JP2005281748A - Material for coating surface of roll for steel sheet heat treatment furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for coating a surface of a roll for a steel sheet heat treatment furnace having excellent thermal impact resistance as well as pickup resistance. <P>SOLUTION: The newly developed material for coating a surface of a roll for a steel sheet heat treatment furnace thermally sprayed on the surface of a hearth roll in a heat treatment furnace is composed of a composite material having a composition comprising, by mass, 20 to 95% ceramics, and the balance one or more kinds of metals selected from Co, Ir, Ni and W with inevitable impurities, and, among the inevitable impurities, the total of easily oxidizable elements of Al, Cr, Mn, Si and Ta is ≤1% in particular. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface coating material for a steel sheet heat treatment furnace roll, and in particular, covers the surface of a roll (hereinafter referred to as a hearth roll) that continuously conveys a steel strip in an annealing furnace, and rolls from the steel strip. The present invention relates to a composite material effective for preventing so-called “pickup” such as iron oxide and iron powder on the surface.

  In general, in an annealing furnace for annealing a steel plate (steel strip), a number of hearth rolls are provided in order to continuously carry in, carry out, and carry out the steel strip. Since these hearth rolls are used continuously for a long period of time in an atmosphere of high temperature reduction or oxidation, the oxides, iron powder, etc. of the concentrated elements of the steel plate react, adhere and deposit on the surface. “Pickup” occurs. When this pick-up occurs, the pick-up is transferred to the surface of the steel strip conveyed by the hearth roll, and surface flaws are generated, so that the quality of the steel strip is remarkably deteriorated. Moreover, in order to prevent such quality deterioration, the problem also arises that the operation is interrupted and the hearth roll must be replaced.

For this reason, measures for preventing such pickup are conventionally applied to the surface of the hearth roll. Specifically, the surface of the roll is protected with a composite material composed of ceramics such as Al ₂ O ₃ and an alloy that bonds them (see Patent Documents 1 and 2), or ZrO ₂ or the like is formed on the upper surface of the bonding layer. A method of forming a ceramic layer is known (see Patent Document 3). Further, the surface is coated with a cermet-based thermal spray coating composed of Mo and ZrO ₂ (see Patent Document 4), ZrO ₂ : 60 to 95%, any one or more of CaC ₂ , Co, Ni, etc. A roll coated with the material to be included has also been proposed (see Patent Document 5). Furthermore, a technique is also disclosed in which the roll is spray-coated with a cermet layer containing 15 vol. Or more and less than 72 vol. Of silicon carbide, silicon nitride, or a compound thereof having a metal silicon content of 1 wt% or less (the balance W) (See Patent Document 6).
Japanese Unexamined Patent Publication No. 63-199857 JP-A-6-45863 JP 63-26183 A Japanese Unexamined Patent Publication No. 63-42324 JP-A-57-40885 JP 61-174317 A

However, the method such as the composite material of ceramic and alloy described above is excellent in wear resistance and peel resistance, but an easily oxidizable element such as Al or Cr contained in the alloy forms an oxide, and the steel plate (Band) Because of the mutual reaction with the oxide formed on the surface, there was a problem of poor pick-up resistance. In addition, the ZrO ₂ -based thermal spray coating is excellent in pick-up resistance, but is insufficient in toughness and thermal shock resistance, and is caused by temperature rise / fall in the annealing furnace and temperature difference generated between the steel plate contact surface and the non-contact surface. There was a problem of peeling due to thermal stress.

  In view of such circumstances, an object of the present invention is to provide a surface coating material for a steel sheet heat treatment furnace roll that is excellent not only in pick-up resistance but also in thermal shock resistance.

  The inventor has intensively studied to achieve the above object, and the results have been embodied in the present invention.

  That is, the present invention comprises one or more base metals selected from Co, Ir, Ni, Mo and W, ceramics dispersed in the base metal, and the balance of the inevitable impurities, and the content of the ceramics Is a surface coating material for a roll for a steel sheet heat treatment furnace, wherein the total amount of Al, Cr, Mn, Si, and Ta among the inevitable impurities is 20% by mass or less. In this case, the ceramic preferably contains partially stabilized zirconia or stabilized zirconia.

  Since the surface coating material of the steel sheet heat treatment furnace roll according to the present invention has excellent thermal shock resistance and pick-up resistance in a high temperature atmosphere, the reaction between the hearth roll and the steel sheet component is performed in an annealing furnace for heat treatment of the steel sheet. It became difficult to occur and the long-term durability of the hearth roll became possible. It should be noted that the present invention exerts a remarkable effect in extending the useful life even when applied not only to the hearth roll but also to a hearth hardware that requires the same function. is there.

  First, in the surface coating material for a steel sheet heat treatment furnace roll according to the present invention (hereinafter simply referred to as a surface coating material), Co, Ir, Ni, Mo containing inevitable impurities are used as the base metal for coating the surface of the hearth roll. , 1 or 2 types selected from W were employed. This is because these elements originally have excellent heat resistance at high temperatures and are essential metals for ensuring thermal shock resistance.

In addition, ceramics were further uniformly dispersed in these base metals to further improve pickup resistance. In this case, as the ceramic, in the present invention, oxide ceramics such as ZrO ₂ , Y ₂ O ₃ , YCrO ₃ , HfO ₂ , and ZrSiO ₄ , and boride ceramics such as CrB ₂ , TiB ₂ , ZrB ₂ , and HfB ₂ are used. , MoSi ₂ , Cr ₃ Si, TiSi _{2 and} other silicide ceramics, ZrC, Mo ₂ C, Cr ₃ C ₂ , HfC and other carbide ceramics, and ZrN, HfN, TiN and other nitride ceramics are used. it can. This is because these ceramics are extremely stable even at high temperatures and do not react with the steel plate components, so that the pick-up resistance of the hearth roll is well maintained.

  Moreover, the addition amount of ceramics shall be 20-95 mass%. This is because if the amount is 20% by mass or less, the effect of improving pick-up resistance is small, while if it exceeds 95% by mass, the thermal shock resistance is lowered.

The important point of the present invention is that, in addition to the above two requirements, among the inevitable impure elements associated with the base metal, in particular, the oxidizable elements of Al, Cr, Mn, Si and Ta are severely restricted. It is. According to the inventor's investigation, when these elements (excluding Al, Cr, Mn, and Si constituting the ceramic) are present, the heat treatment furnace is usually an inert atmosphere of 3% H ₂ -N ₂ , This is because it is considered that a substance causing a pickup is easily formed by reacting with a small amount of oxide contained in the steel strip in contact therewith. Then, when it examined focusing on those content, if a total content is 1 mass% or less, it will not produce a reaction with the ingredient which the steel plate which contacts a hearth roll and runs contains. The present invention was completed by adding a heading and limiting the amount thereof.

In the above-described surface coating material according to the present invention, ZrO ₂ is selected as the ceramic, and CaO, MgO, K ₂ O ₃ , CeO ₂ , Y ₂ O _{3 and the} like are added to the so-called “partially stabilized zirconia”. Alternatively, “stabilized zirconia” is preferably contained. This is because the crystal form of ZrO ₂ is changed from the monoclinic system to the cubic system, the volume change due to temperature is relaxed, and the thermal shock resistance can be improved.

  Hereinafter, the characteristics of the surface coating material (hereinafter simply referred to as the surface coating material) of the steel sheet heat treatment furnace roll according to the present invention will be described in Examples.

  The left column of Table 1 shows the component composition of the prototype surface coating material. No. Nos. 1 to 20 are examples of the present invention. Reference numerals 21 to 30 are comparison columns that deviate from the requirements of the present invention (the requirements that deviate are underlined). Of the comparative examples, No. Reference numeral 30 denotes a conventional representative surface coating material.

These prototype materials are sprayed onto the surface of a 40 mm wide x 40 mm long x 15 mm thick SUS310 plate to produce a large number of test pieces, and the results are evaluated by performing a pick-up resistance test and a thermal shock test at high temperatures. The effect of the present invention was confirmed. The test conditions are as follows, and the evaluation results are collectively shown in the right column of Table 1.
(Pickup resistance test)
Test Method: As shown in FIG. 1, the pick-up source 3 is sandwiched between the test pieces 2, held in the atmosphere furnace 1 at 1000 ° C. for 100 hours, and then the reaction state between the sprayed coating on the surface of the test piece 2 and the pick-up source 3 To evaluate.

Test temperature: 1000 ° C
Pickup source: FeO, MnO, SiO ₂ powder sprayed on the surface of high-tensile steel plate Load: 2kg
Holding time: 100Hr
Atmosphere: 3% H ₂ —N ₂
Evaluation: The area ratio of the pickup generated on each test piece was measured by an optical microscope and calculated.
(Thermal shock test)
Test method: The test piece is held at 1000 ° C. for 30 minutes, then dropped into water, and the test piece is pulled up from the water until the sprayed surface coating material is peeled off.

Test atmosphere: In the air Evaluation: Number of times until peeling occurs

  From Table 1, it is apparent that the surface coating material according to the present invention is superior to the surface coating material of the comparative example (No. 30) that has been used conventionally in terms of pick-up resistance and thermal shock resistance.

It is a figure which shows an anti-pickup test method.

Explanation of symbols

1 Atmosphere furnace 2 Test piece 3 Pickup source

Claims (2)

  It consists of a base metal composed of one or more selected from Co, Ir, Ni, Mo, W, ceramics dispersed in the base metal, and the remaining inevitable impurities, and the content of the ceramic is 20 to 95% by mass A surface coating material for a steel sheet heat treatment furnace roll, wherein the total amount of Al, Cr, Mn, Si and Ta among the inevitable impurities is 1% by mass or less.   2. The surface coating material for a roll for a steel sheet heat treatment furnace according to claim 1, wherein the ceramic contains partially stabilized zirconia or stabilized zirconia.

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