JPS6028578B2 - Cast steel casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a cooling metal for mirror steel that is used on a part or the entire surface of a mold for the purpose of improving the internal properties of steel castings (zen steel).

Senko products have the advantage of having fewer restrictions on shape than rolled or forged products, but when cast into sand molds,
As the size of the product increases and the shape becomes more complex, there is a drawback that internal defects inevitably arise within the twill mass due to the coagulation phenomenon.

Conventionally, as a preventive measure to control the solidification conditions within the mirror steel, an iron block or steel block, usually called a cold metal, was used on the mold surface, and the key mass portion opposite to these blocks was cooled. A method of promoting cooling solidification is used,
Qiangang's internal quality improvements have been effective.

However, experience has shown that cracks tend to occur on the surface of Senko products when exposed to a cold metal, and that the tendency for cracks to occur increases as the size of the product and the area of the cold metal increases. The following phenomena have been cited as causes of this phenomenon.

In other words, the difference between applying a chill mold to a sand mold and a sand mold is that the surface of the steel that the chill metal touches is rapidly cooled, and shrinkage stress occurs rapidly due to solidification, and the cold metal is made of metal. It is the soul and does not follow the deformation caused by the solidification and contraction of the twilled steel at all, rather the chilled metal expands due to temperature rise and exhibits a behavior that goes against the solidification and contraction of the mirror steel, which promotes cracking. This means that it acts on

Also, to prevent cracking of the surface of the skin where cold gold is applied,
Conventionally, there is a method of sanding, but sanding causes a problem in that the effect of improving the internal properties of steel steel by chilling metal is significantly reduced due to the insulating properties of sand.

Conventionally, there was no appropriate method to prevent surface cracking when using this cooling metal, and solvents and welding repairs were required to remove cracks that occurred on the mirror surface, resulting in significant manufacturing costs and process losses. There is a need to establish a method to prevent this.

Techniques for preventing cracks on the twill surface include flutes for coin coins for rolling and casting, and corrugated molds.

Macroscopically, the cross-sectional shape of these mirror ingots is simple, square, rectangular, or circular, and cracks that occur as the steel ingot solidifies occur on its outer periphery and in the height direction of the steel ingot. Therefore, it is known that the inner surface of the mold is provided with unevenness in only one direction parallel to the axis of the steel ingot. The shape of the unevenness of a flute or corrugate is generally composed of complex curves that take into consideration the shrinkage of the steel ingot, but as a result, so-called vertical cracks on the steel ingot surface are almost completely eliminated. It is thought that this has been prevented.

However, in Zeni-ko, the fin surface that is hit by the cold metal is
Although the area is much smaller than the mold for steel ingots, which requires flutes or corrugations, cracks still occur. This is due to the fact that stress in multiple directions on the surface of the coin that the gold touches must be considered.

It is well known that stress is vector-composed,
When the resultant force of sardine stress in many directions exceeds the material strength, it is inevitable that cracks will occur in a direction perpendicular to the direction of the resultant force. In other words, regarding the mirror surface of the steel steel that comes into contact with the chiller, consideration must be given to dealing with stress in multiple directions. The present invention was completed as a result of detailed analysis of the shrinkage stress of the key surface during casting of cast steel from the above-mentioned points. The purpose of casting is to form desired unevenness on the surface to divide the shrinkage stress of the surface.

It is well known that cracking generally occurs when the stress applied to that part exceeds its proof strength, and to prevent cracking, it is necessary to increase the strength of the material or reduce the stress. .

In the case of coin keys, the strength of the material is determined by the range required by the material properties of the product, and the strength of the material is limited to the coin release surface during casting. It is impossible to destroy it. Also, from the point of view of the tensile stress on the coin surface during casting, this stress is generated by solidification shrinkage, and the total amount of stress on that surface is determined by the shape and width of the release surface of the twill steel. It is impossible to increase or decrease it arbitrarily. If the size of the chiller is small, the total amount of stress generated on the surface of the chiller that comes into contact with the chiller will be small, so cracks will not occur.
In other words, according to the research conducted by the present inventors, when a chiller with a width and length of less than 20 m2 (hereinafter referred to as a small chiller) is used alone, However, there is no concern about cracks in the surface of the cold iron, but if multiple of these small chillers are lined up and made into an aggregate, and either the width or length is 20 mm or more, or the chiller itself is 20 mm long. If you use something that exceeds the ship's armpit (hereinafter referred to as a large chiller),
The susceptibility of cast skin to cracking increases rapidly.

Measures to reduce the magnitude of the stress that causes this cracking by reducing the cooling effect on the surface of the halberd, in other words, by reducing the thickness of the chiller and the area of the chiller exposed to the rust surface. This is putting the cart before the horse by ignoring the aim of improving the internal properties of the fin steel through the cooling effect of the chilled metal. In order to prevent internal defects in mirror steel, it is necessary to use a chiller with the necessary thickness and width, that is, a large chiller, and in addition, there is a method to prevent cracks on the surface of the steel that the chiller touches. There must be. Based on the above-mentioned study on the cracking of the casting surface of casting steel that has been applied with a chilled metal, the present inventors dispersed the stresses acting in multiple directions on the casting surface, and calculated the absolute value of the combined stress. As a means to keep the temperature below the strength of the steel and thereby prevent cracks from occurring on the key skin, the surface that comes into contact with the mirror skin of the cold metal (chilled metal surface) is made of metal that is continuous not only in one direction but in multiple directions. This idea was based on a method of casting steel that creates irregularities that form patterns.

Hereinafter, details of the present invention will be explained with reference to the drawings.

Figure 1 is an example of a large flat chiller that embodies the basic idea of the present invention. This is a method in which orthogonal lattice-shaped grooves 3 are provided on the chiller surface 2 that is in contact with the outer surface 4 of the chiller 1, and as a result, the outer surface 4, which is a large solidification and shrinkage stress field, is surrounded by the grooves. By setting the absolute value of the stress in the stress field divided into small stress fields for each range to a sufficiently small value within the crack generation limit of the village power of the rust surface 4, the occurrence of cracks in the surface area 4 is prevented. It is something.

In this case, the grooves have the role of dividing the surface of the surface into small stress fields, and grooves that are too shallow are ineffective for this purpose.

As shown in FIG. 2, the depth F of the groove varies depending on the deposit conditions at the time, but experiments conducted by the present inventors have confirmed that for normal casting, approximately five or more ribs are sufficient. At the same time, if the angle between the side wall 5 of the groove 3 and the chilled metal surface 2 is close to 90 degrees, the constraint of the surface 4 by the groove 3 will be too strong, and the contraction stress of the surface 4 will be concentrated around the groove 3. It has been found that this angle is usually required to be 120 degrees or more, and desirably around 135 degrees, in order to make it easier to create. Furthermore, when the line of intersection between the side wall 5 of the groove 3 and the cold metal surface 2 forms a ridgeline with a clear angle, this ridgeline is transferred to the casting surface 4, and a corner 6 is formed on the casting surface 4. The corners 6 must be smoothly rounded because they become places where stress is concentrated and encourage cracking. It was confirmed that the radius of curvature R of the roundness should be greater than the depth F of the groove 3 in order to expect a stress relaxation effect. In addition to the above, the grooves increase the surface area of the steel and provide a shrinkage allowance for the rust skin to relieve the shrinkage stress of the rust skin due to solidification and temperature drop.

The angle of the side wall of the groove and the roundness of the ridgeline where the groove meets the cold metal surface also serve to ensure smooth contraction of the mirror surface. Furthermore, the factors that determine the amount of shrinkage of the pad 4 are mainly the groove depth F and the groove interval A.

Although the light green curvature is a secondary factor, although it has a large effect on the stress concentration described above, it has a small effect on the increase in the surface area as a shrinkage allowance. In experiments conducted by the present inventors regarding the hollow cylindrical body, it was found that the following conditions are necessary to prevent the mirror surface 4 from cracking. [Groove spacing/Groove depth] [
Remaining chiller surface after port cutting]'1}Outer side chiller...
Within 20 times Within 80%'2-Inner side cooling metal
・・Within 12 times ・Within 70% '3} Bottom cooling metal・
...within 12 times and within 70% The reason why the restrictions for the outer chiller are looser than those for other chillers is that air gaps are created due to solidification shrinkage of rusted steel. Further, although it is not necessarily necessary to satisfy the above two conditions at the same time, it is desirable to satisfy both conditions. Figure 3 shows the effect of preventing cracking in the case where grid-like grooves are formed on the surface of a large flat chiller using the procedure described above and this is actually used for casting products.

(The diagonal lines in the figure indicate the amount of repair due to cracking.) If the above-mentioned precautions are taken, the cracking of the coin surface that comes into contact with the chiller will be significantly reduced. Furthermore, it was confirmed that even when the above-mentioned chiller with grid-like grooves was applied to a cylindrical outer mold, the results were comparable to those of the large planar chiller. However, when a cylindrical core chiller or a spherical chiller is used, the stress state acting on the core becomes more complex, and the orthogonal lattice grooves are insufficient to prevent cracking in the core. It turns out.

As a result of considering countermeasures, we came up with the idea of dividing the stress generated in the surface 4 into, for example, three directions or six directions, and as shown in Figs. There is a method of carving grooves 3 forming a continuous hexagonal pattern (Fig. 4 b) on the cold metal surface 2 as shown in Fig. 4a).
As shown in (Figure 4c) (Figure 4d), for example, in a triangular or hexagonal continuous pattern, a cone or vice-principal cone is placed at the apex of the triangle (E-roha) or the apex of the hexagon (E-roha-niho-he). This was realized by providing a spherical surface (FIG. 6a) or a spherical surface (FIG. 6b). At this time, the intervals between the grooves 3 and the recesses 8, the way the green is rounded, etc. are the same as in the case of the lattice grooves (FIGS. 1 and 2). (In this case, the point is to disperse the stress, and depending on the case, it is not necessary to purchase a pentagonal or octagonal shape.) Also, depending on the case, the cold metal may weld with the molten steel that has been cast. .

The welding phenomenon can be prevented by applying a coating agent to the cold metal surface. However, the surface of the chiller is coated with a material having low thermal conductivity, which reduces the effect of cooling the mirror steel and improving the internal quality by the chiller. Therefore, it is necessary to make the coating thickness of the mold coating agent as thin as possible, and according to the studies conducted by the present inventors, it is necessary to take care that the coating thickness does not exceed 5 skins. If you keep this point,
It is permissible to apply a mold coating agent to a cooling metal that has been provided with crack prevention measures according to the present invention. Examples of the present invention will be described below.

Example 1 An example in which the cooling metal of the present invention is applied to a thick part of mirror steel with uneven wall thickness is shown below.

Target product: Upper plate type steel product with support lug (upper plate type wall thickness 20 ribs, weight including mirror 12 mon) Material: SC49 (0.25% C, 0.40% Si, 0.
95%Mn) Product shape: Upper plate-like hemispherical inner radius: 155 Support lug dimensions: Length: 40 m, Lower side: 40 m, Upper cape: 100 Side neck: 50 m Applicable situation of chiller Applicable range: Support lug machine and Lower side cooling plate thickness: 10mm Side cooling plate area: 400 x 50 Cutting type on the side cooling plate: Orthogonal cross groove Cutting shape: Groove depth: 25 Side groove width: 5mm Green curvature of the proboscis groove: 5 mm Groove spacing: 25 mm As a result of Example 1, the surface was in good condition with no cracks, and the support lug part was of good quality with no defects in the radiation inspection results. Ta.

Example 2 A production result of a coin steel product, which is one of the present invention, is shown in which a cold metal having a continuous triangular pattern with a cone provided at the apex of the triangle is cast on the entire surface of the core.

Target product: Ribbed arc-shaped steel product (product thickness 25mm, weight including coin 21t600) Material: SC
49 (0.25%C, 0.40%Si,'0.94%M
n) Shape: Overall width 1935 skin, cylindrical surface width 1635 side, rib width 150 side, total product height 1800 side, cylinder inner radius 15
5. Application status of the cooling iron Applicable range: Full cooling metal on the inner mirror surface of the cylindrical part of the product Thickness: 50 mm Type of cut into the cooling metal: Triangular apex cooling with a continuous triangular pattern Shape of cut into gold: 11 mm, depth: 45 costo-conical Cut center spacing: 183 As a result of carrying out the above procedure, the distribution of stress in three or six directions on the surface of the cut surface is as follows: In the case of a shaped core chiller or a spherical chiller, it is even more effective than the stress distribution method in two directions, and the amount of maintenance and repair of the core surface to remove cracks is further reduced, making it virtually impossible. It became zero.

The situation is shown in Figure 5. (The shaded area in the figure indicates repair due to cracking.) Example 3 Application example of coating agent Target product: Thick plate and flat plate product Thickness: 20 mm, width: 180 mm, length: 2500 mm Material: S
C46 (0.2%C, 0.40%Si, 0.80%Mn
)Bottom flat plate integrated chiller Applicable chiller thickness: 300mm side, width 180mm, length 2500mm Anti-crack measures: Orthogonal cross groove Groove depth: 25 ribs, groove width: 5mm Groove spacing: 25mm Under these conditions, coating agents as shown in Table 1 were used.

As can be seen from Table 1, even when the coating agent was applied, no wrinkling occurred and there was no change in the healthy layer.

As mentioned above, it is possible to provide grooves in the cold metal surface of mirror steel in a lattice shape or in a continuous pattern such as a triangle or hexagon, and furthermore, to form grooves in a continuous pattern or in the apex position of a hexagon, etc. By providing a spherical recess, it is an extremely effective industrial method to prevent cracking when using a wide area chiller for the purpose of improving the internal quality of mirror steel. This is a very useful invention, as the amount of repair work required for rusted surfaces, which has a significant impact on the cost and construction period of steel steel, is greatly reduced.

In addition to the above-mentioned method, the present invention can also be applied to casting using an external mold, and of course this does not depart from the scope of the present invention.

The present invention has been described above, and the embodiments of the present invention are as follows.Core 1 In a chiller used for a part or the entire surface of a mold when casting mirror steel, one or more of them are arranged as a mold. On the chiller surface (the surface that comes into contact with the coin skin) of a chiller whose width and length are each 20 mm or more,
Orthogonal lattice-shaped grooves are provided, and the side walls of the grooves have an angle between vertical and horizontal with respect to the chiller surface, and the corners formed by the intersections of the side walls and the chiller surface are rounded. A method for casting sickle steel according to the claims.

2. A steel casting according to the claims, in which the radius of curvature of the roundness provided at the corner formed by the intersection of the side wall of the groove on the chiller surface and the chiller surface is equal to or larger than the depth of the groove. Law.

3. The steel casting method as claimed in the claims, wherein the depth of the chilled metal surface is five ribs or more.

4 The interval between the grooves on the chiller is within 2M of the groove depth for the outer side chiller, the remaining coolant surface after groove cutting is within 80%, and the inner side chiller and the bottom The steel casting method according to claim 1, wherein the groove spacing of the chiller is within 12 times the groove depth, and the remaining coolant surface after grooving is within 70%.

5. The mirror steel casting method according to the claims, wherein the shape of the grooves provided on the chilled metal surface is a continuous triangular or hexagonal pattern instead of a lattice shape.

6. The coin steel according to the claims, in which the shape of the grooves provided on the chiller surface is replaced by a lattice-like shape, and in which conical or vice-principal conical recesses are provided at positions corresponding to the apexes of a triangle or hexagon. Casting method.

7. The cast steel according to the claims, in which the shape of the grooves provided on the chilled metal surface is replaced by a lattice shape, and in which spherical or truncated spherical depressions are provided at positions corresponding to the vertices of a triangle or hexagon. Casting method.

8. A steel casting method as claimed in the claims, in which, when casting using a chilled metal surface, a mold coating agent is applied to the chilled metal surface to a thickness of 5 skins or less.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of grid-like grooves on a cold metal surface, Figure 2 is a rough diagram of the cross-sectional shape of the grooves, and Figure 3 is a schematic diagram of grid-like grooves on a large flat cold metal surface. Chart of crack prevention effect when attached, 4th
The figure is a schematic diagram of triangular or hexagonal continuous pattern grooves and dents, Figure 5 is a diagram comparing the amount of repair on the core cold metal surface with curvature, and Figure 6 is a diagram of the vice principal's cone. It is a schematic diagram of the recess a and the vice principal's spherical recess b. 1...Cold metal, 2...Cold metal surface, 3...Groove, 4.
...Mirror surface, 5...Groove side wall, 6...Corner corner, 7...
・Bottom of the groove, 8...concavity, A...groove spacing, F...
Groove depth, R... corner radius of curvature. Fig. 1 Fig. 2 Fig. 3 Fig. 4 (Q) Fig. 4

Claims (1)

[Claims] 1. Casting is performed by forming desired unevenness on the cold metal surface of a cold metal used for part or the entire surface of the mold during casting of cast steel to divide the shrinkage stress of the casting surface. Steel casting method. 2 A lattice-like groove is provided perpendicular to the chiller surface, the angle between the side wall of the groove and the chiller surface is 120° or more, and the corner at the intersection of the side wall and the chiller surface has a curvature. A method for casting cast steel according to claim 1, wherein R is given. 3. The steel casting method according to claims 1 and 2, wherein grooves forming a continuous square pattern are formed on the chilled metal surface.