JPH0196355A - Wear-resistant composite roll material - Google Patents

Abstract

PURPOSE:To suppress the generation of casting defects at the time of casting and to obtain the sound title roll material by specifying its compsn. consisting of C, Si, Mn, Ni, Cr, Mo, W, V and Fe and regulating the amt. of solid solution C. CONSTITUTION:The title roll material contains, by weight, 1.5-3.5% C, 0.3-3.0% Si, 0.3-1.5% Mn, <=2.0% Ni, 3.0-7.0% Cr, <=8.0% Mo, <=20.0% W and 3.0-12.0% V, furthermore contains at need <=5.0% Nb, consists substantially of the balance Fe and satisfies the value of <=1.0 C-(0.06Cr+0.063Mo+0.033W+0.18V+0.13Nb) as well. In the material, the amt. of solid solution C except C forming the hard carbide of various metals to which wear resistance shall be provided is suppressed. By this method, the steel executable of forming a sound roll having no generation of segregation in the outer layer contg. crystallized carbide, sufficiently retaining wear resistance and having no casting defects such as shrinkage cavity can be obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a wear-resistant composite roll material for hot or cold rolling, and particularly to a wear-resistant composite roll material that reduces the occurrence of casting defects during casting. It is.

[Conventional technology]

Conventionally, cast iron composite rolls manufactured by centrifugal casting have been widely used as hot or cold rolling rolls that require wear resistance. Most commonly, this composite roll has an outer layer made of a cast iron-based material that has crystallized carbides with high wear resistance, and an inner layer made of gray cast iron or ductile cast iron with high toughness. When manufacturing such a composite roll by the centrifugal casting method, there are restrictions on the materials that can form the inner and outer layers. That is,
The outer layer is W, V, Nb+ Tt+ Ta+ Zr+
It is effective to improve wear resistance by forming the material with a material that crystallizes a large amount of carbide formed by elements such as Iff, but it is difficult to manufacture such an outer layer and inner layer by centrifugal casting. , which is practically impossible for the following reasons.

First, carbides formed by the above elements have a different specific gravity from the outer layer molten metal, and as a result of centrifugal separation during the outer layer formation, they are not uniformly dispersed and tend to segregate. In addition, many of the above elements have a strong tendency to oxidize,
Welding with the inner layer in the atmosphere is extremely difficult. Furthermore, in the centrifugal casting method, toughness is generally ensured by using gray cast iron or ductile cast iron with crystallized graphite as the material forming the inner layer, but the material forming the outer layer contains the above-mentioned materials. If the steel contains a large amount of elements that have a strong tendency to become white, the outer layer components will slightly dissolve into the inner layer, which will inhibit the graphitization of the inner layer and cause it to become brittle. Since carbides are concentrated near the layer boundaries, they are brittle and easily cause peeling of the outer layer starting from the boundaries and other problems.

Next, the tensile strength of gray cast iron or ductile cast iron that forms the inner layer of rolling rolls is generally 55 kg/
The limit is about 11" ml, and the elongation value is less than 1%. Therefore, if you try to obtain a value higher than this, it is necessary to use steel thread material for the inner layer, but it is not possible to manufacture it by centrifugal casting. It is difficult.

In other words, when the inner layer molten metal is poured after the outer layer molten metal is cast and the inner part of the outer layer is melted and joined, the inner layer has a higher melting point than the outer layer, so there is a boundary where the inner and outer layer components are molten and mixed. This is because the final solidified layer is likely to cause casting defects at this boundary.

On the other hand, as rolling rolls, those having an integral structure by shrink fitting or assembling the outer layer material and the shaft material are also used. However, recent rolling rolls have significantly improved wear resistance in order to streamline rolling by rolling a large amount at once, and to improve the dimensional accuracy of the rolled material. is becoming necessary. At the same time, in order to improve the dimensional accuracy of rolled materials, methods of bending the roll shaft in the opposite direction to the deflection caused by rolling and operations that increase the amount of reduction in one rolling stand have become widely adopted. The bending stress applied to the shaft has become extremely large, and it has become necessary to improve the strength of the roll shaft. In this case, if the above-mentioned shrink-fitting or assembled rolls are used, there are problems such as slippage between the outer layer and the shaft material during rolling, or the outer layer being susceptible to cracking. For this reason, the outer layer and the shaft must be completely integrally joined metallically.

As a means for simultaneously satisfying the above-mentioned requirements, a casting overlay method as described in, for example, Japanese Unexamined Patent Publication No. 61-60256 is effective. That is, a shaft material made of steel is loosely fitted coaxially into the inside of a mold consisting of a refractory frame surrounded by an induction heating coil on the outside and a cooling mold coaxially installed under this frame. The molten metal that is to form the outer layer is injected into the gap formed between the mold and the shaft material, and is welded to the shaft material. By solidifying this molten metal and moving together with the shaft material, the molten metal is continuously formed around the shaft material. It is made by pouring meat on top. The applicant has already filed an application for a wear-resistant alloy composite roll using a wear-resistant molten alloy as the outer layer molten metal and a method for manufacturing the same (patent application filed in 1983).
2-69666).

[Problem that the invention seeks to solve]

The improved method described above makes it possible to firmly weld the wear-resistant outer layer to the outer periphery of the strong shaft material.
When the outer layer contains large amounts of carbide-forming elements such as V, Nb, and Ti in order to impart wear resistance, the viscosity of the molten metal becomes particularly high, making the so-called feeder effect less effective. However, there is a problem in that casting defects such as cavities are likely to occur.In the cast overlay method, such casting defects are likely to occur at the boundary between the outer layer overlay material and the shaft material. When casting defects exist, they not only significantly reduce the strength of the welded joint between the outer layer and the shaft material, but also reduce the strength of the entire roll, making it unsuitable for the harsh rolling conditions of recent years.

On the other hand, by suppressing the alloy components forming the outer layer to a predetermined amount, the inherent carbide formation properties or wear resistance are reduced. It has been found that the riser effect can be promoted and the occurrence of casting defects can be prevented without causing any problems.

An object of the present invention is to provide a wear-resistant composite roll material that can solve the problems existing in the prior art and can significantly suppress the occurrence of casting defects during casting.

[Means for solving problems]

In order to solve the problems existing in the above-mentioned prior art, in the first invention of the present application, C1,5 to 3.5, Sin,
3-3. 0, Mn0.3-1.5, Ni2.0 or less, Cr3.0-7.0, Mo8.0 or less, W20.
0 or less, V 3. 0 to 12.0% by weight, with the remainder essentially consisting of Fe and C-(0,06Cr+0
．． 033W + 0.063Mo + 0.18V) value to 1
．． We adopted technical means to keep the value below 0.

Further, in the second invention of the present application, C1.5 to 3.5,
Si0.3-3.01Mn0.3-1.5, Ni2. O
Below, Cr3.0-7.0, Mo8.0 or less, W2O,
0 or less, V 3. 0 to 12.0, Nb5. Contains O or less in each type amount%, the remainder substantially consists of Fe, and C-(
0.06Cr + 0.033W + 0.063Mo
+0, 18 V + 0.13 Nb) was taken to be 1.0 or less.

The reason for limiting the content of each alloying element in the present invention and the basis for each coefficient of Cr, W, M□, V, and Nb content will be described.

C: 1.5 to 3.5% C is one of the basic elements constituting cast iron, and in particular, in the wear-resistant composite roll material of the present invention, MC, M4O2, MzC, M2O that should impart wear resistance It is an essential element for forming hard carbides such as. And this amount is 1.5
If it is less than %, the amount of carbides produced is small, which is disadvantageous because it not only fails to provide sufficient wear resistance, but also increases the primary crystal temperature and inhibits castability. On the other hand, if it exceeds 365%, it is not preferable because the toughness decreases and it becomes unsuitable as a roll material.

Si: 0.3 to 3.0% Si is an element necessary as a deoxidizing agent, and must be contained in an amount of 0.3% or more. In addition, St is M, W in C carbide,
W is contained by replacing elements such as Mo.

This is effective for reducing the use of expensive elements such as Mo.

However, if it exceeds 3.0%, it is disadvantageous because, like C, the toughness decreases.

Mn: 0.3 to 1.5% Mn is also effective as a deoxidizing agent like the above-mentioned Si, and is also effective for fixing S@MnS as an impurity, and must be contained in an amount of 0.63% or more.

However, even if the content exceeds 1.5%, it is not preferable because the above effects will not be significantly promoted.

Ni: 2.0% or less It is effective to include a small amount of Ni in order to improve hardenability, but if it exceeds 2.0%, the amount of retained austenite becomes excessive and no improvement in hardness can be expected.

Moreover, it is inconvenient because it causes accidents such as cracking due to transformation during use.

Cr: 3.0 to 7.0% Cr is an element necessary for improving hardenability and forming carbides, and is contained in an amount of 3.0% or more. However, 7.0%
Exceeding this is disadvantageous because Cr-based carbides become excessive. That is, Cr-based carbide, for example M23C6, is MC,
It is undesirable because it has lower hardness than M4C31M6C and MzC and reduces the wear resistance required as a roll material.

Mo: 8.0% or less Mo is M2O, ? It has the effect of forming crystallized carbides such as hC, and is contained in order to form a solid solution in the matrix to improve hardenability and temper hardness.

However, an increase in Moi is undesirable because it reduces the amount of MC, M, and C, which are the hardest carbides in the roll material of the present invention, and the upper limit is set at 8.0%.

W: 20.0% or less W is also an effective component for forming crystallized carbides such as M2O and MzC, like the above-mentioned Mo. However, like Mo, the hard MC carbide decreases as the content increases, so it is preferable to set the upper limit to 20.0%.

V: 3.0 to 12.0% (1) is an essential element for forming M, C2 carbide, which contributes most to improving wear resistance, and must be contained in an amount of at least 3.0% or more. However, because it has a high affinity with oxygen, the oxidation reaction in the molten metal becomes intense.12.
If the content exceeds 0%, dissolution in the atmosphere becomes virtually impossible, which is disadvantageous.

Nb: 5.0% or less In the second invention of the present application, Nb is a substituting element for V, and has the effect of crystallizing and forming MC carbides finely and uniformly. However, like the above-mentioned V, it has a high affinity for oxygen, so it is not preferable to include it in an amount exceeding 5.0% because it will intensify the oxidation reaction in the molten metal and make dissolution in the atmosphere impossible.

Next, the greatest feature of the present invention is that each of the above-mentioned alloying elements is limited, and in the first invention, C-(0°06Cr10
．． 033W+0.063Mo+0.18V) is set to 1.
0 or less, and in the second invention, C(0
,06Cr+ 0.033'W + 0.063Mo+
0.18V +0.13Nb) is set to 1.0 or less. If this value exceeds 1.0, as is clear from the examples described below, the difference between the solidification temperature range of the molten metal, that is, the temperature at which primary crystals occur and the temperature at which solidification is completed, becomes large, resulting in a decrease in the riser effect. This is undesirable because it often causes cavities and other casting defects. The value in parentheses above (hereinafter referred to as Cba
The coefficient by which each alloying element is multiplied to determine the amount of carbon (referred to as shows. For example, in the case of Cr, the unique carbide is Crz
Since it is iC&, the amount of Cr contained is all Cr2. In order to form C, the amount of C(χ) is =0.06XCr(%) (where Mc and Mar are the atomic weights of C and Cr, respectively). Similarly, other alloying elements Mo, W, V,
When calculating the coefficient assuming carbide for Nb, the first
The result will be as shown in the table.

Table 1 Therefore, the value of Cba 1 in the first invention is 0.06Cr
By 100.063Mo+0.033W+0.18V,
The straightness of Cba 1 in the second invention is 0.06Cr +
Each can be calculated by 0.063Mo +0.033W +0.18V 10, 13Nb.

[For production]

With the above configuration, the solidification temperature range of the molten metal, that is, the difference between the primary crystal generation temperature and the solidification completion temperature, is suppressed to, for example, 210°C or less, preventing the occurrence of cavities and other casting defects, and improving wear resistance. Therefore, it can be expected that the roll material will have a good quality.

[Example] Figure 1 shows the solidification temperature range and C-Cb in an example of the present invention.
It is a diagram showing the relationship with al, in which the values for the roll material of the alloy components shown in Table 2 are plotted (the means for casting the roll material will be described later).

As is clear from Figure 1, the comparative materials all have a wide solidification temperature range <(212°C or higher) and a C-Cbal
The O value was large in all cases, and the occurrence of cavities was observed in all cases. On the other hand, in the examples of the present invention, no cavities or other casting defects were observed in the above examples, and roll materials with perfect welding between the outer layer and the shaft material could be obtained.

The solidification temperature range is 199°C' or less in all cases, and the C-Cbal value is 1.0 or less.

Next, FIG. 2 is a longitudinal sectional view of a main part showing an example of an apparatus for casting a composite roll using the wear-resistant composite roll material of the present invention. In the figure, reference numeral 1 denotes a refractory frame, which is made of a heat-resistant material and is formed into a funnel shape with a circular cross section and tapered and parallel peripheral walls at the upper and lower parts. An induction heating coil 2 formed in an annular shape so as to enclose the refractory frame 1 is disposed outside the refractory frame 1, and a coil 2 having the same inner diameter as the lower end of the refractory frame 1 is disposed at the lower end of the refractory frame l. A buffer mold 3 having an annular shape is provided coaxially with the refractory frame 1. Next, a water-cooled mold 4 having an inner diameter equal to that of the buffer mold 3 and the groove is coaxially disposed in the lower part of the loose mold 3. The above-mentioned members are coaxially assembled and fixed in place to form a combination mold 9.

With the above configuration, the shaft material 5 to form the shaft portion of the roll is vertically charged into the combination mold 9, and the bottom end of the shaft material 5 is closed with an outer diameter equal to the inner diameter of the combination mold 9 and the outer diameter between the paths. A member (not shown) is fixed, and the lower end thereof is attached to a shaft material lifting mechanism (not shown). Note that it is preferable that the shaft member 5 be formed of cast steel or forged steel to have the same diameter. Next, a molten metal 7 made of the wear-resistant composite roll material of the present invention, which is to form the outer layer of the roll, is poured into the space formed by the refractory frame 1 and the shaft material 5. The surface of the molten metal 7 is coated with molten flux 6 for heat insulation and oxidation prevention, and is heated and stirred by an induction heating coil 2 to prevent the molten metal 7 from solidifying. Arrow A in the figure indicates the flow direction of the molten metal 7. Next, when the shaft member 5 is successively lowered together with the closing member, the molten metal 7 is also lowered and reaches the buffer mold 3 and the water-cooled mold 4, whereupon solidification begins gradually. On the other hand, the surface of the shaft material 5 is partially melted by the heat of the molten metal 7 and mixed with the molten metal 7.

After the molten metal 7 gradually solidifies and becomes a solid-liquid coexistence region 10, the shaft material 5 and the outer layer 8 are completely welded together. As the shaft material 5 descends, the surface of the molten metal 7 also gradually descends, so while the surface is maintained at a constant level by appropriately replenishing the molten metal 7, the solidification interface 10' of the molten metal 7 is within the range of the buffer type 3. control so that it enters the room. Since the wear-resistant composite roll material of the present invention can suppress the solidification temperature range to a narrow range as described above, the solid-liquid coexistence region 10 becomes narrower, the riser effect becomes more effective, and the shrinkage defects are reduced. It will no longer occur. As described above, a wear-resistant composite roll can be obtained in which the outer layer 8 having high wear resistance is integrally welded to the outer periphery of the shaft material 5.

In this example, a composite roll was described using the wear-resistant composite roll material of the present invention as an outer layer using a cast overlay method, but there is a risk that segregation of carbides, which contribute to improving wear resistance, may occur due to centrifugal separation. Apart from certain centrifugal casting methods, it can of course be applied to other static casting methods, etc., and it is possible to achieve a riser action by narrowly suppressing the solidification temperature range, and also to reduce the resulting evacuation, cavities, etc. The effect of preventing casting defects can be expected as well.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above,
No segregation occurs in the outer layer containing crystallized carbides,
Moreover, it is possible to obtain a healthy composite roll without cavities or other casting defects while maintaining sufficient wear resistance.

[Brief explanation of the drawing]

Figure 1 shows the solidification temperature range and C-Cb in the embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a main part showing an example of an apparatus for casting a composite roll using the wear-resistant composite roll material of the present invention. 5: shaft material, 7: molten metal, 8: outer layer. Patent applicant: Hitachi Metals, Ltd., /”−' −′
\-/' Figure 1 C-Cbat, (%) Figure 2 Director General of the Patent Office Kunio Ogawa Indication of the 1 case 1985 Patent Application No. 2kQ78F No. 2 Title of the invention Wear-resistant composite roll material 3 Amendment Relationship with the patent applicant's case 6. Subject of amendment by patent applicant ``Claims'' of the specification and ``Contents of invention amendment 1'' The scope of claims on page 1 of the specification is corrected as shown in the parentheses below. r(1) ct, s ~3.5, Si 0.3~3
．． 0, Mn O, 3 to 1.5, Ni 2.0 or less, Cr
3.0-7.0, eclipse 8. θ or less, W 20.0 or less,
■ Contains 3.0 to 12.0% by weight, with the remainder being substantially Fa.
and C(0,06Cr+0.063 Mo
A wear-resistant composite roll material having a value of +0.033 W +0.18 V) of 1.0 or less. (2) C1.5-3.5, Si 0.3-3.0,
Mn 0.3-1.5゜Ni 2.0 or less, Cr 3.
0 to 7.0, Mo 8.0 or less, W 20.0 or less, V
3.0-12.0, Nb 5. Contains less than O ffi% by volume. The remainder essentially consists of Fe and C-(0,06Cr
+0.063 Mo+0.033 W+0.18 V+
A wear-resistant composite roll material having a value of 0.13 Nb) of 1.0 or less. 2. Same book, page 7, line 10 and page 11, lines 11 to 1
2 rows r C-(0,06Cr + 0.033 W
+0.063Mo+0.18V) J respectively r
C-(0.06Cr+0.063 Mo+0.033
Correct it as W+O, L8 V)J. 3. The same book, page 7, lines 17 to 18 and page 11, line 1
r C-(0,06Cr+0.033
W+0.063 Mo+〇, 18 V+0.13 Nb
)J respectively rC(0,06Cr+0.063 Mo
+0.033 W+0.18 V+0.13 Nb)J
I am corrected. that's all

Claims (1)

[Claims] (1) C1.5-3.5, Si0.3-3.0, Mn0
．． 3 to 1.5, Ni 2.0 or less, Cr 3.0 to 7.0,
Mn8.0 or less, W20.0 or less, V3.0-12.0
Contains each weight%, the remainder substantially consists of Fe, and C
-(0.06Cr+0.033W.+0.063Mo+
A wear-resistant composite roll material having a value of 0.18V) of 1.0 or less. (2) C1.5-3.5, Si0
．． 3 to 3.0, Mn 0.3 to 1.5, Ni 2.0 or less,
Cr3.0-7.0, M8.0 or less, W20.0 or less,
Contains V3.0 to 12.0, Nb 5.0 or less by weight,
The remainder essentially consists of Fe and C-(0.06Cr
+0.033W+0.063Mo+0.18V+0.1
A wear-resistant composite roll material having a value of 3Nb) of 1.0 or less.