KR20120097064A - Device for estimating a pin-hole defect of solidified shell in continuous casting process and method therefor - Google Patents

Abstract

PURPOSE: An apparatus and a method for predicting pinhole defect of a solidification shell in a continuous casting process are provided to estimate the probability of pinholes using a gas generation index obtained from the properties of mold powder and casting speed and thus to properly change casting conditions or methods. CONSTITUTION: An apparatus for predicting pinhole defect of a solidification shell in a continuous casting process comprises a memory(110) which stores work parameter data about the properties of mold powder according to steel type and casting speed, which are input from outside, and a control unit(190) which calculates a gas generation index using an element among the powder properties, capable of generating gas through combustion, and casting speed stored in the memory and predicts the probability of pinholes in a solidification shell using the calculated gas generation index. [Reference numerals] (110) Memory; (130) Input unit; (150) Casting speed detecting unit; (170) Display unit; (190) Control unit

Description

DEPICE FOR ESTIMATING A PIN-HOLE DEFECT OF SOLIDIFIED SHELL IN CONTINUOUS CASTING PROCESS AND METHOD THEREFOR}

The present invention relates to an apparatus and method for predicting pinhole defects of a solidified shell in a playing process for predicting the possibility of pinhole defects of the solidified shell in a continuous casting process.

In general, a continuous casting machine is a facility for producing cast steel of a certain size by receiving a molten steel produced in a steelmaking furnace and transferred to a ladle (Tundish) and then supplied to a continuous casting machine mold.

The continuous casting machine includes a ladle for storing molten steel, a casting mold for initially cooling the molten steel introduced from the tundish and the tundish into a strand having a predetermined shape, and a plurality of strands connected to the mold to move the strand formed in the mold Of pinch rolls.

In other words, the molten steel tapping out of the ladle and the tundish is formed of a strand having a predetermined width, thickness, and shape in a mold and is transferred through a pinch roll, and the strand transferred through the pinch roll is cut by a cutter to have a predetermined shape. It is made of a slab (Slab), Bloom (Bloom) or billet (Billet) having a cast.

An object of the present invention is to predict the pinhole defects of the solidification shell in the continuous casting process using the properties of the mold powder and the casting speed to predict the pinhole defects of the solidification shell pinch defect in the playing process that can appropriately remove or reduce the pinholes generated An apparatus and a method thereof are provided.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular embodiments that are described. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, There will be.

Pinhole defect prediction device of the solidification shell of the present invention for realizing the above object, the memory is stored the operation variable data for the properties and casting speed of the mold powder for each steel type input from the outside; And a control unit for calculating a gas generation index using a casting rate and a factor capable of generating gas by combustion among physical properties of the powder stored in the memory, and using the calculated gas generation index to predict a pinhole generation probability of the solidification shell. It can include;

The controller may acquire the pinhole generation index by using the calculated gas generation index and the set constant value, and predict the pinhole generation probability of the solidification shell using the obtained pinhole generation index. The constant value may be a value derived by a correlation between the gas generation index and the actual pinhole defect.

Physical properties of the powder stored in the memory may include C total, CO ₂ generation amount and LOI (Loss of Ignition).

The controller may calculate the gas generation index by dividing the physical properties of the powder by the casting speed.

The casting speed is detected in real time through the number of revolutions of the pinch roll, and further comprising a circumferential speed detector for storing the detected casting speed in the memory, wherein the control unit to the casting speed and the memory detected through the circumferential speed detection The gas generation index can be calculated using the properties of the stored powder.

Pinhole defect prediction method of the solidified shell of the present invention for realizing the above object, the step of calculating the gas generation index by using the casting speed and the factor that can generate gas by the combustion of the physical properties of the mold powder; Calculating a pinhole generation index by using the calculated gas generation index and the set constant value; And predicting the pinhole generation probability of the solidification shell using the pinhole generation index calculated above.

Specifically, the physical properties of the mold powder may include C total, CO ₂ generation amount and LOI (Loss of Ignition).

The gas generation index can be obtained by dividing the physical properties of the powder by the casting speed.

As described above, according to the present invention, after obtaining the gas generation index using the properties of the mold powder and the casting speed, and predicting the possibility of pinhole generation using the obtained gas generation index, the casting operation conditions or the corresponding method is appropriately changed. By doing so, there is an advantage of reducing the occurrence of pinholes or appropriately removing the generated pinholes.

1 is a side view showing a continuous casting machine according to an embodiment of the present invention.
FIG. 2 is a conceptual view illustrating the continuous casting machine of FIG. 1 based on the flow of molten steel M. Referring to FIG.
FIG. 3 is a conceptual view illustrating a distribution form of molten steel M in the mold of FIG. 2 and a portion adjacent thereto.
4 is a view for explaining the pinhole defect of the solidification shell.
5 is a view showing a pinhole defect prediction device of the solidified shell according to an embodiment of the present invention.
6 is a graph showing the pinhole defect ratio for each steel type.
7 is a flowchart illustrating a pinhole defect prediction process of a solidification shell according to an embodiment of the present invention.
8 is a graph showing the correlation between the gas generation index and the pinhole generation index according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like elements in the figures are denoted by the same reference numerals wherever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a side view showing a continuous casting machine according to an embodiment of the present invention.

Continuous casting is a casting process in which a molten metal is continuously cast into a bottomless mold while continuously drawing a steel ingot or steel ingot. Continuous casting is used to manufacture simple products such as squares, rectangles, circles and other simple cross-sections, and slabs, blooms and billets, which are mainly for rolling.

The type of continuous casting machine is classified into vertical type, vertical bending type, vertical axis difference bending type, curved type and horizontal type. 1 and 2 illustrate a curved shape.

Referring to FIG. 1, the continuous casting machine may include a ladle 10, a tundish 20, a mold 30, secondary cooling tables 60 and 65, a pinch roll 70, and a cutter 90. have.

A tundish 20 is a container for receiving molten metal from a ladle 10 and supplying molten metal to a mold 30. Ladle 10 is provided in a pair, alternately receives molten steel to supply to the tundish 20. In the tundish 20, the supply rate of the molten metal flowing into the mold 30 is controlled, the molten metal is distributed to each mold 30, the molten metal is stored, and the slag and the nonmetallic inclusions are separated.

The mold 30 is typically made of water-cooled copper and allows the molten steel to be primary cooled. The mold 30 has a pair of structurally opposed faces open to form a hollow portion for receiving molten steel. In the case of manufacturing a slab, the mold 30 includes a pair of barriers and a pair of end walls connecting the barriers. Here, the short wall has a smaller area than the barrier. The walls of the mold 30, mainly short walls, may be rotated away from or close to each other to have a certain level of taper. This taper is set to compensate for shrinkage due to solidification of the molten steel M in the mold 30. The degree of solidification of the molten steel (M) will vary depending on the carbon content, the type of powder (steel cold Vs slow cooling), casting speed and the like depending on the steel type.

The mold 30 maintains the shape of the strands extracted from the mold 30 and forms a strong solidification angle or solidified shell 81 so that molten metal, which is still less solidified, does not flow out. Play a role. The water-cooled structure includes a method of using a copper pipe, a method of drilling a water cooling groove in the copper block, and a method of assembling a copper pipe having a water cooling groove.

The mold 30 is oscillated by the oscillator 40 to prevent the molten steel from sticking to the wall of the mold. Lubricants are used to reduce friction between the mold 30 and the strands during oscillation and to prevent burning. Lubricants include splattered flat oil and powder added to the molten metal surface in the mold 30. The powder is added to the molten metal in the mold 30 to become slag, as well as the lubrication of the mold 30 and the strands, as well as the prevention of oxidative and nitrification of the molten metal in the mold 30, thermal insulation, and non-metallic inclusions on the surface of the molten metal. It also performs the function of absorption. In order to inject the powder into the mold 30, a powder feeder 50 is installed. The part for discharging the powder of the powder feeder 50 faces the inlet of the mold 30.

The secondary cooling zones 60 and 65 further cool the molten steel primarily cooled in the mold 30. The primary cooled molten steel is directly cooled by the spray means 65 for spraying water while maintaining the solidification angle by the support roll 60 not to be deformed. Strand coagulation is mostly achieved by the secondary cooling.

The drawing device adopts a multidrive method using a plurality of sets of pinch rolls 70 and the like to pull out the strands without slipping. The pinch roll 70 pulls the solidified tip of the molten steel in the casting direction, thereby allowing the molten steel passing through the mold 30 to continuously move in the casting direction.

The cutter 90 is formed to cut continuously produced strands to a constant size. As the cutter 90, a gas torch, a hydraulic shear, or the like can be employed.

FIG. 2 is a conceptual view illustrating the continuous casting machine of FIG. 1 based on the flow of molten steel M. Referring to FIG.

Referring to this figure, the molten steel (M) is to flow to the tundish 20 in the state accommodated in the ladle (10). For this flow, the ladle 10 is provided with a shroud nozzle 15 extending toward the tundish 20. The shroud nozzle 15 extends to be immersed in the molten steel in the tundish 20 so that the molten steel M is not exposed to air and oxidized and nitrided. The case where molten steel M is exposed to air due to breakage of shroud nozzle 15 is referred to as open casting.

The molten steel M in the tundish 20 flows into the mold 30 by a submerged entry nozzle 25 extending into the mold 30. The immersion nozzle 25 is disposed in the center of the mold 30 so that the flow of molten steel M discharged from both discharge ports of the immersion nozzle 25 can be symmetrical. The start, discharge speed, and stop of the discharge of the molten steel M through the immersion nozzle 25 are determined by a stopper 21 installed in the tundish 20 corresponding to the immersion nozzle 25. Specifically, the stopper 21 may be vertically moved along the same line as the immersion nozzle 25 to open and close the inlet of the immersion nozzle 25. Control of the flow of the molten steel M through the immersion nozzle 25 may use a slide gate method, which is different from the stopper method. The slide gate controls the discharge flow rate of the molten steel M through the immersion nozzle 25 while the sheet material slides in the horizontal direction in the tundish 20.

The molten steel M in the mold 30 starts to solidify from the part in contact with the wall surface forming the mold 30. This is because heat is more likely to be lost by the mold 30 in which the periphery is cooled rather than the center of the molten steel M. By the way that the periphery is first solidified, the back portion along the casting direction of the strand 80 forms a shape in which the unsolidified molten steel 82 is wrapped in the solidified shell 81.

As the pinch roll 70 (FIG. 1) pulls the tip portion 83 of the fully solidified strand 80, the unsolidified molten steel 82 moves together with the solidified shell 81 in the casting direction. The uncondensed molten steel 82 is cooled by the spray means 65 for spraying the cooling water in the above movement process. This causes the thickness of the uncooled steel (82) in the strand (80) to gradually decrease. When the strand 80 reaches a point 85, the strand 80 is filled with the solidification shell 81 in its entire thickness. The solidified strand 80 is cut to a predetermined size at the cutting point 91 and divided into slabs P such as slabs.

Meanwhile, in FIG. 1, a device including a support roll 60 and a pinch roll 70 is also called a strand, and the strand 80 described in the present invention is formed between the mold 30 and the cutter 90. The solidified shell 81 and the unsolidified molten steel 82 which are moved are called.

The shape of the molten steel M in the mold 30 and the portion adjacent thereto will be described with reference to FIG. 3. FIG. 3 is a conceptual view illustrating a distribution form of molten steel M in the mold 30 and adjacent portions of FIG. 2.

Referring to FIG. 3, a pair of discharge ports 25a are generally formed at the bottom of the immersion nozzle 25 on the left and right in the drawing. The shapes of the mold 30 and the immersion nozzle 25 are assumed to be symmetrical with respect to the center line C, and thus only the left side is shown in this drawing.

The molten steel M discharged together with the argon (Ar) gas from the discharge port 25a draws a trajectory flowing in the upward direction A1 and downward direction A2 as indicated by arrows A1 and A2. do.

The powder layer 51 is formed on the upper part of the mold 30 by the powder supplied from the powder feeder 50 (see FIG. 1). The powder layer 51 may include a layer existing in a form in which the powder is supplied and a layer sintered by the heat of the molten steel M (sintered layer is formed closer to the unsolidified molten steel 82). Below the powder layer 51, a slag layer or a liquid fluidized layer 52 formed by melting powder by molten steel M is present. The liquid fluidized bed 52 maintains the temperature of the molten steel M in the mold 30 and blocks the penetration of foreign matter. A portion of the powder layer 51 solidifies at the wall surface of the mold 30 to form the lubrication layer 53. The lubrication layer 53 functions to lubricate the solidified shell 81 so as not to stick to the mold 30.

The thickness of the solidification shell 81 becomes thicker as it progresses along the casting direction. The portion of the solidification shell 81 located in the mold 30 is thin, and an oscillation mark 87 may be formed by oscillation of the mold 30. The solidification shell 81 is supported by the support roll 60, the thickness thereof is thickened by the spray means 65 for spraying water. The solidification shell 81 may be thickened and a bulging region 88 may be formed in which a portion protrudes convexly.

As such, the mold powder used in the continuous casting process is introduced into the liquid form between the solidification shell 81 and the mold 30 during casting to perform heat transfer and lubrication between the mold 30 and the solidification shell 81. . Carbon is used to control the rate at which the mold powder changes into a liquid phase. However, carbon in the powder is burned by the heat provided in the molten steel, and carbon monoxide (CO) is generated by the combustion reaction. The carbon monoxide generated in this way is trapped in the solidification shell 81 during casting, causing bubble defects such as pin holes in the solidification shell 81 as shown in FIG. 4. In order to cast various steels, powders with different physical properties are used in consideration of the solidification characteristics of each steel type.

In general, in the casting process in which argon is blown into the immersion nozzle 25, argon injection is reported to be a major factor for generating pinholes, but pinholes may also be generated by carbon monoxide and other gases generated when the mold powder is melted. have.

Therefore, the present invention is intended to predict the possibility of pinhole defects in the solidified shell through the factors of the powder that can generate gas by combustion, and the casting factors that govern the combustion and oxidation rate and powder consumption of the powder.

FIG. 5 is a diagram illustrating a pinhole defect predicting device of a solidification shell according to an exemplary embodiment of the present invention, wherein the predicting device 100 includes a memory 110, an input unit 130, a peripheral speed detection unit 150, a display unit 170, and The control unit 190 includes.

The memory 110 stores operation variable data of at least one of steel grades, casting speeds, and properties of mold powders collected or input from the outside. Here, the physical properties of the powder include a factor capable of generating a gas by combustion. Physical properties of the mold powder stored in the memory 110 may include, for example, C total, amount of CO ₂ generated, and a loss of ignition (LOI).

The input unit 130 receives and sets data on various operating variables including physical properties of the powder from the outside.

The peripheral speed detection unit 150 detects the casting speed in real time through the rotation speed of the pinch roll 70 and stores the detected casting speed in the memory 110 according to the control signal. Here, the casting speed may be detected in real time through the main speed detection unit 150, but may be directly input from the user through the input unit 130, or may be provided from a system for controlling the speed of the pinch roll.

The display unit 170 displays a pinhole defect prediction result of a solidified shell or a GUI screen for inputting various operation variables in a text or graph.

The controller 190 calculates a gas generation index (GGI) by using a casting speed and a factor capable of generating gas by combustion among physical properties of the powder stored in the memory 110, and calculates the calculated gas generation index (GGI). By using it to predict the pinhole generation probability of the solidification shell (81). The controller 190 may obtain a pinhole generation index (PGI) using the calculated gas generation index and the set constant value, and predict the pinhole generation probability of the solidification shell using the obtained pinhole generation index. For example, the controller 190 calculates the gas generation index by dividing the physical properties of the powder by the casting speed, and calculates the pinhole generation index using the calculated gas generation index and the set constant value. Here, the constant values are about 95% of the correlation between the pinhole defects and the actual pinhole defects after the gas generation index (GGI) is generated, and the values are derived from the correlations.

The controller 190 may calculate the pinhole generation index using the casting speed set through the input unit 130 or calculate the pinhole generation index in real time using the casting speed input through the main speed detection unit 150. At this time, the properties of the mold powder according to the steel type in both methods may use the value stored in the memory 110.

The physical properties of the powder used for each steel type are shown in Table 1 below.

That is, the physical properties of the powder and its component content may vary by steel type. Basically, the physical properties of the mold powder may include basicity, viscosity, C total, CO ₂ generation amount, and LOI. The composition of these mold powders is basically provided in the specification of the powder.

Powder properties utilized in the gas generation index in the present invention is C total, CO ₂ generation amount and LOI (Loss of Ignition), the component content of such factors may vary by steel type as shown in Table 1. Here, C total [%] is a factor for controlling the melting rate of the powder, CO ₂ generation amount [%] is the amount of gas generated by reaction with O ₂ supplied to the atmosphere during carbon combustion, LOI (Loss Of Ignition) [% ] Is the amount of weight loss of the powder caused by combustion upon melting of the powder. The C total [%] is a percentage in the total ingredient content of the powder. CO ₂ amount [%] is the percentage of the amount of CO ₂ that the amount of CO ₂ generated during the combustion in the entire amount of powder is detected in the sample compared to the total amount of equipment. LOI [%] is a loss of Ignition, a percentage of the total amount of gas consumed when the powder is burned, and means a weight loss due to combustion of CO, CO ₂ , and organic binders, which are factors of weight loss.

Looking at the pinhole defect rate by steel type under the operating conditions shown in Table 1, as shown in FIG. That is, when casting using different powders (A to E) according to the characteristics of the steel type, it can be seen that the pinhole defect ratio (the percentage converted to 1/10) is different for each steel type. Accordingly, it is difficult to predict the occurrence of pinhole defects due to the characteristics of steel, powder properties, and casting speed.

Therefore, in the present invention, the factors that can generate gas by combustion in the physical properties of the mold powder, C total, CO ₂ , Loss of Ignition (LOI), and the casting factors that govern the combustion and oxidation rate and powder consumption of the powder The gas generation index is calculated using the casting speed, and the calculated gas generation index is calculated with a set constant to obtain a pinhole generation index for predicting the possibility of pinhole generation.

In the above, C total is a factor for controlling the melting rate of the powder, and generates gas (CO; C + CO ₂ = 2CO) during melting of the powder. The amount of CO ₂ generated is the amount of gas (C + O ₂ = CO ₂ ) generated by reacting with oxygen (O ₂ ) supplied in the atmosphere during carbon combustion. Loss of Ignition (LOI) is a weight reduction amount of the powder generated by combustion when melting the powder, and may be a weight reduction amount due to CO generation, CO ₂ generation, and combustion of the binder.

7 is a flowchart illustrating a pinhole defect prediction process of a solidification shell according to an embodiment of the present invention, which will be described with reference to the accompanying drawings.

First, the prediction apparatus 100 receives the operation variable including the physical properties of the mold powder capable of generating a gas by steel type casting speed and combustion through the input unit 130 and stores it in the memory 110 (S1). . Here, the controller 190 may obtain a casting speed through the main speed detection unit 150 and store the casting speed in real time in the memory 110. Physical properties of the mold powder may include, for example, C total, CO ₂ generation amount, and Loss of Ignition (LOI).

Subsequently, the controller 190 calculates a gas generation index (GGI) using the properties of the steel powder and the casting speed Vc stored in the memory 110 (S2).

Here, the gas generation index may be calculated by Equation 1 below.

Equation 1

However, Vc [m / min] is the casting speed, C total [%] is a factor controlling the melting rate of the powder, and the amount of CO ₂ generated [%] is generated by reacting with O ₂ supplied in the atmosphere during carbon combustion. The amount of gas, and LOI (Loss Of Ignition) [%] is the amount of weight loss of the powder caused by combustion upon melting of the powder.

Properties of the powder used in Equation 1, C total, CO ₂ generation amount and LOI (Loss of Ignition) are factors that can generate gas by combustion.

After obtaining the gas generation index as described above, the controller 190 calculates a pin hole generation index (PGI) using the calculated gas generation index and the set constant value (S3). Here, the constant value is a value derived by the correlation between the gas generation index (GGI) and the actual pinhole defect.

The pinhole generation index PGI may be calculated by Equation 2 below.

Equation 2

However, GGI is a gas generation index.

Here, the first constant value may be a number greater than the second constant value, the first constant value may be a value between 2 and 3, the second constant value may be a value between -1 and 1. have. The first constant value and the second constant value may vary according to the method of expressing the gas generation index and the quality change according to the operating conditions such as the casting speed.

As shown in FIG. 8, the gas generation index GGI and the pinhole generation index PGI have a linear relationship under different operating conditions. In FIG. 8, the dot is the actual pinhole defect occurrence rate, and the solid line is the predicted value (PGI) according to the present invention. Here, the first constant value according to the correlation between the GGI and the PGI may be '2.3768', and the second constant value may be '0.2362'. In conclusion, the predictive model accuracy (R ² ) was 95.2%.

As such, the controller 190 predicts the possibility of pinhole generation in real time according to the physical properties of the steel powder and the casting speed through the pinhole generation index (PGI) (S4), and the predicted result as the PGI index through the display unit 170. The alarm sound may be output through a predetermined alarm means when the displayed or predicted pinhole defect exceeds the set reference value.

The pinhole defects generated as described above are removed by a process such as scafing because the pinhole defects are defects having a bubble-like shape on the surface of the solidification shell, for example, the slab. Scarping is the operation of melting the slab surface by about 3 to 4 mm.

Here, when the pinhole generation index (PGI) is less than '3', for example, since the number or size of defects of the pinholes actually present in the slab is small, the pinhole generation index may be directly added to the rolling process after the scarping. If the '3' or more is a large amount of pinholes on the surface of the slab will require at least two repeated scarfing.

Therefore, the user can appropriately change the casting operation conditions or the corresponding method according to the prediction result, thereby reducing the occurrence of pinholes or removing the generated pinholes appropriately.

The present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

10: ladle 15: shroud nozzle
20: Tundish 25: Immersion Nozzle
30: mold 40: mold oscillator
50: powder feeder 51: powder layer
52: liquid fluidized bed (liquid) 53: lubricated bed (solid)
60: support roll 65: spray
70: pinch roll 80: strand
81: solidified shell 82: unsolidified molten steel
83: tip 85: solidification completion point
90: cutting machine 91: cutting point
100: predictor 110: memory
130: input unit 150: speed detection unit
170: display unit 190: control unit

Claims (11)

A memory storing operating variable data on properties and casting speeds of mold powders for each steel type input from the outside; And
A control unit that calculates a gas generation index by using a casting rate and a factor capable of generating gas by combustion among physical properties of the powder stored in the memory, and predicts the pinhole generation probability of a solidification shell using the calculated gas generation index. Pinhole defect prediction device of the solidification shell in the playing process including;
The method according to claim 1,
The control unit obtains the pinhole generation index by using the calculated gas generation index and the set constant value, and pinhole defect prediction device of the solidification shell in the playing process for predicting the pinhole occurrence probability of the solidification shell with the obtained pinhole generation index .
The method according to claim 1,
Physical properties of the powder stored in the memory pinhole defect prediction device of the solidification shell in the playing process including the C total, CO ₂ generation amount and LOI (Loss of Ignition).
The method according to claim 1,
The control unit pinhole defect prediction device of the solidified shell in the playing process for calculating the gas generation index by dividing the physical properties of the powder by the casting speed.
The method according to claim 2,
And said constant value is a value derived by a correlation between a gas generation index and an actual pinhole defect.
The method according to claim 1,
The main speed detection unit for detecting the casting speed in real time through the rotational speed of the pinch roll, and stores the detected casting speed in the memory,
The control unit pinhole defect prediction device of the solidification shell in the playing process for calculating the gas generation index by using the casting speed and the physical properties of the powder stored in the memory detected by the main speed detection unit.
Calculating a gas generation index by using a casting speed and a factor capable of generating gas by combustion in physical properties of the mold powder;
Calculating a pinhole generation index by using the calculated gas generation index and the set constant value; And
Predicting the pinhole occurrence probability of the solidification shell using the pinhole generation index calculated above; Pinhole defect prediction method of the solidification shell in the playing process comprising a.
The method of claim 7,
Physical properties of the mold powder C total, CO ₂ generation amount and LOI (Loss of Ignition) comprising a pinhole defect prediction method of the solidified shell in the playing process.
The method of claim 7,
The gas generation index is pinhole defect prediction method of the solidification shell in the playing process obtained by dividing the physical properties of the powder by the casting speed.
The method of claim 7,
The gas generation index (GGI) is a pinhole defect prediction method of the solidification shell in the playing process is calculated by the following equation (1).
Equation 1

However, Vc [m / min] is the casting speed, C total [%] is a factor controlling the melting rate of the powder, and the amount of CO ₂ generated [%] is generated by reacting with O ₂ supplied in the atmosphere during carbon combustion. The amount of gas, LOI (Loss Of Ignition) [%] is the amount of weight loss of the powder caused by combustion when melting the powder.
The method of claim 7,
The pinhole generation index (PGI) is calculated by Equation 2 below, wherein the first constant value is a number greater than the second constant value pinhole defect prediction method of the solidification shell in the playing process.
Equation 2

However, GGI is the gas generation index.

Images