JPH0617538B2 - High-strength three-roll for H-shaped steel rolling - Google Patents

Description

The present invention relates to a sleeve roll for H-shaped steel rolling used in a universal mill.

<Prior Art> Generally, when rolling H-shaped steel, a universal mill as shown in Fig. 1 is generally used from the viewpoint of productivity and quality assurance. The rolled material 16 is a horizontal roll 1 and a hard roll. 1
The horizontal roll 1 is usually assembled by shrink-fitting the sleeve roll 3 on the arbor 2, while the hard roll 4 is a floating roll by fitting the bearing 17 into the sleeve roll 5. It is built into the mill.

The sleeve rolls 3 and 5 are generally required to have the following characteristics. That is, the inner surface side is tough enough to withstand shrink fit stress, stress during rolling, etc., and the outer surface side is seizure resistance, wear resistance, crack resistance, skin resistance to ensure product quality. Roughness is required.

In order to meet these requirements, conventionally, as shown in FIGS. 1 and 2, a composite roll having an outer layer 6 and an inner layer 7 made of different materials has been used as a sleeve roll. , Spheroidal graphite cast iron, high C% adamite material is used, and the inner layer material is spheroidal graphite cast iron,
Graphite steel and adamite materials are used.

<Problems to be Solved by the Invention> However, with the recent high demand for ensuring the quality of rolled material, as for the outer layer material, in the case of spheroidal graphite cast iron, the wear resistance is high, and in the case of high C% adamite, There is a problem with seizure resistance.

Regarding the inner layer material, the rolling conditions have become more and more stringent in recent years due to energy-saving measures and technological innovations.As a result, the conventional material is cracked in the radial direction of the roll due to insufficient strength of the inner layer, which causes cracking. There is a problem that leads to an accident.

FIG. 3 shows a crack occurrence situation of the horizontal roll sleeve roll 3, and FIG. 4 shows a crack occurrence situation of the hard roll sleeve roll 5. In the latter case, a bolt hole 9 for bolting the bearing pressing lid 8 is usually screwed at the end of the roll, and it can be said that the situation is more severe in terms of strength.
In the figure, reference numeral 10 indicates a crack generated in the sleeve rolls 3 and 5.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides a composite sleeve for H-type steel rolling, which has seizure resistance and wear resistance as an outer layer material and excellent toughness as an inner layer material. To provide rolls, the following measures were taken for that purpose. That is,
Chemical composition is% by weight, C: 2.0 to 3.2% P: 0.1 or less Si: 0.6 to 2.5% S: 0.1% or less Mn: 0.4 to 1.5% Ni: 2.5 or less Cr: 0.5 to 2.0% and less than 1.5 Si% Mo: 0.2-2.0% The balance consists essentially of Fe, and the structure is a matrix mainly composed of pearlite, an outer layer formed of a graphite crystallized high carbon adamite material composed of graphite and cementite, and a chemical composition in a weight percentage of C: 0.3 to 0.95% S: 0.1 or less Si: 0.2 to 1.0 Ni: 0.5 to 3.0% Mn: 0.2 to 1.5% Cr: 0.5 to 2.5% P: 0.1% or less Mo: 0.1 to 0.8% and Nb: 0.1 to 0 0.8%, the balance is essentially Fe
A composite structure is formed by fusion-bonding an inner layer formed of cast steel of 1 to the above.

<Example> Hereinafter, an example of the present invention will be described in detail together with a manufacturing method thereof with reference to the drawings.

In the present invention, a high C% adamite material having crystallized graphite is used for the outer layer of the sleeve roll, and special cast steel is used for the inner layer, and the centrifugal casting method is suitable as the manufacturing means.

FIG. 5 shows a case where both the outer layer 6 and the inner layer 7 are centrifugally cast, and FIG. 6 shows that after the outer layer 6 has been centrifugally cast, the die in which the outer layer is cast is erected to form a static mold. The case where the inner layer casting material is statically cast into the mold is shown. According to such a casting method, the outer layer 6 and the inner layer 7 are easily metallurgically welded and integrated. In the figure, 11 is a centrifugal casting mold, 12 is a mold,
Band for hot water stopper made of sand mold or refractory brick, 13
Is a rotating roller, 14 is a molten metal ladle, and 15 is a pouring gutter.
Although FIG. 5 shows a centrifugal casting method having a horizontal rotating shaft (so-called horizontal centrifugal casting method), a centrifugal casting method having a rotating shaft in an oblique or vertical direction (so-called diagonal centrifugal casting method). Of course, it can also be manufactured by a force casting method or a vertical centrifugal casting method.

In the production of the sleeve roll according to the present invention, there may be a problem of welding between layers and a problem of penetration of alloy elements into other layers. As a means for surely solving this problem, an intermediate layer can be further provided at an arbitrary position between the respective layers, if necessary. However, the intervention of the middle class should be decided after considering the necessity and economic efficiency.

Next, details of the material of the sleeve roll of the present invention will be described. First, the outer layer, which has excellent seizure resistance, crack resistance, and wear resistance, is, by weight%, C2.0 to 3.2%, Si0.6 to 2.5%, and Mn.
0.4-1.5%, P0.1 or less, S0.1% or less, Ni2.5% or less, Cr
0.5-2.0% and <1.5Si%, Mo0.2-2.0% each weight%
It is made of a material containing the balance Fe and ordinary impurities, or a material containing 0.1% by weight or less in total of one or two or more of Ti and Al: Zr, if necessary, in the above components.

(1) Chemical composition (% by weight, balance Fe and ordinary impurities) C: 2.0 to 3.2% C is contained mainly for the purpose of seizure resistance, so 2.0% or more is contained. If it is less than 2.0%, the amounts of cementite and graphite are small and the seizure resistance deteriorates. However, if it exceeds 3.2%,
The amount of cementite and graphite increases, which causes a problem in terms of crack resistance.

Si: 0.6 to 2.5% Si crystallizes graphite and improves the seizure resistance of the matrix. If it is less than 0.6%, graphite that improves seizure resistance cannot be crystallized, and the indirect seizure resistance of the matrix also deteriorates. But 2.5
If it exceeds%, the base becomes brittle.

Mn% 0.4-1.5% Mn removes the damage of S and contributes to the increase of hardness and seizure resistance.
If it is less than 0.4%, there is no effect, while if it exceeds 1.5%, the material becomes brittle.

P: 0.1% or less P enhances the fluidity of the molten metal and imparts wear resistance and seizure resistance, but keeps it to 0.1% or less because it makes the material brittle.

S: 0.1% or less S, like P, makes the material brittle, so keep it below 0.1%.

Ni: 2.5% or less Ni increases the matrix hardness, but on the other hand, it feels the high temperature stability of the structure and deteriorates the rough surface resistance. If it exceeds 2.5%, problems occur in the above points.

Cr: 0.5-2.0% and less than 1.5 x Si% Cr improves the wear resistance of the matrix as well as the stability of cementite. If it is less than 0.5%, cementite is reduced and abrasion resistance is insufficient. However, if it exceeds 2.0%, graphite is not crystallized and seizure resistance is deteriorated. In order to stably crystallize graphite even with an increase in Cr, it is necessary to satisfy the condition of less than 1.5 × Si% relative to the Si content.

Mo: 0.2 to 2.0% Mo enhances the base hardness, but if it is less than 0.2%, its effect is not sufficient. However, if it exceeds 2.0%, there is no corresponding effect and it is economically disadvantageous.

Ti, Al, Zr alone or in combination: total amount 0.1% or less C content of this material is in the range of 2.0 to 3.2%, casting cavities are likely to occur, and one or more of the above elements should be contained. As a result, a healthier material can be obtained. At this time, since all of the above elements are strong deoxidizers, excessive addition causes a peroxidation state and impairs the fluidity of the molten metal. For this reason, they are kept to less than 0.1% in total.

On the other hand, the inner layer having excellent toughness is C: 0.3 to 0.95 by weight%.
%, Si: 0.2 to 1.0%, Mn: 0.2 to 1.5%, P: 0.1% or less, S: 0.1% or less, Mi: 0.5 to 3.0%, Cr: 0.5 to 2.5
%, Mo: 0.1 to 0.8%, Nb: 0.1 to 0.8%, the balance being substantially Fe, and the reasons for limiting the components are as follows.

C: 0.3 to 0.95% If C% is too low, it is necessary to raise the melting temperature, which is a cost problem. If the C% difference between the outer layer and the inner layer becomes large, defects may occur in the welded portion. For the above reasons, it should be 0.3% or more. On the other hand, the range of not forming cementite and imparting toughness is 0.95% or less.

Si: 0.2 to 1.0% Si is added for deoxidation, but if it is less than 0.2%, its effect cannot be expected, while if it exceeds 1.0%, it dissolves in ferrite and makes the material brittle.

Mn: 0.2-1.5% Mn combines with S to eliminate the adverse effect of S, but if it is less than 0.2%, this effect does not occur, while if it exceeds 1.5%, the toughness of the material deteriorates significantly.

P: 0.1% or less P is an impure element and makes the material brittle, so 0.1% or less is set as a range in which no problem occurs.

S: 0.1% or less S is also an impure element like P and makes the material brittle.
The range with less effect is 0.1% or less.

Ni: 0.5 to 3.0% Ni increases the hardenability and is effective for toughness, but if it is less than 0.5%, it has almost no effect, while it is kept to 3.0% or less from the economical aspect.

Cr: 0.5 to 2.5% Cr is effective for toughening by increasing hardenability, but if it is less than 0.5%, it has almost no effect, while if it exceeds 2.5%, it becomes chilled and rather becomes brittle.

Mo: 0.1 to 0.8% Mo, like Ni and Cr, increases the hardenability of the material and contributes to strengthening. If it is less than 0.1%, its effect is small, while if it exceeds 0.8%, it becomes too hard and brittle.

Nb: 0.1-0.8% Nb contributes to lowering the carbon content of the base due to the refinement of the structure and the formation of Nb carbide, and to the toughness. If it is less than 0.1%, its effect is small, while if it exceeds 0.8%, its effect is small. Is saturated, which is economically disadvantageous.

In order to further improve the inner layer material in addition to the above components, Fe
The following components may be contained in place of a part of the above.

Ti, Al, Zr: Total of one kind or two kinds or more is 0.2% or less. Since the inner layer has a lower C% than the outer layer, defects are likely to occur.
Therefore, 0.2 or less is added for the same reason as for the outer layer.

The sleeve roll according to the present invention comprises an outer layer and an inner layer containing the components described above, and a heat treatment for raising the temperature to an austenite range in order to secure the toughness of the material and the target hardness, and wear resistance, This is accompanied by heat treatment at a temperature below the eutectoid transformation temperature for the purpose of tempering, isothermal transformation, and strain relief.

Specific examples will be described in more detail below.

Manufacturing example of a composite sleeve roll having a roll diameter of 950φ, an outer layer thickness of 80 mm, and an inner layer thickness of 110 mm.

(1) Rotate the centrifugal casting mold to the desired rotation (650 rpm),
The outer layer molten metal shown in Table 1 was cast at a casting temperature of 1390 ° C.

(2) When the outer layer was almost solidified, the inner layer material molten metal shown in Table 1 was cast on the inner surface of the outer layer under the same rotation as in (1) at a casting temperature of 1540 ° C.

(3) As a result of observing the cross section of the obtained sleeve roll, it was confirmed that the outer layer and the inner layer were completely welded and integrated. Moreover, when the mechanical properties of the inner layer were examined, Sample No.
In 1 (comparative example), the tensile strength was 91.0 kg / mm ² , and the elongation was 2.3%. With conventional ductile materials (40 to 50 kg / mm ² , 0.5 to 1.0)
%), A considerable improvement in toughness was observed, and sample No. 2
In (Example), tensile strength 99.0 kg / mm ² , elongation 3.3% and Nb
Both the tensile strength and the elongation are improved as compared with the case where no is added. This is because the characteristics of the low C% material were exhibited due to the fine structure and the formation of Nb carbide.

<Effects of the Invention> As described above, in the tough sleeve roll for H-shaped steel rolling of the present invention, the outer layer thereof is formed of a graphite crystallization high C adamite material having a specific chemical composition and a specific structure, and the inner surface is made to have a special chemical composition. Since it is made of cast steel and both are welded and integrated, wear resistance, seizure resistance, crack resistance and toughness can be combined. In particular, the inner layer is C: 0.3 to 0.95%, N
b: Since it is formed of a special cast steel containing 0.1 to 0.8%, it is possible to suppress the formation of cementite, while at the same time it is possible to reduce the carbon content of the base due to the refinement of the structure and the formation of Nb carbide. It has high strength and high elongation and excellent toughness. Therefore, if the sleeve roll is used in a universal mill, the occurrence of roll cracking can be reliably prevented, and the wear and seizure of the roll due to use can be prevented, and therefore the work of roll replacement and the like can be reduced as much as possible. It is remarkable that it is possible to improve productivity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a roll in a universal mill during H-shaped steel rolling, FIG. 2 is a cross-sectional view of a sleeve roll,
FIGS. 3 and 4 are side views of the sleeve roll showing a crack occurrence state, FIG. 5 is a sectional view of a centrifugal force casting mold showing a centrifugal force casting state of the inner layer, and FIG. 6 is a stationary casting of the inner layer. It is sectional drawing of the stationary mold which shows a state. 1 ... Horizontal roll, 3.5 ... Sleeve roll, 4 ...
Vertical roll, 6 ... outer layer, 7 ... inner layer, 10 ... crack, 11 ...
… Centrifugal casting mold, 12 …… band.

Claims (1)

[Claims] 1. The chemical composition is% by weight, C: 2.0 to 3.2% Si: 0.6 to 2.5% Mn: 0.4 to 1.5% P: 0.1 or less S: 0.1% or less Ni: 2.5% or less Cr: 0.5 to 2.0% And less than 1.5 Si% Mo: 0.2-2.0% The balance consists essentially of Fe, the structure is a matrix mainly composed of pearlite, and an outer layer formed of graphite crystallized high carbon adamite material composed of graphite and cementite, and a chemical composition. Is weight%
C: 0.3 to 0.95% Si: 0.2 to 1.0% Mn: 0.2 to 1.5% P: 0.1% or less S: 0.1% or less Ni: 0.5 to 3.0% Cr: 0.5 to 2.5% Mo: 0.1 to 0.8% Nb: A tough sleeve roll for H-type steel rolling, characterized by being integrally welded with an inner layer formed of cast steel consisting of 0.1 to 0.8% balance Fe substantially.