JPH02141523A - Production of hearth roll for heat treatment furnace - Google Patents

Abstract

PURPOSE:To provide the title roll having excellent and stable build up resistance even under a high-temp. service condition by forming an Ni-based alloy layer having a specific component compsn. and metal structure to the front layer of the barrel part of the roll. CONSTITUTION:The Ni-based alloy layer 12 consisting of 10 to 30wt.% Cr, 10 to 30% Co, 3 to 15% Al, and the balance substantially Ni is formed by a welding method, etc., on the base body 11 in the barrel part of the hollow cylindrical roll made of a heat resisting alloy. The alloy layer 12 is then subjected to an aging treatment at 600 to 900 deg.C to precipitate and disperse an intermetallic compd. phase in the gamma phase base to produce the barrel part 10 of the roll; thereafter, the barrel part is fitted via a spacer 30 to a roll shaft body 20 to assemble the hearth roll. Further, the elements of >=1 kinds among 0.5 to 10% Mo, 0.5 to 5% Ti, 0.5 to 10% W, and 0.5 to 10% Nb are added at <=10% to the above-mentioned Ni-based alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing hearth rolls (rolls for conveying steel materials) in a heat treatment furnace.

[Conventional technology]

Steel heat treatment furnaces such as steel plate continuous annealing furnaces (furnace temperature: approx. 600 to 1
Conventionally, heat-resistant cast steel, typically JIS G51225CH, has been used as the material for the body of hearth rolls (300℃).
High Cr-high Ni system such as 13,5CH22 or its F
High-grade heat-resistant cast steel in which part of e is replaced with YXCo, W, etc. has been used.

The practical use of the hearth roll in a high-temperature atmosphere furnace also poses a problem in that build-up is likely to occur on the surface of the body. Build-up is a phenomenon in which surface oxides (scale) and metal powder on the steel material adhere to or bite into the surface of the body, and adhere through chemical reactions, causing roughness and damage to the surface of the body. When it occurs,
This causes scratches on the surface of the subsequent steel material, significantly reducing its quality and yield.

As a countermeasure to this problem, recently, C
Ni-based alloy containing r, Al, Y (35Cr10A l
Attempts have also been made to form a coating layer of (-0,5Y-Ni) or to coat with ceramic such as alumina (AI□03) or zirconia (ZrO□).

[Problem to be solved by the invention]

Although it is possible to obtain a build-up reduction effect by coating the body surface of the hearth roll with the Ni-based alloy,
The effect is small in a high temperature range exceeding 1000°C. Furthermore, although ceramic coatings have low wettability to molten materials on the steel surface scale and exhibit excellent build-up resistance, they tend to crack and peel due to mechanical and thermal shock, and lack stability as a roll protective film. .

The present invention has been made for the purpose of solving the above-mentioned problems regarding hearth rolls for heat treatment furnaces.

[Means and effects for solving the problems] The method for manufacturing a hearth roll according to the present invention includes coating the outer peripheral surface of the metal base of the roll body with Cr: 10-30%, Co: 10-30%, A
l: 3 to 15%, the remainder substantially consists of Ni, or if desired a part of Ni, Mo: 0.5% to 10%, Ti
:0.5% to 5%.

A Ni-based alloy layer was formed that was substituted with one or more elements selected from the group of W: 0.5% to 10%, Nb: 0.5% to IO%, and the total amount was 10% or less. Later, the Ni
It is characterized in that an intermetallic compound phase is precipitated and dispersed in the T-phase matrix by subjecting the base alloy layer to aging heat treatment at a temperature of 600 to 900°C.

The body surface layer of the hearth roll according to the present invention is made of a Ni-based alloy having the above-mentioned chemical composition and a metal structure in which an intermetallic compound phase such as a γ'' phase (NiaAl) is precipitated and dispersed in a T-phase base. As shown in the Examples below, it exhibits excellent and stable build-up resistance even in a high temperature range exceeding 1000°C.

The reason why the Ni-based alloy layer forming the body surface layer of the hearth roll according to the present invention exhibits stable build-up resistance in a high temperature range is due to the excellent precipitation strengthening of intermetallic compound phases such as T" phase (gamma prime). Due to its action, it has high strength and strength even in high temperature range.
A barrier that maintains hardness and reduces the occurrence of scale intrusion of heavy steel materials into the surface, and that stable oxide films such as Cr and AI formed on the surface suppress reactions with steel surface scale. This is thought to be due to the synergistic effect of physical and chemical factors such as functioning as a layer. Next, N forming the body surface layer of the hearth roll of the present invention
The reason for limiting the components of the i-based alloy will be explained.

Ni: Ba1ance? Ni is a base constituent element and exhibits excellent high-temperature properties when alloyed with Cr, Co, etc. In addition to stabilizing the γ phase of the base, it is a basic element for forming the N i3 A ] phase called the γ゛ phase, which is precipitated and dispersed in the base, and other intermetallic compound phases.

Cr: 10-30% Cr has the effect of increasing oxidation resistance, corrosion resistance, etc.
By reducing the amount of solid solution of elements such as AI and Ti in the phase base, it is effective in increasing the amount of precipitation of intermetallic compound phases such as T phase. These effects can be obtained by adding 10% or more, but since adding more than 30% leads to weakening of the base, it is set at 10 to 30%.

Co: 10-30% CO has the effect of improving oxidation resistance, corrosion resistance, etc. In particular, Cr
The effect is enhanced by the coexistence of Further, in addition to solid solution strengthening of the T-phase matrix, it has the effect of increasing the precipitation amount of intermetallic compound phases such as γ゛ phase, like Cr. To obtain these effects, 10% addition is required. The effect increases as the amount increases, but on the other hand, the precipitation of the T' phase is suppressed due to the balance with the Ni amount, so the upper limit is set at 30%.

Al: 3 to 15% Al forms an intermetallic compound phase such as Ni3Al or NiA1, and increases the strength and hardness of the base due to its precipitation strengthening effect. The effect is obtained by adding 3%, and increases as the amount added increases, but if it exceeds 15%, it becomes difficult to form an alloy layer on the base surface of the roll body (for example, overlay welding). Become. Therefore, the content was set at 3 to 15%.

The body surface layer of the hearth roll of the present invention is formed of a Ni-based alloy having a component composition in which a part of Ni is replaced with one or more elements selected from the following element group, if desired. The reason for setting the upper limit of the total amount to 10% when two or more elements are added in combination is to avoid the embrittlement of the alloy base due to the addition of large amounts and the difficulty of forming an alloy layer on the surface of the body base (for example, This is to avoid deterioration in build-up weldability, etc.).

Mo: 0.5 to 10% Mo is Ni and/or T phase (N i 3 A 1 )
Alternatively, by substituting some of the AI atoms to cause lattice strain in the T' phase, the precipitation strengthening effect of the γ' phase is enhanced. This effect appears when 0.5% or more is added, but adding a large amount weakens the base, so the upper limit is set at 10%.

Ti: 0.5 to 5% Ti, like the above Mo, is a component of Ni that constitutes the γ゛ phase.
By substituting some atoms or AI atoms, the precipitation strengthening effect of the T phase is enhanced. Further, it precipitates as a Ni3Ti phase and contributes to improving the base strength due to its precipitation strengthening effect. At least 0.5% is required to fully express this effect, and the effect becomes stronger as the amount added increases, but 5%
%, it becomes difficult to form an alloy layer as in the case of Al, so it was set to 0.5 to 5%.

W: 0.5 to 10% W, like Mo, replaces some of the Ni and AI atoms in the Ni and Al phases and enhances its precipitation strengthening effect.

This effect appears from 0.5%, but if it exceeds 10%, the base becomes brittle, so it was set at 0.5 to 10%.

Nb: 0.5 to 10% Nb also has the effect of enhancing the precipitation strengthening effect of the Ni3Al phase as described above, and also replaces the entire amount of A1 to form the Ni3Nb phase to strengthen the base. This effect is 0
．． It can be obtained by adding 5% or more, but if it exceeds 10%, the base becomes brittle. Therefore, the content was set at 0.5 to 10%.

In the body of the hearth roll of the present invention, a layer made of the Ni-based alloy is formed by overlay welding or the like on the surface of a metal cylindrical body prepared as a body base, and the Ni-based alloy layer is subjected to aging heat treatment. Manufactured by When forming a Ni-based alloy layer by overlay welding, any welding method may be used. For example, plasma powder welding may be applied to form metal powder (single Ni-based alloy powder) adjusted to a predetermined composition. In addition, a mixed powder made by blending two or more types of metal powder to have a predetermined composition may also be used) as a build-up material to form a bead in an inert atmosphere, and after welding, the bead surface is machined. In addition, it may be finished to a predetermined surface roughness. In addition, the Ni-based alloy layer can be formed by using a metal powder having a predetermined composition as a sintering material, and forming a compacted powder layer by hot pressing, hot isostatic pressing, or cold isostatic pressing. It can also be formed as a sintered body layer by a combination of formation and sintering, or a cast casting method can be applied to inject and solidify molten alloy around the metal cylinder that is the body base. It is also possible to form it by.

The aging heat treatment of the Ni-based alloy layer formed on the outer circumferential surface of the body base is performed at a temperature of about 600 to 900°C for an appropriate time (for example, 5
~15 hours) by heating and holding. By this aging heat treatment, Ni, AI, or a part of the Ni atoms and AI atoms become 'rt, Mo, W, N, in the γ phase base.
T” phase with a composition substituted with elements such as b, NiA
A metal structure in which intermetallic compound phases such as l phase and Ni3Ti phase are precipitated and dispersed is formed. The lower limit of the aging heat treatment temperature was set at 6°OoC in order to promote the precipitation and dispersion of the above-mentioned intermetallic compound phases, and the reason why the upper limit was set at 900°C is that if the aging heat treatment temperature is exceeded, the precipitated phase This is because coarsening, deformation of the roll body, etc. occur.

The body obtained through the aging heat treatment of the Ni-based alloy layer as described above is assembled into a hearth roll by combining it with a separately prepared roll shaft.

FIG. 1 shows an example of the cross-sectional structure of the hearth roll of the present invention. (10) is a body portion on which the heated steel material is supported;
(20) is a shaft attached to the body. The roll body (10) has a base body (11) which is a hollow metal cylinder.
and the Ni-based alloy layer (12) formed as a surface layer. The Ni-based alloy layer (12
) may have a layer thickness of about 1 to 10 mm. In addition,
In the figure, the roll shaft (20) is a long material that passes through the body (10), and has an internal water cooling structure with a cooling water passage hole (21) formed in its axial center. 20) and the body (10) are fitted together via spacers (30, 30), but of course this is just an example, and the shape of the roll shaft (20) and internal water cooling may vary. Structure and body (
The fitting structure etc. with 10) are not limited to this. In addition, the base body (11) of the body (10) and the shaft body (20
) is a heat-resistant alloy material conventionally used as a constituent material of this type of roll, such as 5CH13, 5C.
Any material having material characteristics necessary for the usage environment conditions, such as H22, may be selected and used.

〔Example〕

(1) Preparation of test material The roll body base (11) is a heat-resistant alloy (25Cr2O).
Overlay material for forming a hollow cylindrical body (outer diameter 130 mm, body length 480 mm) made of (Ni-INb-0, 4C-Fe, 5CH22 equivalent material) and a surface layer (12) made of Ni-based alloy by overlay welding. Prepare metal powder (average particle size: 101007z) adjusted to the prescribed composition and Jl composition, perform overlay welding on the surface of the base (11) by plasma powder welding method, and after welding, overlay welding on the surface of the overlay layer. The body (10) was manufactured by adding machining.

The layer thickness (after machining) of the built-up layer (12) is approximately 4 mm.

The roll body (10) is attached to a separately prepared roll shaft (
20, 20) via the spacer (30), and
It was assembled into the hearth roll shown in the figure.

(II) Build-up test The above-mentioned hearth roll was placed in a test furnace (furnace temperature 1150°C), and as shown in Fig. 2, the roll was rolled with an ordinary steel plate (S) placed on the surface of the roll body. was rotated at a rotational speed of 5 PPM, and the presence or absence of buildup on the surface of the book body (sintered body layer surface) after a total of 1000 hours of operation was visually observed.

Table 1 shows the composition of the body surface layer of each sample hearth roll and the results of the build-up test. In the table, No. 1 to 8 are
This is an example of the invention in which the surface layer of the body is composed of a sintered body layer having a predetermined composition according to the present invention. No. 101 and No. 102 are comparative examples, No. 101 is an example in which the roll body is a centrifugally cast hollow cylinder made of heat-resistant cast steel equivalent to 5CH22, which is a typical conventional hearth roll material, and No. 102 is an example ,
This is an example in which a Ni-Cr-A I-Y alloy coating layer was formed on the surface of the same hollow cylinder as the roll body base of No. 1 to 8. In addition, in the table, "Build-up resistance" column "
"○" indicates that no build-up occurred, "XX" indicates that significant build-up occurred, and "×" indicates that the build-up was slightly increased by 1" to the extent that it caused surface flaws on the steel plate. It means.

From this test result, the conventional hearth roll (No. 10
1) and the roll (No. 102) having a Ni = Cr-AI-Y system alloy coating layer, build-up cannot be avoided, whereas invention examples Nos. 1 to 8 cannot be avoided during high-temperature long-term operation. It can be seen that the material also has stable build-up resistance.

〔Effect of the invention〕

The hearth roll according to the present invention has excellent and stable build-up resistance even under high-temperature usage conditions of over 1000°C because the surface layer of the body is a Ni-based alloy layer having a certain composition and metal structure. have. In addition, the surface layer has strong adhesion to the body base and is unlikely to crack or peel. Therefore, it maintains a healthy surface without roughness over a long period of time, significantly reduces the cost and labor required for roll maintenance, improves the operating efficiency of heat treatment furnaces, and improves the surface quality and quality of steel to be treated.
Effective in improving yield.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a cross-sectional structure of a hearth roll according to the present invention, and FIG. 2 is an explanatory diagram showing a procedure for a build-up test related to an example. 10: Hearth roll body, 11: Body base, 12: Ni
Base alloy layer, 20: roll shaft, S: steel plate.

Claims (1)

[Claims] 1. Cr: 10 to 30 on the outer peripheral surface of the metal base of the roll body.
%, Co: 10 to 30%, Al: 3 to 15%, and after forming a Ni-based alloy layer consisting essentially of Ni, the Ni
A hearth roll for a heat treatment furnace with excellent build-up resistance, characterized in that an intermetallic compound phase is precipitated and dispersed in a γ-phase matrix by subjecting the base alloy layer to aging heat treatment at a temperature of 600 to 900°C. manufacturing method. 2. Cr: 10-30 on the outer peripheral surface of the metal base of the roll body
%, Co: 10-30%, Al: 3-15%, and M
o: 0.5-10%, Ti: 0.5-5%, W: 0.5
After forming a Ni-based alloy layer consisting of one or more elements selected from the group of Nb: 0.5 to 10%, a total amount of 10% or less, and the remainder substantially Ni, the Ni A hearth roll for a heat treatment furnace with excellent build-up resistance, characterized in that an intermetallic compound phase is precipitated and dispersed in a γ-phase matrix by subjecting the base alloy layer to aging heat treatment at a temperature of 600 to 900°C. manufacturing method.