JPS591141B2 - Metal casting method and its equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to casting elongated metal articles, such as billets, in a mold of at least the same length as the cast article.

The present invention includes significantly improved surface properties such as, but not limited to, smoothness, distribution of subsurface inclusions, to control the solidification rate of metal articles during casting. Provide improved physical and morphological properties of cast metals.

The present invention also provides improved internal microstructure of cast articles.
That is, in both continuous casting and discontinuous casting, metal solidification occurs along the solid-liquid phase interface during casting, that is, at the interface between the cast film (5hell) that is solidifying during casting and the molten metal, that is, the hot water. Many attempts have been made to control the speed at which

These attempts involved introducing molten metal into the mold, followed by
and separately characterized by the use of expensive and space-consuming additional equipment added to the basic casting equipment to regulate the flow of molten metal around the solid-liquid interface. Ta.

Such an additional device is the Tzavaras (Tzavaras).
) required a molten metal agitation device and an induction coil around the mold or cast article, as described in U.S. Pat.

These induction coils produce a moving magnetic field within the molten metal, removing or suppressing columnar dendrites, producing improved dispersion of chemical solutes, and layering of inclusions within the main portion of the cast article. The moving magnetic field induces flow along the interface to suppress core porosity.

My U.S. Pat. No. 3,517,725, issued June 30, 1970, teaches billets of steel and other metals to be molded in closed-ended cooled molds that are relatively isolated from the source of molten metal. A continuous metal casting technique is described.

The closed-ended mold forms a cast film for the billet being cast, through which molten metal flows into a relatively receding mold that is further away from the source of the molten metal. At the end of the billet, form the outer casting membrane of the billet.

At the end on the side of the molten metal source, the billet casting number may occupy at least 40 parts of the cross-sectional area of the mold.

In this technique, the flow of metal debris along the solid-liquid interface changes the solidification microstructure from the interface where it would normally exist, resulting in an improved microstructure.

However, the mold moving relative to the billet shell tends to impart some surface regularity to the cast article, which is common to all continuous casting techniques.

In contrast to the continuous casting technique of said US Pat. No. 3,517,725, when casting metal in a cooled or uncooled mold of at least the same length as the cast article, It was customary to pour molten metal into a mold to a predetermined height within the mold.

During such casting, the casting film solidifies against the mold;
Molten metal flows through the casting membrane from bottom to top in a liquid orientation.

However, during such casting between mold beams, a casting film is formed which is considerably less than 40 times the cross-sectional area of the mold.

While such volumetric flow into the mold is relatively large, there is little or no washing effect of the relatively large liquid core on the solid-liquid interface.

Therefore, unless otherwise controlled, the rate of solidification cannot be effectively regulated, and solidification occurs with undesired growth of columnar dendrites, resulting in local solute concentration and Separate inclusions occur and center porosity occurs, all of which are undesirable in a cast microstructure.

The present invention overcomes many of these drawbacks of the prior art.

The object of the present invention is to obtain the effectiveness of such a solidification control device as a function of the introduction of molten metal into the mold, at least primarily, without the use of such expensive and cumbersome additional devices. The object of the present invention is to improve casting techniques for generally elongated metal articles and metal articles having melting points in the range of about 1088°C to 1643°C.

According to the present invention, it is possible to cast metal articles having properties that are at least comparable to, and in many cases superior to, metal articles made using the prior art, while requiring less time and energy to be cast compared to the prior art. , the method of the present invention enables the production of metal articles at low cost with lower consumption of materials.11 The method of the present invention introduces molten metal from a molten metal source through the bottom part of the mold;
During casting, the molten core (which occupies a small cross-sectional area of the mold (both 40φ)
The process consists of flowing molten metal into a mold to form a solidified casting number with a molten core, and flowing the molten metal from a source of molten metal through the molten core toward the top of the mold.

According to the casting method of the present invention, the cast article after solidification of the molten core has a crystalline structure consisting of relatively fine grains throughout its cross-section, reducing chemical segregation and thus Physical properties are improved, for example, 304 stainless steel cast by the casting method of the present invention has yield strength and tensile strength increased by a factor of 10 to 15 compared to 304 stainless steel cast by the conventional casting method, Ductility increased by 30 factors.

Furthermore, cast articles cast by the casting method of the present invention have a much higher degree of hot workability than cast articles cast by conventional casting methods.

Furthermore, according to the casting method of the present invention, the special alloy cast can undergo surface conditioning.
Since rolling can be performed without performing rolling, the yield up to rolling can be improved.

The invention will now be explained in detail with reference to the drawings.

As shown in FIG. 1, a molten metal source 10 is shaped like a ladle and can contain molten metal to be cast.

The metal source is provided with a lid piece 12 for sealing the ladle in a gas-tight manner and is fastened with a lock 14, and an inlet 16 for pressurizing the metal source, such as nitrogen, is provided through the lid.

The lid 12 has a refractory tubing section 18 depending near its bottom within the source.

The inside of this tube piece 18 has a passage 2 extending through a refractory block 20 supported by the lid piece 12.
It is connected to 2.

A gate 23, shown in the open position, communicates the passageway 22 with a refractory nozzle 24.

The nozzle 24 extends into the lower end of an elongated mold 26.

The cross-sectional shape of this mold is, for example, circular, and the mold is inclined with respect to the vertical line.

In practice, this inclination may be about 86°. In principle, this mold can be vertical, but if it is vertical, this tends to cause problems that are not practical due to the influence of the fluid pressure of the molten metal in the mold.

These problems include the relatively thick wall structure of the mold and the relatively high pressure required to force the molten metal through such a vertical mold.

A vertically oriented mold produces a relatively small meniscus in the molten metal, and such a small meniscus is truly desirable for reasons discussed below.

It is clear that this device cannot operate if the mold is horizontal, with the meniscus extending from one end of the mold to the other.

The upper end of the mold 26 is closed by a cap 28, which is provided with a through vent to allow gases generated by the casting operation to pass through and for molten metal to exit (thereby indicating that the mold is filled). be.

Although the mold 26 is shown in FIG. 1 with its middle portion melted, at the beginning of the casting operation the mold is continuous from the bottom to the top.

In the illustrated version of the invention, the mold 26 is of a molten nature, such that the mold or a portion thereof is filled with molten metal and then melted, the molten metal filling the mold completely. Before it melts away, it solidifies on the walls of the cold part of the mold.

This will become clearer as will be described later.

A plurality of longitudinally extending tube sections 27 are spaced apart from each other around the mold 260 to conduct a source (not shown) of a coolant such as water.

This coolant is injected to the outside of the mold from a valve nozzle 30 during the casting operation, as will be described below.

The valve nozzle 30 is controlled by a thermocouple 32 spaced along the axis of the mold and placed toward the side of the mold.

Thermocouple 32, which senses the rising temperature within the mold, is connected to an injection control system (not shown) that keeps the coolant injection directed toward the lower end of the mold throughout the operation of filling the mold with molten metal.
The cooling front is coupled to advance the cooling front along the axial portion of the mold before and after the meniscus 330 of the molten metal within the mold during the mold heating period.

However, after the advancing meniscus, at a distance indicated by numeral 35, the coolant to the mold is stopped, causing that section of the mold to melt the casting shell.

The mold 26 is approximately 0.20 cal/crrl/cm/
°C/sec to 0.65 cal/ca/cm/ °C
It is made of a metal with a high thermal conductivity in the range of /sec and a melting point in the range of about 476°C to 754°C.

The mold has a wall thickness of about 1.27 mm to 12.70 mm for a length of about 7.62 m to 60.46 m.

Such molds have a maximum thermal conductivity of approximately 0.25 cal/
crA/cm/'C/sec and has a melting point of approximately 1
It is used to cast metals in the range of 088°C to 1643°C.

However, the mold described above is only a preferred example, and other types of bottom pouring molds can also be used in the present invention.

The mold 26 is supported by columnar support pieces 34 arranged at intervals along the axial direction of the mold, as shown in FIGS. 1 and 2. The upper end of one of the support pieces 340 is shown in FIG. This is shown below.

As can be seen, the mold 26 is in substantially only line contact with the support structure to allow the coolant spray to cover the entire mold and prevent premature melting of the mold. be.

This support piece has a V-shaped recess 38 with high heat transfer properties.
A hollow, open-ended metal block 36 is provided.

A block 36 is secured to the upper end of the post 34 and its recess 38 receives the mold as shown.

A tank, indicated by the reference numeral 40, is supported by each support piece 34 and extends below the mold 26 to capture coolant that falls onto the mold 26 and to catch the coolant that falls onto the mold 26 as it melts. capture molten metal from

This tank 40 is equipped with suitable baffles 42 to capture coolant and molten metal from the mold.

Tank 40 is provided with a suitable outlet (not shown) for periodic cleaning of accumulated metal.

The metal from the mold is in a molten state as it falls and solidifies in contact with water coming into or to tank 40.

The apparatus of FIG. 1 is shown during a casting operation.

In other words, the mold 26 is filled with molten metal, but the filling is not completed yet.

Before starting casting work, the mold 26 is inserted into the casting nozzle 24.
During assembly, a quantity of foundry powder 44 is inserted into the lower part of the mold, usually in a plastic container which burns off when exposed to molten metal, exposing the powder to the molten metal. Powder 44 borders the molten metal but has a low density so that it lies above the meniscus of the metal as shown.

The action of the powder is as described below.

At the beginning of the casting operation, pressurized gas is introduced into the metal source 10 through the inlet 16 and molten metal enters the inlet end of the tube section 18 and into the nozzle 24 through the block 20 and then through the open gate valve 23. Further, the bottom of the mold 26 is reached.

The mold filling rate is controlled by increasing the gas pressure within the metal source 10.

This adjustment of gas pressure can be accomplished by any suitable known means.

For example, a servo-controlled valve may be provided in the conduit between the gas source and the inlet 16 and controlled in response to the pressure within the molten metal source 10.

As the level of metal filling in the mold progresses, the metal in contact with the cooled mold forms a solidifying shell 46 that occupies a small portion of the cross-sectional area of the mold, and with a molten heart 48 flowing through it,
The introduction of molten metal into the mold prevents columnar dendrites from growing during the period when the liquid core 48 flushes the solid/liquid interface partially formed by the shell 46 and fills the mold. This is how it is done.

This sweeping action by the liquid core 48 may, at least in part, cause the growth of the dendrites to be approximately the same size in all directions, or may produce other microscopic structures. It seems that you will get it.

Such a sweeping action of the liquid core prevents the formation of so-called porridge areas between the true liquid core and the solidifying shell, thereby achieving the desired solidification of the cast article. Create a temperature gradient.

This temperature gradient exists both longitudinally and transversely to the axial direction of the casting.

Each solute element tends to be evenly distributed throughout the casting and some of the inclusions tend to be trapped by the foundry powder 44 as the mold is filled, allowing the molten metal to wash away the foundry powder. .

Such chemical and physical effects during casting operations are described in U.S. Pat. No. 36,936 to Tzavaras.
97 for details.

The aforementioned inclusions are formed before the metal solidifies, and are mainly oxides that are stable at high temperatures.

The inclusions formed during the solidification process are mostly sulfides, tellurides, arsenides, nitrides and certain oxides.

Common inclusions in steel are compounds of various solutes or deoxidizers used in the steel in combination with oxygen, sulfur, and rarely nitrogen.

As mentioned above, for example, the solute in steel is an element other than iron, such as an alloying element.

Pressure injection of cast metal as described above ends when mold 26 is filled to the top.

When the mold lighting operation is completed, the gate valve 23 is closed and the injection of the remaining coolant is also shut off.

When the coolant jets are shut off, the temperature of the remaining parts of the mold increases and the mold melts, but the cast article remains unsupported by these pillar supports, just as the mold was previously supported by these pillar supports. It remains supported by the pieces.

However, the portion of the mold 260 into which the cap 28 is inserted does not melt.

Metal products cast in this way exhibit superior surface properties compared to other products.

It is clear that several similar molds may be filled simultaneously from a single metal source if desired.

Pressurized injection of molten metal is as described above with respect to casting, but the mold 26 may be filled by vacuum injection or may be filled from the bottom by another injection method.

Casting example 1 The metal to be cast is carbon maximum 0.08%, manganese maximum 2.0%, silicon maximum 1.0%, chromium 18-
It is A15I-304 stainless steel consisting of 20% nickel, 8-11% nickel, 0.04% maximum phosphorus, 0.03% maximum sulfur, and iron, and is in solid phase at 1427°C and liquid phase at 1510°C.

Thermal conductivity at 100°C 0.39 cal/cry
/cm/'C/sec.

The composition of the mold is aluminum alloy 2024, which consists of 4.5 parts copper, 1.5 parts magnesium, 6 parts manganese, and aluminum, and is in a solid phase at 502°C and in a liquid phase at 638°C.

The thermal conductivity is 0.45 cal/cra at 250℃.
/cm/'C/sec.

The length of the mold is 30.48 m, the wall thickness is 4.75 mrr, the internal cross section is 100 mm x 100 strokes, and the mold light density by pressure injection is 4.834 kg/cni/min.
, the speed of the liquid core is about 31.39 m/min and its diameter is about 5
0.8 books].

In this casting example (3), the angle of inclination of the mold was about 7 degrees with respect to the horizontal, and the cooling rate was about 570 liters per minute.

Casting example ■■ The metal to be cast is nichrome, and its composition is:
It is as follows.

Ni 77-7 Cr19-20% Fe Maximum coefficient of 1.0 C Maximum coefficient of 0.25 Mn Maximum coefficient of 25 Si O,75-1,5 coefficient S Maximum coefficient of 0.03 And this metal is in liquid phase at 1400℃ and 1350
Solid phase at ℃, thermal conductivity is 0.13 at 100℃
4 cal! , /c〃i/ crn, / 'C/ se
It is c.

The mold was made of aluminum alloy 2024, and its composition was as follows.

Cu 4.5 coefficient Mg 1.5 coefficient Mn 6 coefficient AI The remaining part and the mold are in a liquid phase at 638°C and a solid phase at 502°C, and the thermal conductivity is 0.45 cal / at 25°C.
The length of the mold is 6.1 meters, the inner diameter of the mold is 63.5 mm, and the wall thickness of the mold is 3.18 mm.

The filling ratio was 5.98Ay/cy4/m1n (189,
3kti/m1n), the diameter on the liquid core or melt is 31,7 mm, and the velocity on the melt is 30.5 m
/min.

It is.

Casting Example ■ The metal to be cast is Inconel 600, and its composition is as follows.

Fe 6-10 coefficient Cr14-17% Mn Maximum 1.0 coefficient C Maximum 0.15 coefficient Cu Maximum 0.5 coefficient Si Maximum 0.5 coefficient S Maximum 0.015 coefficient Ni The remaining part and this metal are 1425 It is in liquid phase at 1395°C.
Solid phase at ℃, thermal conductivity is 0.03 at 100℃
6 cal/cfl/c@/℃/sec.

The mold is the same aluminum alloy as in casting example ①.

The length of the mold is 14.02 meters, the inside dimensions of the mold are 152.4 gates x 230.2 orders, and the wall thickness of the mold is about 5.08 mm.

. The filling ratio is 3.805 @10A/m 1n(1
178.2 kg/m1n), the diameter of the liquid core or melt is 81.08 mm, and the velocity of the melt is 27.
．． The speed is 4m/min.

FIG. 3 is a diagram illustrating the different metal grout proportions for molds with different cross-sectional areas.

As seen in the figure, one mold with a cross-sectional area of 25.81c4 has approximately 2,39-23.9 @/1y7t,/m i
An example of introducing molten metal at a rate of n is shown.

Also, for a mold with a cross-sectional area of 967 and 74 cm, approximately 0.239-
It may be filled at a rate of 4.78 kq/ca/min.

It is indicated that a mold having a cross-sectional area between the above ranges should be filled with a filling ratio between the above ranges.

Although several versions of the present invention have been described above with respect to methods and apparatus for casting metal articles, it will be appreciated that various modifications and variations can be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

Fig. 1 is a side view showing a part of the casting apparatus of the present invention during casting operation, Fig. 2 is a sectional view taken along line 2-2 in Fig. It is a graph which shows the molten metal introduction rate regarding a casting mold. Figures 4, 6, and 8 show 0.22 inch (approximately 7.62 cm) outer diameter metal articles cast by the casting method and casting apparatus of the present invention and rolled. 0.5
Cross section of a wire with an outer diameter of 59 cm (15x magnification)
, transverse section (100x magnification) and longitudinal section (100x magnification)
FIG. Figures 5, 7, and 9 show 20 inch x 20 inch (approximately 50.8 cm x 50.8 cm) cast by conventional methods.
cm) ingots through the conventional cooling, reheating, rolling, grinding, and rolling processes.
FIG. 3 is a micrograph showing a cross section (15x magnification), a cross section (100x magnification), and a longitudinal cross section (100x magnification) of a wire having an outer diameter of about 0.559 cm). Figures 10, 11, and 12 show a 12 inch x 12 inch (approximately 30.48 cm) cast by conventional methods.
×30,'4 s cm) bar was made through the conventional processing process as described above.
These are micrographs showing each longitudinal section of the edge, the middle part between the edge and the center, and the center of a rod having an outer diameter of 68 cyi at a magnification of 100 times. Figures 13, 14, and 15 show 3.5-inch (approximately 8.89 cm) cast by the casting method and casting apparatus of the present invention.
The edge, the middle part between the edge and the center, and the longitudinal direction of the center of a bar with an outer diameter of 0.54 inches (approximately 1.389) made by rolling a bar with an outer diameter of fn) Cross section magnification 100
These are micrographs each shown at magnification.

Claims (1)

Claims: 1. A casting method for casting a metal article in an elongated mold having a cross-sectional area substantially between 25.8c4 and 967.74crtf, and at least as long as the metal article to be cast. (b) molten metal is passed from a source of molten metal through the bottom portion of the mold to create a cross-sectional area of 25.8 cm and 77 f; for the template of 2.39 kq/crA/min and 23.9
kq/crA/min, and for a mold with a cross-sectional area of 967.74 crtt, 0.2
39kg/crA/min and 4.78 kg/crt
1. / min in, and for a mold with a cross-sectional area between the two cross-sectional areas, introduce the molten metal at a filling ratio between the two light-weight ratios; (c) molten metal; flowing along the mold by applying a pressure differential between the source of molten metal and a top portion of the mold; and a) cooling the mold while regulating the flow of molten metal along the mold. (e) flowing molten metal from said molten metal source to extend said casting shell and molten top toward a top portion of said mold; A casting method characterized by solidifying the molten surface. 2. Cooling the mold comprises directing a jet of coolant onto at least a portion of the walls of the mold and cooling the walls of the mold while the molten metal is flowing past the melt. Casting method according to claim 1, characterized in that it comprises ceasing the jet of coolant onto the part. 3 (a) a molten metal source 10; (b) a bottom portion having an opening and a top portion;
5.8c4 and 967.74crtt and at least as long as the elongated metal article to be cast, and arranged to receive molten metal from said molten metal source. (c) connecting the molten metal source 10 and the top portion of the mold by applying pressure to the surface of the molten metal in the molten metal source to regulate the flow of molten metal along the mold; arranged to create a pressure difference between the molten metal and
a source of pressurized gas for introduction into the opening of the mold; and 2) a source of coolant (27, 3) for cooling the mold.
0); A casting device for casting an elongated metal article. 4. Casting apparatus according to claim 3, characterized in that the coolant supply source is provided with a valve nozzle 30 that can be tightened.