JPS5915736B2 - Manufacturing method of composite steel ingot for forging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a composite steel ingot for forging, and more particularly to a method for producing a composite steel ingot for making a composite steel ingot that facilitates the joining of a core material and a cast material to ensure the production of a completely integrated forged product. The purpose is to provide a manufacturing method.

Forged steel products include steel types such as alloy steels containing C, r, Ni2Mo, etc., and high carbon steels containing up to about 1 modulus of C. These steel types tend to develop columnar crystals during solidification, so the center of the steel ingot is It is easy to develop cavities due to coagulation and shrinkage.

In most cases, such cavities are crimped during forging and are not considered defects in the product, but if the cavities are significantly developed or the forging process ratio cannot be maintained sufficiently due to the shape of the product. remains as a product defect.

Therefore, if it is necessary to completely avoid the occurrence of cavities, the core material is set in the mold beforehand when casting the steel ingot, and the molten steel is poured into the steel ingot to surround the core material. A method of manufacturing may be used.

The casting method is also used to manufacture products that are made of different materials on the inside and surface, such as rolls, which are preferably hard on the surface and tough on the inside, but are also integral.

However, in this type of casting method, a large core material that occupies the core part of the steel ingot is often used, so it has a large heat capacity and the surface temperature does not rise slightly even when it comes into contact with molten steel during casting. First, it cannot be welded to the cast material and integrated with the cast material.

Therefore, it is necessary to completely join the boundary parts and integrate them by crimping during forging.

Conventionally, the cross-sectional shape of this core material has been circular or quadrilateral depending on whether the cross-sectional shape of the steel ingot is flat, square, or flat. When the value was small, it was difficult to completely join the boundary between the core material and the cast material.

In order to solve the drawbacks and problems of the conventional composite steel ingots for forging as described above, the present invention improves the forging process ratio by making the cross section of the core material into a circular or quadrilateral periphery with corrugations. To provide a method for manufacturing a composite steel ingot, in which the boundary between the core material and the cast material can be completely crimped and joined even when the material is small.

The present invention is used to avoid cavities formed in the center when manufacturing large steel ingots for forging, or when manufacturing forged products made of composite materials with different materials on the inside and surface. The method used was to place a steel material with a thickness or diameter of 5 or more sieves in advance into a cast iron mold, and then pour the molten steel that would form the surface layer using the bottom pouring method to form the core material. In the manufacturing method of composite steel ingots by casting, the core material surface is cut in advance so that it is uniform in the height direction and forms a waveform in the cross section, and the wave height and pitch of the waveform are adjusted. h/D≧0.01 1/h≦3 where h: Wave height α of the surface corrugation l Pitch box of the surface corrugation D: Thickness or diameter of the core material By making the forging process ratio This is a method for manufacturing a composite steel ingot for forging, which is characterized in that it facilitates joining of the core material and the surface cast material even when the material is small, and complete crimping and joining of the boundary portion is performed.

Next, the configuration of the method of the present invention will be explained in detail based on specific embodiments.

FIG. 1 is an explanatory diagram of a specific example of the method of the present invention, in which a core material 5 is suspended from a hanging fixture 4 via a hanging rod 3 inside a mold 2 placed on a surface plate 1. The steel is charged in advance, and molten steel 7 is injected through the upwelling port 6 by a bottom pouring method to form a cast material 8.

When the steel ingot is large and multiple hot water outlets are used, the core material 5
Instead of hanging it, fix it on the surface plate 1,
It is also possible to provide around the core material.

The cross-sectional shape of the core material 5 is selected to be approximately similar to the cross-sectional shape of the steel ingot, and is rectangular, square, or circular.

However, if the core material surface is completely flat or cylindrical, there is no problem if the forging ratio is sufficiently large, but when the forging ratio is as small as 2 to 3, the gap between the core material 5 and the cast material 80 It was discovered that the joint was insufficient and could not be completely integrated.

This creates a gap between the core material and the cast material during rolling reduction.
This is due to the lack of force in mutual pressing.

Therefore, we thought that if we apply a corrugated process to the surface of the core material to prevent it from sliding laterally, the core material and the cast material will be strongly pressed against each other, and a good crimping condition will be exhibited. When a cast steel ingot was produced with a corrugated half circumference and a cylindrical surface on the other half, and stretch forging was performed at a forging ratio of 3, the corrugated portion was completely joined, but the cylindrical surface was not joined. There were some incomplete parts.

If only the crimping during forging is considered, the corrugation on the surface of the core material has the same effect even if it is applied in the height direction. It is inappropriate to add corrugations in the height direction.

That is, the surface of the core material must be uniform in the height direction.

The corrugated shape on the surface of the core material is appropriately selected taking into account the difficulty of cutting and cracks at the boundaries that occur during casting, but corrugates or flutes are generally used.

Triangular shapes are easy to cut if there is no problem with cracking during solidification.

In addition to cutting, there are other methods for creating corrugations on the surface of the core material, such as casting or forging, but in either case, complete bonding with the cast material cannot be achieved unless the oxidized scale on the surface of the core material is completely removed. Therefore, some cutting work is unavoidable.

The purpose of adding corrugations to the surface of the core material is to restrain the relatively free plastic flow between the cast material and the core material during forging, so in order to obtain sufficient restraining force, the shape must be carefully selected. Conditions are necessary.

In order to find this condition, we forged a number of composite steel ingots with different cross-sectional shapes of the core material, and investigated the bonding state at the boundary between the core material surface and the cast material.

That is, using 20 to 200 ton blank and flat molds, composite steel ingots are made using core materials with varying wave height h, pitch 1, and diameter or thickness D as defined in Fig. 2. It was manufactured and subjected to stretch forging at a forging ratio of 2S, and the bonding state of the boundary between the core material surface and the cast material was investigated using ultrasonic flaw detection.

The results are shown in Figure 3. If h/D≧0.01 and l/h≦3, where D is the diameter or thickness of the core material, the boundary will be completely joined and there will be no defects. I found something that was unacceptable.

Note that the core material used here cannot achieve its original purpose unless it remains solid without melting during casting or solidification of molten steel, so the diameter or thickness of the core material is 5 cm.
It needs to be IrL or higher.

The present invention specifies the surface shape of the core material when manufacturing a composite steel ingot by the casting method, and according to this method, the composite steel ingot is forged and the boundary between the core material and the cast material is The complete integration ensures a product of much superior quality compared to conventional composite steel ingot forgings.

[Brief explanation of drawings]

Figure 1 is a schematic explanatory diagram of the method for manufacturing composite steel ingots. FIG. 3 is a drawing showing how defects occur due to unbonded boundaries due to the relationship between the wave height, pitch, diameter, or thickness of the core material. 1...Surface plate, 2...Mold, 3...Hanging rod, 4...
・Hanging metal fittings, 5... core material, 6... bath outlet, 7...
- Molten steel, 8...Casting material, h...Wave height, l...Pitch, D...Diameter or thickness of core material.

Claims (1)

[Claims] 1. The core material in the cast iron mold has a thickness or diameter of 5 CI.
In a method for producing a composite steel ingot by placing a steel material of rL or more in advance and pouring molten steel into the core material using a bottom pouring method; ,
Cutting is performed in advance to form a waveform that is uniform in the height direction and in the cross section, and the wave height and pitch of the waveform are h/D≧0.01 1/h≦3 where h: surface waveform A method for producing a composite steel ingot for forging, characterized in that the pitch of the surface corrugation is equal to the thickness or diameter of the core material.