The name of the invention: composite roll for the outer layer material and the rolling of the rolling for the composite roll
Technical field
[0001] The present invention, the outer layer member rolling for a composite roll for use in hot rolling and which is related rolling composite rolls of the outer layer.
Background technique
[0002] Rolling composite rolls used in the hot rolling, the wear resistance with excellent outer layer in contact with the steel sheet, surface roughening resistance and crack resistance are desired. For this reason, the outer layer material constituting the roll outer layer, high-speed steel cast iron material is used (for example, see Patent Document 1).
[0003] In recent years, rolling the pitch from the viewpoint of productivity becomes shorter, the heat load of the roll outer layer surface is increased. Further, the steel sheet being rolled is also becoming thin and hard, the wear of the roll outer layer is also increasing.
Roll surface, because they are repeatedly exposed to water-cooled high-temperature and about 30 ℃ of about 1000 ℃ at the time of rolling, surface heat cracks are caused by thermal shock, and even more microscopic organization dropout occurs. The extent of these heat crack and organizations fall off shallow and surface roughening resistance is said to be good. Heat crack and tissue shedding preferentially prone to grain boundaries of the eutectic carbide that becomes a final solidified portion.
[0004] The outer layer is exposed to heating by the high-temperature heat treatment such as heat and the austenite by the intermediate layer or inner layer of the molten metal after solidification. During this heating, when raised to a temperature that exceeds the melting point of the grain boundary eutectic carbide of the outer layer material is melting eutectic carbide part, it was found that a cavity is formed. The outer layer of the surface roughening resistance is lowered due to the formation of cavities, roll life since the damage of the roll surface becomes deep may become shorter.
CITATION
Patent literature
[0005] Patent Document 1: Laid-Open Publication No. 05-320819

Summary of the invention
Problems that the Invention is to Solve
[0006] Outer layer of high speed steel cast iron material, Cr, Mo, W, V, Nb, Fe and the like are attached is C, mainly forms a MC type carbide. This carbide contributes to the improvement of wear resistance by increasing the ambient temperature and high temperature hardness. By undergo thermal shock at the time of rolling, but a crack is generated in the outer surface, it, partial melting in the secondary eutectic carbides weak grain boundaries thermal shock is present as compared to the MC type carbide He elucidated that.
[0007] And, cause a partial melting occurs in the secondary eutectic carbides, have found that a B of the secondary eutectic carbides. That is, when casting the high B concentrations molten, mixed with concentrated is B in the secondary eutectic carbides, the lower the melting point of the secondary eutectic carbides, partial melting is found that prone.
[0008] However, B is, effects or as a melt cleaning during casting, is an effective component for improving the hardenability, B to be to also contain trace amount, it is possible to good quenching.
[0009] The purpose of the present invention, by containing the B amount of the secondary eutectic carbides in a trace amount, increase the strength and melting point of the secondary eutectic carbides, the rolling for a composite roll which can improve the surface roughening resistance layer wood and this is to provide a rolling for the composite roll to the outer layer.
Means for Solving the Problems
[0010] The outer layer material of rolling for the composite roll of the present invention,
there is provided a outer layer material of rolling for a composite roll,
in mass%, C: 1.8% to 2.5% or less, Si: over 0% 1. 0% or less, Mn: 0% to 1.0% over less, Ni: 0% to 0.5% over less, Cr: 8.0% beyond the 3.0% or less, Mo: 2.0 percent beyond 10.0% or less, W: 0% to beyond 10.0% or less, V: 0% to over 10.0% or less, B: 0% to beyond less than 0.01%, and the balance It contains Fe and unavoidable impurities.
[0011] Outer layer member, at mass%, Nb: 0.01% to 2.0% or less and / or Ti: it is desirable to further containing 0.01% to 1.0%.
[0012] Solidification rate during casting of the outer layer material, it is desirable that the 8 mm / min or more.
[0013] The outer layer material comprises a secondary eutectic carbides, it is desirable that the melting temperature of the secondary eutectic carbides is greater than 1100 ° C.. Further, the weight percent of the B concentration in the outer layer material surface B (t1), when the mass% of B concentration in the outer layer member inner surface and the B (t2), is B (t2) -B (t1) ≧ 0.002 it is desirable.
[0014] In addition, rolling for the composite roll of the present invention,
the above-mentioned outer layer material and the outer layer comprises an inner layer or the intermediate layer and the inner layer on the inside of the outer layer material.
Effect of the invention
[0015] The outer layer material for rolling the composite roll of the present invention, by adjusting the B content as described above, it is possible to reduce the B content in the secondary eutectic carbides. This can prevent from it is possible to improve the strength of the secondary eutectic carbides, which even when exposed to high temperature of about 1100 ° C. After coagulation secondary eutectic carbides and melting. The outer layer of the high-speed steel rolls with no erosion part secondary eutectic carbides, can exhibit excellent surface roughening resistance.
[0016] Rolling for a composite roll with the outer layer material of the present invention as the outer layer, the intensity of secondary eutectic carbides are high, excellent surface roughening resistance. Accordingly, the tissue shedding of outer surface can be reduced, thereby reducing the depletion of the outer layer with that and this to reduce the grinding frequency of the outer surface during rolling.
[0017]
outer layer material constituting the outer layer of the rolling for the composite roll of the present invention is a high-speed steel cast iron material, containing the following ingredients. In the following, if not specifically indicated, "%" is% by weight.
[0018] C: 1.8% to 2.5% or less
C is mainly Fe and bound to M and Cr 7 C 3 to form a high hardness composite carbide of the type, bound Mo, V, Nb, W, such as the , MC type, M 6 C-type, M 2 high hardness composite carbide of the C type or the like is also formed. For this high-hardness composite carbide formation, it is necessary to C% greater than 1.8%, more preferably 1.85% or more. On the other hand, C becomes fragile together upon content carbide increases beyond 2.5%, the crack resistance is deteriorated, defined as 2.5% or less, and more preferably not more than 2.25% .
[0019] Si: 0% to over 1.0%
Si is added because it is an element necessary for securing and deoxidation of fluidity. On the other hand, since it exceeds 1.0%, the hardenability becomes brittle material decreases, the amount of Si should be 1.0% or less beyond 0%.
[0020] Mn: 0% to over 1.0%
Mn has the function of increasing hardenability. Also generates MnS bonded to S, it is an effective element to prevent embrittlement due to S. On the other hand, since the lead when the content too large a drop in toughness, the Mn content is defined below 1.0% over the 0%.
[0021] Ni: 0% to 0.5% or less over
Ni is to reduce the high-temperature hardness, although small additive amount is desired, in making large rolling composite roll, a sufficient quenching speed during heat treatment If not obtained and, when the hardenability of the material itself at a low C and high V-related material of as in the present invention is deteriorated, and added for the purpose of hardenability improvement. Lower limit of the content of Ni is preferably set to 0.01%. On the other hand, Ni, since the decrease in hot hardness exceeds 0.5% increases, the upper limit of 0.5%, preferably 0.3%.
[0022] Cr: 3.0% to 8.0% or less
Cr improves the hardenability and solid solution in the base. In addition, to form a eutectic carbides together with Mo and W. To improve the hardenability, it is necessary to contain Cr 3.0% or more, if it exceeds 8.0% Conversely, since the eutectic carbide increases, decreases the tensile strength of the material, Cr is , prescribed in the 3.0% to 8.0%. Preferably, Cr is 6.5% or less 3.5% or more.
[0023] Mo: 2.0% or more and 10.0% or less
Mo is, Fe, bound Cr, Nb, C and together with W, mainly M . 7 C-type, M . 6 C-type, M 2 to form a composite carbide of the type C contributes to the improvement of wear resistance by increasing the ambient temperature and high temperature hardness. Therefore, at least 2.0% or more, preferably to contain more than 4.0%. On the other hand, when the content too much to stabilize the residual austenite, since the high-hardness not be obtained, the upper limit is 10.0%, preferably defined to 7.0%.
[0024] W: 0% 10.0% or less beyond
Similarly W also, Fe, Cr, Mo, combines with C along with Nb, forms a composite carbide, the improvement of the wear resistance by increasing the ambient temperature and high temperature hardness to be contained in order to contribute to. On the other hand, when the content too much, leading to a decrease in toughness, exacerbate the heat crack resistance. For this reason, the upper limit is specified in 10.0%. Preferably, the upper limit of W is 2.0%.
[0025] V: 0% to beyond 10.0% or less
V is, Fe, Cr, Mo, combines with C along with W, mainly constitute the MC-type carbides during solidification, the wear resistance by increasing the ambient temperature and high temperature hardness contribute to the improvement.
[0026] MC-type carbide containing V contributes to improvement of the wear resistance by increasing the ambient temperature and high temperature hardness. The MC type carbide is produced in the branch in the thickness direction, of suppressing plastic deformation of the base, the mechanical properties, further contributes to the improvement of crack resistance. On the other hand, when the content too much, carbide is susceptible to segregation. For this reason, the upper limit of V is 10.0%, preferably prescribed in 8.0%.
[0027] B: 0% to beyond less 0.01%
B may be contained since it has an effect of increasing the hardenability due to dissolved it B in the matrix. The content of B is preferably set to the lower limit 0.0002%. For large casting mass as rolling composite roll, but to increase the cooling rate is generally difficult, by improving the hardenability becomes easy to obtain a good hardened structure. On the other hand, it lowers the melting point of the secondary eutectic carbide when the content is too large, because the material is brittle undesirable, content in the cast iron material to make the upper limit of 0.01%.
[0028] It should be noted that, compared to the primary carbides such as fine MC carbides crystallized at the time of casting of the outer layer material, the coarse secondary eutectic carbides final solidification, along with the B is much more concentrated than base, the base amount of B B concentration in the secondary eutectic carbides with increasing the higher. Secondary eutectic carbides, in addition to the concentration of B becomes higher secondary eutectic carbides become coarse, falls melting point. In this way lower the melting point of the secondary eutectic carbides, at the time of the high-temperature heat treatment such as heat and the austenite by the intermediate layer or inner layer of the molten metal after the outer layer solidification, the molten secondary eutectic carbides, erosion-shaped cavity occur. And, because the grain boundaries of the secondary eutectic carbides are brittle compared to the other parts, but the rough surface of the rolling occur preferentially in this secondary eutectic carbides, this erosion is, will further promote the trend . However, by adjusting the B content in the outer layer, it is possible to solve this problem. Further, by the solidification rate of the outer layer material and 10 mm / min or higher, retaining the B in the matrix, since it reduces the amount of B secondary eutectic carbides, it is possible to suppress the occurrence of erosion. By it was possible to suppress the occurrence of corrosion, thereby improving the outer layer of the surface roughening resistance. Further, by providing the density difference in the B concentration at the surface (outer surface) of the B concentration and the outer layer material on the inner surface of the outer layer material, homogeneous material is obtained at high-temperature heat treatment of the outer layer. B concentration difference can be adjusted such as by splitting the addition of B to the molten metal. Specifically, the weight percent of the B concentration in the outer layer material surface B (t1), when the mass% of B concentration in the outer layer member inner surface and the B (t2), the value of B (t2) -B (t1) is it is preferable that the 0.002 or more. More preferably 0.003 or more.
Incidentally, the value of B (t2) -B (t1) is too large, since the B concentration in the outer layer member inner surface is too high, preferably 0.008 or less, more preferably 0.005 or less.
[0029] The outer layer may further contain the following components.
[0030] Nb: 0.01% to 2.0% or less and / or Ti: 0.01% to 1.0
Nb has, Fe, bound Cr, Mo, C and together with W, mainly forms a MC type carbide and contributes to improvement of wear resistance by increasing the ambient temperature and high temperature hardness. Moreover, Nb, together with the MC-type carbides finely dispersed, has the effect of refining the tissue mechanical properties, further contributes to the improvement of crack resistance. Therefore, Nb is 0.01% or more, preferably to contain 0.1% or more. On the other hand, when the content too much, carbide is susceptible to segregation. For this reason, the upper limit of Nb is 1.0%, preferably defined in 0.5 percent.
[0031] Furthermore, Ti may generate oxides in the melt, reduces the oxygen content in the molten metal, thereby improving the integrity of the product, product oxides of solidification structure to act as a crystal nucleus fine there is an effect on the reduction. On the other hand, there is a problem that remains is the inclusion of containing too many. Therefore, even when adding Ti, the content to be equal to or less than 1.0% 0.01%.
[0032] The outer layer material of the present invention contains the component, the remainder is formed of Fe and inevitably mixed impurities.
[0033] Further, it may in the remainder contains P and S, in which case, it is preferable to define the components as follows. P content is 0.08%, the content of S exceeds respectively 0.06%, oxidation resistance, because the toughness falls, P and S are each 0.08% or less, 0.06% it is preferred. Preferably, the upper limit of the P and S to 0.05% or less. Meanwhile, P is a suitable be contained beyond 0% so improving the machinability, it is desirable to contain more than 0.015%. Further, S is, for improving the machinability combine with Mn, it is preferable to be contained by more than 0%, and preferably contains more than 0.005%.
Brief description of the drawings
[0034] [1] Figure 1 is a photograph was subjected to dyeing penetrant to a test piece of Example 3 which is an invention example.
FIG. 2 is a photograph was subjected to dyeing penetrant to a test piece of Comparative Example 2.
[3] FIG. 3 is a photograph showing an enlarged view of corrosion sites in FIG.

DESCRIPTION OF THE INVENTION
[0035] Rolling composite roll of the present invention, an outer layer to be subjected to rolling, the intermediate layer and / or an inner layer on the inside of the outer layer can be constituted by the shaft member. As an inner layer material constituting the inner layer, high-grade cast iron, ductile iron, can be exemplified a material having a toughness of graphite steel or the like, can be exemplified adamite material as an intermediate layer material constituting the intermediate layer.
[0036] The outer layer, were melted the molten alloy of the outer layer material of the above-mentioned components, for example, it can be cast by centrifugal force casting and static 置鋳 structure. Centrifugal force casting, vertical (rotation axis is the vertical direction), inclined (rotation axis oblique direction) and the horizontal (rotation axis is horizontal direction) may be either.
[0037] At the time of casting of the outer layer material, the solidification rate is a 8mm / min or more. Adjustment of the solidification rate can be performed by air cooling or water cooling the mold.
[0038] By thus defining the solidification rate of the outer layer material, it is possible to increase the B content in the base, it is possible to suppress the mixing of B to the secondary eutectic carbides.
[0039] The cast outer layer material, Dari cast the inner layer or the intermediate layer and the inner layer, the composite roll for rolling by like shrink fitting is manufactured.
[0040] Preferably, the rolling for the composite roll, subjected to a quenching treatment. B, which may be improved hardenability, in the present invention, the minute that B is not concentrated in the secondary eutectic carbides, because they contained a lot in the matrix, to further enhance the hardness of the base by quenching can.
[0041] The outer layer according to the present invention, the components, by applying the solidification rate may be the Vickers hardness of the secondary eutectic carbides example 1500HV ~ 1900HV. The reason why the rose hardness is believed to be because the B amount of the secondary eutectic carbides is reduced.
[0042] Then, for rolling the composite rolls composed of the outer layer material as the outer layer serves to suppress the coarsening of the secondary eutectic carbides, strength and, when the melting point is raised, receiving a thermal shock in the heat treatment and rolling It can also prevent the secondary eutectic carbides is missing and melting.
[0043] Observation of the prepared surface of the outer layer, the area ratio of MC-type carbide is between 7% and 15%, the area ratio of the secondary eutectic carbides from 1% to 6%, and the balance base. Adjust the amount of Bs, further, by adjusting the solidification rate, it was possible to suppress the growth of the secondary eutectic carbides. This means that it is possible to reduce the area ratio of the secondary eutectic carbides. The measured B amount in the outer layer, the B content in the outer layer surface is 0.006%, the B content in the outer layer the inner surface is 0.009%, the weight percent of the B concentration in the outer layer material surface B (t1 ), when the mass% of B concentration in the outer layer member inner surface and B (t2), the value of B (t2) -B (t1) was 0.002 or more.
[0044] Rolling for a composite roll with the outer layer material of the present invention as the outer layer, the intensity of secondary eutectic carbides are high, excellent surface roughening resistance. Therefore, it is possible to suppress the loss of the outer layer surface during rolling, it is possible to reduce the consumption of the outer layer with the grinding frequency of the outer surface reduction and thereto.
[0045] Rolling for a composite roll composed of an outer layer material of the present invention as the outer layer, in particular, is suitable for application to the front and the middle stand of operational stability is required hot finish rolling.
Example [0046] In an induction furnace, and it melted the molten alloy of the various components shown in Table 1 was subjected to centrifugal casting. The solidification rate of the outer layer material during casting was adjusted to 8 mm / min or more. In Table 1, Examples 1 to 5 are invention examples. Incidentally, Comparative Example 1 and Comparative Example 2, B weight of the outer layer member exceeding 0.01%.
[0047] [Table 1]

[0048] After cast the outer layer material, casting the inner layer, to prepare a rolling composite roll.
[0049] Obtained are subjected to hardening rolling composite roll. Quenching, it performs a forced air cooling using a large fan, and the cooling rate in the roll surface from the austenitizing temperature to 700 ℃ so as to be 900 ℃ / h or more.
[0050] The rolling composite rolls of Examples and Comparative Examples were subjected to quenching, was subjected to machining, one side has more than 30mm is cut out thickness about 10mm of the test piece respectively plural portions, as shown in Table 2 , held for 30 minutes at a temperature of 1050 ℃ ~ 1125 ℃, dyeing penetrant inspection conducted on each specimen to observe the state of its surface. In Table 2, "○" is the test pieces erosion was not confirmed in the dyeing penetrant inspection, "×" is erosion was observed specimen.
[0051] [Table 2]

[0052] Referring to Table 2, none of the Examples 1 to 5 are invention examples, even when held for 30 minutes at 1050 ℃ ~ 1125 ℃, the melting of the secondary eutectic carbides has not occurred It is seen. Figure 1 is a photograph of the test piece of the invention Example 3. Referring to FIG. 1, no instruction pattern was observed on the surface of the test piece.
[0053] This is because, in the test piece of Example, by the solidification rate was 8mm / min, B is often left in the base, which means that it is possible to suppress the contamination of the secondary eutectic carbides. In other words, by thickening the incorporation of B into the secondary eutectic carbides is prevented, it can improve the hardness of the secondary eutectic carbides, even when held at high temperature secondary eutectic carbides it can be seen that it is possible to prevent the melting or deficient.
[0054] On the other hand, the comparative example can not be verified melting damage to 1050 ° C. In the secondary eutectic carbides, it is understood that corrosion was observed in 1100 ° C. or higher. Figure 2 is a photograph of the test piece of Comparative Example 2. Referring to FIG 2, an instruction pattern secondary eutectic carbides is dissolved at a plurality of places of the surface of the test piece is observed. 3 is an enlarged photograph of instruction patterns of FIG. As shown in the figure, than the indicated pattern, it can be seen that the organization is missing. This is a result of B is mixed with concentrated in the secondary eutectic carbides, which means that the secondary eutectic carbides is melted by a high temperature.
[0055] It should be noted that, for the example, in the case was held under the conditions of 1150 ℃ × 30min, the melting of the secondary eutectic carbides has been confirmed.
[0056] The above description is for the purpose of illustrating the present invention, limiting the invention set forth in the appended claims, or should not be going through to Kirichijimi range. Further, each part structure of the present invention is not limited to the above embodiments, it is needless to say various modifications are possible within the technical scope described in the appended claims.
Industrial applicability
[0057] The present invention is useful outer layer material for rolling the composite rolls used in the hot rolling and it to rolling for a composite roll according to the outer layer.

The scope of the claims
[Claim 1] An outer layer material of rolling for a composite roll,
in mass%, C: 1.8% to 2.5% or less, Si: 0% to over 1.0% or less, Mn: over 0% 1 .0% or less, Ni: 0% to 0.5% over less, Cr: 8.0% beyond the 3.0% or less, Mo: 10.0% exceeding 2.0% or less, W: 10.0 percent beyond the 0% or less, V: 0% to beyond 10.0% or less, B: 0% to beyond less than 0.01%, contains a balance of Fe and unavoidable impurities,
that the outer layer material of rolling for a composite roll which is characterized.
[Claim 2] At wt%, Nb: 0.01% to 2.0% or less and / or Ti: further containing 0.01% to 1.0%,
the outer layer member rolling composite roll defined in claim 1 .
[Claim 3] Solidification rate during casting is 8 mm / min or higher,
according to claim 1 or claim 2 the outer layer member rolling composite roll defined.
[Claim 4] The outer layer material comprises a secondary eutectic carbides, the secondary eutectic melting temperature is higher than 1100 ° C. carbide,
the outer layer member rolling composite roll according to any one of claims 1 to 3.
[Claim 5] The weight percent of the B concentration in the outer layer material surface B (t1), when the mass% of B concentration in the outer layer member inner surface and the B (t2), B and (t2) -B (t1) that is ≧ 0.002 the outer layer material for rolling the composite roll according to any one of claims 1 to 4, characterized.
[6.] The outer layer material according to any one of claims 1 to 5 and an outer layer comprises an inner layer or the intermediate layer and the inner layer on the inner side of the outer layer material,
a composite roll for rolling.