JPH01107943A - Continuous casting method for phosphor bronze strip - Google Patents

Abstract

PURPOSE:To prevent the development of crack in a strip product by cooling the strip made of phosphor bronze below the min. gap part of twin rolls in continuous casting machine at the specific temp. and regulating load per unit of width into the prescribed range. CONSTITUTION:The molten phosphor bronze 5 composing of 7-9.5wt.% Sn, 0.03-0.3% P and the balance Cu with impurities is poured into a pouring basin 6 between the twin rolls 3, 4 in the continuous casting machine. Then, the strip surface temp. is controlled so as not to exceed 900 deg.C to the strip 10 below the min. gap part 9 of the cooling rolls through surface temp. detectors 20, 21 and cooling nozzles 22, 23 and further, the load per unit width P/l is regulated in the range shown by the inequality I. The phosphor bronze plate having wide solid-liquid coexistent zone is controlled to the prescribed temp. and further, as the load per unit width is regulated to the prescribed quantity, the development of crack on the strip surface is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for continuously producing crack-free, sound phosphor bronze thin plates directly from molten metal.

[Conventional technology]

Phosphor bronze has superior spring properties compared to other copper alloys, and has excellent corrosion resistance and solderability, so it is widely used in spring materials and connector materials that require electrical conductivity. However, since phosphorous copper contains a large amount of Sn and P, which have large segregation coefficients, a concentrated phase of Sn and P is likely to be formed at the grain interface during solidification of the ingot. Therefore, deep cracks due to liquid film brittleness are likely to occur on the surface of the rolled plate during inter-rolling.

The production of thin sheets of phosphor bronze required multiple cycles of cold rolling and annealing.

In order to minimize the number of repetitions, it is preferable to cast as thin a plate as possible, and for this reason, a method of casting thin slabs by horizontal continuous casting has been adopted. However, in the horizontal continuous casting method, when pulling the slab out of the mold, frictional force is generated between the mold and the slab, so it is necessary to pull out the slab intermittently (applying vibration or oscillation). Surface defects caused by this are likely to occur on the slab surface, reducing product yield. Furthermore, the minimum wall thickness that can be produced using the horizontal continuous casting method is several times thicker than the thickness obtained by the normal manufacturing process that includes hot rolling, and for this reason, it is also necessary to use annealing and cold rolling. It required repetition and a lot of energy.

On the other hand, the twin roll method is known as a method for directly manufacturing thin plates from molten metal, with the aim of reducing rolling and associated steps. The twin-roll method referred to here is not a special manufacturing method for ultra-thin sheets with a thickness of 500μ or less, such as amolus aus or quenched ribbon, but a general method for manufacturing sheets with a small thickness (both 11 and 6- or less). The purpose is to obtain a thin plate, and the cast thin plate is made into a final product by the next step of cold rolling.In recent years, this continuous thin plate casting method using the twin roll method has been used to produce various types of sheets, including Affi alloy. It is being put into practical use for metals.

However, for metals and alloys for which direct continuous casting of thin sheets from molten metal using the twin roll method has reached a stage where it has been put into practical use or close to it, the solid-liquid coexistence region (the difference between the liquidus temperature and the plane phase temperature) ) is limited to those with almost no or short ones, and with respect to alloys such as phosphor bronze, which have an extremely long solid-liquid coexistence region, almost no attempts have been made to apply them, let alone put them into practical use. There wasn't.

[Problems to be solved by the present invention]

The major problem that makes it difficult to manufacture phosphor bronze FJjM directly from molten metal using the twin roll method is that compared to other alloys with a short solid-liquid coexistence zone, the resulting thin plate is more likely to have many cracks on its surface. That is the point. In other words, even if an attempt is made to produce a thin plate of phosphor bronze directly from the molten metal using the twin roll method under the same conditions as for alloys with a short solid-liquid coexistence region, the plate pulled out from the rolls will break into many pieces. Even if a thin plate is formed, many deep cracks always occur on the surface, making it impossible to obtain a Bl gold plate.

The object of the present invention is to solve the above problem of cracking.

The purpose of this project is to establish a technology for directly manufacturing phosphor bronze thin plates using the twin roll method.

[Means to solve problems]

The gist of the present invention to achieve the above object is as follows: Sn 77-9.5wt, X, P; 0.
03~0.3 豐(, χ, 1 yen when molten phosphor bronze consisting of the balance Cu and impurities is directly cast into a thin plate using a twin roll continuous casting machine consisting of a pair of cooling rolls rotating in opposite directions. controlling the amount of cooling so that the surface temperature of the plate after passing through the narrowest gap between the rolls does not exceed 900°C;
Preferably, in addition to this, the slab is provided with one roll. Board width j! A method for continuous casting of phosphor bronze thin plates is characterized in that the load 11P per (ms+) is controlled within the range of the following formula (1) % formula % (1).

[Details of the Invention In order to solve the above problem, the presenters investigated and studied the causes of cracks that occur in thin plates obtained by applying the twin roll method to phosphor bronze. As a result, it was found that there are mainly two types of cracks that occur frequently: One of them is periodic transverse cracks that occur after the closest point (narrowest gap) between both rolls, and this mainly depends on the surface temperature of the plate pulled out from between the rolls and stress such as bending that occurs on the plate. do.

The second type is cracks that occur at or before the closest point between two rolls, and each crack has no direction, and the frequency of crack occurrence is determined by the force (hereinafter referred to as rolling load) exerted on the thin plate of the rolls. Mainly depends.

The present invention has been made based on the above findings,
Sn; 7-9.5wt, X, P; 0.
03~0.3wt,! .

There is a roll spacing set to the target plate thickness for a phosphor bronze molten metal consisting of the remainder Cu and impurities.
When the solidified shell is cooled by two cooling rolls rotating in opposite directions and the solidified shell is rolled down at the narrowest gap, the temperature of the plate surface immediately below the narrowest gap between the two rolls is 900℃ or less. If controlled, the first crack can be prevented, and if the rolling load P per plate width 1 (am) by both rolls is limited to the range of equation (1) above, the second crack can be prevented. This is what I found possible.

Figure 1 shows a typical example of a twin-roll continuous caster for phosphor bronze suitable for carrying out the method of the present invention. This is an internally cooled cooling roll that rotates in the direction, and the phosphor bronze molten metal 5 in the tundishe 1 passes through a nozzle 2 and is continuously poured into a pool 6 formed on the circumferential surface of the cooling roll 3.4. Injected.

The molten metal in this pool 6 forms solidification shelves 8 on both surfaces of the cooling roll 3.4, and these are pressed and rolled at the narrowest gap 9 of the cooling roll 3.4 to continuously form a thin plate 10. be done. Cooling water is passed under the surface of the cooling rolls 3 and 4 using rotating shafts, and the surface temperature is appropriately controlled by adjusting the amount of water flowing through the rolls. Also, the distance between the bearings 11 and 12 of the cooling roll 3.4 is the same as that between the members 13 and 14, and the distance between the bearings 11 and 12 is the same as that between the guide arms 15 and 16! 1ljIff, and a rolling device attached to one guide arm 16 applies rolling between the two rolls. This rolling load is measured by a load cell 18 attached to the other guide arm 15.

On the other hand, a surface temperature measuring device 20.21 for detecting the surface temperature of the thin plate 10 passing through the narrowest gap 9 of the cooling roll 3.4 is installed near the narrowest gap 9 and slightly. It is installed at a remote location and constantly detects the surface temperature of the thin plate that is continuously passed through it.

Further, cooling nozzles 22 and 23 are installed to spray and seal a cooling medium onto the surface of the thin plate 1o immediately below the narrowest gap 9. As this cooling medium, a gas such as air or Ar gas, or mist is used.

When carrying out the method of the present invention in the apparatus shown in FIG. 1, the solidification shelves 8 that have grown on the surfaces of both cooling rolls 3. Ideal manufacturing conditions are such that a value of 10 is obtained. Solidification shelf in this case, 8
refers to the region of solid-liquid coexistence with a solid phase ratio having a deformation resistance of 9 from the plate-shaped body formed on the roll surface, and therefore under ideal manufacturing conditions in the twin-roll method. In the case of an alloy having almost no solid-liquid coexistence region, the thin plate 10 passes through the narrowest gap 9 in an almost completely solid state. In addition, if there is a solid-liquid coexistence region, but it is short, the thin plate 10 may have a slight liquid phase in the center of the thickness, but the surface layer of the thin plate is in a complete phase state, and the thin plate 10 closes the narrowest gap 9. pass. However, in the case of phosphor bronze, the solid-liquid coexistence region is long, so even if the solidified shelf 8 coalesces at the narrowest gap 9, the liquid phase tends to remain at the grain boundaries near the thin plate surface, and the liquid phase itself Since there is no strength at all, the thin plate easily splits into two pieces due to minute stress.Therefore, the thin plate of phosphor bronze can be obtained directly from the molten metal using twin rolls under the same conditions as alloys with almost no or short solid-liquid coexistence zone. Even if an attempt is made to do so, there are many cracks in the thin plate, which may even lead to the thin plate being torn.

The present inventors determined the roll peripheral speed v, the contact length X in the rotational direction between the solid shell and the cooling roll, and the rolling load P.

By changing various conditions such as the roll material and secondary cooling conditions, the horizontal cracks that occur periodically in the phosphor blue W4YL plate and the plate surface temperature directly under the roll (the maximum temperature that is achieved by reheating after the thin plate is separated from the roll surface) ) and transverse cracking, we obtained Figure 2. As shown in the figure, the surface temperature of the plate at which the number of cracks decreases varies depending on the P level, but when it is set to 900°C or less, a remarkable effect of reducing cracks is observed. From this, it has become clear that the surface temperature of the plate directly under the roll needs to be at most 900°C or less, and that the lower the temperature, the more desirable it is. In order to control the temperature immediately below the narrowest gap to 900°C or less, the temperature is measured by the surface temperature measuring device 20.21 and a cooling medium is injected onto the plate surface through the cooling nozzle 22.23. Be practical.

On the other hand, increasing the rolling load is also effective in lowering the surface temperature of the plate. However, in the case of phosphor bronze, the solidified shell is fragile, so cracks are likely to occur due to force when pressed by rolls, so the value P/ The relationship between l and over-pressure and cracks caused by force was investigated. As a result, Figure 3 was obtained. From the same figure, P/l is 15kg
It can be seen from the force that the number of cracks increases when the pressing force is as small as f/Imm. From this, the value of P/Il is 15k
It is necessary to cast phosphor bronze by controlling the pressure to be as low as gf/m+s or less. However, P/j! If it is O, it will flow out in an unsolidified state or break out due to recuperation, making it impossible to obtain a sound thin plate.Therefore, the rolling load should be at least a value exceeding 0.

It has been found that the problem of frequent cracking can be solved if thin sheets of phosphor bronze are manufactured directly from molten metal by the twin roll method under the above conditions, and 1. According to the method of the present invention, the above-mentioned objectives have been effectively achieved. It is something.

〔Example〕

Cu-8wt, P content in XSn is 0.05-0.2
5wt, 100kg of molten metal changed in the range of χ was rolled with a roll diameter of 4.
A thin plate was produced directly from the molten metal using a pair of copper cooling rolls with a roll body length of 200 mm and a water-cooled interior.

At that time, the surface temperature of the plate after the narrowest part 9 between the rolls is controlled to be 900"C or less by adjusting the roll circumferential speed V and the contact length X, and the rolling load P is controlled at the value of P/ffi. The range was set to be 5 to 15 kgf/s + s.For comparison, manufacturing was performed when the temperature after the narrowest roll gap 9 was 930°C and when the value of P/j! was 25 kgf/mm. The plates obtained under each manufacturing condition were pickled and color checked, and the occurrence of cracks on the plate surface was evaluated by the number of cracks per unit area.The results are summarized in Table 1. Indicated.

From Table 1, it can be seen that according to the manufacturing method of the present invention, phosphor bronze thin plates can be manufactured satisfactorily without cracking.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view showing an example of a twin-roll continuous casting machine suitable for carrying out the method of the present invention, and Fig. 2 shows the narrowest gap between the rolls when a thin plate of phosphor bronze is continuously cast using the apparatus shown in Fig. 1. Figure 3 shows the relationship between the coffin surface temperature just below the coffin and the number of horizontal cracks. Figure 3 shows the P/
It is a relationship diagram between l and the number of cracks. 1.Tonpush, 2.Nozzle, 3.4.
・Internally cooled cooling roll, 5. Molten phosphor bronze, 6. Pool, 7, 8. Solidified shell formed on the surface of the cooling roll, 9. Narrowest part of the cooling roll, 10.・Casted thin plate, 17... Reduction device, 18
...Load cell, 21.22 ...Surface temperature detector, 22.23...Cooling nozzle.

Claims (2)

[Claims] (1) Sn; 7-9.5wt. %, P; 0.03-0.
3wt. %, the balance being Cu and impurities, when directly casting a molten phosphor bronze into a thin plate using a twin-roll continuous casting machine consisting of a pair of cooling rolls rotating in opposite directions.
The surface temperature of the plate after passing through the narrowest gap between both rolls is 900℃.
A continuous thin plate casting method for phosphor bronze that is characterized by controlling the amount of cooling so as not to exceed ℃. (2) Sn; 7-9.5wt. %, P; 0.03-0.
When directly casting molten phosphor bronze containing 3 wt% Cu and impurities into a thin plate using a twin-roll continuous casting machine consisting of a pair of cooling rolls rotating in opposite directions, the narrowest gap between the two rolls is The surface temperature of the plate after passing is 900℃
The amount of cooling is controlled so that the amount of cooling is not exceeded, and the load P per plate width l (mm) applied to the slab by both rolls is calculated using the following formula (1) 0 (kgf/mm) < (P/l) ≦ 15 (kgf/mm
)...A method for continuous casting of phosphor bronze thin plates, characterized by controlling the casting within the range of (1).