JP2596928B2 - Outer layer material of two-layer roll - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an outer layer material of a two-layer centrifugal casting roll applied to a wear-resistant portion of a papermaking machine, an ironmaking machine, or the like.

[Conventional technology]

Conventional two-layer centrifugal casting rolls having wear resistance are manufactured by a mold method having a high cooling rate after casting and a sand mold method having a slow cooling rate. The mold method is considered unsuitable because the core thickness is too large to produce a large diameter size (outer diameter of 30 inches or more), and it is a product when producing a wide variety of rolls from small diameter (above) to large diameter A sand mold is used for stability.

The outer layer hardness of the two-layer centrifugal casting roll by the sand mold method is 74 to 77 in terms of shear hardness (Hs). At this time, the outer layer has a base material of pearlite to troostite and has a carbide in an area ratio of 40 to 50%.

[Problems to be solved by the invention]

If the roll surface hardness is not currently subjected to any special surface treatment, the sand mold method is about Hs76 and has a certain degree of abrasion resistance, but the polishing cycle is 1 to 3 due to rough surface due to abrasion of the roll surface. It is said to be about a month.

[Object of the invention]

The present invention is intended to extend the polishing cycle due to the wear to achieve the roll life and cost saving by the sand mold method.

[Means for solving the problem]

In the present invention, C: 3.4 to 4%, Ni: 1.5 to 3%, M
o: 0.5 to 2.5%, Cr: 2 to 3%, V: 1 to 2.5%, the balance being substantially Fe, carbide area ratio of 40 to 60%, and hardness Hs of 80 or more An outer layer material of a two-layer roll having abrasion resistance and skin roughness resistance produced by a centrifugal casting method characterized by the following.

[Action]

The present invention is intended to increase the hardness by the formation of bainite in the base structure and increase the hardness by increasing the amount and refinement of carbides. V is added for dispersion (miniaturization).

Hereinafter, the reasons for limiting the components of the outer layer material of the multilayer roll by the sand mold method and the reasons for limiting the carbide area ratio will be described.

Ni and Mo; In order to increase the toughness and hardness of the base structure, that is, to make it bainite (in other words, to make it non-martensite), Ni is 3% or less by weight% (hereinafter the same), and Mo is 2.5%
It is preferable that the content of Ni be 1.5% or more and the content of Mo be 0.5% or more for non-troostite or non-pearlite. Therefore, Ni; 1.5-3% and Mo; 0.5-2.5%.

V; This is a component necessary for uniform dispersion of carbides,
If it is less than 1%, there is no effect on fine dispersion of carbides, and if it exceeds 2.5%, eutectic formation of V carbides starts and it becomes impossible to finely uniform the carbides.

Cr; the amount of carbide is determined by the amount of Cr and C, and Cr is 2%
If it is less than 3, carbide growth is large and the area ratio is
If it is less than 40% and exceeds 3%, the area ratio of carbide exceeds 60% and becomes brittle, so Cr is set to 2-3%.

C: The amount of the base structure and the carbide is determined by the amount of C, and within the range of the above Mo, Ni, V, Cr and carbide area ratio, the amount of C is 3.4 to
4% is needed.

As described above, the carbide area is determined mainly by the amounts of Cr and C.
If it is less than 40%, the hardness will be insufficient even if the carbides are dispersed, and if it exceeds 60%, the embrittlement of the outer layer material will increase and cracks will easily occur.

Further, generally, both Si and Mn are added as deoxidizers, but if the Si content is less than 0.2%, the degree of hardening of the matrix becomes sensitive and the crack resistance tends to decrease. Adversely affect the degree. On the other hand, if Mn is less than 0.5%, it adversely affects the structural stability of the matrix, and if it exceeds 0.8%, it is likely to be sensitive to hardening of the matrix. Therefore, Si is 0.3-0.6%, M
n is preferably in the range of 0.5 to 0.8%.

〔Example〕

Hereinafter, specific examples of the outer layer material of the multilayer roll of the present invention will be given to demonstrate the effects of the present invention. An example is shown in Table 1.

As is apparent from Table 1, cracks occur due to insufficient hardness of the outer layer or a decrease in thermal shock resistance in the two-layer roll having the conventional material as the outer layer, but the outer layer material of the present invention has a high hardness (Hs). = 80-85) can be achieved. In addition,
In the table, “Production impossible due to crack generation (insufficient thermal shock resistance)” means a product that has cracked during product manufacture.

G By sand type centrifugal casting method according to No.75, the inner layer is made of ordinary cast iron (casting temperature 1300 ° C) and the outer layer is made of No.1 and No.4 in Table 1 (casting temperature 1320 ° C), 529φ x outer layer 30t X Inner layer 50t x 7,000
Was cast. FIGS. 1 (a) and 1 (b) show micrographs (100 times magnification) of the metal structures of these outer layers. As can be seen from FIG. 1 (a) of the conventional material (No. 1 of Table 1), the material of the present invention (No. 5 of Table 1) is composed of a large eutectic carbide and a troostite matrix. Was composed of fine carbides and an upper bainite structure, and had a sufficiently satisfactory hardness target.

〔The invention's effect〕

According to the product of the present invention, the conventional polishing cycle due to abrasion and rough skin (time required for abrasion pits having a surface roughness of about 50 to 100 seconds) is 2 months (about 1500 hours), but 6 months (about 4000 hours).
r) could be extended.

[Brief description of the drawings]

FIG. 1 is a photomicrograph (100 ×) of the metal structure of the outer layer material of one embodiment of the present invention and the outer layer material of the conventional material, (a) is the outer layer material of the conventional material, and (b) is one of the present invention. It is an outer layer material of an example.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kihachi Hashimoto, Inventor Hiroshima Research Institute, Hiroshima City 4-4-2, Kannonshinmachi, Hiroshima City (72) Inventor Kazuo Baba 5007, Itozakicho, Mihara City Mitsubishi Heavy Industries, Ltd. Inside Mihara Works (72) Inventor Hiroshi Matsuura 5007 Itozakicho, Mihara City Inside Mihara Works, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-57-149450 (JP, A)

Claims (1)

(57) [Claims] (1) In terms of% by weight, C: 3.4 to 4%, Ni: 1.5 to 3%, M
o: 0.5 to 2.5%, Cr: 2 to 3%, V: 1 to 2.5%, the balance being substantially Fe, carbide area ratio of 40 to 60%, and hardness Hs of 80 or more An outer layer material of a two-layer roll having abrasion resistance and surface roughness resistance produced by a centrifugal casting method characterized by the following.