JPH0247241A - Wear-resistant material for roll for rolling - Google Patents

Abstract

PURPOSE:To provide cracking resistance together with slip resistance, in addition to wear resistance characteristic of a high-chromium material, by specifying respective contents of C, Cr, and Mo in a steel and also adding proper amounts of Ni and V. CONSTITUTION:A wear resistant material has a composition consisting of, by weight, 0.8-2.2% C, 3-13% Cr, 1-3% Mo, <=2% Ni, <=0.5% V, and the balance essentially Fe. Since Ni is preferentially distributed into a matrix structure, the addition of Ni is effective in improving hardenability. The addition of V is effective in improving wear resistance. When this material is applied to rolls for rolling, high-quality rolls having superior wear resistance and combining cracking resistance with slip resistance can be supplied.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a wear-resistant material that has both crack resistance and slip resistance, and is applied to rolling rolls, particularly hot rolling rolls. .

[Prior Art] Typical properties required of a roll material for hot rolling are wear resistance and surface roughening resistance. Conventionally, adamite material with 1.5 to 2% C and a small amount of alloying elements has been widely used for this type of roll, or recently, adamite material with 2% C added has been widely used.
．． A high chromium cast iron material containing 5 to 3% CRR and 15 to 20% CRR and an appropriate alloy has been developed, and its application is rapidly expanding due to its good wear resistance.

High chromium cast iron has extremely hard chromium carbide and good hardenability, resulting in high hardness and excellent wear resistance, and its dense structure makes it easy to form hard oxides on the surface. It has also received good reviews for its resistance to rough skin.

In addition, as a rolling roll wear-resistant material, foreign patent E1
There are conventional techniques such as those described in Publications No. 125394 and EP252828.

[Problems to be Solved by the Invention] In recent rolling, new technologies such as large reduction and high speed high pitch rolling have been adopted, and rolls are worthy of being used under extremely severe conditions. In other words, the thermal load on the rolls increases, making them more likely to crack, and the increased bite angle due to large reductions causes slips, which hinders production and can even damage the rolls and other equipment in the event of a major slip accident. There is. In this regard, the aforementioned high chromium cast iron material contains a large amount of brittle carbides, so it is easy to crack and F! It has the disadvantage that the i coefficient is small and slips easily occur.

Therefore, the present invention aims to provide a material that has not only the wear resistance of high chromium materials but also crack resistance and slip resistance.

[Means for solving the problem] The wear-resistant material for rolls of the present invention basically has a C content of 0.8
~2.296 and improves crack resistance by suppressing brittle carbides, as well as increasing the coefficient of friction and improving slip resistance. In order to crystallize chromium carbide, Cr is controlled to 3 to 13%, and appropriate amounts of Mo and Ni are added to improve hardenability. Furthermore, in order to improve wear resistance, 0.5!6 or less of V, which forms the hardest and densest carbide, is added.

[Function] The reason why the content of C is limited to the above range of 0.8 to 2.2+k is as follows. That is, if C is less than the lower limit, there will be little crystallization of hard carbides, and the wear resistance will deteriorate significantly, and no improvement can be expected compared to conventional adamite materials. On the other hand, when the upper limit is exceeded, the amount of carbides increases and the wear resistance improves, but the toughness decreases, impairs the crack resistance, and the coefficient of friction also decreases, creating a risk of slipping, making it impossible to achieve the object of the present invention. .

The content of Cr is selected in balance with C in order to crystallize M2C-based chromium carbide, which is much harder than normal Fc-based carbide. That is, when C is 0.8%, Cr
If C is 3% or less, M3C type carbide, if C is 2.2%, C
When r is 13% or more, M23C6 carbide and M7
Since carbides that are softer than C3 carbides crystallize, they must be controlled within the above range.

Mo mainly forms carbides, but since a part of it is distributed in the base structure, it is effective in crystallizing hard Mo2G carbides and improving the hardenability of the base structure, and is preferably 1% or more and 3% or less. That is, if it is less than 1%, the distribution to the base structure is small and there is no effect on improving hardenability, whereas if it is more than 3%, the MO□C carbide increases too much and the material becomes brittle instead. In this respect M
0.1-1% of O is too low, whereas patent EP252
The 3 to 8% shown in No. 828 is too high to fully exhibit the properties of high chromium materials.

Since Ni is preferentially distributed to the base structure, it is effective in improving hardenability. However, since it has a side effect of inhibiting rough skin resistance, it is limited to 2% or less.

Furthermore, addition of V is extremely effective in improving wear resistance. In other words, the VC-based carbide formed by V is very hard and improves wear resistance, but since it crystallizes finely, it does not become brittle, and it also has a large effect on roughening resistance during hot rolling. A surface oxide film is easily formed, and the surface roughness resistance is also improved. However, since it is very expensive, it is limited to within 0.596.

In addition, Si and Mn, which are not essential components but are useful elements in melting technology for reasons such as deoxidizing the molten metal, may each be included in an amount of about 0.5.1%. Further, impurities such as P and S may be contained as long as they are about 0.03% or less of those contained in ordinary castings, and these do not impair the effects of the present invention in any way.

[Actual Hti Example] As an example of the present invention, a work roll for a rough rolling mill for hot strip and a sleeve roll for rolling a section steel were manufactured. Casting was done using a centrifugal casting method to produce a composite type, but the inner layer material was ductile cast iron for the hot strip mill rough rolling mill work roll of Example (1), and ductile cast iron for the shape steel rolling mill of Example (2). Graphite cast steel was used for the sleeve roll, which was subjected to quenching and tempering type heat treatment to obtain a sound roll having the material properties shown in Table 1.

In addition, FIG. 2 schematically shows the structure of the composite roll in Example (+), and FIG. 3 schematically shows the structure of the composite sleeve roll in Example (2), where 1 is the outer layer,
2 is the inner layer, 3 is the arbor, and 4 is the shrink-fitting location.

The above roll was subjected to actual rolling, and as shown in Table 1, good wear resistance was confirmed, and no slips or abnormal cracks occurred.

Table 2 shows the results of laboratory evaluations of the abrasion resistance and F9 friction coefficient of several materials within the scope of the claims of the present invention, including the above-mentioned examples, and good characteristics were confirmed for all of them. .

／ ／ ／ ／ ／ ／ [Effects of the Invention] By applying the present invention to rolling rolls, it becomes possible to supply high-quality rolls that have good abrasion resistance, as well as crack resistance and slip resistance. It also has great value.

[Brief explanation of the drawing]

FIG. 1 shows microscopic metallographic photographs of the present invention and conventional materials. Note that the magnification is 100 times. FIG. 2 is a sectional view schematically showing the structure of the composite roll in Example (1), and FIG. 3 is a sectional view schematically showing the structure of the composite sleeve roll in Example (2). 1...Outer layer, 2...Inner layer, 3...Arbor, 4...
・Burning areas

Claims (1)

[Claims] 1. C: 0.8 to 2.2% (weight %, same hereinafter) Cr:
A wear-resistant material for rolling rolls containing 3 to 13% Mo: 1 to 3%, 2% or less of Ni, and 0.5% or less of V, with the remainder being substantially iron.