JPS6159385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for processing Ti-containing steel plate scrap to produce a molten raw material for producing spheroidal graphite cast iron.

(Prior Art) Melting raw materials include various used alloy material scraps, cast-back scraps, cutting scraps, and the like. These dissolved raw materials usually contain various harmful elements.

Harmful elements include those contained or applied to the surface of the material to improve its inherent characteristics, those that are unavoidably included in the material itself, and those deposited on the surface.

Melting and refining of metals is usually carried out by charging melting raw materials into a melting furnace maintained at a high temperature. The molten raw material is charged into the melting furnace after adjusting its shape or size as produced, or as a pressed nodule. These are stacked at the bottom of the furnace at the start of melting, and when melting progresses and the molten metal is retained at the bottom of the furnace, they are charged into the molten metal.

Conventional molten feedstocks are contained within their voids and gases, such as atmospheric oxygen, which serve to remove harmful elements, are exposed to the atmosphere. Therefore, when molten raw materials are charged to the bottom of a high-temperature furnace or to the molten metal held in a furnace, the above-mentioned atmospheric oxygen dissipates into the atmosphere or is replaced by other useless gases, eliminating harmful elements. It slags and is useless for separation from the molten metal.

(Problem to be solved by the invention) Conventionally, Ti-containing steel sheet scrap has been used as a raw material for melting in the production of spheroidal graphite cast iron, but the Ti contained in this material inhibits spheroidization and reduces the spheroidization rate. was made low. The present invention makes Ti harmless by treating Ti-containing steel plate scraps using a simple method, so that it can be advantageously used as a melting raw material for producing cast iron.

(Means for Solving the Problems) The present invention incorporates oxygen, which is useful for removing Ti, which is a harmful element, into the gaps of Ti-containing steel plate scraps, and prevents it from dissipating into the atmosphere during melting.
The gist is that the molten raw material for producing spheroidal graphite cast iron is characterized by press-molding Ti-containing steel plate scraps into nodules, and immersing the nodules in molten spheroidal graphite cast iron to seal the pores of the nodules. It is in the manufacturing method.

The present invention contains oxygen that combines with Ti while melting the metal, turns it into slag, and causes it to float and separate from the molten metal.
The pores that are open to the atmosphere on the surface of the Ti-containing steel sheet scrap aggregate are sealed by immersing them in molten spheroidal graphite cast iron.

(effect) 〓〓〓〓
The mechanism by which Ti is removed when Ti-containing steel plate scrap nodules are used as a raw material will be described with reference to the diagram. Partially melted molten metal 6 in a melting furnace having a heating element 8 and a lining 7
Close the pores 5 on the inside surface with spheroidal graphite cast iron 2,
When a molten raw material containing gas 5 for removing Ti is charged, it receives buoyancy from the bath water and V ₂
The relational expression =S・V ₁・1.033/W holds true and it floats on the molten metal.

Here, V ₂ (cm ³ ) is the volume of gas contained in Ti-containing steel sheet scrap in the molten metal, and V ₁ (cm ³ ) is the volume of gas in the atmosphere.
Oxygen volume contained in Ti-containing steel sheet waste nodules, S
(cm ² ) represents the surface area of the portion of the Ti-containing steel plate scrap agglomerate in contact with the molten metal, and W (Kg) represents the weight of the Ti-containing steel plate scrap agglomerate. Katsuko represents a unit.

Next, this spheroidal graphite cast iron layer 2 melts at the portion where it comes into contact with the molten metal, and the molten metal enters the layer 2 until the internal atmospheric pressure and the molten metal pressure are balanced. Here, the Ti-containing steel plate scrap nodules continue to melt while entraining the oxygen contained inside them. In this state, Ti
and oxygen react very effectively, and the reaction product turns into slag and floats to the surface, separating it from the molten metal. The encapsulated oxygen is not lost until the nodule raw material is completely dissolved and contributes to the reaction with Ti.

Example 1 An example in which spheroidal graphite cast iron was cast using steel sheet scrap containing Ti as a force melting raw material will be described. Since Ti has a negative effect on the properties of spheroidal graphite cast iron, especially on its ductility, it is desirable to reduce it as much as possible. The steel plate used here contains 0.2% Ti to give it unique properties. Chemical components other than Ti
0.01%C, 0.03%Si, 0.1%Mn, 0.014%P, 0.016
%S, balance iron. This steel plate scrap was pressure-formed at a pressure of 80 kg/cm ² to form a cube with a side of 500 mm.
Several pieces of this were made, and each side of a part of them was immersed in molten spheroidal graphite cast iron to a depth of 5 cm to form a pore-closing layer. in advance
Two steel plate scraps with a unit weight of 500 kg with closed pores were charged into a 2T low frequency furnace in which 500 kg of spheroidal graphite cast iron was melted, making the total charge weight 1500 kg, and the temperature was raised to a maximum of 1450°C and melted. The final chemical composition is added to this molten metal.
Fe that is carburized and silicified to become 3.5% C and 2.5% Si, and contains 10% Mg, which is 1.5% based on the weight of the molten metal.
-The Si-Mg alloy was placed on the bottom of a ladle to receive the metal, and then spheroidized. After inoculating 3 kg of Fe-Si alloy containing 75% Si, it was cast into a JIS No. B Y block mold.

Next, 500 kg of spheroidal graphite cast iron was melted in advance in a 2T low frequency furnace with a unit weight of 500 kg without pore closure.
Two pieces of scrap steel plate were added, and the spheroidal graphite cast iron was melted and a Y block was cast in the same manner as when scrap steel plate with closed pores was used.

Collect samples for analysis from these Y blocks,
We conducted a Ti analysis and investigated the ratio of the amount of Ti after casting to the total amount of Ti in the charged raw material, that is, the Ti removal rate, and found that when steel scrap without pore closure was used, the Ti removal rate was 25%. In contrast, the rate was 75% with closure. When examining the elongation in a tensile test, there was a difference of 3%.When examining the microscopic structure, a difference was found in the spheroidization rate, with the former being 55% and the latter being 80%.
It was %.

[Brief explanation of the drawing]

FIG. 1 is a side view of the melted raw material that has undergone pore filling. 2... Pore-closing layer of spheroidal graphite cast iron, 4...Ti
Containing steel plate scrap nodules, 5...oxygen, 6...molten metal, 7...
...Lining of the melting furnace, 8...Heating coil. 〓〓〓〓

Claims (1)

[Claims] 1. A method for producing a melted raw material for producing spheroidal graphite cast iron, which comprises pressurizing and molding Ti-containing steel plate scraps to form nodules, and immersing the nodules in molten spheroidal graphite cast iron to seal the pores of the nodules.