JP2939351B2 - Twin roll casting of phosphor bronze sheet with excellent internal properties. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-roll casting method for a phosphor bronze sheet having excellent internal properties.

[0002]

2. Description of the Related Art Phosphor bronze is mainly used as a spring material and is used in a Cu-4-8% Sn alloy in an amount of 0.03-0.35%.
% P is added, and the toughness and elasticity are improved as compared with bronze. Utilizing wear resistance, it is also used for gears and bearings. It is also known that the addition of lead (free-cutting phosphor bronze) improves machinability. Directly casting a phosphor bronze thin plate with a twin-roll continuous casting machine has been proposed, for example, in Japanese Patent Application Laid-Open No. 1-107943. In order to achieve this, it is extremely important to obtain good surface properties and internal properties. Internal defects of the slab are represented by porosity generated during solidification of the slab, but a twin-roll type casting method of a phosphor bronze thin plate having excellent internal properties has not yet been established industrially.

[0003]

SUMMARY OF THE INVENTION When a thin sheet of phosphor bronze is continuously cast by a twin-roll caster, columnar crystals develop in a quenched portion by a roll, and fine equiaxed crystals are formed inside the slab having a slow cooling rate. And with porosity. The present invention proposes a twin-roll type casting method of a phosphor bronze sheet having a low porosity and excellent internal properties.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to pouring a melt of phosphor bronze into a twin-roll continuous casting machine and directly casting a thin plate. This is a twin-roll casting method for a phosphor bronze thin plate having excellent internal properties, wherein the casting is performed under the condition that the relationship between the roll rotation speed and the roll diameter satisfies the following equation.

1050 ≦ ud × d ≦ 1650, u: roll rotation speed (rpm) d: roll diameter (cm) The present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a twin-roll caster for explaining an embodiment of the present invention. In FIG. 1, two opposing rolls (1, 2) are made of a water-cooled copper alloy having a diameter of 30 cm and a width of 10 cm. The rolls 1 and 2 have a rotary drive device (not shown) using an electric motor and a slab pressing device 3 using a spring. By controlling the roll rotation speed and the roll interval, a thin cast piece 7 having a desired plate thickness can be manufactured. The molten metal pool 4 is held by pressing a side dam 5 made of a facing refractory plate against a rotating roll side surface. 6 is the solidification completion point,
8 is a roll kiss point. The distance between the roll kiss points P and Q indicates the gap D (mm) between the rolls. A slab 7 made of twin rolls is wound around a coil and further cold rolled.

[0006] Phosphor bronze in the present invention is intended for components based on JIS and systems based on them. According to the experiments of the present inventors, when continuously casting thin sheet slabs having a sheet thickness of 0.5 mm to 5 mm with a twin-roll caster, when the pouring temperature is adjusted to a superheat degree of molten metal of 70 ° C. to 200 ° C., It was confirmed that the porosity generation area ratio inside the piece was extremely small. It is known that during the solidification of phosphor bronze in continuous casting, dissolved gas is generated and porosity is generated inside the slab,
The present invention is based on the finding that porosity is generated in the fine equiaxed zone in the solidification structure, and eliminates the fine equiaxed zone by setting the degree of superheating of the molten metal to 70 ° C. or higher. On the other hand, if the temperature exceeds 200 ° C., the slab temperature is too high and the slab is broken due to poor solidification. Therefore, the degree of superheat of the molten metal is set to 70 ° C to 200 ° C.

[0007] It has also been found that the rotation speed and roll diameter of a roll in a twin-roll caster have a close relationship with the formation of a fine equiaxed zone in a thin slab. Assuming that the roll diameter is constant in this example, as the roll rotation speed is lower, the complete solidification point rises from below the kiss point of the twin roll to the kiss point. As a result, the cooling rate increases to the center of the sheet thickness, the fine equiaxed crystals disappear, and the porosity disappears. On the other hand, if the rotation speed is too low (the plate thickness is too thick), the cooling speed at the center of the plate thickness decreases due to the heat transfer resistance of the plate itself, so that fine equiaxed crystals are generated again and porosity is generated. FIG. 2 shows the generation of fine equiaxed crystals from the relationship between the roll diameter d and the roll rotation speed u. That is, 1050 ≦ ud × d ≦ 1650, u: roll rotation speed (rpm) d: roll diameter (cm) In zone C satisfying the above conditions, the cooling rate increases to the center of the plate thickness, and fine equiaxed crystals disappear. , No porosity is generated.

When the value of u × d is less than 1050, that is, in zone B, the thickness of the thin slab becomes too large, the cooling rate at the center of the thickness decreases, fine equiaxed crystals are generated, and porosity is reduced. Is generated. In the zone A exceeding 1650, the completely solidified point is below the roll kiss point, and the cooling rate at the center of the sheet thickness is reduced, resulting in slow cooling. Therefore, fine equiaxed crystals are generated and porosity is generated.

[0009]

[Example 1] Phosphor bronze (Cu-5.5% Sn-0.1% P) using a twin-roll caster shown in FIG.
Was cast into a thin plate slab having a thickness of 2 mm. The melting point of this phosphor bronze is 1022 ° C. Table 1 shows the degree of superheat of the molten metal (° C.) and the area ratio of porosity (%).

[0010]

[Table 1]

The value of u × d here was 1250.

Example 2 Using the casting machine of Example 1,
A 2 mm-thick thin plate slab of phosphor bronze (Cu-5.5% Sn-0.1% P) was cast. The degree of superheat of the molten metal was 90 ° C. Table 2 shows u × d and the porosity generation area ratio.

[0013]

[Table 2]

The porosity generation area ratio was calculated by the following method. A section is taken in the casting direction of the fine equiaxed crystal zone at a half width of a thin plate slab having a thickness of 2 mm × 100 mm, and the porosity generation thickness of the cross section is set to a and the slab thickness is set to b (FIG. 3).
(A)). The measurement range was 0.5 mm in length as one location, and five locations were sampled over the entire length, and the average a / b was determined to obtain the porosity generation area ratio.

[0015]

According to the present invention, the superheat degree of the molten metal is selected, and a thin sheet of phosphor bronze is directly cast by a twin-roll caster in accordance with an appropriate value of the rotation speed of the twin rolls × the roll diameter to obtain a thin sheet slab having excellent internal properties. You can get.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the present invention.

FIG. 2 is a table showing a relationship between a rotation speed of a roll diameter and a porosity generation rate of a twin roll casting machine.

FIGS. 3A and 3B are explanatory diagrams of a porosity generation area ratio. FIG.

[Explanation of symbols]

 1, 2 twin rolls 5 side dam 6 solidification completion point 8 roll kiss point

Continuation of front page (72) Inventor Kenichi Miyazawa 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Central Research Division (56) References JP-A-1-107943 (JP, A) JP-A-63 -30156 (JP, A) JP-A-63-195253 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11/00-11/22

Claims (1)

(57) [Claims] 1. Injecting a molten phosphor bronze into a twin-roll continuous casting machine and casting a thin plate directly, adjusting the pouring temperature to a superheat degree of the molten metal of 70 ° C. to 200 ° C. A twin-roll casting method for a phosphor bronze thin plate having excellent internal properties, wherein the casting is performed under the condition that the relationship with the roll diameter satisfies the following expression. 1050 ≦ ux × d ≦ 1650, u: Roll rotation speed (rpm) d: Roll diameter (cm)