JPS6237314A - Roll for heat treating furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a roll that is disposed in a heat treatment furnace and conveys a material to be heat treated, which has excellent wear resistance and prevents build-up. The present invention relates to a heat treatment furnace roll (hereinafter referred to as a hearth roll).

(Prior art) For example, when continuously annealing a steel plate, 300 to 12O0℃
The steel sheets are passed through an oxidizing or reducing atmosphere, but since the hearth rolls used to transport the steel sheets are used continuously for long periods of time, their surfaces are subject to wear and tear. Adhering oxides or iron powder are deposited on the surface of the nozzle roll, forming what is called a build-up.

When such wear, pill doors, and bulges occur, the surface of the steel sheet is damaged while it is being conveyed on the hearth rolls, causing deterioration of the quality of the steel sheet, and sometimes immediately interrupting production operations. The surface of the hearth roll is forced to be ground and maintained.

For this reason, we have changed the material of hearth rolls from the past.
Alternatively, as described in Japanese Patent Publication No. 57-29549, attempts have been made to thermally spray zirconia', alumina, etc. onto the roll surface.

However, many of these known attempts have not been able to be fully satisfactory in terms of hot wear resistance or prevention of pill door formation. -2661 publication, Cr2O3 is 30 to 7
A heat-treated roll formed with a coating layer of an inorganic material containing 0% and the remainder consisting of At2O3, and patent application No. 59-14417
No. 6 contains 70 to 90 Cr2O3, and the remainder is At2O.
．． We have provided a heat-treated roll in which a coating 1 of an inorganic material made into a solid solution is formed.

(Problems to be Solved by the Invention) The present invention solves the problem of Cr2O3-At2Os of a hearth roll coating layer consisting of CrO and At2O3, which is a prior invention.
As a result of examining the composition of the solid solution and contaminant components,
The purpose of the present invention is to invent and provide a hearth roll having better pill resistance and spill resistance than the prior invention.

(Means for solving the problems) The present invention provides Cr2O5 with an Nl ratio in the range of 1:9 to 9:1.
This is a hearth roll having a surface layer containing -At2O5 solid solution of 97 weight i (4 or more), metal Cr being 0.5% by weight or less, and the remainder consisting of unavoidable impurities.

The present invention will be explained in detail below.

In general, At2O3 (melting point 2O45°C), Cr2O3 (
(melting point: 2275°C) has a high melting point, poor reactivity with metals, high hardness, and wear resistance.

However, Cr2O and At2o3 are present on the surface of the hearth roll.
When a coating layer is formed, if it is used at a temperature of 700° C. or higher and the temperature is lowered, peeling occurs during the first thermal history, making it difficult to use as a hearth roll. As a countermeasure for this, Cr2O3
We have focused on the fact that and At2O3 form a complete solid solution over the entire region. So Cr2O3 has A, /,
2O. It has been found that by dissolving 10 to 9 ON in solid solution, the coating becomes thermally stable and peeling of the coating is suppressed. Therefore, Cr2O3-At2 with a weight ratio in the range of 1:9 to 9:1.
Various types of coating layers made of O5 solid solution have been used as hearth rolls, but in some cases build-up occurs between the rolls, while in others no build-up occurs at all. Therefore, as a result of intensive studies on the pill door mechanism, we found that 0 metal Cr was present in the Cr, O, -At2O3 solid bath.
．． It was found that build-up occurs when the amount exceeds 5%.

Next, Table 1 shows the results of the peel resistance test and Table 2 shows the results of the build-up test, which were used as the basis for the numerical limitations of the coating material according to the present invention. Peeling resistance test is 5C) 12 of 30X50X5W
2 A sample in which a coating layer of various Cr2O3-At2O3 solid solutions was formed (sprayed) on the outermost surface of cast steel was heated at 100°-c x
Peeling resistance was determined by repeatedly immersing the sample in water after heating for a o minutes and checking the number of times peeling occurred. In the build-up test, iron oxide powder, which is the raw material for the pill door, is placed between two flat plates of the sample prepared using the same procedure as the peeling resistance test, and a load is applied on top of the iron oxide powder. The raw material and the two flat plates were rubbed together, the atmosphere was adjusted to N2 (95 degrees) -) I2 (5 degrees), heated at 1000°C for 5 hours, and after cooling, the surface of the coating layer The condition was observed and the pill door and f properties were determined.

As can be seen from this result, in the Cr2O3-At2O3 solid solution, the ratio of the solid solution is 1:9 to 1:9 as shown in A3 to 5.
It can be seen that in the range of 9:1, durability is exhibited for 10 times or more, and peeling resistance is significantly improved.

In addition, cr2O3-At2O of the coating layer used in this test
s Ib The composition other than the solid solution is C that has not been made into a solid solution.
r2O3, At2O5 and SIO, which is an unavoidable impurity,
Tt02. Cab.

MgO, Fe2O3, etc.

The composition of Cr2O3-At2O3 solid solution is 1:9 by weight
In the range of ~9:1, the Cr2O3-Al2O3 solid solution
It can be seen that when the test is performed on a 7-weight plate and the metal Cr content is 0.5% by weight or less, build-up is less likely to occur.

(AIo, 11, 12.15, 16, 17.19.2O
．． 21) Among them, especially when the metal Cr content is less than 0.2 weight coefficient, it becomes extremely small (11.12, 16, 1
7.2O°21), and when the metal Cr content was 0.01% or less, no buildup was observed in experiments.

In addition, Cr2O, -At2O. Techniques for reducing metallic Cr in the solid solution include, for example, methods of performing oxidation treatment, pickling, etc. in the manufacturing process of the solid solution powder, and methods of suppressing reduction of Cr2O3 by using a non-reducing atmosphere during thermal spraying. .

Examples will be described below.

(Example) The outermost surface of a roll made of heat-resistant n-steel was coated with &11°17. shown in Table 2.
A coated layer of 2O and flat plate 14 was formed by thermal spraying, and ground to a surface smoothness of 100 μm or less to obtain a roll for a heat treatment furnace. Furthermore, as a conventional product, we have prepared a roll made of heat-resistant cast steel.

The above five types of rolls for heat treatment furnaces are used in actual steel sheet heat treatment furnaces (
Table 3 shows the results of use for 3000 hours at a temperature of SOO to 1050°C and N2-) (in a 2-H2O atmosphere).

As can be seen from Table 3, no build-up was observed in the product of the present invention even after use for 3,000 hours.

(Effects of the Invention) As shown in the above examples, the pill-resistant and pill-resistant covering skin of the present invention does not cause build-up even when used for a long time, contributing to extending the life of the roll. .

Claims (1)

[Claims] Cr_2O_3-Al in the range of 1:9 to 9:1 by weight
Contains 97% by weight or more of _2O_3 solid solution and contains metal C
A roll for a heat treatment furnace having a surface layer in which r is 0.5% by weight or less and the remainder consists of unavoidable impurities.