JPS62133054A - Antioxidant for heat treatment of titanium - Google Patents

Abstract

PURPOSE:To prevent oxide scales from occurring on the surface of a Ti material by applying a top coat composed mainly of oxides of high-m.p. metals and an under coat having SiO2 and B2O3 as matrix in heating a Ti material in a heating furnace, etc. CONSTITUTION:The Ti material is heated to 890-930 deg.C in a heating furnace with oxidizing atmosphere as in the case of hot rolling. At this time, in order to prevent the formation of oxide scales on the Ti material surface, the inner coat prepared by forming a powder of oxides of high-m.p. metals such as MgO, ZrO2, Al2O3, etc., into slurry condition by use of a binder such as starch, PVA, water glass, etc., is applied and then dried. Next, a powder mixture having, by weight, 35-70% (SiO2+B2O3) as matrix and further containing two or more kinds among 0-20% F, 0-30% oxides of alkaline earths, 0-40% oxides of alkali metals, and 0-15% (Al2O3+ZrO2) is formed into slurry condition by use of above-mentioned binder, which is applied as outer coat onto the above- mentioned coat. In this way, formation of oxide scales of Ti caused by heating in an oxidizing atmosphere can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an antioxidant suitable for preventing the formation of oxide scale on titanium during heating of titanium in a general oxidizing atmosphere furnace.

(Prior art) Like general steel, titanium is heated to a heat treatment temperature (generally 890 to 930°C) higher than the α→β transformation temperature (882°C) in a heating furnace prior to rolling. When heated or when using a general oxidizing atmosphere furnace, the oxidation rate is much faster than that of steel, and a # scale layer is formed.

This scale is difficult to completely peel off during descaling before rolling, has higher hardness than base metal, has poor malleability, and causes scale defects on the top of the product surface during rolling. This requires extra work in the process, and at the same time, a drop in yield due to grinding becomes unavoidable.

Such losses are significant.

For this reason, various attempts have been made to use antioxidants before heating for titanium, as in steel, but titanium oxidizes at a much faster rate than steel, and antioxidants have no effect.
It has not been put into practical use until now. Therefore, heating titanium is
It is customary to carry out the process in a vacuum or in a non-oxidizing atmosphere-controlled furnace.

(Problems and Structure of the Invention) In view of the above-mentioned points, an object of the present invention is to prevent the generation of oxide scale during heating of titanium using a special antioxidant, and its structure is as follows. . That is, (1) a primer containing a high melting point metal oxide;
An antioxidant for titanium heat treatment consisting of iOz+ I12 island (material and a topcoat whose pour point is below the heat treatment temperature of titanium) (2) a basecoat whose main component is a high melting point metal oxide, and Si
O2+8%, 0++ 35-70wtX, and 0 fluorine
~20wt$, alkali metal oxide O~40wt$, alkaline earth oxide'jJ1g.

~30wt%, AI□0*”Zr0z O~15wt
This is an antioxidant for titanium heat treatment consisting of an overcoating agent whose main components are any two or more of the following: and whose pour point is below the heat treatment temperature of titanium.

(Function) As mentioned above, the antioxidant of the present invention is composed of a top coat and a base coat, and by melting the top coat in a heating furnace, the molten film completely shields the titanium base metal and atmospheric gas. In addition, the high-melting point top coat does not melt in the heating furnace, preventing fusion and reaction between the upper molten film and the titanium base metal, and also prevents the high-melting point undercoat from melting in the heating furnace. Due to the presence of the layer, the antioxidant can be easily peeled off and removed.
It will be completely doable.

(Details of the Invention) The present invention will be explained in detail below. 6 The antioxidant of the present invention basically consists of a primer containing a high-melting point metal oxide as a main component and a flowable material based on SiO2+8°0.3. It consists of two layers with a topcoat that is below the heat treatment temperature of titanium. In particular, when the antioxidant of the present invention is applied to a titanium base metal and placed in a heating furnace, the topcoat quickly melts to form a film layer, and has appropriate wettability (surface tension) for the basecoat layer. It also has the property of shielding the titanium metal from contact with oxygen (and nitrogen and carbon oxide gas) in the heating furnace atmosphere and preventing oxidation of titanium.

A preferred component of the top coat is 5i02+ 11 as the base material.
20° Contains 35 to 70 wt, χ, and 0 to fluorine
20wt$, alkali metal oxide glue O~40wt$, upper alkali oxide 0~:10wt$, Al2O:+”Z
It contains any two components of rO20~15wt$. Furthermore, the pour point of this top coat must be lower than the heat treatment temperature of titanium.

S i02 + 8203 as a base material is: 15wt
If it is less than 1, it will be difficult to form a melted film, and 70wt$
If the amount is too high, it will be difficult due to the relationship with other ingredients. Also, fluorine.

Alkali metal oxides and alkaline earth oxides have wave points,
Viscosity 1: These are added to adjust the surface tension, but if each upper limit is exceeded, the pour point and viscosity will decrease, making it impossible to maintain a sufficiently thick and uniform molten film in the heating furnace, and preventing oxidation. I can't wait anymore. Furthermore, a reaction occurs between the molten film and the primer, making it impossible to maintain a proper molten film, and furthermore, fusion between the titanium metal and the molten film occurs, resulting in oxidation in the deska link after heat treatment. Since it would be difficult to completely remove the inhibitor, each upper limit was defined as described above.

AIz03. ZrO2 is mainly blended to adjust the pour point and viscosity, and if it exceeds the limit value, crystals tend to precipitate, making it difficult to maintain a molten film. For these reasons, the top coating agent is limited to the above components.

In addition, when titanium metal coated with a second coat is processed in a heating furnace and then sent to the descaling process to be cooled, even if the second coat cools down properly, the freezing point of the top coat may be affected by the heat treatment. It has been experimentally confirmed that if the temperature is higher than 300°C subtracted from the temperature, the antioxidant can be removed without any problems using the descason. In addition, the fluorine in the formulation is N
It is formulated in the form of compounds such as aF, CaF, and Na5AII'6.

The primer is used to prevent fusion between the top coat and the titanium base metal melted in the heating furnace, and to completely remove the antioxidant during the scaling after the heating furnace. It is used between the base metal and the top coat to prevent the base metal from reacting and forming scale.

Therefore, the top coat is a molten top coat that has poor reactivity and has a moderate surface tension. Is it a high melting point metal oxide with a low level?8
It is yellow. Examples of such materials include MgO, Z
rO□, he1203, etc. are desirable. In addition, Mg0,2r
02°Δ1203 does not need to be a pure substance, as long as it satisfies the characteristics of a high melting point metal oxide.

It may be a mixture with other substances.

In addition to the main components of the undercoat and topcoat described above, binders, surfactants, etc. may be added as necessary. As the binder, starch, p, v, Δ6, water glass, etc. are used.

The method of applying the antioxidant 11Z agent is to apply the top coat and base coat each per liter.
Add 0.5 to 5 wt$ of binder to the fine powder, make a slurry, apply a primer to the titanium metal, and after drying, apply a top coat! Ii After being washed and dried, it is inserted into a heating furnace.

(Example) Table 1 below shows an example of a titanium slab that was coated with the antioxidant of the present invention and then heated at 900°C for 3 hours in a general heating furnace.
Shown below.

In Table 1, No. A to D are examples of the present invention, and No. E to D are examples of the present invention.
There are comparative bite examples, and E to H are cases where only the primer is used, ■
If the melting point of the paint is lower than the melting point of the paint, and if the pour point of the paint is higher than the heat treatment temperature of titanium, then the K is - the paint contains 820:1 of SiO2+. Indicate the case. All of the comparative examples failed in the overall evaluation.

(Effects of 95If) As explained above, the anti-oxidation agent of the present invention can coat the titanium base metal well to prevent oxidation when the titanium is heated, and can be easily peeled off during descaling. Its practical and industrial value is enormous.

Claims (2)

[Claims] (1) An undercoat mainly composed of a high melting point metal oxide and a Si
An antioxidant for titanium heat treatment consisting of O_2+B_2O_3 as a base material and a top coating agent having a pour point below the heat treatment temperature of titanium. (2) Undercoating agent mainly composed of high melting point metal oxide and Si
O_2+B_2O_335-70wt%, and 0 fluorine
~20wt%, alkali metal oxides 0-40wt%, alkaline earth oxides 0-30wt%, Al_2O_3+Z
An antioxidant for titanium heat treatment consisting of an overcoating agent which mainly contains any two or more of rO_20 to 15 wt% and has a pour point below the heat treatment temperature of titanium.