JPH0820842A - High speed steel type composite roll and its production - Google Patents

Abstract

PURPOSE:To produce a high speed steel type composite roll formed by integrating, by welding, an internal layer composed of tough cast steel material with the internal surface of an external layer composed of high speed steel type material. CONSTITUTION:An external layer, composed of high speed steel type cast iron material having 1.0-1.9wt.% carbon content, is centrifugally cast. After the external surface of the external layer is solidified and while the internal surface temp. of the cast external layer stays at a temp. more than the solidification temp. of a cast steel material for forming internal layer, the molten metal of this cast steel material is cast, at a temp. more than the internal surface temp. of the external layer, into the internal surface of the external layer. The internal layer material after welding has a chemical composition consisting of, by weight, 0.4-0.8% C, 1.1-3.0% Si, 0.2-1.0% Mn, <=0.5% Ni, <=1.5% Cr, <=1.0% Mo, <=1.0% W, <=1.5% V, and the balance essentially Fe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite roll in which an inner layer made of a cast steel material having a toughness is welded to the inner surface of an outer layer made of a high-speed cast iron material, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, high-speed composite rolls have been manufactured in which an outer layer, which is a layer used for rolling, is formed of a high-speed cast iron material having excellent wear resistance and an inner layer is formed of a steel material having excellent toughness. As the high-speed cast iron material, for example, a material having the following chemical composition (wt%) is disclosed in JP-A-4-176840.

C: 1.0-3.0%, Si: 0.1-2.0
%, Mn: 0.1 to 2.0%, Cr: 3.0 to 10.0%, M
o: 0.1 to 6.0%, W: 1.5 to 10.0%, V or Nb, a total of one or two kinds: 3.0 to 10.0%, the balance being substantially Fe. The high speed cast iron material containing Mo, W and V is It has excellent properties at high temperature, and has high hardness crystallized carbides such as VC, M ₂ C, and M ₆ C in its structure, so it has extremely good wear resistance and rough skin resistance. Suitable as an outer layer material of a composite roll.

Conventionally, as a method of manufacturing a composite roll, after an outer layer made of a high alloy wear resistant material is centrifugally cast, a molten metal for an inner layer made of a tough cast iron material is cast on the inner surface of the outer layer and the inner layer is welded and integrated to the inner surface of the outer layer. There is a way to do it. When the HSS-based composite roll is cast by such a method, if the inner layer solidifies before the inner surface of the outer layer, shrinkage cavities occur at the boundary between the outer layer and the inner layer. Therefore, in order to secure the weldability between the outer layer and the inner layer, a material having a lower melting point than the high-speed cast iron material forming the outer layer is required as the inner layer material, and normally ductile cast iron or graphite steel is used.

On the other hand, in order to form the inner layer of the composite roll with a tougher material, an inner layer member made of a low alloy steel for machine structure such as SCM material is manufactured in advance, and is disclosed in JP-A-60-
According to the continuous casting overlay method disclosed in Japanese Patent No. 180660, an outer layer is continuously cast on the outer peripheral surface of the inner layer, or HSS powder is applied to the outer peripheral surface of the inner layer by hot isostatic pressing (HIP). The outer layer is formed by sintering and integrating.

[0006]

However, in order to carry out the continuous casting surfacing method and the HIP method, a special device is required, and such a device is expensive. For this reason, there is a demand for a method of manufacturing a tough composite roll having an inner layer by conventional compounding by casting. The present invention has been made in view of the above problems, and an object thereof is to provide a high-speed composite roll in which an inner layer made of a cast steel material having toughness is weld-integrated on the inner surface of an outer layer of a high-speed material and a suitable manufacturing method thereof. And

[0007]

The HSS-based composite roll of the present invention has a chemical composition of C wt.% On the inner surface of the outer layer made of HSS cast iron material having a content of 1.0 to 1.9 wt%.
: 0.4 to 0.8%, Si: 1.1 to 3.0%, Mn:
0.2 to 1.0%, Ni: 0.5% or less, Cr: 1.5% or less, Mo: 1.0% or less, W: 1.0% or less,
V: 1.5% or less, and the inner layer consisting essentially of Fe is welded by centrifugal casting.

In the method for producing a composite roll of the present invention, an outer layer made of a high-speed cast iron material having a C content of 1.0 to 1.9 wt% is centrifugally cast, and the outer surface of the outer layer is solidified and then cast. When the inner surface temperature of the outer layer is equal to or higher than the solidification temperature of the cast steel material for forming the inner layer, the molten cast steel material is cast into the inner surface of the outer layer at the inner surface temperature of the outer layer or higher, and the inner surface of the outer layer has a chemical composition of wt%.
And C: 0.4 to 0.8%, Si: 1.1 to 3.0%, M
n: 0.2 to 1.0%, Ni: 0.5% or less, Cr: 1.5
% Or less, Mo: 1.0% or less, W: 1.0% or less,
V: A method of depositing an inner layer of 1.5% or less, and the balance being essentially Fe. At this time, when the outer layer is thick, the chemical composition (wt%) is C:
1.0 to 1.5%, Si: 0.2 to 1.5%, Mn: 1.5% or less, Cr: 2.0 to 6.0%, 2 × Mo + W: 3.0 to
7.0%, V: 2.0 to 4.0%, and the balance substantially consisting of Fe is preferable.

[0009]

When the inner surface temperature of the cast outer layer is equal to or higher than the solidification temperature of the cast steel material for forming the inner layer, that is, the solidus line (solidification end temperature), the casting temperature of the cast steel material is equal to or higher than the inner surface temperature of the outer layer. It is possible to solidify the inner layer made of a cast steel material in which the unsolidified portion of the inner surface of the outer layer is melted on the inner surface of the solidified outer layer. Therefore, shrinkage cavities do not occur at the boundary between the outer layer and the inner layer, and good welding can be obtained.

The C content of the inner layer material is 0.4 to 0.8.
%, The cast steel material for forming the inner layer is C from the outer layer
Even if the content of C is taken into consideration, the C content does not become 0.8% or more, and although the solidified temperature of the cast steel material for forming the inner layer is higher than that of the outer layer material, the content of high Si described later is included. Combined with this, the solidification temperature difference between the two does not exceed 90 ° C., and the cast steel material can be cast after a considerable portion of the outer layer material molten metal has solidified. Further, even if a high alloy component of the outer layer is mixed in the molten cast steel material, the C content is low, so that the formation of primary carbide is small, and the toughness is largely deteriorated as in the case of casting graphite steel or ductile cast iron. Does not occur.

Further, in the present invention, the Si content of the inner layer material is regulated to 1.1 to 3.0%, the Si content of the cast steel material for forming the inner layer is in a range close to this range, and the melt flowability is improved. ,
If it is pulled, the weldability is improved. Furthermore, because of the high Si composition, the freezing point is lowered, and the difference in freezing point temperature with the outer layer material is reduced, so that the casting temperature can be lowered, so that the melting amount of the inner surface of the outer layer is reduced, and thus, Cr, Mo,
The amount of W and V elements mixed in can be reduced, bainite transformation can be suppressed, and pearlite transformation can be promoted. Even if the quenching speed is increased to increase the hardness of the outer layer, the inner layer is hardened by the bainite transformation during heat treatment. It becomes difficult to do so, and deterioration of the toughness of the inner layer during heat treatment of the outer layer can be prevented.

Further, by using the outer layer material according to claim 3, even when the outer layer has a thickness of more than 140 mm, segregation of Mo, W and V in the outer layer can be suppressed, and the outer layer can be suppressed. Can be used effectively.

[0013]

EXAMPLES As the outer layer material used in the present invention, a high-speed cast iron material containing 1.0 to 1.9 wt% C,
Any one can be used. The reason for limiting C is that if it is less than 1.0%, the amount of carbides such as Cr, Mo, W, and V decreases, and the wear resistance decreases, while if it exceeds 1.9%, it is a cast steel for forming the inner layer. The difference in freezing point from the material becomes excessively large, and defective welding tends to occur. Below, an example of the composition of the outer layer material and the reasons for the limitation are described. However, the reason for limiting C is omitted because it is as described above.・ Outer layer high speed cast iron material composition example (wt%) C: 1.0 to 1.9%, Si: 0.2 to 1.5%, Mn: 1.5
% Or less, Cr: 2.0 to 8.0%, 2Mo + W: 3.0 to 14
%, V: 2.0 to 8.0%, the balance being substantially Fe.・ Reason for component limitation Si: 0.2 to 1.5% If less than 0.2%, deoxidizing action and melt flowability are insufficient, while if over 1.5%, hardenability deteriorates and the material becomes brittle. Become.

Mn: 1.5% or less Mn combines with S to form MnS, prevents brittleness due to S, and improves hardenability and wear resistance. If it exceeds, the material becomes brittle. Cr: 2.0 to 8.0% Cr forms a solid solution in the matrix and improves hardenability, and at the same time, a part of the Cr combines with C to form a carbide, which improves wear resistance. If it is less than 2.0%, such action is insufficient,
On the other hand, if it exceeds 8.0%, its action is saturated and the material becomes brittle.

2Mo + W: 3.0 to 14% Mo and W combine with C to form M ₂ C type or M ₆ C type carbides, which improve wear resistance and part of them are contained in the matrix. It forms a solid solution and contributes to secondary hardening. Since Mo has twice the effect of W, the component range is defined by the sum of twice the Mo content and the W content (2Mo + W). 2Mo +
If W is less than 3.0%, such an effect is too small, and it is preferable to contain W in an amount of 6.0% or more. On the other hand, if it exceeds 14%, the amount of carbides increases, the toughness decreases, and
Retained austenite is stabilized by Mo and W dissolved in the matrix, and it is difficult to obtain high hardness.

V: 2.0 to 8.0% V combines with C to form a high-hardness MC type carbide to improve wear resistance. If it is less than 2%, the amount of carbide is small and the wear resistance is insufficient. On the other hand, if it exceeds 8.0%, it becomes difficult to prevent segregation even if the cast wall thickness is suppressed to 140 mm or less. In addition to the above alloy components, the balance is substantially formed of Fe. However, S and P, which are impurity elements, make the material brittle, so it is preferable that the content be as small as possible, and both are preferably kept to 0.1% or less.

In the composition range of the outer layer, segregation can be relatively easily prevented by adjusting the casting temperature up to a thickness of the outer layer (when cast) of about 140 mm.
When a thick outer layer having a thickness of 50 mm or more is cast, the segregation cannot be prevented even by adjusting the casting temperature. In this case, C: 1.5% or less, Cr: 6.0
% Or less, 2 × Mo + W: 7.0% or less, and V: 4.0% or less, it becomes possible to cast even a thick wall of about 200 mm without causing segregation. In addition, since the content of high alloy components is suppressed,
The amount mixed into the inner layer is also reduced, and the toughness of the inner layer is improved. The reasons for limiting the upper limits of the above components are as follows.

When C exceeds 1.5%, the solidification temperature range (the temperature difference between the liquidus and solidus) is widened, and the alloy components are apt to be biased during solidification. On the other hand, Cr, Mo and W
Has a low content in the primary crystal (initial solidification part), tends to be concentrated in the final solidification part, and is easily segregated. Therefore, from the viewpoint of preventing segregation, it is preferable to keep the content below the above content. Further, V crystallizes as primary austenite with MC type carbide having a low specific gravity, but when it exceeds 4.0%, the difference in specific gravity between primary crystals (austenite and MC type carbide) and the unsolidified molten metal becomes large, Segregation easily occurs due to gravity or centrifugal force.

The state of segregation is such that the high alloy component is formed in a layered form in the form of carbide on the inner peripheral surface side of the outer layer. The effective use layer is reduced, and in the case of the cylindrical composite roll for H-section steel rolling in which the H-section steel is roll-formed on the side surface of the roll, rolling defects on the forming surface are caused. On the other hand, after the outer layer is cast, the melt composition of the inner layer cast on the inner surface thereof is appropriately set in consideration of the amount of penetration from the outer layer so that the following composition is obtained after welding, for example, the C content is 0.8% or more. And the Si content does not fall below 1.1%. Hereinafter, the chemical composition (wt%) of the inner layer cast steel material after welding and the reason for the limitation will be described.・ Composition of inner layer cast steel material after welding C: 0.4 to 0.8%, Si: 1.1 to 3.0%, Mn:
0.2 to 1.0%, Ni: 0.5% or less, Cr: 1.5% or less, Mo: 1.0% or less, W: 1.0% or less, V
: 1.5% or less, the balance is substantially Fe. Reason for limiting components C: 0.4 to 0.8% C is preferably as low as possible for improving the toughness, but if less than 0.4%, the original hot water is used. Of the outer layer material becomes too high, and the temperature difference from the freezing point of the outer layer material becomes too large, and defective welding tends to occur. On the other hand, if it exceeds 0.8%, net-like cementite will be formed during casting and during high temperature heat treatment, resulting in a decrease in toughness.

Si: 1.1 to 3.0% Si has the functions of lowering the freezing point of the molten metal, improving the flowability of the molten metal, and promoting the pearlite transformation. 1.
If it is less than 1%, the effect is too small, and preferably 2.
It is preferable to contain 0% or more. On the other hand, if it exceeds 3.0%, the material becomes brittle.

Mn: 0.2 to 1.0% Mn combines with S to form MnS and has an action of preventing embrittlement due to S, but if it is less than 0.2%, such action is insufficient. If it exceeds 1.0%, the material becomes brittle. Ni: 0.5% or less Ni is effective in strengthening the matrix, but has the effects of increasing hardenability and suppressing pearlite transformation. 0.5%
If it exceeds, pearlite transformation is significantly suppressed, bainite transformation is likely to occur, and toughness deteriorates.

Cr: 1.5% or less, V: 1.5% or less Cr and V increase hardenability and suppress pearlite transformation. If it exceeds 1.5%, similarly to Ni, bainite transformation occurs and the toughness deteriorates. In addition, Cr0.4
%, Mo content of about 0.2% improves the toughness of the inner layer material, but normally, a larger amount than that is inevitably mixed from the outer layer. Therefore, it is not necessary to positively contain these elements as a molten metal component, and the lower the better. The same applies to Mo and W below.

Mo: 1.0% or less, W: 1.0% or less Mo and W, like Ni and Cr, increase hardenability and suppress pearlite transformation. If 1.0% is exceeded, Ni, Cr
Similarly to, the bainite transformation occurs and the toughness deteriorates. In addition to the above alloy components, the balance is substantially formed of Fe. However, the impurity elements S and P are similar to those of the outer layer, i.e., 0.
It is better to keep it below 1%.

Next, specific examples of the present invention will be given. Example A HSS cast iron material shown in Table 1 below was centrifugally cast into a horizontal centrifugal casting mold having an inner diameter of 640 mm and a length of 1300 mm. The mold rotation speed was 140 in GNo., The outer layer casting temperature was 1435 ° C., and the casting thickness was 70 mm.

When the temperature of the inner surface of the outer layer reached 1400 ° C., the molten metal for forming the inner layer described in the same table was cast on the inner surface of the outer layer at a casting thickness of 115 mm. The casting temperature was 1560 ° C. After the inner layer was solidified, the rotation of the mold was stopped, the mold was separated, and dimension processing and heat treatment were performed to obtain a plurality of cylindrical composite rolls of outer diameter φ600 × inner diameter φ340 × length 215 mm.

[0026]

[Table 1]

When the composite roll was subjected to an ultrasonic flaw detection test, it was confirmed that the outer layer and the inner layer were completely welded. The outer layer thickness was 25 to 35 mm thinner than the casting thickness. The results of analysis of the composition of the inner layer after welding are also shown in Table 1. Next, after holding the composite roll at 1100 ° C. for 2 hours, it is quenched by forced air cooling and then at 550 ° C. for 10 hours.
The tempering heat treatment for holding hr was repeated 3 times. After performing such heat treatment, a test piece was taken from the inner layer and a tensile test was performed. As a result, the tensile strength was 680 MPa and the elongation was 1.
It was confirmed that 3% was excellent in toughness.

Comparative Example Using the high speed cast iron material for the outer layer and the cast steel material for the inner layer shown in Table 2, a cylindrical composite roll was laterally centrifugally cast under substantially the same conditions as in the examples.

[0029]

[Table 2]

When the cross section of the composite roll was visually observed, defective welding was observed at the boundary between the outer layer and the inner layer. Table 2 also shows the analysis results of the composition of the inner layer after welding.
Next, after subjecting the composite roll to a heat treatment under the same conditions as in the example, a test piece was taken from the inner layer and a tensile test was conducted.
As a result, the tensile strength was as good as 720 MPa,
The elongation is 0.3%, and the toughness is significantly deteriorated.

[0031]

According to the present invention, although a cast steel material is used as the inner layer material, the weldability between the outer layer and the inner layer is excellent, and the formation of primary carbide in the inner layer is small, and the outer layer is hardened. It is possible to suppress the bainite transformation of the inner layer during the heat treatment and prevent the toughness of the inner layer from deteriorating.

As the outer layer material, C: 1.0 to 1.5
%, 2 × Mo + W: 3.0 to 7.0%, V: 2.0 to
By using a high-speed cast iron material having a specific composition containing 4.0%, it is possible to suppress the formation of segregation even in a thick outer layer having a wall thickness of about 200 mm, and manufacture a high-quality composite roll. can do.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B22D 19/16 FC22C 37/10 38/46 (72) Inventor Hiroaki Katayama 64 Nishimukojima-cho, Amagasaki-shi, Hyogo Stock Company Kubota Amagasaki Plant (72) Inventor Cho Morikawa 64 Nishimukaijima-cho, Amagasaki City, Hyogo Prefecture Kubota Amagasaki Plant Co., Ltd. (72) Inventor Yutaka Tsujimoto 64, Nishimukaijima-cho Amagasaki City, Hyogo Prefecture Kubota Amagasaki Plant Co., Ltd.

Claims (3)

[Claims] 1. The chemical composition is wt% on the inner surface of an outer layer made of a high-speed cast iron material having a C content of 1.0 to 1.9 wt%.
C: 0.4 to 0.8%, Si: 1.1 to 3.0%, Mn: 0.2 to 1.0%, Ni: 0.5% or less, Cr: 1.5% or less, Mo: 1.0% or less, W: 1.0% or less, V: 1.5 % Or less, and the inner layer of which balance is substantially Fe is welded by centrifugal force casting. 2. An outer layer made of a high-speed cast iron material having a C content of 1.0 to 1.9 wt% is centrifugally cast, and after the outer surface of the outer layer is solidified, the inner surface temperature of the cast outer layer is an inner layer. When the solidification temperature of the cast steel material is equal to or higher than the solidification temperature of the cast steel material, the melt of the cast steel material is cast into the inner surface of the outer layer at a temperature equal to or higher than the inner surface temperature of the outer layer, and the inner surface of the outer layer has a chemical composition of wt%, C: 0.4 to 0.8%, Si: 1.1 to 3.0. %, Mn: 0.2 to 1.0%, Ni: 0.5% or less, Cr: 1.5% or less, Mo: 1.0% or less, W: 1.0% or less, V: 1.5% or less, and an inner layer consisting essentially of Fe. A method for manufacturing a HSS-based composite roll that is formed by welding. 3. The chemical composition (wt%) of the outer layer material is C: 1.0 to 1.5%, Si: 0.2 to 1.5%, Mn: 1.5% or less, Cr: 2.0 to 6.0%, 2 × Mo + W: 3.0 to 7.0. %, V: 2.0 to 4.0%, and the balance being substantially Fe.