JPH0768588B2 - Method for manufacturing metal rolling rolls - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel method for producing a roll for a metal rolling mill, and particularly to a shift type 6 having a high axial strength suitable for cold rolling of a metal.
The present invention relates to a method for manufacturing work rolls for a strip rolling mill.

[Conventional technology]

In the case of rolls for metal rolling mills, slips that occur between the rolls and the material to be rolled during rolling, rolling accidents such as the material to be rolled around the rolls cause thermal shock to the surface of the rolls, and in extreme cases, cracking may occur. Occur.

In addition to this resistance to thermal shock, work rolls are required to have excellent wear resistance in order to maintain good rolling.

In order to improve the thermal shock resistance, it is effective to improve the tempering resistance of the roll itself and perform the tempering at a higher temperature.

Conventional work rolls have C1.2-2.5%, Si0.8-3.0%, Mn≤1%, Cr3.0-6.0 as described in JP-A-63-60258.
%, Mo 0.2% or less, and then tempering was performed after quenching, but in order to obtain hardness of Hs 93 or more,
The tempering temperature was set to 160 ° C or lower.

[Problems to be Solved by the Invention]

In the above-mentioned conventional technology, in order to improve heat resistance and thermal shock resistance, if the tempering temperature is raised to 160 ° C or higher, hardness of Hs93 or higher cannot be obtained, wear resistance decreases, and there is a drawback that good rolling cannot be maintained. It was

An object of the present invention is to provide a method for manufacturing a metal rolling roll having both high resistance and high wear resistance against thermal shock cracking.

[Means for Solving the Problems]

The present invention has a hardness of Hs 88 or more on the surface of a shaft material made of a low alloy steel having a tensile strength of 60 kg / mm ² or more and a chemical composition of C0.5 by weight ratio.
~ 1.5%, Si0.5 ~ 3.0%, Mn1.5% or less, Cr2 ~ 7%, Mo1 ~ 5
%, W0.15 to 0.5%, V0.7 to 1.5%, the balance being a composite structure having an outer layer of a high alloy steel consisting essentially of Fe. The consumable electrode made of the high alloy steel is inserted into the space formed between the concentrically arranged water cooling mold, and the shaft and the cooling mold are rotated in the circumferential direction while the electrolysis is performed under a slag bath. A method for manufacturing a metal rolling roll, characterized in that the consumable electrode is melted by a slag remelting method, and the molten metal is brought into contact with the water cooling mold to solidify the outer layer to the shaft material. It is in.

Further, the present invention is one in which one of Ni and Co is contained in the outer layer in an amount of 5% or less. Further, in the manufacturing method of the present invention, after the outer layer is integrally welded to the shaft material, the outer layer is subjected to progressive quenching in which the fountain is cooled while being heated by low frequency induction heating, and then 30
The tempering treatment is performed at a temperature of 0 to 550 ° C.

In the case of a roll integrated with the above materials, there is a risk of fracture from the inside due to thermal stress during quenching with a fountain, and the toughness of the shaft is inferior, which is disadvantageous to the breakage of the neck during use. . Therefore, the roll has a surface layer portion made of the above material, and the core material has a composite structure made of alloy steel having high toughness.

In quenching, if air blast cooling or oil cooling is performed,
Even if the above materials are used, the surface compressive residual stress is insufficient, and
When tempering was performed at a temperature of 0 ° C or higher, it was difficult to obtain a hardness of Hs93 or higher, so the water was cooled with a fountain. The tempering temperature is particularly preferably 450 to 550 ° C, more preferably 500 ° C to 550 ° C.
C is preferred.

The core material according to the present invention has a tensile strength of 60 kg / mm ² or more and an impact value of 1.5 k.
Low alloy steel with g-m / cm ² or more is preferable, and especially C0.5 by weight.
A forged steel containing ~ 1.0%, Si1% or less, Mn1% or less, Cr1-5%, Mo0.5% or less is preferable.

[Action]

The work roll for cold rolling having the above-mentioned configuration can sufficiently withstand abrasion resistance, surface roughening resistance, and toughness even when used for rolling subjected to large bending. In particular, since it is a roll in which the outer layer is welded to the shaft material by electroslag remelting, the carbide that crystallizes from the molten metal rapidly solidifies without flotation, precipitation, or segregation, so that it is finely and evenly dispersed in the outer layer. Becomes With these, under high pressure of rolled material,
High shape control can be performed soundly and the quality of the surface properties of the rolled material is improved.

In order to solve the problems of the prior art and achieve the above-mentioned object, the inventors of the present invention conducted experiments and obtained the following findings.

The outer layer must be semi-high speed and heat treated to maintain hardness of Hs90 or higher in order to secure abrasion resistance and skin resistance.

The chemical composition of the semi-high-speed steel in the outer layer is specified for the following reason.

C is necessary for formation of carbide and improvement of matrix hardness for improving wear resistance. If the amount is less than 0.5%, the amount of carbides is small and wear resistance is not sufficient. On the other hand, C is 1.5%
If it exceeds, the network carbides precipitated at the grain boundaries increase and the surface roughness and toughness become poor. Especially 0.8-1.2
% Is preferred.

Si is an element necessary as a deoxidizer, and has 0.5% or more,
It also increases tempering resistance. However, if the amount exceeds 3.0%, embrittlement easily occurs. Particularly, 1 to 3% is preferable, and 1.5 to 2.5% is more preferable.

Mn has a deoxidizing action as well as an action of fixing S, which is an impurity, as MnS. However, if its amount exceeds 1.5%, retained austenite increases and stable hardness cannot be maintained, and toughness decreases. In particular, 0.2 to 1.0% is preferable, and 0.2 to 0.5% is more preferable.

If Cr is less than 2%, hardenability is poor, and if it exceeds 7%, Cr
It is inconvenient because the amount of carbides is excessive. Especially 3-6
% Is preferable, and 3.5 to 5% is more preferable.

Mo and W each combine with C to form an M ₂ C or M ₅ C-based carbide, and also form a solid solution in the matrix to strengthen the matrix and improve wear resistance and tempering resistance. However, if it becomes excessive, the amount of M ₆ C-based carbides increases, and the toughness and surface roughening resistance decrease. The upper limit of Mo is 5%, and Mo should be 1% or more. Mo is preferably 1.5 to 4.5%, and W is 0.15 to 0.5.
%.

V forms MC-based carbides and contributes to the improvement of wear resistance.
If it is less than 7%, there is no sufficient effect, and if it exceeds 1.5%, the grindability is significantly impaired. Particularly, it is 0.7 to 1.5%.

Co is an element for forming a solid solution in the matrix to obtain high hardness by high temperature tempering, but if it is less than 5%, its effect is sufficient.

The semi-high speed steel used in the outer layer of the present invention may contain Ni in addition to the above elements. Since Ni has the effect of improving hardenability, it can be added in an amount of 5% or less. If it exceeds this, the retained austenite is increased, resulting in a decrease in hardness and a decrease in surface roughening resistance. In particular, 1% or less is preferable, and 0.1 to 0.5% is more preferable.

Except for the above-mentioned elements, impurities are excluded and the material is essentially Fe.

Next, in the present invention, it is preferable to use a forged steel having Hs of 35 or more as the shaft material. That is, when a net stress of 10 kg / mm ² as a nominal stress is applied to the roll of the present invention, the dimensional effect coefficient is 0.8, the surface effect coefficient is 0.9, and the notch coefficient is 20.
As a result, the required fatigue limit is 36 kg / mm ² , and to obtain it, the hardness should be HS35 or higher.

Next, as a method of joining the outer layer and the inner layer in the present invention, a continuous build-up method utilizing high frequency heating disclosed in Japanese Patent Publication No. 444903 and the like, and disclosed in JP-A-47-2851 and others. There is a method of forming an outer layer by hot isostatic pressing using a powder metallurgy method, a build-up method using an electroslag remelting method disclosed in JP-A-57-2682.

Among them, in the present invention, Example rolls were manufactured by a build-up method utilizing the electroslag remelting method of the following gist. That is, a consumable electrode made of semi-high-speed steel is inserted into the space formed between the shaft material and the concentrically arranged mold, the shaft material and the cooling mold are rotated in the circumferential direction, and electroslag is performed under the slag bath. The outer layer formed by melting the consumable electrode by re-melting and moving the cooling mold coaxially upward with respect to the shaft material to bring the molten metal into contact with the cooling mold and solidify it is welded to the shaft material.

The apparatus used in the present invention comprises a cooling mold 1 whose inside is water-cooled and a rotary platen on which a shaft material and an ignition plate which are coaxially arranged are placed, and a space formed between the cooling mold and the shaft material. A consumable electrode made of high-speed steel is inserted into the, and a current is passed through a carbon brush between the rotating platen and the consumable electrode, and the consumable electrode is melted by the resistance heat of the molten slag. The molten metal contacts with the cooling mold and solidifies to form an outer layer. The work roll thus obtained is further subjected to heat treatment such as quenching and tempering to obtain a hardness of HS90 or higher.

〔Example〕

A roll having a body diameter of 385 mm and a body length of 1480 mm was manufactured by the electroslag remelting method using the shaft material having a diameter of 300 mm in the apparatus described above. The outer diameter of the ingot was 485 mm, the outer diameter was 415 mm by forging at 1100 ° C, and the thickness of the outer layer was 42.5 mm.

The chemical composition of the material of the outer layer is shown in Table 1 (% by weight). This roll was further heat-treated by quenching from 1100 to 1200 ° C and tempering at 120 to 520 ° C. For comparison, rolls of the same size were manufactured for the conventional 3% Cr forged steel. The chemical composition of this material is shown in Table 1. The heat treatment was a heat treatment suitable for this material. The shaft material of the roll of the present invention was C0.9%, 3% Cr forged steel, and its hardness was HS40 (tensile strength at room temperature of about 90 kg / mm ² ).

Figure 1 shows the relationship between tempering temperature and hardness. Example 1
In the case of Example 2, the quenching temperature was 1060 ° C., and the gradual quenching was performed by cooling the fountain while heating only the surface layer portion by low frequency induction heating. After that, subzero treatment was performed at 50 ° C., and tempering was performed at each temperature.

With the conventional roll, the tempering temperature that gives the hardness of Hs93 is
Although it is 160 ° C., in the case of Example 1, it is 520 ° C., and the tempering temperature at which the same hardness is obtained is significantly higher than that of the conventional roll.

In the case of Example 2, the hardness after tempering at 500 ° C. is Hs88, and the effect of Si addition is clearly recognized.

FIG. 2 shows a comparison of thermal shock resistance between Example 1 and a conventional roll. In the test, the material was sampled from the surface of the roll material after forging, and after processing, quenching was carried out, and tempering was carried out at 520 ° C. in the present Example 1 and at 160 ° C. in the conventional roll, and the test was conducted. The test method was such that a test piece having a diameter of 80 mm and a thickness of 40 mm was rotated at 1420 rpm, and a 20 mm square mild steel material was pressed against the test piece with a load of 500 g / mm to perform water cooling.

The crack length on the vertical axis in Fig. 2 is the total length of cracks generated on the surface of the test piece.
While it is 54 mm, in the case of Example 1, it is 23 mm, which is less than half that of the conventional material, and the effectiveness of high temperature tempering is clear.

FIG. 3 shows a comparison of wear resistance. The sliding surface has a diameter of 18
A test piece of mm was subjected to the same heat treatment, and a load of 500 g was applied and slid on # 100 emery paper. Whereas the wear amount of the conventional roll is 230 mg, in the case of Example 1, 120 mg
It can be seen that the wear resistance is also excellent.

As the roll of this Example 1, the roll having the shape shown in FIG. 4 was used, and by using this roll, a rolling mill shown in FIG.
As a result of cold-rolling stainless steel foil with a thickness of less than μm and steel plate for thin plate, compared with the conventional integrated roll
It was confirmed that the wear resistance more than doubled was obtained. Reference numeral 1 is a material to be rolled, 2 is a work roll according to this embodiment, 3 is an intermediate roll, 4 is a backup roll, 5 is an outer layer, and 6 is a core material.

In this Example 3, 0.3% of Co or 1% of Co was added to the case where the amounts of C, Si, Mn, Cr, Mo, V and W are the same as those of Example 1.
A heat shock test and rolling were performed on the outer layer containing the same as described above, and the same quenching and tempering were performed. As a result, the crack length was slightly smaller than that of Example 1, and the wear amount was It was a little less.

〔The invention's effect〕

According to the present invention, even if the surface hardness is the same as that of the conventional roll, since tempering can be performed at a high temperature of 300 ° C. or higher, slip during rolling, resistance to thermal shock generated due to accident, etc. It can be significantly increased while maintaining a comparable wear resistance.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between tempering temperature and hardness of one embodiment of the present invention, FIG. 2 is a comparative diagram of thermal shock resistance, FIG. 3 is a comparative diagram of wear resistance, and FIG. FIG. 5 is a sectional view of a work roll according to the present invention, and FIG. 5 shows a rolling mill using the work roll according to the present invention. 2 ... work roll, 5 ... outer layer, 6 ... core material.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C22C 38/00 301 L 302 E 38/24

Claims (4)

[Claims] 1. A shaft material made of a low alloy steel having a tensile strength of 60 kg / mm ² or more has a hardness of Hs 88 or more and a chemical composition of C by weight ratio.
0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr2 to 7%, Mo1
~ 5%, W0.15-0.5%, V0.7-1.5%, balance is Fe
A method for manufacturing a metal rolling roll having a composite structure having an outer layer of a high alloy steel comprising a high alloy steel in a space formed between a water cooling mold concentrically arranged on the shaft material. The consumable electrode is inserted, and while rotating the shaft and the cooling mold in the circumferential direction, the consumable electrode is melted by the electroslag remelting method under the slag bath, and the molten metal is brought into contact with the water cooling mold. A method for manufacturing a metal rolling roll, characterized in that the outer layer is integrally welded to the shaft member by solidifying and solidifying the outer layer. 2. A shaft material made of a low alloy steel having a tensile strength of 60 kg / mm ² or more has a hardness of Hs 88 or more and a chemical composition of C by weight.
0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr2 to 7%, Mo1
˜5%, W0.15˜0.5%, V0.7˜1.5%, and 5% or less of one of Ni or Co, and the balance having a composite structure with an outer layer of high alloy steel consisting essentially of Fe A method for manufacturing a metal rolling roll consisting of, wherein a consumable electrode made of the high alloy steel is inserted into a gap formed between a water cooling mold concentrically arranged on the shaft material, and the shaft material and While rotating the cooling mold in the circumferential direction, the consumable electrode is melted by an electroslag remelting method under a slag bath, and the melt is brought into contact with the water cooling mold to solidify the outer layer to the shaft material. A method for manufacturing a metal rolling roll, which comprises integrally welding. 3. A shaft material made of a low alloy steel having a tensile strength of 60 kg / mm ² or more has a hardness of Hs 88 or more and a chemical composition of C by weight ratio.
0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr2 to 7%, Mo1
~ 5%, W0.15-0.5%, V0.7-1.5%, balance is Fe
A method for manufacturing a metal rolling roll having a composite structure having an outer layer of a high alloy steel comprising a high alloy steel in a space formed between a water cooling mold concentrically arranged on the shaft material. The consumable electrode is inserted, and while rotating the shaft and the cooling mold in the circumferential direction, the consumable electrode is melted by the electroslag remelting method under the slag bath, and the molten metal is brought into contact with the water cooling mold. After the outer layer is integrally welded to the shaft material by solidifying and then solidifying, the outer layer is subjected to progressive quenching by cooling with a fountain while being heated by low-frequency induction heating, and then tempered at a temperature of 300 to 550 ° C. A method for producing a metal rolling roll, comprising: 4. A shaft material made of a low alloy steel having a tensile strength of 60 kg / mm ² or more has a hardness of Hs 88 or more and a chemical composition of C by weight ratio.
0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr2 to 7%, Mo1
˜5%, W0.15˜0.5%, V0.7˜1.5%, and 5% or less of one of Ni or Co, and the balance having a composite structure with an outer layer of high alloy steel consisting essentially of Fe A method for manufacturing a metal rolling roll consisting of, wherein a consumable electrode made of the high alloy steel is inserted into a gap formed between a water cooling mold concentrically arranged on the shaft material, and the shaft material and While rotating the cooling mold in the circumferential direction, the consumable electrode is melted by an electroslag remelting method under a slag bath, and the melt is brought into contact with the water cooling mold to solidify the outer layer to the shaft material. A method for producing a metal rolling roll, characterized in that, after being integrally welded, the outer layer is subjected to progressive quenching by cooling with a fountain while being heated by low-frequency induction heating, and then tempered at a temperature of 300 to 550 ° C.