CN111496199A - A device for increasing the cooling rate of an ingot and a method of using the same - Google Patents

Abstract

The device for increasing the cooling rate of the ingot mainly includes four parts: the heat insulating material at the bottom of the ingot, the metal mold, the fusible metal mold and the intermediate casting ladle at the top of the mold. The metal mold adopts a bottomless form, which is convenient for the demoulding of the ingot after solidification; the intermediate pouring ladle is located directly above the mold to ensure that the melt is poured into the fusible metal mold upright and prevent the melt from affecting the fusible metal. The mold wall causes impact; the fusible metal mold is placed inside the metal mold, and the mold is solid in the initial stage of gapless metal mold casting, which can solidify the metal melt; when the surface of the melt forms a solidified shell , the meltable mold absorbs the latent heat of melt solidification and melts into a liquid state, and then fills between the ingot and the mold, and keeps the liquid state for a long period of time thereafter until the ingot is completely solidified; the present invention can improve the cooling rate of the ingot , shorten the production cycle of ingots, reduce the macrosegregation of ingots, and refine the microstructure of ingots.

Description

A device for increasing the cooling rate of an ingot and a method of using the same

technical field

The invention belongs to the field of metal mold casting, and relates to a device for increasing the cooling speed of an ingot and a method for using the same.

Background technique

During solidification, increasing the cooling rate has many advantages, such as grain refinement, reduction of macrosegregation, increased solid solubility, increased strength, and enhanced corrosion resistance. Although in the past few decades, researchers have invented many methods to increase the cooling rate, such as: suction casting, stripping method, atomization method, laser surface remelting, etc., but these methods are all at the expense of the size of the product. premise. Therefore, how to obtain a faster cooling rate in a large range is still a major problem in the field of metal solidification.

The cooling rate in the solidification process depends on the thermal diffusion of the ingot, and the main factors affecting the thermal diffusion of the ingot are the following three points: the heat transfer capacity of the mold, the heat transfer capacity of the metal ingot itself, and the interface between the mold and the ingot. heat transfer capacity of the gap. Among them, the heat transfer ability of the interface gap between the mold and the ingot is the decisive factor for the cooling rate during the solidification of the metal mold. However, so far, most of the research has focused on improving the heat transfer ability of the metal mold, and almost no improvement in the metal-mold A study of interfacial heat transfer capability. For example, in the patent CN 107059118 A, a cooling radiator plate is added on the casting mold, and the cooling speed is increased by feeding liquid or inert gas into the cooling pipe on the radiator plate. Patent CN 105586635 A adds a chemical endothermic reaction heat exchanger on the casting mold, and feeds reactants into the heat exchanger during the solidification process of the ingot, takes away the heat generated on the casting mold through the endothermic reaction and increases the cooling speed.

The heat transfer capacity between the metal and the mold can be expressed by the heat transfer coefficient h (InterfacialHeat Transfer Coefficient, IHTC) between the metal and the mold, which is a function of time:

h=Ci(t) ^-n

The heat transfer in the traditional metal mold casting process can be divided into four stages. The first stage is the moment when the liquid metal is poured into the mold. The molten metal and the mold are in complete contact. The only mechanism of heat transfer in this stage is the heat conduction from the liquid metal to the mold, so the interface heat transfer coefficient presents a very high temperature. High value; the second stage begins when a thin solidified shell is formed on the surface of the ingot, and the ingot and the mold are in a semi-contact state. There are three main heat transfer mechanisms at this stage: between the ingot and the mold The heat conduction of the ingot and the casting through the air pockets between the contact surfaces and the heat radiation through the air pockets, so the interface heat transfer coefficient drops rapidly. In the third stage, due to the cooling shrinkage of the ingot and the thermal expansion of the mold, an air gap is formed at the interface between the ingot and the mold. Therefore, the heat transfer mechanism in this stage is mainly that the ingot and the mold pass through the interface air gap. As the heat conduction and heat radiation proceed, the interfacial heat transfer coefficient decreases slowly.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device for increasing the cooling rate of an ingot and a method for using the same; the method eliminates the air gap between the ingot and the ingot by adding a fusible metal mold between the ingot and the mold, Therefore, the heat transfer mode during the solidification process of the ingot can be changed, which can achieve the purpose of increasing the cooling rate of the ingot, shortening the production cycle of the ingot, reducing the macrosegregation of the ingot, and refining the microstructure of the ingot.

In order to achieve the above object, the present invention provides the following technical solutions:

A device for increasing the cooling rate of an ingot mainly includes four parts: insulation material at the bottom of the ingot, a metal mold, a molten metal mold, and an intermediate ladle at the top of the mold. The metal mold adopts a bottomless form, which is convenient for the demoulding of the ingot after solidification; the intermediate pouring ladle is located directly above the mold to ensure that the melt is poured into the fusible metal mold upright and prevent the melt from affecting the fusible metal. The mold wall causes impact; the fusible metal mold is placed inside the metal mold, and the mold is solid in the initial stage of gapless metal mold casting, which can solidify the metal melt; when the surface of the melt forms a solidified shell , the meltable mold absorbs the latent heat of melt solidification and melts into a liquid state, then fills between the ingot and the mold, and remains liquid for a long time thereafter until the ingot is completely solidified.

Further, the bottom insulation material can be selected from alumina ceramic insulation board, zirconia ceramic insulation board, mullite fiber insulation board, etc.;

Further, cast iron, cast steel, red copper, aluminum alloy, etc. can be selected as the metal casting material; other cooling forms such as water cooling, air cooling, chemical reaction cooling, etc. can also be adopted for the surface of the metal casting mold.

Further, the fusible metal mold material needs to be made of a metal with a low melting point, such as aluminum alloy, tin alloy, gallium indium alloy, etc.; the fusible metal mold can be made of the same material as the metal mold;

Further, the thickness of the fusible metal mold depends on the physical properties of the alloy to be cast, including the melting point, latent heat of solidification, specific heat capacity, etc. of the alloy;

Further, the fusible metal mold must reach a certain thickness to ensure that the fusible metal mold is melted after the metal solidification shell is formed, so as to avoid contamination of the melt.

The beneficial effect of the invention is that, by adding a fusible metal mold between the ingot and the mold to eliminate the air gap between the mold and the ingot, thereby changing the heat transfer mode during the solidification process of the ingot, it can improve the Ingot cooling rate, shorten ingot production cycle, reduce ingot macrosegregation, refine ingot microstructure, etc.

Description of drawings:

Figure 1 is a schematic structural diagram of the present invention.

Figure 2 is a schematic diagram of the principle of the present invention.

Figure 3 is the macrostructure of high chromium stainless steel fusible metal casting.

Figure 4 is the macrostructure of high chromium stainless steel fusible metal casting.

Figure 5 is the macrostructure of high chromium stainless steel fusible metal casting.

Detailed ways:

The specific technical solutions of the present invention are further described below with reference to the accompanying drawings, so that those skilled in the art can further understand the present invention.

As shown in Figures 1 and 2, a device for increasing the cooling rate of an ingot mainly includes: a thermal insulation material 1 at the bottom of the ingot; a metal mold 2; a fusible metal mold 3 placed inside the metal mold; Tundish 4 on top of the mould. The metal mold 2 adopts a bottomless form, which facilitates the demoulding of the ingot after solidification; the intermediate pouring ladle 4 is located directly above the fusible metal mold 3 to ensure that the melt is poured into the fusible metal mold 3 upright, Prevent the melt from impacting the fusible metal mold wall; the fusible metal mold 4 is placed inside the metal mold, and in the initial stage of gapless metal mold casting, the mold is solid, and the metal melt can be solidified and formed; When a solidification shell is formed on the surface of the melt, the meltable mold absorbs the latent heat of solidification and melts into a liquid state, then fills between the ingot and the mold, and remains liquid for a long time thereafter until the ingot is completely solidified.

Example 1. In this example, the traditional metal mold material is H13 steel, and its composition is: (wt. %) 0.4 C, 1.0 Si, 0.4 Mn, 5.1 Cr, 1.3 Mo, 1.0 V; fusible metal mold The material is 6061 aluminum alloy, and its composition is: (wt. %) 0.3 Cu, 1.0 Mg, 0.12 Mn, 0.25 Zn, 0.04 Cr, 0.6 Si, 0.7 Fe; the casting alloy is X12CrMoWVNbN10-1-1 alloy steel, and its composition is : (wt. %) 0.12 C, 10.5 Cr, 1.06 Mo, 0.98 W, 0.45Mn, 0.18 V, 0.055 Nb, 0.75 Ni, 0.052 N, 0.09 Si; the insulation material is mullite fiberboard.

In this embodiment, the height of the metal mold and the fusible metal mold are both 108mm; the outer diameter of the metal mold is 118mm, and the inner diameter is 87mm; the inner diameter of the fusible mold is 76mm, and the wall thickness is 5mm; Thickness is 25m. The melting temperature and casting temperature of X12CrMoWVNbN10-1-1 steel are both 1600℃.

For comparison, traditional metal casting is performed in this example. The outer diameter of the metal mold is 118mm, and the inner diameter is 76mm. The melting temperature and casting temperature of X12CrMoWVNbN10-1-1 steel are both 1600℃.

Figures 3 and 4 are the macrostructures of X12 steel ingots obtained by conventional metal mold casting and gapless metal mold casting, respectively. For the ingot cast by traditional metal molds, its macrostructure conforms to the distribution of the typical macrostructure of the ingot, which mainly includes three parts, namely the surface chilled area, the columnar crystal area and the intermediate equiaxed crystal area. CET shift. However, for the ingots cast without gaps, the macrostructure is composed of columnar crystal regions, almost no intermediate equiaxed crystals, and no CET transformation occurs. It can be seen that gapless metal mold casting can greatly improve the cooling rate of the ingot.

Example 2. In this example, the traditional metal mold material is H13 steel, and its composition is: (wt. %) 0.4 C, 1.0 Si, 0.4 Mn, 5.1 Cr, 1.3 Mo, 1.0 V; fusible metal mold The material is 6061 aluminum alloy, and its composition is: (wt. %) 0.3 Cu, 1.0 Mg, 0.12 Mn, 0.25 Zn, 0.04 Cr, 0.6 Si, 0.7 Fe; the casting alloy is X12CrMoWVNbN10-1-1 alloy steel, and its composition is : (wt. %) 0.12 C, 10.5 Cr, 1.06 Mo, 0.98 W, 0.45Mn, 0.18 V, 0.055 Nb, 0.75 Ni, 0.052 N, 0.09 Si; the insulation material is mullite fiberboard.

In this embodiment, the height of the metal mold and the fusible metal mold are both 156mm; the outer diameter of the metal mold is 118mm, and the inner diameter is 96mm; the inner diameter of the fusible mold is 76mm, and the wall thickness is 10mm. The thickness of the mullite fiberboard is 25m. The melting temperature and casting temperature of X12CrMoWVNbN10-1-1 steel are both 1600℃.

Figure 5 shows the macrostructure of the X12 steel ingot. The macrostructure is composed of columnar crystal regions without intermediate equiaxed crystal regions. Compared with the macrostructure of the X12 steel ingot in Fig. 4, the distance between the primary dendrite arms is smaller. We can see that a greater cooling rate can be obtained by adjusting the parameters of the fusible mold.

In addition, it should be understood that although this specification is described in terms of embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (6)

1. An apparatus for increasing the cooling rate of an ingot comprises four parts: the casting method comprises the following steps of (1) casting a heat-insulating material at the bottom of an ingot, a metal casting mold, a fusible metal casting mold and an intermediate casting ladle at the top of the casting mold, wherein the metal casting mold adopts a bottomless form, so that ingot casting demolding after solidification is facilitated; the intermediate casting ladle is positioned right above the casting mold, so that the melt is vertically poured into the fusible metal casting mold, and the melt is prevented from impacting the wall of the fusible metal casting mold; the fusible metal casting mold is placed on the inner side of the metal casting mold, and is solid at the initial casting stage of the gapless metal mold, so that the metal melt can be solidified and molded; after the surface of the melt forms a solidified shell, the fusible mold absorbs the latent heat of solidification of the melt to melt into a liquid state, and then fills between the ingot and the mold, and remains in the liquid state for a long period of time thereafter until the ingot is completely solidified.

2. The device for increasing the cooling speed of the cast ingot according to claim 1, wherein the bottom heat-insulating material can be an alumina ceramic heat-insulating plate, a zirconia ceramic heat-insulating plate, a mullite fiber heat-insulating plate and the like.

3. The device for increasing the cooling speed of the cast ingot according to claim 1, wherein the metal casting material can be selected from cast iron, cast steel, red copper, aluminum alloy and the like; the surface of the metal mold may also be cooled by other cooling means, such as water cooling, air cooling, chemical reaction cooling, etc.

4. The device for increasing the cooling speed of the ingot according to claim 1, wherein the fusible metal casting material is a metal with a low melting point, such as aluminum alloy, tin alloy, gallium-indium alloy and the like; the fusible metal mold may be made of the same material as the metal mold.

5. The apparatus of claim 1, wherein the thickness of the fusible metal mold is determined by the physical properties of the cast alloy, including the melting point, latent heat of solidification, specific heat capacity, etc. of the alloy.

6. An apparatus for increasing the cooling rate of an ingot as set forth in claim 1, wherein the fusible metal mold must be of a thickness to ensure that the fusible metal mold melts after the solidified shell of metal has been formed, thereby avoiding contamination of the melt.

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