JPS5916954A - Roller for continuous casting - Google Patents

Abstract

PURPOSE:To obtain the roller for continuous casting improved in thermal fatigue resistance, by adding Y, rare earth elements or Ca to Cr-Ni steel having a specified composition to form a high-N, Si-contg. gamma structure. CONSTITUTION:The continuous casting roller comprising 0.02-0.25wt% C, 1.0- 4.5% Si, Mn <=5.0%, 15.0-30.0% Cr, 10.0-25.0% Ni, 0.10-0.40% N, 0.001- 0.10%, in total, one or more of Y, rare earth elements and Ca, and the balance Fe and inevitable impurities, and having a metallurigical structure mainly composed of the phase gamma. The group of 0.20-5.0% one or more of Mo and W, 0.10- 2.0% one or more of Ti, Zr, V, Nb and Ta, and 0.2-5.0% Cu are added to said composition at need. By this composition, the wear resistance, high-temp. strength and oxidation resistance, etc. of the roller are improved, and the improvement in the work efficiency of continuous casting equipment and the reduction in the cost of maintenance are contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to materials for various rollers (hereinafter referred to as continuous casting rollers) used in continuous casting equipment. That is, as shown in FIG. 1, the continuous casting roller is usually an apron roller consisting of various parts that pour molten metal into a billet, bloom, or slab of a predetermined shape and size and solidify it, or moves the continuous casting material 9 in a predetermined direction. It consists of a pinch roll 7 and a feed roller 8 that transports the continuous cast material cut at the outlet of the pinch roll.

By the way, the materials for continuous casting rollers are generally rolled,
Materials manufactured by forging and casting are machined to specified dimensions, or the above materials are welded overlay, or surface treatments such as thermal spraying are used.The types of rollers used are There are many types depending on the place of application.

That is, 5US304.321.316.3098°31
Rolled materials such as 0S, rolled and forged materials such as SG, SOM, SNCM, FC, FOD, SO8.

JIS standards for fixing of SCH etc. and centrifugal casting materials, etc.
or its equivalent, and Stellite hardfacing or W
, Thermal spray materials mainly composed of carbides such as Mo are also used.

These depend on the material and dimensions of the billet, bloom, slab, etc. to be continuously cast, as well as the temperature, feed rate, cooling conditions, location where the roller is used, and usage conditions: rollers made of appropriate materials must be used. In any case, these rollers are used under the following severe conditions.

That is, first, the roller surface is subjected to thermal shock and thermal fatigue due to repeated heating and cooling due to continuous casting materials, cooling water, etc., and as a result, cracks often occur on the roller surface. Next, the roller receives a load from the continuous casting material when it comes into contact with the continuous casting material. Therefore, low sea requires high-temperature strength to withstand this load.

Furthermore, the closer the continuously cast material is to the mold, the higher the temperature, and the roller surface oxidizes due to the heat, and the cooling water turns into steam, further promoting oxidation. Depending on the properties of the cooling water, corrosion due to acidic or alkaline components contained therein, or corrosion due to organic substances, etc., may also accelerate damage to the roller surface.

Furthermore, the roller surface is subject to abrasion due to contact with the continuous casting material, and scale peeled off from the continuous casting material surface adheres to the roller surface, causing galling on the roller surface when the continuous casting material is moved, accelerating wear. .

Furthermore, this wear removes the protective oxide film that is effective in preventing oxidative corrosion on the roller surface, thereby promoting wear and tear on the roller surface due to oxidation, etc.

Furthermore, depending on the material of the roller, scale on the surface of the continuously cast material may stick to the roller surface, causing flaws in the continuously cast material. Also, depending on the nature of the cracks that occur in the roller surface pressing, it may promote the fixation of scale.

As mentioned above, the operating conditions for continuous casting rollers are extremely harsh, and in addition to mechanical strength as a roller, there are many other requirements such as thermal shock resistance, thermal fatigue resistance, abrasion resistance, oxidation resistance, corrosion resistance, seizure resistance, etc. These characteristics differ depending on various conditions such as material quality, operating method, etc. Therefore, rollers for continuous casting must be able to adapt as widely as possible to these various conditions.

However, in general, metal materials that are excellent in thermal shock resistance and thermal fatigue resistance tend to be inferior in wear resistance and high-temperature strength, and conversely, materials that are excellent in the latter tend to be inferior in the former. Therefore, none of the standard steels mentioned above are satisfactory as roller materials for continuous casting.

The inventors are not mutually exclusive with each other. With the aim of developing a roller for continuous casting that satisfies the casting properties as much as possible and is relatively inexpensive to manufacture, we conducted numerous actual machine tests and improved the roller material.As a result, we found that the following composition met these requirements. I found out that it is possible.

That is, the gist of the present invention is that the weight is 0002~
025%, St 1.0-4.5%, Mn 5.0
degree or less, Or 15.0-30.0%, Ni 10.
0 to 25.0 ratio, N O, 10 to 0.40 ratio, Y, rare earth elements, and Oa, any one or two or more types total 0
001 to 0.10%, or W,
02 to 5.0% in total of one or more of MO, Ti
.

Contains at least one selected from Zr, V, N111+, Ta, 01 to 20% in total, OuQ, 2 to 50%, and the remainder consists of iron and impurities. , a continuous casting roller characterized in that its metallographic structure is mainly γ phase.

The present invention will be explained in detail below.

First, the reason why the range of components of the roller of the present invention was so limited will be described in section X.

First, C is a γ-forming element and is an important element for strength and wear resistance, and at least 0.02% is required. On the other hand, if it exceeds 0.25%, hardening of the matrix and precipitation of carbides will be excessive, which will promote cracking due to thermal shock and thermal fatigue during use, and will also be unfavorable for workability in rolling and forging during material production. do not have. For the above reasons, the lower limit was set at 0.02%, and the second limit was set at 0.25%.

Next, Si is necessary as a deoxidizing agent, and addition of 10% or more is effective in improving oxidation resistance, seizure resistance, and thermal fatigue resistance. However, if it is added in excess of 45 parts, α
This is undesirable because it promotes the formation of phases, making cracks more likely to occur during forging, rolling, or use, and also reduces the solubility of N during casting, making blow holes more likely to occur.

From the above points, the lower limit was set to 1.0%, and the upper limit was set to 45%.

In addition, Mn is effective as a deoxidizing agent, stabilizes the γ phase of the matrix, and increases the solubility of N. Therefore, the upper limit of Mn is 5.0. %.

Next, Or is an important element indispensable for strength, wear resistance, oxidation resistance, and corrosion resistance, and is effective in improving strength and wear resistance by combining with C, and is solid-solved in the matrix to improve corrosion resistance. In addition, at high temperatures, a protective oxide film is formed on the roller surface, which is effective for oxidation and corrosion resistance. In order to ensure these properties, at least 15.0% or more is required, and if it exceeds 30%, carbides of Or, nitrogen 1. .

Compounds promote cracking and material embrittlement due to the formation of α phase and precipitation of δ phase, which adversely affects thermal shock resistance and thermal fatigue resistance. For the above reasons, the lower limit was set to 150% and the upper limit was set to 300%.

Further, Ni is dissolved in iron and is required to be at least 10.0% in the raw metal of the roller of the present invention. However, if it exceeds 25.0%, the wear resistance deteriorates and the cracking resistance becomes less effective as the added amount is increased, and N1 is also expensive, so the upper limit was kept at 25.0%.

Furthermore, one of the features of the roller of the present invention is that it contains a high concentration of solid solution N. That is, like C, N is a γ phase forming element, and is effective in improving high temperature strength, wear resistance, and thermal fatigue resistance. For this reason, at least 0.10% is necessary, but if it exceeds 0.40, it not only deteriorates the cracking resistance but also causes crack holes during casting. For the above reasons, the lower limit was set to 0ΦQ%, and the upper limit was set to 0.40%.

In addition, Y, rare earth elements, and Oa are powerful deoxidizing agents.
As a desulfurizing agent, it purifies the matrix and at the same time remains on the roller to improve the adhesion of the oxidized film of the SL to the metal surface.

For this reason, it is necessary to have a small amount of one or more of the above elements in the metal at 0001% or more. However, if this exceeds 0.1%, it is not favorable for cracking resistance, and the improvement effect is small even though the amount is increased. Since it is also expensive, the upper limit was set at 0.1%.

Furthermore, in the case of continuous casting rollers, in addition to mechanical strength at high temperatures, it is necessary to have many properties such as thermal shock resistance, thermal fatigue resistance, abrasion resistance, oxidation resistance, corrosion resistance, and seizure resistance. It is necessary that the material be mainly in the γ phase in a use environment involving mechanical strength, thermal shock, and thermal fatigue.

That is, the α phase has inferior high-temperature strength compared to the γ phase, and the α+γ phase has drawbacks such as being susceptible to cracking due to thermal fatigue.

The above is the basic feeling of the roller of the present invention, but in the present invention, in order to further improve thermal fatigue resistance, embrittlement resistance, abrasion resistance, and high temperature strength, Mo is added.

A total of 0.20 to 50 inches of one or more types of W, or Ti.

0.1 to 2.0% in total of one or more of Zr T V r N b s Ta 1 and 02 to 5.0% of Ou
At least one selected from these can be contained.

Next, the reasons for limiting these elements will be explained.

Mo not only strengthens the matrix but also precipitates in the grains and grain boundaries as carbides and is effective in improving high-temperature strength and wear resistance, and when added, at least 0.20% is required to exhibit its effect. Moreover, if it is added in an amount exceeding 50%, the material becomes brittle and unfavorable in terms of thermal fatigue resistance, so the upper limit was kept at 5.0%. Furthermore, when adding W together with W, the total of both needs to be 5% or less for the same reason.

Next, W mainly precipitates in the grains and grain boundaries as carbides and contributes to improving high-temperature strength and wear resistance through age hardening. When added, at least 0.20% is required to exhibit its effect, and if it is added in excess of 5.0%, it forms an α phase, promoting the formation of 6 phases and improving thermal fatigue resistance and thermal shock resistance. Since this is not desirable in terms of performance, the upper limit was set at 5.0. Further, in particular, W is often added together with Mo, but in this case as well, the sum of both must be kept at a factor of 50 or less for the same reason.

Then, Ti is 0. It combines with N to form carbides and nitrides, which are finely distributed within grains and at grain boundaries and are effective in improving high-temperature strength and wear resistance. At least 0.1% is required to exhibit its effect. Furthermore, if the amount exceeds 2.0, it is unfavorable in terms of rolling workability and heat fatigue resistance, so the upper limit was limited to 20.

Also, like Ti, Zr forms carbides and nitrides, and is effective in improving high-temperature strength and wear resistance. In order to exhibit this effect, it is preferable to have at least 0.1% rolling workability, and from the viewpoint of heat fatigue resistance, the upper limit is set at 2Q%.

Next, (2) produces carbides and is effective in terms of high temperature strength and IT1 abrasion resistance. At least 0.1% is required to exhibit this effect. Furthermore, even if it is added in an amount exceeding 2%, the effect is not so great and it is also unfavorable in terms of thermal fatigue resistance, so the upper limit was limited to 20%.

Furthermore, Nb forms fine carbides and is effective in improving thermal fatigue resistance and high-temperature strength. At least 0.1% is necessary to exhibit this effect, and even if added in excess of 20%, the effect will not improve much, but the quality of the material will deteriorate, so the upper limit was kept at 20%.

Further, like Nb, Ta forms fine carbides and is effective in improving the performance of the matrix, and is particularly effective in improving thermal fatigue resistance and high-temperature strength.

At least 0.1% is required to exhibit this effect, and even if added in excess of 2.0%, the effect will not improve much, so the upper limit was set at 2.0%.

Above, T i # Z r + V I N b g
The effect of adding Ta is the same as y, and even when two or more of these are added, the total must be within the range of 0.1 to 20%.

Furthermore, Cu is effective in improving corrosion resistance against cooling water, and in order to exhibit its effect, it is necessary to add at least 02 Cu. If more than 0% is added, it is unfavorable in terms of high-temperature embrittlement due to thermal fatigue and cracking resistance, so the upper limit was kept at 5.0%.

As described above, the roller of the present invention has a metal assembly. Furthermore, the roller of the present invention contains a high concentration of Si in addition to Or and Ni, so it has excellent oxidation resistance at high temperatures, and furthermore, since Sl lowers the stacking fault energy, it also has excellent seizure resistance at high temperatures.

Further, the roller of the present invention, which has a high N/high SL content γ structure strongly deoxidized by Y, rare earth elements, or Ca, has excellent properties as a continuous casting roller material with excellent heat fatigue resistance. By the way, when the effects of thermal shock and thermal fatigue (cracking resistance) are important, roller materials are manufactured by rolling and forging, while in the case of low-temperature parts of continuous casting materials, which are not as affected by thermal shock, it is possible to manufacture roller materials including casting. can.

Next, the effects of the present invention will be described in more detail with reference to Examples.

Example Rollers of various components shown in Table 1 were made, billets,
It was used as a roller in continuous bloom or slab casting equipment, and its lifespan was investigated.

Conventionally, rollers are made of cast, forged or rolled round bars. In addition, all rollers of the present invention, except for No. 12, are forged from 100K9 vacuum melted steel ingots and have a 1lQi
Create a round bar of aφ and machine it to an outer diameter of 100 yx
, a finished roller with an inner diameter of 7 Q mx and a length of 21 Q a+a. Further, No. 12 was finished to the above roller dimensions by direct machining from an ingot.

Table 1 shows the results of using these rollers for billets, blooms, and slabs in the high-temperature section directly below the mold (part of the net roller) and the medium-temperature section of the machine (part of the roller apron roller).

All of the rollers of the present invention exhibited longer lifespans than conventional rollers. In addition, there are various reasons for discarding the rollers, such as abrasion, deformation, and hair cracks, whereas the rollers of the present invention have excellent abrasion resistance, high temperature strength, and oxidation resistance, and are resistant to hair cracks on the surface due to long-term use. It was Matami.

As shown in the above examples, the roller of the present invention has a long life as a continuous casting roller, contributes to improving the operating rate of continuous casting equipment, reduces maintenance costs, and greatly contributes to improving product productivity.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a continuous casting apparatus. 1...mold, 2...foot roller, 3...river/tub roller apron, 4...
... Upper roller apron, 5 ... Middle roller apron, 6 ... Lower M lower apron,
7...Pinch roll, 8...Feed roller, 9...Continuous casting material. Agent: Patent attorney Masamitsu Akizawa and 2 others Figure 7i-1

Claims (8)

[Claims] (1) Weight: 00.02-0625, Si1.0-4
59f+, Mn 5.0% or less, Orl 5. O~30
．． 0%, N1100-25.0 section, NO, 10-0.4
The metal structure is characterized by containing a total of 0001 to 0.10 of any one or more of Y, rare earth elements, and Ca, with the remainder consisting of iron and impurities, and the metal structure is mainly γ phase. A roller for continuous casting. (2) 00.02-025% by weight, Si1.0-45
%, Mn 5.0% or less, Cr 15.0-30.0%,
Ni1O, O~2'5.0, NO, 10~040%
,Y. 0001 to 0.10% in total of one or more of rare earth elements and Da, and further Mo. Contains 0.20 to 5.0% in total of one or two types of W,
The remainder consists of iron and impurities, and the metal structure is mainly γ.
A roller for continuous casting characterized by a phase. (3) OQ by weight, 32~0.25 qb,'Si
1. O~45chi, Mn 5.0% or less, Orl 5.0
~30.0%, Ni100~250%, N010~0
40%, 0.001 to 0.10% by grinding any one or more of Y, rare earth elements, Ca, and 'I'i,
Zr, V, Nb. Contains a total of 01 to 20 of one or more types of Ta,
The balance consists of iron and impurities, and the metal structure is mainly γ.
A roller for continuous casting characterized by a phase. (4) Weight: 00.02-0.25, Si: 1.0
~45%, Mn 5.0% or less, Orl 5. O~30
．． 0%, Ni10.0-250, NO, 10-0
Section 40, contains 0,001 to 0.10% of any one or two or more of Yj rare earth elements and Oa, further contains 02 to 5.0% of O, and the balance is iron and impurities. A roller for continuous casting, characterized in that the metal structure is mainly a γ phase. (5) 00.02-025% by weight, Si 1.0-4.
Section 5, Mn 5.0% or less, Orl 5.0-30.0
%, Ni100~25.0%, NO,1'o~0
40%, Y. Contains a total of 0.001 to 0.10% of one or more of rare earth elements and Oa, and further contains Mo, W (
7) Total of 1 or 2 types: 020-50%, T 1 g
Z r #V, Nb, Ta (7) Contains one or more kinds in total of 0.1 to 2.0, the remainder consists of iron and impurities, and the metal structure is mainly γ phase. A roller for continuous casting. (6) 00.02~'0.25% by weight, Si 1
0~4°5 ratio, Mn 5.0% or less, Or 15.0
~30.0%, Ni 10.0~25.0%, NO
, 10-4.0%, Y. Either one or two or more of rare earth elements and Ca is 0 in total.
．． 001 to 0.10%, furthermore Ti, Zr, V, Nb. 01 to 20% in total of one or more types of Ta, Cu11
0.2 = 5.0%, the balance consists of iron and impurities, and the metal structure is mainly γ
A roller for continuous casting characterized by a phase. (7) By weight co, 02~0.25'J, Si
1.0-4.5%, Mn 5.0%% or less Or
15. O~30.0%, Ni10.0~250%, N
Contains 0% in total of any one or more of O, 10-040%, Y, rare earth elements, and Ca, and 1-010% of OO, and further 0.20% in total of one or two of MO, W.
5.0%, contains 02 to 5.0% Cu, the balance consists of iron and impurities, and the metal structure is mainly γ.
A roller for continuous casting that is characterized by its phase. (8) 00.02-025% by weight, Si1.0-45
Mn 5.0% or less, Or 15.0-30.0
%, Ni10.0-25.0, N010-040,
The total of any one or more of Y1 rare earth elements and Oa is 0.0.01- to C1x=0%, and further M O,
020 to 50% in total of one or two types of W, Ti, Zr,
V. The total of one or more of Nb and Ta is 0.10 to 2.0
1. A continuous casting roller containing 02 to 5.0% of 96.