JPS5959816A - Manufacture of cast iron - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the degree of subcooling in various types of cast iron. Controlled cooling is essential in the production of cast irons such as nodular cast irons, compacted flake graphite cast irons, chilled cast irons and glass molding cast irons.

The purpose of the invention is to predictably control the texture of cast iron.

An object of the present invention is to provide a method for removing coarse graphite flakes in the structure of cast iron.

The present invention has a compact structure in the cast iron structure.
) It provides a means to measure graphite flakes with better consistency.

Another object of the invention is to provide a means for producing cast iron textured nodular or spheroidal graphite with better consistency.
It is to provide.

Another object of the present invention is to provide a means for producing a controlled amount of chilled graphite in chilled &N iron.

It is an object of the present invention to provide a means for producing cast iron used in the production of glass molds with better consistency.

Further objects of the present invention will become apparent from the present specification.

Graphite in cast iron is not in a chemical bond with iron;
Controlling the proportion of graphite is extremely important for cast iron production because of its physical admixture with tF. Therefore, the amount (%) of graphite in iron greatly influences the tensile strength and other properties of iron.

The graphite content in cast iron is usually controlled by adjusting the amount of base material initially used in the production of cast iron, or by adding graphite nodularizing agents (nodula-r12er + sound-transmitting cerium or magnesium) later. It is done by doing.

The present invention relates to this latter adjustment method.

When a graphite nodularizing agent is added to molten cast iron, whether in alloyed or pure form, it first removes the oxygen present in the molten metal.
Combines with nitrogen and sulfur. When added in large amounts, the graphite nodularizing agent turns flaky graphite into dense (co
mpac ted) acts to change the shape into a spherical or spherical shape. This is a well-known industrial method.

A problem with producing cast iron in this way is that the metal to which the graphite nodularizing agent is added often varies with respect to its sulfur, oxygen or nitrogen content. This means that if a predetermined amount of spheronizing agent is added to a bath of molten metal, the amount of active spheronizing agent retained in the bath will be equal to the oxygen, nitrogen or sulfur content mentioned above. It means that it changes variously according to. Therefore, it is impossible to predict the amount of spheroidizing agent available for interaction with the graphite, and it is difficult to adjust the graphite without constant adjustment and measurement of the molten cast iron.

The inventor modulated the effect of the spheronizing agent added to the cast iron melt by passing carbon dioxide bubbles through the cast iron melt,
It was discovered that a predictable amount could be left with the iron.

When a nodularizing agent is added to a cast iron bath, various changes occur in the properties of the graphite in the cast iron, which changes depend on the amount of nodularizing agent available for interaction. These changes are shown diagrammatically in FIG. 1 along with the approximate content of spheronizing agent (in this case magnesium). At point A, the metal contains coarse graphite.

At a score of 8, the graphite becomes dense, and at a score of 0, nodular graphite becomes dominant. At point D, some of the graphite comes to exist as free carbides.

There are no sharp boundaries between one type of graphite and the next. Instead, the relative amounts of each type of graphite gradually change as the magnesium content increases. Magnesium is present in various nuclei (silicates, oxides,
By combining with sulfides, etc.), it provides a certain degree of appropriate cooling. As a result, as the magnesium content increases, the ordinary flaky graphite that occurs due to the presence of these nuclei is effectively removed, resulting in various changes in the texture.

At around 0.005% by weight of magnesium, a considerable amount of moderately cooled +-A J type graphite appears. Magnesium 0.012
Around ~0.015% by weight, various amounts of dense graphite flakes begin to appear in the structure. Magnesium 0.022
Around ~0.025% by weight, spheroidal graphite (nodule
s of graphite) begins to appear.

As the magnesium content increases further beyond this point, the structure becomes completely spherical and free carbides eventually begin to appear in the structure.

The exact magnesium content at which these changes occur depends in part on the exact structure and condition of the matrix to which the magnesium is added. The lines on the graph of FIG. 1 only schematically indicate the contents at which these changes occur. FIG. 1 is used solely to illustrate the changes that occur, and it is not desired to be limited to the particular type or amount of spheroidizing agent or spheroidizing alloy to be added to the melt.

The same phenomenon occurs when a spheronizing agent such as cerium or a dilute-[-challic element is added.

It should be noted that the range of magnesium content within which completely cooled graphite can be reduced is rather limited. Similarly, the range of magnesium content that can produce dense flake graphite is also extremely narrow.

In practice, it is difficult to produce any of these graphite types using magnesium or rare earths (requiring a high degree of control).

The present inventor has treated molten cast iron with magnesium to reduce the
It has been found that after ensuring that more than 0.02 wt. % of magnesilano is retained, passing a bubble of carbon dioxide through the melt removes the excess magnesium, leaving only about 0.005 wt.

The graphite structure in this cast iron is completely of the appropriately cooled type.

Although the same mechanism can be obtained when a rare earth element is used instead of magnesium, it is preferable to use magnesium for -H'k. This is because magnesium is more volatile, easier to remove with carbon dioxide, and is relatively inexpensive.

We also believe that this represents a good starting point for soaking dense flake graphite cast iron or nodular cast iron, or any cast iron in which a well-cooled graphite adjusted to texture ``1'' is required. The present inventor also found out.

For example, if the process of the present invention completely supercools the ilk, the addition of a small amount of magnesium or cerium or other rare earths to the metal of the present invention will make the structure predominant.
It can be made detailed.

On the other hand, adding large amounts of magnesium or cerium or other rare earths can make the structure completely nodular.

When a certain amount of sulfur is added to the metal of the invention,
The cooled graphite can be removed to some extent or completely as desired, resulting in textured, coarse graphite flakes.

The method of the invention consists of adding an excess amount of graphite nodularizing agent to the melt and then passing a bubble of carbon dioxide through the melt to create a fully subcooled structure. This represents one ideal starting platform. However, by using this as a starting point and making the necessary additions to the hot water, various types of graphite can be produced in defined and adjustable amounts.

As an example of the present invention, a gray cast iron bath was taken and magnesium ferrosilicon was added.

The structure of the test piece obtained from this metal was nodular, and the magnesium content was 0.035 @ mass % (second
Figure A).

Carbon dioxide was then bubbled through the bath at a rate of 1'5 cubic feet per ton for 2 minutes. Foaming was carried out using a porous plug lance immersed in the bath. The specimens obtained from the bath at this point were cooled graphite (type A) and 0.00
It showed a magnesium content of 6% (Figure 2B).

The composition of the bath at this point was T, C, 3.52% by weight, Si
2.30% by weight and so, oi% by weight.

This bath was divided into two parts.

Next, we took one portion of this bath rBJ, subdivided it into smaller portions, added various amounts of magnesium ferrosilicon to each portion, and cast a series of specimens 1 inch in diameter. I made it.

The results of microscopic examination of each specimen are shown in FIG. 2 as micrographs CI, C2, C3, and C4.

The magnesium content of these samples is 0.01 each.
0.0.0!5.0.020 and 0.030% by weight.

Another portion of bath rBJ was further subdivided into smaller portions, varying amounts of cerium ferrosilicon were added to each portion, and a series of 1 inch diameter specimens were cast. The results of microscopic examination of each test piece are shown in Fig. 2, micrographs DI and D2.
．． D3 and I) Not shown in 4. The amounts of cerium added to these small portions were 0.02, 0.04, 0.06 and 0.08 heavy ash, respectively.

It is clear from these test results that the addition of 0.02 to 0.06% by weight of cerium resulted in essentially dense monolithic graphite. In addition, the retention amount is approximately 0.02[[
Even when magnesium is added to less than %,
It is also clear that essentially dense flake graphite was formed.

It has also been found that adding approximately 0.5% aluminum by weight to the molten metal improves the ability of cerium to form and eliminate dense graphite. This addition of aluminum is preferably carried out immediately after passing the carbon dioxide through the bath in bubble form. Similarly, adding titanium to the bath after carbon dioxide bubbling treatment has some effect in assisting the action of magnesium.

In general, the addition of cerium with or without aluminum is much better than the addition of magnesium in predictability and is therefore more preferred.

It has also been found that treating the cast iron bath with a spheroidizing agent followed by bubbling with carbon dioxide makes it much easier to add further spheroidizing agent to produce fully nodular cast iron. The nodular cast iron thus produced was fairly consistent in both texture and globular content.

Furthermore, when bubbles of carbon dioxide and carbon dioxide are passed through molten cast iron containing a spheroidizing agent, a variety of coarse graphite flakes can be formed in the structure by continuing to blow bubbles for a long time. I understand.

Thereby, it is possible to adjust not only the amount of properly cooled graphite produced, but also the amount of coarse graphite produced. 1'j
The amount of graphite flakes can be further increased by adding iron sulfide to the melt. This technique is particularly useful in producing cast iron used in making glass molds.

When manufacturing these articles, a del is typically used in a foundry sand mold to create a surface containing cooled graphite.

This operation is made much easier if the molten metal is treated with magnesium and carbon dioxide before casting the glass mold.

Hereinafter, the present invention has been described with a certain degree of specificity in its preferred form; however, this preferred form is disclosed merely as an example, and does not fall within the spirit and scope of the present invention as specified in the claims. Various changes in detail can be made without departing from the

[Brief explanation of drawings]

FIG. 1 is a diagram showing the changes that occur in the properties of a riverboat as the amount of spheroidizing agent (magnesium in this case) added to the molten metal increases. FIG. 2 shows the changes in the shape of graphite that occur before and after the carbon dioxide blowing treatment of the molten metal, and when the amount of other spherical agents added is increased. Agent Patent Attorney Yujou - Outside 26 1g g 闪目酋石 z x 徂目 % Mac9 Neleu A Bottle ``1 FIG, 1

Claims (1)

[Claims] (1) A step of melting an iron raw material having a flaky graphite structure;
A step of adding an excessive amount of graphite spheroidizing agent to the molten metal in order to deoxidize and desulfurize and produce a substantially completely spherical graphite structure, and then '/8'? A method for producing a completely appropriately cooled graphite structure, comprising the step of removing an active graphite nodularizing agent by adding gas to a to produce a substantially completely appropriately cooled graphite structure. . (2) Taking the metal according to claim 1 which has a substantially completely properly cooled graphite structure and adding a graphite nodularizing agent thereto; A dense J1-like structure is created! How to make M. (3) The method according to claim 1, wherein the graphite nodularizing agent is magnesium. (4) The method according to claim 3, wherein the gas is CO2. 3. A method according to claim 2, characterized in that f51 0.5% by weight of aluminum is further added and the graphite nodularizing agent is a rare earth element. (6) Take the metal according to claim 1, which has a graphite structure that has been cooled substantially completely, and add magnesium to the metal to form a magnetic alloy in an amount of less than 0.02% in the molten metal. A method of producing a substantially completely dense schistose tissue, the method comprising an additional step of retaining the lamina. (7) The method further comprises the step of taking the metal according to claim 1 and adding a rare earth element thereto to retain less than 0.02% of the rare earth in the molten metal. A method for producing dense schistose tissue. (8) Producing a substantially completely dense schistose structure comprising an additional step of taking the metal according to the first claim and simultaneously adding aluminum in an amount of 0.05% by weight or less. how to. (9) Adding magnesium to the molten metal until the amount of magnesium retained is greater than 0.02% by weight of the molten metal, and bubbling the molten metal with gas until the percentage of magnesium retained is approximately 0.005% by weight. %. A method of producing a substantially completely properly cooled graphite structure in molten metal. (10) The method according to claim 9, wherein the gas bubbled in during melting is carbon dioxide. (11) Take the metal according to claim 9 that has a graphite structure that has been substantially completely cooled, and add magnesium to the metal to add less than 0.02% of magnesium to the molten metal. A method of producing a substantially completely dense schistose structure, which includes an additional step of retaining temperature. (12. Take the metal described in claim 9 and add a rare earth element to it to retain an amount of rare earth in the molten metal in an amount smaller than 0.02%. 13) An additional step of taking the metal according to claim 9 and simultaneously adding 0.5% by weight or less of aluminum thereto. A method of producing a substantially completely dense schistose tissue comprising: (j4) Adding magnesium to molten iron until the amount of magnesium retained is greater than 0.02% by weight of the molten iron, and bubbling the molten iron with carbon dioxide until the percentage of magnesium retained in the molten iron is approximately A method for adjusting the graphite content in molten iron, which comprises the steps of reducing the graphite content to 0.005% by weight, and then adding a graphite nodularizing agent to the molten iron.