JPH0565577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new composite alloy cast iron, and more specifically to the production of a heat-resistant and corrosion-resistant alloy cast iron made by adding an alkaline earth metal titanate and a boron compound, or further aluminum to the molten cast iron. Regarding the method. The alloy cast iron according to the present invention was discovered in the course of material research for a special alloy cast iron that has heat resistance and corrosion resistance, and is an alloy cast iron that has particularly high durability against molten aluminum. Traditionally, low-pressure casting equipment and die casting equipment for nonferrous light metal alloys such as aluminum alloys, zinc alloys, magnesium alloys, and tin alloys, such as stalks, crucibles, thermocouple protection tubes, and ladle for automatic hot water supply, have been made using standard FC20 to 25. Cast iron is used.
However, these ordinary cast irons suffer from a large amount of corrosion loss against, for example, molten aluminum, and cannot withstand long-term use. In addition, the quality of aluminum castings is degraded due to the contamination of iron and carbon components. In view of the above-mentioned facts, the present inventor conducted a series of research to find new materials to replace these ordinary cast irons. We have created stalks for low-pressure casting of aluminum from cast iron and conducted actual operations to examine the results.
Compared to the 6-day service life, the service life only increased by about 2 to 3 times. Therefore, based on cast iron, the present invention was completed by developing a new idea without being bound by conventional foundry engineering common sense in order to improve the constitution of cast iron composite alloy cast iron. In other words, by adding alkaline earth metal titanate to molten cast iron, a material that is far more corrosion resistant to molten aluminum alloy than conventional FC cast iron or other cast irons can be stably obtained. The composite alloy cast iron described above is obtained by setting the optimum mixing ratio in cast iron and the optimum range of temperature conditions during cast iron production, and by further adding aluminum to molten cast iron containing alkaline earth metal titanate. As shown in the figure, adding alkaline earth metal titanate to molten cast iron can be effective and even better by adjusting the optimum mixing ratio in cast iron, the aluminum addition ratio, and the optimum temperature range during composite alloy cast iron manufacturing. It turns out that the material is available. As a result of further research based on the above-mentioned new facts, the present inventor found that when adding the above-mentioned alkaline earth metal titanate or aluminum together with the above-mentioned alkaline earth metal titanate to molten cast iron, and also coexisting with a boron compound, the desired product can be obtained. The structure of barrel alloy cast iron becomes more dense,
As a result, it was discovered that the corrosion resistance and heat resistance were further improved, and the present invention was thus completed. The alloy cast iron of the present invention will be explained below based on its manufacturing method. In the present invention, an alkaline earth metal titanate and a boron compound, or further aluminum is added to the molten cast iron. As the molten cast iron at this time, conventionally used molten metal can be used, for example, fresh pig iron and some waste iron can be used if necessary, and steel materials,
It is a molten cast iron obtained by melting coke, limestone, and a silicon source. These components are appropriately mixed in consideration of the composition of the target alloyed cast iron to be obtained.
The preferred blend is that the resulting alloy cast iron has a C:2.5~
4.0% by weight (hereinafter simply referred to as %), Si: 2.0 to 4.0%,
Ti: 0.05-1%, or C: 2.5-4.0, Si: 2.2-
3.8%, Cr: 0.2-2%, Mn: 0.1-2%, Ti:
0.05-1%. The composition is such that Al: 1.5 to 4.0%. Preferred silicon sources include ferrosilicon, ferrochrome, ferromanganese, and the like. In the present invention, an alkaline earth metal titanate and a boron compound are added to the molten cast iron, or aluminum is further added, and the molten metal coming out of the melting device is poured to produce an alloy. The melting temperature at this time is 1550-1800℃, and the tapping temperature is 1500-1650℃.
℃, casting temperature 1450~1600℃ preferably 1500~
The temperature is around 1600℃, which is higher than normal conditions. The alkaline earth metal titanate used in this case may be in powder or fibrous form, and examples of preferred examples include beryllium titanate, magnesium titanate, calcium titanate, strontium titanate, and barium titanate. I can do it. The amount of alkaline earth metal titanate added is
It is about 1.5 to 10%, preferably about 2.0 to 7.0%, based on the FC content. Preferred boron compounds include sodium borate (borax), potassium borate, boric anhydride, ferroboron, etc., and the amount of these added is about 0.5 to 3 kg per 120 kg of steel material. The apparatus for producing heat-resistant and corrosion-resistant alloy cast iron of the present invention can be used not only in the Kewpora furnace, which has been used for a long time, but also in an electric melting furnace.
In order to prevent the alkaline earth metal titanate from scattering, it is preferable to use it in the form of a lump. The carbon content of the element C in the composite alloy cast iron used in the present invention is 2.5 to 4.0% by weight, preferably 3.0 to 3.8%. If the carbon content exceeds 4.0%, the composite alloy cast iron becomes too hard, making post-processing such as cutting difficult, and it also becomes brittle, so there is a risk of cracking when subjected to heat shock when used in molten aluminum, for example. Also, 2.5
%, the alloy cast iron structure has a large amount of ferrite (pure iron), and ferrite tends to react with aluminum to form aluminum ferrite, so it dissolves into the molten aluminum and becomes susceptible to corrosion. . Also, Si is 2.0 to 4.0% by weight
Preferably it is 2.2 to 3.8% by weight. When Si exceeds 4.0%, the structure of the alloyed cast iron becomes a structure of graphite and ferrite base due to the graphitization promoting element properties of Si, and the ferrite base becomes susceptible to corrosion as described above. Furthermore, due to segregation, Si tends to exist alone, and if it is eluted into the molten aluminum, it may cause foaming, which is generally referred to as crab foam. Furthermore, if it is less than 2%, the heat resistance deteriorates, causing a problem in heat resistance when used in molten aluminum, for example. Added from alkaline earth metal titanate
Ti is in the range of 0.05 to 1% by weight in cupola operations. It is generally known that when corrosive gases such as oxygen gas or halogen gas enter alloy cast iron, they enter through graphite. Therefore, long fibers and/or graphite in which these fibers are connected can easily allow corrosive gases to enter, causing corrosion or cracks. Therefore, it is necessary to refine the graphite fiber into flakes.
Ti is very effective as a graphite refiner,
Therefore, alloyed cast iron with good corrosion resistance can be obtained. Furthermore, 0.2 to 2% by weight of Cr and/or 0.1 to 2% by weight of Mn are contained as graphite stabilizing elements. Thereby, corrosion resistance can be imparted to the cast iron alloy of the present invention. Furthermore, in the present invention, it is essential to contain Al in an amount of 1.5 to 4.0% by weight. By adding Al, the heat resistance of alloyed cast iron can be improved. If the amount added is less than 1.5% by weight, sufficient heat resistance cannot be obtained. In addition, if it exceeds 4.0% by weight, segregation of Al or flow of molten alloy cast iron may become poor, for example, "porosity" may occur, which may cause casting defects.
This is not desirable as it may cause problems such as: Therefore, in order to improve the corrosion resistance against molten aluminum, it is necessary to make the composite alloy cast iron structure into a cementite base with a molecular formula of Fe ₃ C that shows no reactivity with aluminum, but a completely cementite base is not possible. Also, since it is hard and brittle, the crack mentioned above becomes a problem. Therefore, it is necessary to have a layered structure of cementite and ferrite, that is, a pearlite structure, which has both toughness. This pearlite structure also has as much cementite as possible to create a dense structure, which leads to improved corrosion resistance. In the present invention, this pearlite base can be obtained by particularly forming the above-mentioned specific structure. The heat-resistant and corrosion-resistant alloy cast iron thus obtained was used to make a stalk for aluminum alloy low-pressure casting, and its durability was tested.
During the 30 days of operation, it remained in its original shape without any erosion, an astonishing record. This means that even cast irons such as Silal cast iron, Kralfur cast iron, and Alsilon cast iron, which belong to the conventionally known cast irons such as ductile cast iron, Meekhanite cast iron, and high-aluminum cast iron, and even Ti cast iron with added Ti, are incomparably high. It's about performance. One of the reasons why the heat-resistant and corrosion-resistant alloy cast iron of the present invention has such excellent heat and corrosion resistance is that, in addition to the effect of reducing galvanic corrosion due to the synergistic effect of additives, it also has extremely low water flowability with respect to molten metal. It is thought that this is because the The heat-resistant and corrosion-resistant cast iron alloy of the present invention has excellent heat resistance and durability against crucibles and stalks for aluminum alloy casting, as well as various alloy metals such as copper, tin, nickel, zinc, and lead. It is also useful as a material for these various molten metal objects. Furthermore, this heat-resistant and corrosion-resistant alloy cast iron has good mechanical properties, so it can be expected to have great utility and economic effects. The present invention will be specifically explained below using reference examples and examples. However, in the following examples, parts indicate parts by weight. Reference example 1 The amount of steel mixed at the time of loading into the Kupora furnace is 60
20 parts new pig iron, 20 parts old pig iron, 13 parts coke, limestone
Based on this blended amount, 4 parts of calcium titanate and 0.5 parts of bentonite were kneaded with water, formed into a lump, dried, and added to the top of the furnace together with the above blend. The melting conditions in Qupora are a melting temperature of 1550℃ or higher and a maximum of 1800℃, and a tap water temperature of 1580℃.
It is. The molten metal thus obtained was placed in a forehearth, and 1 part of sodium borate was added to 100 parts of the molten metal.
It was cast at a casting temperature of 1520℃. Reference example 2 The amount of steel mixed at the time of input into the Kewpor furnace is 60
part, 20 parts of new pig iron, 20 parts of old pig iron, 12 parts of ferrosilicon,
13 parts of coke and 10 parts of limestone are mixed with 7 parts of magnesium titanate (per 100 parts of FC) and 0.8 parts of bentonite with water.
It was molded into a block, dried, and added to the top of the furnace together with the above formulation. The Kupora dissolution conditions are reference example 1.
I made it the same as Furthermore, 2 parts of ferroboron (per 100 parts of Fe content) was used in place of 1 part of sodium borate. Reference Example 3 The same method as Reference Example 1 was used. Blend amount is steel material
60 parts, 40 parts of fresh pig iron, 13 parts of coke, Ferrosilicon
10 parts of ferrochrome, 3 parts of ferroboron (based on 100 parts of Fe content), 5 parts of magnesium titanate, and 0.6 parts of bentonite. Example 1 A part of the molten metal produced in Reference Example 1 was placed in a forehearth, and 5 parts of pure aluminum, which had been previously melted in a separate furnace, was added to 100 parts of the molten metal, and cast into a mold. Example 2 A part of the molten metal produced in Reference Example 2 was taken and the molten metal
3 parts of pure aluminum was added to 100 parts by casting. Example 3 The molten metal produced in Reference Example 3 was taken into the forehearth, and the molten metal
4 parts of pure aluminum, which had been previously melted in a separate furnace, was added to 100 parts for casting. Using Reference Examples 1 to 3 and Examples 1 to 3, aluminum alloy low-pressure casting stalks were prototyped. The weight of this stalk was measured in advance. On the other hand, a FC20 stalk was cast for use as a comparative example. This stalk weighed 30.2Kg. Continuous operation tests were conducted on the heat resistance, durability, and corrosion resistance of the cast iron and FC stalk of the present invention by setting them in a low-pressure casting apparatus and operating aluminum alloy casting. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. For 120 parts by weight of iron raw material containing silicon,
Adding a specific amount of alkaline earth metal titanate and 0.5 to 3 parts by weight of a boron compound as a Ti source,
By adding pure aluminum to the molten alloy cast iron obtained by melting and reacting this, the content of each component can be reduced to C: 2.5 to 4.0% by weight and Si: 2.2 to 4.0% by weight.
1. A method for producing heat-resistant and corrosion-resistant alloy cast iron, characterized by obtaining alloy cast iron having a content of 3.8% by weight, Ti: 0.05 to 1% by weight, and Al: 1.5 to 4.0% by weight.