JPS6026610A - Production of cv graphite cast iron - Google Patents

Abstract

PURPOSE:To obtain efficiently a CV graphite cast iron having excellent mechanical characteristics by adding a CV treating alloy consisting of Fe-Mg-Ca-Ce alloy to a molten base metal having a prescribed compsn., subjecting the same to a pocket process treatment, inoculating Fe-Si and casting the molten metal. CONSTITUTION:Silicon steel plate scrap, low-S carburized material and Fe-Si are melted in the remaining molten metal corresponding to FC15 and the molten metal is then desulfurized by using a low frequency induction furance, by which the molten base metal for a spheroidal graphite cast iron consisting of 3.6- 3.9wt% T.C, 1.4-1.6% Si, 0.3-0.4% Mn, 0.044-0.057% P, 0.02-0.03% S and the balance Fe is produced. A CV treating alloy consisting of 1.5Mg-0.4%Ca-3.5%Ce- the balance Fe is added at 1.04-1.15% to the molten base metal which is then subjected to a pocket process treatment. The molten metal is thereafter inoculated by Fe-Si and is cast. The CV graphite cast iron having excellent characteristics such as tensile strength, elongation, hardness, etc. is stably obtd. by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing compacted vermicular graphite cast iron (hereinafter referred to as C, V, graphite cast iron). Using molten metal for spheroidal graphite cast iron with small fluctuation, Fe
- Stable CVV by Mg Ca Ce alloy treatment
The present invention relates to a method for manufacturing lead cast iron.

Essential. Spheroidization treatment with Mg If the molten metal is held without being poured into a mold, Mg escapes from the molten metal over time, causing a so-called fading phenomenon, and the amount of residual Mg rapidly decreases. If the molten metal is held for a long time, the graphite will not become spheroidized.

However, due to the influence of a small amount of Mg, graphite with a rounded tip appears. This cast iron is called compacted vermicular graphite cast iron (C, V, graphite cast iron). This C, V, graphite cast iron ore is inferior to spheroidal graphite cast iron in terms of tensile strength and elongation, but is much better than flake graphite cast iron (inferior to flake graphite cast iron in terms of vibration damping ability, thermal conductivity, etc.) is superior to spheroidal graphite cast iron.

Conventionally, when CV graphite cast iron is produced on-site by addition treatment of Mg-Ca-Ce alloy, it is difficult to know the S content in the redundant accurately, and the addition method is a simple pouring method. The reality is that it is difficult to determine the appropriate amount of addition for CV graphite cast iron production, resulting in decreased effectiveness and uneconomical effects due to excessive addition.

The present invention solves the above-mentioned conventional problems in manufacturing CV graphite cast iron by adding Mg-Ca-Ce iron-based alloy, and efficiently manufactures CV graphite cast iron with excellent mechanical properties. The overall purpose is to provide a method for doing so.

The gist of the present invention is to use a low frequency induction furnace to
A considerable amount of residual hot metal, silicon steel plate layer, low S recarburizer, Fe-8
i is charged and melted, a desulfurizing agent is added to the obtained molten metal, and T
, C: 3.6 to 3.9 mJt%, Si: 1.4, a molten metal for spheroidal graphite pig iron is melted, and the molten metal is subjected to pocket method treatment, inoculated with F'e-8t, and cast. Characteristic C
It is in the manufacturing method of V-graphite cast iron.

The details of the present invention will be described below based on the findings of Examples.

The present invention is characterized in that a low frequency induction furnace is used, and the remaining molten metal equivalent to FC-i5 in the furnace is coated with a silicon steel sheet layer.

The waste pig iron, an electrode graphite layer as a low S recarburizing material, and Fe-8i are suitably blended and melted, and the mixture is transferred to a ladle at a tapping temperature of 1520° C. and desulfurized to obtain a low S molten metal.

Since desulfurization cannot be performed in a molten metal containing St, desulfurization is carried out in a ladle or cupola forehearth using soda ash 9 lime, calcium carbide, or the like as a desulfurization agent. Calcium carbide CαC is preferable from the viewpoint of desulfurization rate, and its addition amount is 0.5% based on the molten metal, and the desulfurization reaction proceeds more quickly as the treatment temperature is higher, so the above range of tapping temperature is preferable.

Thus T, C: 3.6-6.9%, Si: 1.4-1
．． 6%, Mn: [1.3-0.4%, p: 0.
044~O, [357%.

S: The redundant is melted to have a composition range of 0.02 to 0.06% with the balance being Fe. The present inventor has solved this redundancy with 1.5% Mg - 0.4% ca - 3.5% Ce and balance Fe
The alloy was used as a CV treated alloy and the amount added was varied, Fe-81 (Sj: 50%) was adjusted to the number of graphite grains,
In order to prevent IF from chilling and to create a pearlite base ferrite base, 0.5% inoculation was added, cast at 1680-1480°C, and the structure was observed under a microscope to check for CV conversion. In this case 0
Both the pouring method where the 69% additive alloy is simply placed on the bottom of the ladle and pouring the molten metal, and the pocket method where a pocket is constructed at the bottom of the ladle, the additive alloy is placed in it, and the molten metal is poured. As shown in reference photograph I [11], no CV graphite cast iron was obtained.

Next, with 1.1% inlay, when using the pocket method, CV graphite cast iron was obtained as shown in Photo No. 2, but when using the pouring method, no CV graphite cast iron was obtained as shown in Photo No. 3. Furthermore, when adding 1.2%, as shown in Photo IVkL4 (in both the pouring method and the pocket method, a CV graphite structure was observed, but at the same time, a large amount of spheroidal graphite appeared, and furthermore, free cement appeared in the matrix, which was not desirable).

From the above, it was found that an addition amount of around 1.1% is preferable for CV graphite cast iron production, and as a result of repeated experiments with the pocket method addition at around 11%, the result was 1.04 to 1.15% by weight.
Tensile strength within the range of 34 to 404 g //Channel 2. Elongation 4
．． Excellent C of 2-7.0%, hardness HB 160-180
V-graphite cast iron was economically and stably obtained.

Examples will be described below.

Example 1 Using a 6-ton capacity low-frequency induction furnace, residual metal equivalent to FC15, silicon steel plate layer, waste pig iron, low S carburization material of 'electrode graphite scrap, F
E-8i (St: 50%) alloy was suitably mixed and melted, and C60' was added as a desulfurizing agent to 500 to 600 kg of molten metal, which was transferred to a ladle at a tapping temperature of 1520±10'C.
c. Add 0.5% of desulfurized molten metal for spheroidal graphite cast iron. In this case, the redundant composition is controlled to be within the following range.

T, C, two 3. 6-3. 9%, Si:
1. 4 ~1. 6%, Mn2 0.6-0.4
%, p: 0.044-0.057%, S.

0.02-0.03% Balance Fe For the above fried hot water, 1.5% Mg O, 4% Ca-6,
5% Ce-balance Fe alloy'! 1l-0,9,1,1
, 1.2%, and 0.5% of Fe-8t (St: 50%) alloy is added at 1 weight and cast at 1680° to 1480°C.

Two methods were used to add the alloy: the pouring method and the pocket method.The structure of the graphite cast iron obtained was magnified 200 times with a microscope, and the state of the structure observed at one glance is shown in reference photo Nll-1 East 4. show.

Photo 1 shows F
Fe-8i (St:
50%) CV graphite is not observed in the cast iron structure when fc is inoculated at 0.5%, and CVV lead cast iron cannot be obtained with this addition amount.

Photograph N112i has the same (Fe
-Mg-Ca-Ce alloy 11% treated by pocket method and inoculated with 0.5% Fe-8i (St: 50%) 7. T-no! The iron structure is CVV lead cast iron with low CV graphite. Mechanical properties are tensile strength 36'
f', f /Wnn2H elongation 4.2% Brinell hardness value was 16 F.

Photo N [lL3 shows the CV of the alloy 11% processed by the market pouring method and the iron structure of this case.
No graphite carpet was observed. This coarse flaky graphite cast iron is almost the same as photoj'4Nn1 and has a tensile strength of 12 to 16.
'gf/mm2T <0%, Brinell, 1.
-, X values were 126-167.

Photo Nu A shows that 12% of the above alloy was processed by the direct pressure method 7 [or the pocket method] and the same bonding method was applied. ]! In the cast iron low range when doing this, there is a lot of spheroidal graphite (
, and free heptite was also observed, and the tensile strength was 52.6 gf/□2. The elongation is 2''; b, and the Brinell hardness value is 212, which is not favorable at 1° with CVV lead cast iron.

Example 2 Physical properties of CVV lead cast iron obtained by obtaining redundancy in the same manner as in Example 1 and treating this redundancy with CV treatment All Examples 10 alloy addition t was around 11% and addition by pocket method As a result, the tensile strength ranged from 6 A to dOAg//Elongation 4.2 within the range of addition fr 1.04 to 1.15%.
Characteristic values of hardness HB 160-180 were obtained.

Agent: Patent Attorney Sanro Kimura

Claims (2)

[Claims] (1) Using a low-frequency induction furnace, charge and melt a silicon steel sheet layer, low S recarburizer, and Fe-81 into the remaining molten metal equivalent to FC15 in the furnace, and add a desulfurization agent to the resulting molten metal. Addition of Fe
A method for producing CVV lead cast iron, which comprises inoculating with -84 and casting. (2) In melting the redundant molten metal for spheroidal graphite cast iron, the redundant iron and the electrode graphite having the above composition are melted as a low-pressure S carburizing material, and the redundant is used in the CV treatment table. A method for manufacturing CVV lead cast iron according to claim 1.