JPS61110746A - Pearlite-base cv graphite cast iron - Google Patents

Abstract

PURPOSE:To obtain as-cast pearlite-base CV graphite cast iron having superior mechanical properties and wear resistance by specifying a composition consisting of C, Si, Mn, Mg, Cu, Mo and Fe. CONSTITUTION:This pearlite-base CV graphite cast iron consists of, by weight, 3.5-4.2% C, 2.0-3.3% Si, <=0.8% Mn, 0.005-0.040% Mg, 0.3-2.0% Cu, 0.1-0.4% Mo and the balance Fe with inevitable impurities and has a matrix structure consisting of >=about 70% pearlite and the balance ferrite. The cast iron has superior mechanical properties and wear resistance, causes hardly shrinkage defects and dross defects, and also has superior castability, so the thickness and weight of a casting can be reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to as-cast pearlite CV black button cast iron whose matrix structure is a mixed structure of pearlite and ferrite, and specifically relates to mechanical properties and wear resistance. This relates to excellent as-cast pearlitic CV graphite cast iron, which is used for thin-walled castings, lightweight castings, etc.

(Prior art) As CV graphite cast iron, there is CV graphite cast iron manufactured by a manufacturing method as shown in Japanese Patent Application Laid-open No. 150314/1983, which has a sulfur content of 0.025% by weight or less. Eutectic melt (about 3.0-4.5% by weight of carbon, about 1.0-3.5% by weight of silicon, about 1.2% by weight of manganese)
up to about 0.1% by weight of phosphorus and the remainder iron, and the iron composition can solidify to rat iron if untreated. ) and mixing the melt with at least one dilute-containing additive to form a stable dilute oxysulfide, thereby reducing the Henry's sulfur activity in the melt to about 0.004. and 0.035, and the melt was then solidified.

(Problems to be Solved by the Invention) This conventional Cv graphite cast iron is insensitive to changes in cooling rate and has a matrix structure of ferrite, resulting in a problem of reduced mechanical properties and wear resistance.

(Means for solving the problems) The means for solving the above problems are as follows: C: 3.5-4.2%, Si: 2.0-3.
3%, Mn: 0.8% or less, Mg: 0.005-0,
040%, Cu: 0. 3-2. 0%.

Mo: 0.1-0.4%, the balance is Fe and inevitable impurities. Pearlitic CV graphite cast iron. Carbon is 3%.
．． If it is less than 5%, there is a strong tendency to chill, and if it exceeds 4.2%, abnormal graphite tends to crystallize during solidification.
It was limited to 4.2%.

If the silicon content is less than 2.0%, the tendency to chill becomes large; 3.
If it exceeds 3%, it becomes a ferrite base, so 2.0 to 3.
It was limited to 3%.

Manganese is effective for stabilizing pearlite, but if contained in a large amount, it increases the tendency to chill, so it was limited to 0.8% or less.

If magnesium is less than o, oos%, Cv graphite cannot be obtained, and if it exceeds 0.040%, graphite tends to become spheroidized, so it was limited to 0.005 to 0.040%.

Copper is a pearlite stabilizing element, and if it is less than 0.3%, the ability of copper to form pearlite is weak, and if it exceeds 2.0%, even if it is present, the effect of stabilizing pearlite can be further improved. First, it is limited to 0.3 to 2.0% because it precipitates at the eutectic cell boundary and reduces toughness.

Molybdenum is limited to 0.1 to 0.4% because if it is less than 0.1%, the pearlitizing ability of molybdenum is weak, and if it exceeds 0.4%, it will precipitate at the boundary of the eutectic cell and cause carbides to crystallize. .

(Example) Hereinafter, an example showing a specific example of the above means will be described.

20 & total carbon content 3.0-4.2% in high frequency furnace.

Si2゜O ~ 3.2%, Nn 0.8% or less, 2001%
Hereinafter, a molten cast iron consisting of SO, 01-0.3% was melted, and this molten metal was heated to 1450°C with Cub, 3-2.0%, M
0.1 to 0.4% of Fe-Sl-M was added.
After adding g and processing the molten metal, it was cast into a CO mold, and a 1 inch Y block, stepped wall thickness sensitive test piece, diameter 5
A 01m round bar test piece was taken, and a tensile test was conducted in the as-cast state.
Vickers hardness test and friction wear test were conducted.

Table 1 shows the composition of various cast iron materials, and Table 2 shows their mechanical properties. Further, FIG. 1 shows the results of the Vickers hardness test, and FIG. 2 shows the results of the friction and wear test.

As can be seen from Table 1 and Table 2, invention materials 2 and 3.4 are comparative materials 1.
Mechanical properties are improved compared to As shown in Figure 1, the invention materials 2 and 3.4 have higher hardness than comparative material 1, and the change in hardness due to the difference in wall thickness is small, so the mass effect is small. As shown, 1 Invention materials 2 and 3.4 have a smaller amount of wear than Comparative material 1, which indicates that they have excellent wear resistance. As a result of investigating the occurrence of sink marks and dross in the graded wall thickness sensitive test piece, it was found that it was at least equivalent to flaky graphite cast iron. Figures 3 and 4 are micrographs of the CV graphite cast iron of the present invention (3% nital corrosion, 1 magnification: 1
00 times), Cv graphite is crystallized in a mixed matrix structure of pearlite and ferrite.

(Effect of the invention) The present invention produces the following effects.

The CV graphite cast iron of the present invention has a matrix structure consisting of 70% or more of pearlite and the balance of ferrite, so it has good mechanical properties and wear resistance, and has low occurrence of sink defects and dross defects, so it has excellent castability. ing. For this reason,
This greatly contributes to making castings thinner and lighter.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between wall thickness and hardness, Fig. 2 is a graph showing the wear test results of the invention material and comparative material, Fig. 3 is a micrograph showing the metal structure of invention material 3, and Fig. 4 is a graph showing the relationship between wall thickness and hardness. The figure is a micrograph showing the metal structure of Invention Material 4.

Claims (1)

[Claims] In terms of weight ratio, C: 3.5-4.2%, Si: 2.0-3.
3%, Mn: 0.8% or less, Mg: 0.005 to 0.0
40%, Cu: 0.3-2.0%, Mo: 0.1-0.
Pearlitic CV graphite cast iron, characterized in that the remainder consists of Fe and inevitable impurities.