten iron warm, the insulated casting ladle requires a certain amount of molten iron in the casting ladle, and the amount of molten iron should be greater than the amount of molten iron in the transfer ladle, and then the transfer ladle is used to continuously replenish the molten iron. As the molten iron in the casting ladle stays in the casting ladle for too long, the molten iron has poor nucleation ability, and the tendency of overcooling, chilling, shrinkage, and shrinkage cavities increases. This phenomenon is especially obvious in gray cast iron. The cast gray iron products have coarse graphite, a high proportion of chilling, and obvious shrinkage and shrinkage cavities. The defective rate is seriously exceeded, resulting in the inability to produce.

[0005] At present, the most important means to improve the overcooling of gray cast iron is inoculation. Inoculation mainly refers to a process of improving the performance of molten iron by adding inoculants before the molten iron enters the mold cavity. Due to the design of the insulation casting ladle, inoculation can no longer be carried out in the insulation casting ladle, and can only be carried out in the transfer ladle or in the flow during pouring. The inoculant used in the transfer ladle has been tested in large quantities, and a variety of inoculants such as ordinary silicon barium, silicon strontium, silicon zirconium, and high barium have been used for trial. It was found that the high barium (barium>10 parts) with the longest inoculation time is difficult to completely solve the problem of insufficient inoculation effect of molten iron in the insulation casting ladle. Flow inoculation is the last inoculation of molten iron into the mold cavity, and the final inoculation addition amount is 0.1-0.2 parts, but it can play a good inoculation effect. On this basis, we have also tried a variety of current mainstream inoculants such as ferrosilicon, silicon barium, high barium, and silicon strontium, and found that the effects are very limited. Therefore, it is very important to invent a new inoculant that can effectively inhibit the inoculation decline of gray cast iron products caused by the long time of the insulation pouring ladle. If this problem cannot be solved, the insulation pouring ladle will be difficult to promote and apply in casting production. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an inoculant for improving the heat preservation of molten iron in a pouring ladle to solve the above problems.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: an inoculant for improving the molten iron conditions of a heat-insulating casting ladle, the inoculant is composed of the following parts by weight: magnesium: 1-3 parts, rare earth elements: 0.2-1.5 parts, strontium: 0.2-1.2 parts, silicon: 60-70 parts, and the rest is iron and impurities that are difficult to remove.

[0008] As a further embodiment of the present invention, the rare earth element is lanthanum or cerium.

[0009] As a further solution of the present invention, the inoculant is a granular ferrosilicon-based alloy, and the ferrosilicon-based alloy has a particle size of 0.2-0.8 mm.

[0010] As a further solution of the present invention, the silicon element in the inoculant exists in the form of a compound of silicon and iron; the rare earth element in the inoculant exists in the form of a compound of rare earth and silicon.

[0011] A method for preparing an inoculant for improving the molten iron condition of a heat-insulating casting ladle, the specific steps are as follows: Step 1, weigh the magnesium ingot and put it into the medium frequency furnace for heating and melting; Step 2: weigh ferrosilicon and rare earth, and add them into the charging bucket in the order of ferrosilicon and rare earth spheroidizer in advance; the charging bucket is hoisted to the top of the furnace by a crane, and the discharge port is opened to add the materials; Step 3: After the material in the furnace is melted, add the weighed strontium, and after the remaining materials are completely melted and the temperature reaches the requirement, add strontium and smelt into a uniform inoculant; Step 4: Add strontium for 30 seconds and then immediately tap the iron into an ingot mold to form an alloy block; Step 5: crushing the alloy block and screening it according to the required particle size; Step six: pack as required after screening.

[0012] As a further solution of the present invention, the smelting time of the rare earth inoculant is 40-60 minutes. Strontium is an active element and will be rapidly oxidized when added into the furnace. Therefore, the strontium should be poured out as soon as possible after melting. Through experimental determination, the alloy is produced in 30 seconds, and the uniformity, absorption rate and loss rate of strontium reach the most balanced state.

[0013] As a further solution of the present invention, the medium frequency furnace is configured as a medium frequency melting furnace with a frequency of 10-40 kHz and a power of 200-400 kW.

[0014] As a further solution of the present invention, the temperature in the furnace in step three is 1400-1450°C.

[0015] Since the present invention adopts the above technical solution, the present invention has the advantages and positive effects that: the present invention can effectively improve the nucleation ability of molten iron, improve the tendency of supercooling, chilling, shrinkage and shrinkage cavity, thereby improving product quality. DETAILED DESCRIPTION

[0016] Example 1 The invention discloses an inoculant for improving the heat preservation of molten iron in a casting ladle. The inoculant is composed of the following parts by weight: 1 part of Mg, 0.2 parts of lanthanum, 0.2 parts of Sr, 60 parts of Si, and the rest of iron and impurities that are difficult to remove. The inoculant is a granular ferrosilicon-based alloy with a particle size of 0.2-0.8 mm. The silicon element in the inoculant exists in the form of a compound of silicon and iron. The rare earth element in the inoculant exists in the form of a compound of rare earth and silicon.

[0017] A method for preparing an inoculant for improving the molten iron condition of a heat-insulating casting ladle, the specific steps are as follows: Step 1, weigh the magnesium ingot and put it into the medium frequency furnace for heating and melting; Step 2: weigh ferrosilicon and rare earth, and add them into the charging bucket in the order of ferrosilicon and rare earth spheroidizer in advance; the charging bucket is hoisted to the top of the furnace by a crane, and the discharge port is opened to add the materials; Step 3: After the material in the furnace is melted, add the weighed strontium, and after the remaining materials are completely melted and the temperature reaches the requirement, add strontium and smelt into a uniform inoculant; Step 4: Add strontium for 30 seconds and then immediately tap the iron into an ingot mold to form an alloy block; Step 5: crushing the alloy block and screening it according to the required particle size; Step 6: After screening, pack as required; The smelting time of the rare earth inoculant is 40 minutes, the medium frequency furnace is set to a medium frequency smelting furnace with a frequency of 10 kHz and a power of 200 kW, and the temperature in the furnace in step three is 1400°C.

[0018] Example 2 The invention discloses an inoculant for improving the heat preservation of molten iron in a pouring ladle, wherein the inoculant is composed of the following parts by weight: 1.8 parts of Mg, 0.8 parts of cerium, 0.7 parts of Sr, 65 parts of Si, and the rest of the parts are iron and impurities that are difficult to remove; The inoculant is a granular ferrosilicon alloy with a particle size of 0.2-0.8 mm; the silicon element in the inoculant exists in the form of a compound of silicon and iron; and the rare earth element in the inoculant exists in the form of a compound of rare earth and silicon.

[0019] A method for preparing an inoculant for improving the molten iron condition of a heat-insulating casting ladle, the specific steps are as follows: Step 1, weigh the magnesium ingot and put it into the medium frequency furnace for heating and melting; Step 2: weigh ferrosilicon and rare earth, and add them into the charging bucket in the order of ferrosilicon and rare earth spheroidizer in advance; the charging bucket is hoisted to the top of the furnace by a crane, and the discharge port is opened to add the materials; Step 3: After the material in the furnace is melted, add the weighed strontium, and after the remaining materials are completely melted and the temperature reaches the requirement, add strontium and smelt into a uniform inoculant; Step 4: Add strontium for 30 seconds and then immediately tap the iron into an ingot mold to form an alloy block; Step 5: crushing the alloy block and screening it according to the required particle size; Step 6: After screening, pack as required; The smelting time of the rare earth inoculant is 50 minutes, the medium frequency furnace is set to a medium frequency smelting furnace with a frequency of 25 kHz and a power of 300 kW, and the temperature in the furnace in step three is 1420°C.

[0020] Example 3 The invention discloses an inoculant for improving the heat preservation of molten iron in a pouring ladle, wherein the inoculant is composed of the following parts by weight: 2.8 parts of Mg, 0.7 parts of lanthanum, 0.8 parts of cerium, 1.0 parts of Sr, 61 parts of Si, and the rest of the parts are iron and impurities that are difficult to remove; The inoculant is a granular ferrosilicon alloy with a particle size of 0.2-0.8 mm; the silicon element in the inoculant exists in the form of a compound of silicon and iron; and the rare earth element in the inoculant exists in the form of a compound of rare earth and silicon.

[0021] A method for preparing an inoculant for improving the molten iron condition of a heat-insulating casting ladle, the specific steps are as follows: Step 1, weigh the magnesium ingot and put it into the medium frequency furnace for heating and melting; Step 2: weigh ferrosilicon and rare earth, and add them into the charging bucket in the order of ferrosilicon and rare earth spheroidizer in advance; the charging bucket is hoisted to the top of the furnace by a crane, and the discharge port is opened to add the materials; Step 3: After the material in the furnace is melted, add the weighed strontium, and after the remaining materials are completely melted and the temperature reaches the requirement, add strontium and smelt into a uniform inoculant; Step 4: Add strontium for 30 seconds and then immediately tap the iron into an ingot mold to form an alloy block; Step 5: crushing the alloy block and screening it according to the required particle size; Step 6: After screening, pack as required; The smelting time of the rare earth inoculant is 40 minutes, the medium frequency furnace is set to a medium frequency smelting furnace with a frequency of 40 kHz and a power of 400 kW, and the temperature in the furnace in step three is 1450°C.

[0022] Comparative Example 1 Compared with the embodiment, the only difference is that the inoculant of the present invention is replaced by a common silicon-barium inoculant.

[0023] Comparative Example 2 Compared with the example, the only difference is that the inoculant of the present invention is replaced by a silicon strontium inoculant.

[0024] Comparative Example 3 Compared with the embodiment, the only difference is that the inoculant of the present invention is replaced by a common rare earth and magnesium-containing inoculant.

[0025] Test method: Use an imported 5-ton insulation casting furnace with a normal molten iron volume of 2-4 tons. Add 1 ton of new molten iron every 8-10 minutes. Control the temperature of the molten iron in the insulation casting furnace at 1400-1420℃ to produce gray cast iron intermediate shell products. Use high-barium inoculant in the sub-package, add it into the sub-package, add the inoculant along with the molten iron flow when pouring the casting, and test the casting after production.

[0026] One package of each of Examples 1-3 and Comparative Examples 1-3 was produced, and 10 castings were randomly selected for metallographic and casting defect inspection. The inspection results are summarized and recorded as follows: Graphite structure: Example 1: Type A graphite + a small amount of type D and type E graphite, graphite size 5-6; Example 2: Type A graphite + a very small amount of type D and type E graphite, graphite size 5-6; Example 3: Type A graphite + a very small amount of type D and type E graphite, graphite size 5-6; Comparative Example 1: 30 parts of type A graphite + 70 parts of type D and E graphite, graphite size 4; Comparative Example 2: 80 parts of type A graphite + 20 parts of type D and E graphite, graphite size 4-5; Comparative Example 3: 90 parts of type A graphite + type D and E graphite, graphite size 5 levels.

[0027] Cementite: Example 1: 7 pieces had no cementite, and 3 pieces had cementite content <1.0 part; Example 2: 8 pieces without cementite, 2 pieces with cementite content <1.0 part; Example 3: 9 pieces had no cementite, and 1 piece had cementite content <1.0 part; Comparative Example 1: Cementite appeared in all 10 pieces, of which 8 pieces had cementite > 5.0 parts; Comparative Example 2: 6 pieces without cementite, 2 pieces with cementite <1.0 part, and 2 pieces with cementite <3.0 part; Comparative Example 3: 7 pieces had no cementite, 2 pieces had cementite <1.0 part, and 1 piece had cementite <3.0 part.

[0028] Shrinkage Porosity: Example 1: 2 pieces have micro-shrinkage, the shrinkage size is 2mm²; Example 2: 1 piece has micro-shrinkage, the shrinkage size is 2mm²; Embodiment 3: No shrinkage porosity; Comparative Example 1: All of them have shrinkage, and 3 of them have shrinkage holes; Comparative Example 2: 3 pieces have shrinkage, and the shrinkage area is 6mm²; Comparative Example 3: 2 pieces of shrinkage, the shrinkage area size is 4mm².

[0029] Through the above analysis of the test results of Examples 1-3 and Comparative Examples 1-3, the inoculant of the present invention has a significantly better inoculation effect than ordinary silicon-barium, silicon-strontium inoculants and rare earth magnesium inoculants in the production of gray cast iron intermediate shells in an insulated casting furnace; the inoculation effect, reduction of the tendency of white cast iron and reduction of the proportion of shrinkage and porosity have achieved very good results; and the inoculation effect achieved in Example 3 is the most obvious.

[0030] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. An inoculant for improving the hot metal conditions of a heat-insulating casting ladle, characterized in that: The inoculant is composed of the following parts by weight: 1-3 parts of magnesium, 0.2-1.5 parts of rare earth elements, 0.2-1.2 parts of strontium, 60-70 parts of silicon, and the rest of iron and impurities that are difficult to remove.

2. The inoculant for improving the molten iron condition of the heat preservation casting ladle according to claim 1, characterized in that: The rare earth element is lanthanum or cerium.

3. The inoculant for improving the molten iron condition of the heat preservation casting ladle according to claim 1, characterized in that: The inoculant is a granular ferrosilicon-based alloy, and the ferrosilicon-based alloy has a particle size of 0.2-0.8 mm.

4. The inoculant for improving the molten iron condition of the heat preservation casting ladle according to claim 1, characterized in that: The silicon element in the inoculant exists in the form of a compound of silicon and iron; the rare earth element in the inoculant exists in the form of a compound of rare earth and silicon.

5. A method for preparing an inoculant for improving the molten iron condition of a heat-insulating casting ladle according to any one of claims 1 to 4, characterized in that: Specific steps as follows: Step 1, weigh the magnesium ingot and put it into the medium frequency furnace for heating and melting; Step 2: weigh ferrosilicon and rare earth, and add them into the charging bucket in the order of ferrosilicon and rare earth spheroidizer in advance; the charging bucket is hoisted to the top of the furnace by a crane, and the discharge port is opened to add the materials; Step 3: After the material in the furnace is melted, add the weighed strontium, and after the remaining materials are completely melted and the temperature reaches the requirement, add strontium and smelt into a uniform inoculant; Step 4: Add strontium for 30 seconds and then immediately tap the iron into an ingot mold to form an alloy block; Step 5: crushing the alloy block and screening it according to the required particle size; Step six: pack as required after screening.

6. The method for preparing an inoculant for improving the molten iron condition of a heat-insulating casting ladle according to claim 5, characterized in that: The smelting time of the rare earth inoculant is 40-60 minutes.

7. The method for preparing an inoculant for improving the molten iron condition of a heat preservation casting ladle according to claim 5, characterized in that: The medium frequency furnace is set as a medium frequency melting furnace with a frequency of 10-40kHZ and a power of 200-400kW.

8. The method for preparing an inoculant for improving the molten iron condition of a heat-insulating pouring ladle according to claim 5, characterized in that: The temperature in the furnace in step 3 is 1400-1450°C.