JPH0565575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new composite alloy cast iron, and more particularly to a composite alloy cast iron made by adding an alkali metal titanate and a boron compound or further aluminum to molten cast iron. The alloy cast iron of 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 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 alkali metal titanate to molten cast iron, it is possible to stably obtain a material that is much more resistant to corrosion against molten aluminum alloy than conventional FC cast iron or other cast irons, and moreover, By setting the optimum blending ratio of and the optimum range of temperature conditions during cast iron manufacturing, composite alloy cast iron obtained by further adding aluminum to molten cast iron containing alkali metal titanates can be made into cast iron as described above. By adjusting the optimal blending ratio, aluminum addition ratio, and optimal temperature range during composite alloy cast iron production, we have found that simply adding alkali metal titanate to molten cast iron can be effective and produce even better materials. found. As a result of further research based on the above-mentioned new facts, the present inventor found that when adding the above-mentioned alkali metal titanate or aluminum to molten cast iron, and also coexisting with a boron compound, the resulting target alloy It was discovered that the structure of cast iron becomes more dense, and as a result, corrosion resistance and heat resistance are further improved, and the present invention has now been completed. The alloy cast iron of the present invention will be explained below based on its manufacturing method. In the present invention, an alkali metal titanate and a boron compound, or further aluminum are added to the molten cast iron. As the molten cast iron in this case, conventionally used molten metal can be used, such as cast iron obtained by melting steel, coke, limestone, and silicon source using fresh pig iron and some waste pig iron if necessary. It is molten metal. These components are appropriately mixed in consideration of the composition of the target alloyed cast iron to be obtained. A preferred composition is that the resulting alloy cast iron contains C: 2.5 to 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:
The content is 0.05-1% and Al: 1.5-4.0%. Preferred silicon sources include ferrosilicon, ferrochrome, ferromanganese, and the like. In the present invention, an alkali metal titanate and a boron element 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 to 1800°C, the tapping temperature is 1500 to 1650°C, and the casting temperature is 1450 to 1600°C, preferably about 1500 to 1600°C, which are higher than normal conditions. The alkali metal titanate used in this case may be in powder or fibrous form, and examples of preferred examples include lithium titanate, sodium titanate, and potassium titanate, and salts of rubidium and cesium are preferred. It is hard to say that it is particularly preferable. The amount of alkali metal titanate added is 1.5 to 10%, preferably 2.0% to the FC component.
~7.0%. Preferred examples of boron compounds include sodium borate (borax), potassium borate, boric anhydride, and ferroboron, and the amount of these added is 0.5 per 120 kg of steel material.
~3Kg. The apparatus for manufacturing cast iron and composite alloy cast iron of the present invention can be used not only in the Kupora furnace, which has been used for a long time, but also in an electric melting furnace. In the case of the Kupora furnace, the alkali metal titanate is used in bulk to prevent scattering. It is preferable. 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 with molten aluminum, for example. . Also, 2.5
%, the alloy cast iron structure has a large amount of ferrite (pure iron), and since ferrite has the property of easily reacting with aluminum to form aluminum ferrite, it is easily leached into the molten aluminum, resulting in 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. Ti added from an alkali metal titanate is in the range of 0.05 to 1% by weight in cupola operation. 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 graphite fibers into flaky fibers, and Ti is very effective as a graphite refiner, and therefore alloy 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. Moreover, if it exceeds 4.0% by weight, it is not preferable because it causes segregation of Al or poor flow of the molten alloy cast iron, resulting in, for example, "porosity" that causes poor casting. 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 66 to 80 days of operation, it remained in its original shape without any erosion, an astonishing record. This means that even cast irons such as Silar 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, cannot be compared. It is high 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 of this, but it is not clear. The heat-resistant and corrosion-resistant alloy cast iron of the present invention has excellent heat resistance and durability against crucibles and stalks for aluminum alloy cast iron, 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 be widely used and economically effective. 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 blended amount at the time of loading into the Kewpor furnace is steel material
60 parts of fresh pig iron, 15 parts of coke, and 10 parts of limestone.To this amount, 5 parts of potassium titanate and 0.6 parts of bentonite are kneaded with water and formed into a lump.
The dried material was added to the furnace top along with the above formulation. The melting conditions at Cupola are a melting temperature of 1550°C.
The maximum temperature is 1800℃, and the hot water temperature is 1580℃. The molten metal thus obtained was placed in a forehearth, 1 part of sodium borate was added to 100 parts of the molten metal, and cast at a casting temperature of 1520°C. Reference example 2 The amount of steel mixed at the time of input into the Kewpor furnace is 60
30 parts of new pig iron, 10 parts of old pig iron, 15 parts of ferrosilicon,
A mixture of 13 parts of coke and 10 parts of limestone was mixed with 6 parts of potassium titanate and 0.7 parts of bentonite with water, molded into a lump, dried, and added to the top of the furnace together with the above mixture. Cupola dissolution conditions were the same as in Reference Example 1. Also, replace 1 part of sodium borate with 2.5 parts of ferroboron (however, Fe content is 100
) was used. 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, 15 parts of coke, 2.5 parts of old pig iron, 10 parts of ferrosilicon, 2 parts of ferrochrome, 2 parts of ferroboron, 5 parts of lithium titanate, and 0.6 parts of bentonite (per 100 parts of Fe content) It was hot. 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 placed in a 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, Stokes for aluminum alloy low-pressure casting was prototyped.
The weight of this Stokes 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 cast iron. The results are shown in Table 1. 【table】

Claims (1)

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