KR100836399B1 - Manufacturing method of gray cast iron CVI cast iron - Google Patents

Abstract

The present invention relates to a manufacturing method of gray cast iron-based CGI cast iron, and more particularly in the existing gray cast iron manufacturing line (LINE) by controlling the amount of carbon (C), silicon (Si), other trace elements and residual magnesium (Mg) The present invention relates to a manufacturing method of gray cast iron-based CGI cast iron, which enables to manufacture materials such as cylinder blocks for large engines having excellent castability (shrinkage, fluidity) and mechanical properties without changing equipment and materials.

To this end, the present invention is carbon (C) 3.45 ~ 3.55wt%, silicon (Si) 2.3 ~ 2.4 wt%, magnesium (Mg) 0.003 ~ 0.005wt%, copper (Cu) 0.5 ~ 0.7wt%, chromium (Cr) 0.04 to 0.06 wt%, tin (Sn) 0.06 to 0.08 wt%, manganese (Mn) 0.3 to 0.35 wt%, phosphorus (P) less than 0.1 wt%, sulfur (S) less than 0.1 wt%, balance iron (Fe) and Other inevitable impurities are contained, and the carbon equivalent (CE) provides a method for producing gray cast iron-based CGI cast iron, characterized in that 4.3 ± 0.04wt%.

Gray cast iron, CGI, composition, carbon, silicon, carbon equivalent, cylinder block

Description

Method for manufacturing gray cast iron CCI cast iron

1 is a schematic diagram illustrating a method of manufacturing a gray cast iron-based CGI cast iron product according to the present invention compared with a conventional method,

Figure 2 is a graph showing the results of measuring the solidification process of the molten metal in the process of manufacturing the CGI cast iron products and conventional products according to the present invention,

3 is an electron micrograph comparing the CGI cast iron product structure and the existing product structure according to the present invention,

Figure 4 is a photograph of the surface observed for the CGI cast iron products and conventional products according to the present invention.

The present invention relates to a manufacturing method of gray cast iron-based CGI cast iron, and more particularly in the existing gray cast iron manufacturing line (LINE) by controlling the amount of carbon (C), silicon (Si), other trace elements and residual magnesium (Mg) The present invention relates to a manufacturing method of gray cast iron-based CGI cast iron, which enables to manufacture materials such as cylinder blocks for large engines having excellent castability (shrinkage, fluidity) and mechanical properties without changing equipment and materials.

Conventionally, in order to secure mechanical properties (tensile strength), the CGI cast iron is manufactured by precisely controlling magnesium inoculation in the spherical graphite cast iron base (BASE). For this, a precise control device and high-quality materials having a low content of phosphorus and sulfur are used. In addition, there was a high possibility of material defects and poor casting due to sensitive to changes in conditions.

Conventional CGI cast iron, as shown in Table 1 below, carbon (C) 3.6 ~ 3.8wt%, silicon (Si) 1.9 ~ 2.1 wt%, magnesium (Mg) 0.01 ~ 0.015wt%, copper (Cu) 0.05wt % Or less, chromium (Cr) 0.05 wt% or less, manganese (Mn) 0.25 to 0.4 wt%, phosphorus (P) 0.05 wt% or less, sulfur (S) 0.05 wt% or less, and the carbon equivalent is 4.45 ± 0.05. It is managed.

Method for producing a CGI cast iron product based on such a conventional composition, as shown in the accompanying Figure 1, after dissolving the above composition, and then adding a cerium additive, a cover material, a magnesium hardener, and then thermal analysis and need Therefore, after the additional inoculation, it is progressing including the temperature measurement and the injection process in the mold.

However, when molding a product using the conventional conventional CGI cast iron, as indicated by the arrow in the accompanying Figure 4, a large amount of shrinkage defects occur in the cylinder block, there was a problem that the non-uniform material dimensions occur.

The present invention has been made in view of the above, as a constant amount of inoculum in gray cast iron composition and control the structure by the amount of silicon to ensure a stable material, reinforce the matrix structure by adding a trace metal element to the molten metal It provides excellent mechanical properties, and provides excellent manufacturing method for manufacturing gray cast iron CGI cast iron, which has excellent quality stability and excellent mechanical properties compared to conventional spherical cast iron CGI. The purpose is.

The present invention for achieving the above object: iron (Fe) as a main component, carbon (C) 3.45 ~ 3.55wt%, silicon (Si) 2.3 ~ 2.4 wt%, magnesium (Mg) 0.003 ~ 0.005wt %, Copper (Cu) 0.5 ~ 0.7wt%, Chromium (Cr) 0.04 ~ 0.06wt%, Tin (Sn) 0.06 ~ 0.08wt%, Manganese (Mn) 0.3 ~ 0.35wt%, Phosphorus (P) less than 0.1wt% , Sulfur (S) is contained less than 0.1 wt%, the carbon equivalent (CE) provides a gray cast iron-based CGI cast iron composition, characterized in that 4.3 ± 0.04wt%.

The present invention for achieving the above object is 3.45 ~ 3.55wt% of carbon (C), 2.3 ~ 2.4 wt% of silicon (Si), 0.003 ~ 0.005wt% of magnesium (Mg), 0.5 ~ 0.7wt% of copper (Cu), Chromium (Cr) 0.04-0.06 wt%, tin (Sn) 0.06-0.08 wt%, manganese (Mn) 0.3-0.35 wt%, phosphorus (P) less than 0.1 wt%, sulfur (S) less than 0.1 wt%, balance iron (Fe) and other unavoidable impurities are contained, and the carbon equivalent (CE) is dissolved in a gray cast iron-based CGI cast iron composition of 4.3 ± 0.04wt%, and then a 3.0 kg Mg-containing hardener is added to the kg of the melt by 500 kg. The manufacturing method of the gray cast iron system CGI cast iron characterized by keeping the amount of residual Mg at 0.004-0.001 so that this molten metal can be measured and injected into a metal mold | die immediately.

Hereinafter, the present invention will be described in more detail.

Gray cast iron-based CGI cast iron composition of the present invention is compared with the existing composition in Table 1 below, by adjusting the amount of carbon (C), silicon (Si), other trace elements and residual magnesium (Mg) conventional gray cast iron Iron (Fe) is the main component to produce materials such as cylinder blocks for large engines with excellent castability (shrinkage, fluidity) and mechanical properties without changing equipment and materials in the production line. 3.45 ~ 3.55wt%, Silicon (Si) 2.3 ~ 2.4wt%, Magnesium (Mg) 0.003 ~ 0.005wt%, Copper (Cu) 0.5 ~ 0.7wt%, Chromium (Cr) 0.04-0.06wt%, Tin (Sn) 0.06 ~ 0.08wt%, manganese (Mn) 0.3 ~ 0.35wt%, phosphorus (P) less than 0.1 wt%, sulfur (S) is contained less than 0.1 wt%.

Here, the reason for the addition of each component contained in the cast iron of the present invention and the reason for limiting the content range are as follows.

1) Carbon (C) 3.45 ~ 3.55wt%

Carbon is added to maximize the process graphite crystallization ratio, and if less than 3.45wt%, graphite fragmentation occurs, and if it exceeds 3.55wt%, graphite spheroidization shrinkage occurs, so it is preferable to limit it to 3.45 ~ 3.55wt%. .

2) Silicon (Si) 2.3 ~ 2.4 wt%

Silicon is added to the product to secure the ferrite 5-10% properties, if less than 2.3wt% graphite fragmentation occurs, if it exceeds 2.4wt% coarse graphite and ferrite excess is secured, it is recommended to limit to 2.3 ~ 2.4 wt% .

3) Magnesium (Mg) 0.003 ~ 0.005wt%

Magnesium is added to promote CGI graphite nucleation and growth. Graphite fragmentation occurs when less than 0.003wt%, and graphite spheroidization and shrinkage defects occur when it exceeds 0.005wt%. Therefore, it is preferable to limit the amount to 0.003 to 0.005wt%. Do.

4) Copper (Cu) 0.5 ~ 0.7wt%

Copper is added in order to secure the physical properties through pearlite stabilization, the hardness is lowered if less than 0.5wt%, too high hardness is exceeded 0.7wt%, so limited to 0.5 ~ 0.7wt%.

5) Chromium (Cr) 0.04 ~ 0.06wt%

Chromium is added for the graphite micronization, the hardness is lowered when less than 0.04wt%, cementite is formed when exceeding 0.06wt%, brittleness and shrinkage occurs, it is limited to 0.04 ~ 0.06wt%.

6) Tin (Sn) 0.06 ~ 0.08wt%

Tin is added for stabilization of pearlite, and if it is less than 0.06 wt%, the hardness is lowered. If it is more than 0.08 wt%, cementite is formed and explosive graphite is generated, so it is limited to 0.06 to 0.08 wt%.

7) Manganese (Mn) 0.3 ~ 0.35wt%

Manganese is also added for graphite micronization, the hardness is lowered if less than 0.3wt%, cementite is formed if it exceeds 0.35wt%, brittleness and shrinkage occurs, it is limited to 0.3 ~ 0.35wt%.

8) Phosphorus (P) less than 0.1 wt%

Phosphorus promotes pearlite stabilization, but if it is controlled at more than 0.1 wt%, brittleness is generated, so that the content is controlled at less than 0.1 wt%.

9) sulfur (S) less than 0.1 wt%

Sulfur assists CGI graphite formation, but if it is managed at more than 0.1wt%, the formation of CGI graphite is poor, so the content is controlled at less than 0.1wt%.

At this time, the carbon equivalent (CE) is determined by the carbon content + (silicon content × 1/3), and can be adjusted for reasons such as reduced shrinkage failure of the product, reduced flow failure, securing properties.

For example, when the carbon content of 3.45 to 3.55 wt% + (2.3 to 2.4 wt% x 1/3) of carbon is calculated, the carbon equivalent is 4.22 to 4.45 wt%.

However, according to the present invention, if the carbon equivalent is less than 4.26wt%, graphite flattening occurs, and if it exceeds 4.34wt%, shrinkage and poor flow occur in the product. Therefore, it is preferable to adjust the content ratio to 4.26 ~ 4.34wt%. Do.

Referring to Figure 1 attached to a method for producing a gray cast iron product using the CGI gray cast iron composition of the present invention as follows.

According to the present invention, carbon (C) 3.45 ~ 3.55wt%, silicon (Si) 2.3 ~ 2.4 wt%, magnesium (Mg) 0.003 ~ 0.005wt%, copper (Cu) 0.5 ~ 0.7wt%, chromium (Cr) 0.04 ~ 0.06wt%, Tin (Sn) 0.06 ~ 0.08wt%, Manganese (Mn) 0.3 ~ 0.35wt%, Phosphorus (P) less than 0.1wt%, Sulfur (S) less than 0.1wt%, balance iron (Fe) and others Inevitable impurities are contained, and the carbon equivalent (CE) is 4.3 ± 0.04wt% of gray cast iron-based CGI cast iron composition, and since the in-house components are correctly secured, Mg sphere without the conventional thermal analysis and additional inoculation control process It is possible to measure temperature and inject directly into mold by adding only fire.

That is, after the dissolution process, 3.0 kg of the Mg content of 2.0% of the molten material is added to 500 kg of the molten metal to further maintain the residual Mg of the product at 0.004 to 0.001. Can be.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Example

Carbon (C) 3.40 wt%, Silicon (Si) 2.35 wt%, Magnesium (Mg) 0.004 wt%, Copper (Cu) 0.6 wt%, Chromium (Cr) 0.05 wt%, Tin (Sn) 0.07 wt%, Manganese ( Mn) 0.3 wt%, phosphorous (P) 0.1 wt%, sulfur (S) 0.1 wt%, residual iron (Fe) and other unavoidable impurities, and the carbon equivalent (CE) is adjusted to 4.2 wt% gray cast iron-based CGI After dissolving the cast iron composition, 3.0 kg of the Mg content of 2.0% was added to 500 kg of molten metal to maintain the residual Mg of the product at 0.004 to 0.001. CGI cast iron products were made.

Comparative example

Conventional CGI cast iron, ie, carbon (C) 3.7 wt%, silicon (Si) 2.0 wt%, magnesium (Mg) 0.01 to wt%, copper (Cu) 0.05 wt% or less, chromium (Cr) 0.05 wt% or less, manganese (Mn) 0.3 wt%, phosphorus (P) 0.05 wt% or less, sulfur (S) 0.05 wt% or less, the carbon equivalent is dissolved in a cast iron composition managed to about 4.45, cerium additives, cover material, magnesium spheres After the fire was put in, after thermal analysis and additional inoculation, the CGI cast iron was manufactured through the temperature measurement and in-mold injection process of the molten metal.

Experimental Example 1

The solidification process of the molten metal for the Examples and Comparative Examples was measured, and the results are as shown in the attached graph of FIG.

As shown in the graph of Fig. 2, the CGI product of the present invention has a wide working area, excellent castability and quality, and a low maximum injection temperature due to the realization of the optimum working area, thereby preventing shrinkage of the product. Could know.

Experimental Example 2

The CGI cast iron products prepared according to Examples and Comparative Examples were etched through an etching process, and then the surface thereof was observed by an electron microscope. The results are as shown in FIG. 3.

As shown in Figure 3, the embodiment according to the present invention is CGI 95%, spherical 0 ~ 5%, and the pearlite and ferrite 90 ~ 95%, 5 ~ 10%, respectively, the comparative example is CGI 80%, It was found that the spherical shape was 10%, and the pearlite and ferrite were 100% and 0%, respectively.

In addition, as a result of observing the surface of the CGI product, the product according to the embodiment of the present invention as shown in the photograph of Figure 4 can be observed that there is no shrinkage failure and the material dimensions are constant, the existing product according to the comparative example shrinkage It can be seen that a large amount of defects occur and the material dimensions are uneven.

As described above, according to the manufacturing method of the gray cast iron-based CGI cast iron according to the present invention, the amount of inoculant is constantly added in the gray cast iron composition, and the structure is controlled by the amount of silicon to secure a stable material, and the trace metal element is added to the molten metal. By strengthening the base structure by adding, it is possible to secure excellent mechanical properties, and it has excellent quality stability even when using materials with high phosphorus and sulfur content in operation, and gray cast iron CGI cast iron with better mechanical properties than conventional spheroidal cast iron CGI. There is an advantage in providing a composition.

Claims (2)

delete Carbon (C) 3.45 ~ 3.55wt%, Silicon (Si) 2.3 ~ 2.4 wt%, Magnesium (Mg) 0.003 ~ 0.005wt%, Copper (Cu) 0.5 ~ 0.7wt%, Chromium (Cr) 0.04 ~ 0.06wt%, Tin (Sn) 0.06 ~ 0.08wt%, Manganese (Mn) 0.3 ~ 0.35wt%, Phosphorus (P) less than 0.1wt%, Sulfur (S) less than 0.1wt%, balance iron (Fe) and other unavoidable impurities After dissolving the gray cast iron-based CGI cast iron composition of 4.3 ± 0.04wt%, the carbon equivalent (CE) was added 3.0kg of the Mg content of 2.0% of the hardener to maintain the residual Mg of the product at 0.004 ~ 0.001. The manufacturing method of the gray cast iron-based CGI cast iron, characterized in that the molten metal can be injected directly into the mold by measuring the temperature.

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