JPS59223155A - Manufacture of roll overlaid by tinkering - Google Patents

Abstract

PURPOSE:To improve casting adhesion of a high chromium cast iron to a roll core part by preheating the outside surface of the roll core part to a specific temp. or above then casting the high chromium cast iron. CONSTITUTION:A circular columnar or cylindrical roll core part 1 of steel is installed concentrically at the center of a high frequency induction heating coil 2 and the outside surface of the core part 1 which is kept covered with a reducing flux 5 is heated by a high frequency induction to>=500 deg.C. The power source for a high frequency induction heating coil 2 is turned off and cooling water is run in the coil 2. The molten high chromium cast iron 8 in a ladle 7 is then charged into the space between a master mold 3 and the core part 1 to adhere the high chromium cast iron to the core part 1 by casting. The roll overlaid by tinkering is thus manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing rolls, and particularly to a method for manufacturing overlay rolls that have excellent machinability and wear resistance and are inexpensive to manufacture.

Rolls that require excellent wear resistance can be roughly divided into three types depending on the manufacturing method: monolithic casting rolls, two-layer centrifugal casting rolls, and weld overlay rolls. An overview of each is shown below.

(1) One-piece casting roll A wear-resistant material such as nihard cast iron or high chromium cast iron is cast in a sand mold or metal mold (2. The entire roll is manufactured from this wear-resistant material.

(2) Two-layer centrifugal casting roll A two-layer roll manufactured by casting a wear-resistant material into the outer layer using a centrifugal casting method and casting cast iron into the inner layer using a hanging method.The inner layer is made of cast iron with excellent rigidity. As a result, machining of the inner surface is easier than with integral casting rolls.

(3) A high carbon high chromium welding rod (5
~4φ, chemical component example C: 3.5%, Si:
0.6%, Mn: L2%, Cr: 2
0.1%, Nb: 3.5%, Mo: 4
．． 6%).

However, each role has its drawbacks:

(1) One-piece cast roll Normally, the inner surface of the roll is mated to the shaft, so machining is required, but since the inner surface 1 is made of a hard wear-resistant material that is difficult to machine, machining is not possible. This requires a long time and increases the cost of the roll.

(2) Two-layer centrifugal casting roll In order to improve the casting of the outer layer and inner layer, the casting interval between the outer layer and inner layer and the respective casting temperatures must be strictly controlled, so advanced casting technology is required. be.

(3) The diameter of the welding overlay roll welding rod is relatively small at 3 to 4 cm, and the rod movement speed (welding speed) is slow, so welding takes a long time.
This increases the cost of rolls.

The present invention eliminates the above-mentioned drawbacks, and provides a method for manufacturing an overlay roll that is easy to machine, has excellent wear resistance, and is inexpensive.

That is, in the present invention, a cylindrical or cylindrical steel yarn roll core is installed concentrically in the center of a high-frequency induction heating coil, and the outer surface of the roll core is coated with a reducing flux and high-frequency After induction heating, the power to the high frequency induction heating coil is turned off, and while cooling water is flowing through the heating coil, a high chromium system is separately melted in the gap between the roll core and the outer mold to which the high frequency induction heating coil is fixed. The present invention relates to a method for producing a cast overlay roll, which comprises casting molten cast iron and casting the high chromium cast iron onto the roll core.

The new ideas of the present invention are listed below.

(1) In order to ensure complete adhesion between the roll core and the cast high chromium cast iron, the outer surface of the roll core should be preheated to 500°C or higher by high-frequency induction heating.

(2) In order to prevent the roll core from being oxidized while the roll core is preheated as described above, the outer surface of the roll core is coated with a reducing flux such as anhydrous sodium borate or borax during preheating. .

(3) Using the refractory material to which the high-frequency induction heating coil is fixed as an outer mold, turn off the power to the high-frequency induction heating coil, and keep water flowing into the coil between the outer mold and the roll core. Casting molten high chromium cast iron.

The method of the present invention can be applied to the manufacture of mill rolls for crushing coal, raw ore, and the like.

Figures 1 and 2 are diagrams showing an embodiment of the method of the present invention. Figure 1 shows a situation in which the outer surface of the roll core is preheated by a high-frequency induction heating coil, and Figure 2 shows a situation in which the outer surface of the roll core is preheated by a high-frequency induction heating coil. Each figure shows a state in which high chromium cast iron molten metal is being cast into the roll core.

In Figures 1 and 2, 1 is a roll core made of steel thread material, and is usually made of carbon steel cast steel (8C42 or 8C46).
) as well as low alloy cast steel products (8CMn1, 2.3.5.8
C8iMn 2, SCMnCr 2.3.4.8C
MnM 3 , SCCrMn 1,3 , S
CMnCrM2. 3, SCNCrM 2 ),
Stainless steel castings (scs 1.2゜11, ~24)
, all cast steel products such as heat-resistant steel cast products (8CH4-3, 11-22), or low alloy steel forged products (5Fv1-3.5FVV 1-3) in addition to carbon steel forged products (SF45).
, alloy steel forgings for high temperature pressure vessel parts (8PHV 12A
, ~5PHV 26B), stainless steel forgings for high temperature pressure vessel parts (5USl'i'304~SUS s
A7H) and other forged steel products.

2 is a high-frequency induction heating coil, and 2a and 2b are terminals of the heating coil, respectively.0 This high-frequency induction heating coil 2
Refractory materials such as magnesia, chromium magnesia, alumina, dolomite, silica, zircon, corundum, and clay3
This refractory material 3 serves as an outer mold, as shown in FIG. Note that cooling water is allowed to flow inside the heating coil 2 (J), and 2a is the cooling water inlet pipe,
2b also serves as an outlet pipe for cooling water. 4 is a lower mold for casting high chromium cast iron into the gap between the roll core 1 and the outer mold 3.

5, 1% of the roll core is heated by the high frequency induction heating coil 2.
- A reducing flux coated on the outer surface of the roll core 1 in order to prevent the outer surface of the roll core 1 from being oxidized during preheating, including anhydrous sodium borate, sodium borate, boric acid, borax, and A mixture of one or two of these with silica, alumina, etc. is used.

Reference numeral 6 denotes an upper mold installed on the outer mold 3 and the roll core 1, and is a ladle for casting 07ij high chromium cast iron molten metal 8, which also serves as a pouring port and a feeder.

9 indicates the molten metal 8 poured into the gap between the outer mold 3 and the roll core 1, and 101d indicates the cast layer in which the molten metal 9 solidified in the roll core. C: 2.5~s, 5t16
.

Si: 0.50-2.0%, Mn: 0
．． 6-1.5%.

Cr: 15.0-30.0%, lcMo, Nb
, V, B, or a combination of the two.
The amount of these alloying elements added is MO: o, s ~ s %
, Nb: 0.5-8qI, ■=1-10qI) and B:
It is desirable to set it as 0.2-2.0 ratio. An example of the chemical composition of high chromium cast iron is shown in the table below.

(H) Next, the operating procedure of the method of the present invention will be explained with reference to FIG. 1.2.

The roll core 1 is made of the above-mentioned copper-based material, and its radius is determined by the thickness of the cast overlay layer, for example 30 mm, depending on the finished dimensions.
The roll core 1 is placed in the center of the refractory material 3 to which the high-frequency induction heating coil 2 is fixed, and placed on the lower mold 4. At this time, three refractory materials are arranged concentrically with the roll core 1.

Next, the above-mentioned reducing flux powder 5 is placed between the refractory material 3 and the roll core 1 to coat the outer surface of the roll core 1.

Then, an upper mold 6 is installed above the roll core 1 and the refractory material 3 that forms the outer mold.

Then, an electric current is applied to the heating coil 2 while water is flowing inside the high-frequency induction heating coil 2 from the inlet pipe 2a, and the outer surface of the roll core 1 is heated to a temperature of 500°C or higher (for example, about 800°C).
Heat to.

In addition, in the method of the present invention, the reason why the heating temperature of the outer surface of the roll core 1 is set to 500°C or higher is because if the heating temperature is lower than 500°C, the casting layer and the roll core will not be sufficiently cast, and the heating temperature will be lower than 500°C. This is because the layer may peel off and fall off during use of the roll. Further, the upper limit of the heating temperature does not need to be extremely high, and is preferably about 1,000° C., taking into consideration all aspects of row production. Furthermore, the heating temperature also differs depending on the size of the roll core 1, and the smaller the roll core 1, the easier it is to cool down before the casting layer is cast. The smaller the temperature, the higher the temperature.

Turn off the power to the high-frequency induction heating coil 2, and while cooling water is flowing inside the coil 2, the high chromium cast iron molten metal 8, which is completely melted in a separate melting furnace, is placed in the ladle 7 to form the roll core 1 and the refractory material 3, which becomes the outer mold. Pour hot water into the gap between.

The poured molten metal 9 first solidifies from the outer mold 3 shell 11, which is cooled by the heating coil 2 through which cooling water flows, and solidifies to the upper end of the roll. At this time, the reducing flux 5 is molten and has a lower specific gravity than the molten high chromium cast iron, so it floats to the top of the molten high chromium cast iron 9 and rises as the molten metal 9 is poured, as shown in Fig. 2. and is discharged.

After solidification of the molten metal 9 is completed, the upper mold 6. When the refractory material 3 to which the lower die 4 and the high-frequency heating coil 2 are fixed is removed, a cast overlay roll in which high chromium cast iron is cast on the outer surface of the roll core 1 is obtained.

The method of the present invention described in detail above can provide the following effects.

(1) Since high chromium cast iron is cast after the outer surface of the roll core is preheated to 500° C. or higher, it is possible to improve the casting condition with the roll core.

(2) During preheating of the roll core, the outer surface of the roll core is coated with reducing flux, which prevents the formation of oxide scale on the outer surface of the roll core and improves the quality of the cast high chromium cast iron. The casting distance between the roll core and the roll core is further improved.

(3) The high-chromium cast iron that was cast with the power to the high-frequency induction heating coil turned off and the cooling water continued to flow into the coil solidifies, so the high-chromium cast iron in the outer layer becomes quenched and has a dense structure. It exhibits excellent wear resistance.

(4) Since the hardened outer layer (high chromium cast iron) is cast by casting, it can be manufactured in a shorter time than welded overlay rolls.

(5) Since steel thread material is used as the roll core, machining of the roll core is easy.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing an embodiment of the method of the present invention. Sub-agents 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] A cylindrical or cylindrical steel yarn roll core is installed concentrically in the center of a high-frequency induction heating coil, and the outer surface of the roll core is coated with a reducing flux.1. 500℃
After high-frequency induction heating as described above, the power to the high-frequency induction heating coil was turned off, and while cooling water was flowing through the heating coil, a mixture was separately melted into the gap between the roll core and the outer mold to which the high-frequency induction heating coil was fixed. Casting high chromium cast iron molten metal 1-
1. A method for producing a cast overlay roll, which comprises casting the high chromium cast iron onto the roll core.