JPH0255645A - Cooling roll for producing rapid-cooled strip - Google Patents

Abstract

PURPOSE:To prevent deformation of a roll and seizing by fusing to the roll surface and to stably obtain a rapid-cooled strip having excellent surface characteristic by making a material specifying heat conductivity, proof stress, hardness and tensile strength of the cooling roll for forming molten metal to the strip by forcedly rapid-cooling and solidifying. CONSTITUTION:The material of the cooling rolls 1a, 1b for receiving flowing- down stream of the molten metal and forming to the strip by forcedly rapid- cooling and solidifying is specified. That is, the material satisfying >=0.5Cal/ cm.s. deg.C thermal conductivity, >=30kg.f/mm<2> to 0.2% proof stress, >=150 Vickers hardness (Hv 5g), >=40kg.f/mm<2> tensile strength and >=5% elongation, is used. By this method, the deformation of the roll and the fusion to the roll surface are prevented and the rapid-cooled strip having excellent surface characteristic can be stably produced over for a long time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a cooling roll suitable for use in a process of directly manufacturing a metal ribbon from molten metal using rolls such as a twin-roll method or a single-roll method. It is something.

(Prior art) A popular method for directly producing metal ribbon from molten metal (hereinafter referred to as molten metal) is to flow the molten metal from a nozzle onto the circumferential surface of a cooling roll that rotates at high speed and rapidly solidify it on the circumferential surface. Are known. Methods using this cooling roll include the single roll method and the twin roll method. For example, when manufacturing wide thin sheets with a thickness of 1 mm or less such as amorphous alloy ribbon, high silicon steel ribbon, and stainless steel ribbon. The twin roll method is considered to be advantageous in terms of the surface properties and shape of the plate, and its industrialization is progressing.

The twin roll method uses a pair of cooling rolls l as shown in Figure 1.
a, the pouring nozzle 2 is placed in the roll kiss area where lb contacts with pressure
Since the molten metal 3 is injected and squeezed between the rolls and rolled at the same time as cooling, the cooling rolls used must have high strength, toughness, and hardness to improve the surface accuracy of the rolls. is requested.

For example, the material of such a cooling roll is disclosed in Japanese Patent Application Laid-Open No. 1986-
High-speed steel, cemented carbide, etc., such as those disclosed in Japanese Patent No. 119650, can be used, but not only do they have low heat conductivity, resulting in insufficient heat removal, but also the wrapping of the ribbon around the cooling roll is difficult. It is unsuitable for manufacturing quenched ribbons because it generates cracks and also generates beam racks.

Therefore, copper rolls are usually mainly used, for example,
Cu-Cr, Cu-Zr and C which have good thermal conductivity and high strength are disclosed in Japanese Patent No. 7-77918.
Copper alloys such as u-Be are widely used as rapid solidification rolls. Such copper alloy rolls are effective in laboratory scale or small-scale processes with a heat size of 500 kg or less, but microscopic cracks (hereinafter referred to as arc cracks) occur on the roll surface, and if the roll is operated for a long time, it becomes difficult to use. Molten steel was inserted into this hair arc crack and the ribbon was wound around the rolls, eventually resulting in breakouts and the like, which sometimes forced the interruption of operations.

(Problems to be Solved by the Invention) Problems with conventional cooling rolls made of prepared alloys are summarized as follows.

(1) Seizure on the surface of the cooling roll, winding of the ribbon...Especially when manufacturing a ribbon with a thickness of 1 mm or less, the circumferential speed of the cooling roll is high and the thermal conductivity of the cooling roll is low. Problems such as attachment may occur.

(2) Roughness and wear on the surface of the cooling roll...(1) above
Even if a highly thermally conductive material that satisfies the above conditions is applied to the cooling roll, such materials generally have low hardness, especially high-temperature hardness, so long-term operation will cause surface roughness and wear, which will be transferred to the surface of the ribbon. and contaminate the product board.

(3) Roll deformation...Especially in the twin-roll method, roll reduction is performed, so if the roll kiss part is exposed to a high-temperature cloud atmosphere (over 400°C), the high-temperature strength deteriorates and high-temperature deformation is likely to occur, resulting in roll deformation. As a result, variations in the thickness of the ribbon become noticeable.

(4) Arc crack on the roll surface...(1) above
Copper alloys with high thermal conductivity and high strength at high temperatures are suitable as roll materials that satisfy requirements (3). However, when these copper alloy rolls are applied to the twin roll method, Due to fatigue, for example, precipitation hardening copper alloys (Cu-
(Be, Cu-Cr, Cu-ZrCr, etc.), grain boundary cracks, so-called hair cracks, occur, making long-term operation impossible.

Therefore, it is an object of the present invention to provide a cooling roll that can solve the various problems described above.

(Means for Solving the Problems) As a result of intensive research by the inventors to solve the above-mentioned problems, we found that applying a cooling roll made of a material having the following characteristics is extremely effective in achieving the intended purpose. We obtained knowledge that it is effective.

That is, the present invention provides a cooling roll that receives a falling flow of molten metal and forces the molten metal to rapidly solidify to form a thin ribbon, and has a thermal conductivity of 0.5 caf/Cm -s or more,
Furthermore, at 400℃, 0.2% yield strength: 30 kg
f/mm2 or more, Vickers hardness (Hv 5g)
+150 or more, tensile strength: 40kgf/mm
This is a cooling roll for producing a quenched ribbon, characterized by being made of a material that satisfies an elongation of 2 or more and an elongation of 25% or more.

Here, specific examples of materials suitable for the cooling roll according to the present invention are as follows.

(1) Zr:O, old ~ 0. Iwt% (hereinafter simply referred to as %) Cr: 0.3 to 0.5% Ni+1.5 to 2.5% Ti: 1. A composition containing O to 2.0% Fe: 0.01 to 0.1%, with the remainder consisting of Cu and inevitable impurities.

(2) Be: 0.5-1.0% (:o:1.4~2.5% 8g: 0.9~2.0% , with the remainder consisting of Cu and unavoidable impurities.

(3) Be: 0.2-0.8% Ni: 1.4-2.5% Zr: 0.1-0.9% , with the remainder consisting of Cu and unavoidable impurities.

(Function) Next, the reason for limiting the material of the cooling roll according to the present invention will be explained.

Thermal conductivity: Q, 5 cai! /am-s ・℃ When manufacturing a ribbon with a thickness of 1 mm or less, as is the object of this invention, as shown in Figure 2, the surface temperature of the roll kiss portion (maximum surface temperature) depends on the material of the roll, especially the thermal conductivity. It differs due to the difference in heat removal effect caused by the difference in rate. As shown in the figure,
For example, iron roll (thermal conductivity λ=0.010.05ca
When using A/cm-s ・t), the surface temperature of the roll kiss part is 600 to 900℃, and similarly, when using a copper roll (λ-0, 2 to 1, Ocan/am-s ・t), the surface temperature of the roll kissing part is 600 to 900℃. ~400℃.

On the other hand, in the experiments conducted by the inventors, the temperature of the roll kiss part was 400℃.
It has been confirmed that when the temperature exceeds 900°C, winding occurs, and at around 900°C, the roll material changes and a reaction layer is generated at the interface, causing seizure. Therefore, in order to avoid winding and seizure on the roll and adverse effects on the solidified structure of the fabricated ribbon,
Copper rolls, which have higher thermal conductivity than iron rolls, are advantageous.

Therefore, the inventors developed a copper roll (sleeve thickness 5 to 20 m).
The relationship between the temperature of the roll kiss part and the thermal conductivity was investigated in the production of rapidly quenched ribbons using quenching method (internal water cooling). As shown in Figure 3, the temperature of the roll kiss area was increased to 400°C.
To keep the thermal conductivity below 0.5 cal/cm-s・℃
It turns out that you can do the above.

0.2% proof stress at 400℃: 30 kgf /
A cooling roll of mm2 or more is usually shrink-fitted around a sleeve. Shrinkage fit is 1/1000D~2/100OD
(D: outside diameter of the roll), tensile stress is applied to the roll, and in the twin roll method, rolling solidification is performed by rolling down between two rolls, so compressive stress corresponding to the rolling edge is applied to the roll surface. The load is applied, and thermal stress (compressive stress) is generated due to the rise in roll surface temperature. Therefore, it is important that the cooling roll has sufficient strength to withstand these stresses.

The results of calculations of the thermal stress acting on the cooling roll, the rolling edge stress, and the shrink fit stress are shown in FIG. 4. The figure shows roll outer diameter: 550mm, roll width: 500m.
This is an example of manufacturing using two cooling rolls with m and sleeve thickness of 10 mm and a reduction blade of 1 t, and calculations were performed using the finite element method.

In the same figure, the maximum stress generated at the roll kiss part is 30 kg.
less than f/mm2. Therefore, the yield point stress is set to 30 kgf.
Since large plastic deformation does not occur if the deformation is suppressed to approximately 30 kgf/mm2, 0.2% proof stress is used as a guideline.

Pinkers hardness at 400°C (Hv 5g):
The relationship between the surface roughness and Vickers hardness of a cooling roll of 150 or more is
As shown in the figure, in order to avoid area A where the roll surface is extremely rough and causes curling or seizure, and area B where the roll surface is rough and adversely affects the sheet shape, Hv 5g is 150.
It turns out that you can do the above.

Tensile strength at 400℃' 40kgf/mm2
In the twin roll method described above, as shown in FIG. 6, thermal fatigue occurs due to repeated heating and cooling at high temperatures, and hair cracks occur on the surface of the cooling roll.

As shown in Figure 4, the maximum stress at the roll kiss portion is approximately 30 kgf/mm2, and this stress is amplified by the cyclic thermal fatigue pattern shown in Figure 6. Based on these backgrounds and various experiments, the tensile strength at 400 t: is 40 kgf/
If it is at least mm2, it can sufficiently withstand the stress applied to the roll.

Elongation at 400°C = 5% or more It is believed that the ductility of the cooling roll also affects the occurrence of hair cracks, and the following formula (%) is used as a guideline for thermal deformation in copper rolls. However, α: Coefficient of linear expansion (= 16.5xlO-1l'/l
), the thermal deformation at 400℃ is less than 1%, but if we take into account localized concentrated deformation and the influence of the rolling blade, it is necessary to consider the deformation elongation at 400℃.
The elongation at is 5% or more.

Furthermore, the above-mentioned excellent mechanical properties can be obtained by the materials suitable for the cooling roll of the present invention described in the above-mentioned means for solving the problems, including (1) Cu-Zr-Cr-Ni-Ti-Fe alloy (2) Cu-Be-Co-Ag alloy (3)
Precipitation hardening alloys such as Cu-Be-N 1-Zr alloys are the main ones.

In this alloy, all intermetallic compounds such as (1) (F
e, N+, Co) xTIy phase grain refinement and <l
r, Cr) xCuy phase coexistence, in (2) CU+t-
(Be, (:o, Ag) y phase, Cu-
(Be, Ni), Cu-Zr phase fine particles precipitate at the grain boundaries, forming an alloy with high strength and high ductility.

(Example) Using cooling rolls made from various sleeves made of the materials shown in Table 1, a plate thickness of 0.
A quenched ribbon having a thickness of 5 to 0.6+ nm and a plate width of 500 mm was produced.

Manufacturing conditions Steel type: 4.5%Si -Fe Cooling roll 2 Roll diameter 550mm (outer diameter) Roll width 500mm Sleeve thickness: IO city Roll circumferential speed: 5m/s Tapping temperature: 1600℃ Heat size: 3 to ribbon production Table 1 also shows the results of observing the winding of the ribbon around the roll and the surface of the roll after manufacture, as well as measuring the surface roughness of the cooling roll.

As is clear from the table, the cooling roll according to the present invention (
When Nos. 1 to 5) were used, the roll wear was slight, and there was no wrapping, seizure, or cracking at all, but thermal conductivity, hardness at high temperatures, and tensile strength were Comparative examples (Nos. 6 to 15) in which the strength, 0.2% proof stress, and elongation were out of the invention range had some disadvantages.

(Effects of the Invention) Thus, according to the cooling roll according to the present invention, no roll deformation, no burning, no wrapping occurs on the roll surface during the production of the quenched ribbon, and the surface roughness and abrasion of the roll surface are slight and the surface is smooth. Since no cracks occur, a quenched ribbon with excellent surface properties can be stably produced over a long period of time.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the procedure for producing rapidly cooled metal ribbon using twin rolls. Figure 2 is a graph showing the change in surface temperature of the roll kiss area over time when an iron roll and a copper roll are used as cooling rolls. Figure 3 is a graph showing the relationship between roll kiss temperature and thermal conductivity, Figure 4 is a graph showing the distribution of stress in the circumferential direction on the sleeve surface when a copper alloy roll is used, and Figure 5 is a graph showing the relationship between Vickers hardness and thermal conductivity. Figure 6 is a graph showing the relationship between roll surface roughness and thermal fatigue cycle pattern. la, lb...cooling roll 2...pouring nozzle 3...molten metal

Claims (1)

[Claims] 1. A cooling roll that receives the falling flow of molten metal and forces it to rapidly solidify to form a thin ribbon, and has a thermal conductivity of 0.5ca.
l/cm・s・℃ or more, and further at 400℃, 0
．． 2% proof stress: 30kgf/mm^2 or more, Vickers hardness (Hv5g): 150 or more, tensile strength: 40kgf
/mm^2 or more and elongation: 5% or more.