JPH05315A - Hot lubricating method - Google Patents

Abstract

PURPOSE:To provide the method for forming a lubricating film which can prevent the seizure arising at the time of hot rolling iron and steel materials. CONSTITUTION:The solid powder of an alkaline metal oxide, etc., is supplied to the surface of a hot working material to cause the reaction of the scale layer formed on the surface of the hot working material and the solid powder and to melt the powder to form a molten film before the execution of hot working. This film is used at the lubricating film. The lubricating film is higher in reactivity as the material and adhesiveness than the conventional lubricants and, therefore, the effect of preventing the seizure is higher than the effect of the conventional lubricants.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to hot rolling or perforation of a steel material such as a thin plate, a thick plate, a bar steel and a steel pipe (ordinary steel, ultra low carbon steel, stainless steel, etc.) using a lubricant. The present invention relates to a hot lubrication method for carrying out the above process.

[0002]

2. Description of the Related Art Conventionally, as a lubricant used for hot working, a liquid lubricant in which one kind or a mixture of two or more kinds of mineral oil, synthetic ester, grease and the like is known (Japanese Patent Laid-Open No. 63-309590). Gazette). Also known is a lubricant prepared by mixing a solid powder (graphite, silicate, BN, iron oxide, etc.) with a liquid lubricant such as the mineral oil, synthetic ester, grease, etc. (Japanese Patent Laid-Open No. 63-230796). , JP-A-63-254195).

As a method of supplying the hot lubricant, a water injection method, a steam atomizing method, or an air atomizing method is used, and it is used for an inlet of a friction surface to be hot worked or a working tool such as a rolling roll or a plug for drilling. A method of attaching and supplying is known.

[0004]

The purpose of using a lubricant during hot working is mainly to prevent seizure that occurs on the friction surface between the working tool and the hot worked steel material, and to prevent wear of the working tool. Can be reduced. Since seizure has a great influence on the surface quality of steel products, it is desired to prevent it completely. It is generally said that this seizure occurs when a hot-worked steel material is processed, and a new surface generated due to an increase in surface area comes into contact with a processing tool. A hot lubricant is used to prevent seizure by preventing contact between the new surface and the processing tool.

However, the conventional hot-working lubricant or the method of supplying the lubricant cannot completely prevent seizure that occurs during working on the friction surface between the working tool and the hot-worked steel material. This is because the conventional liquid lubricant burns and disappears in the temperature range where hot working is performed. This is because the original lubrication effect cannot be exhibited. In order to make up for these drawbacks, a lubricant in which a solid powder is mixed with a liquid lubricant is also used. However, even with such a lubricant, a lubricating film cannot be stably formed on the newly-generated surface, so that a sufficient lubricating effect cannot be exhibited and baking cannot be completely prevented. Therefore, the present invention provides a lubricant capable of forming a stable lubricant film on a new surface generated during processing and a method of supplying the lubricant.

[0006]

In order to solve the above-mentioned problems, according to the present invention, before hot working,
It is characterized in that a lubricating film is formed on the surface of the hot-rolled steel material and then processed. A scale layer (oxide layer) is formed on the surface of the hot-worked steel material depending on the material temperature. When this oxide layer enters the working friction area, it may scratch the working tool, or may be pressed into the hot-worked steel material to become a flaw. Therefore, the hot working may be performed after removing the scale with a scale breaker before performing the hot working. In the present invention, Li ₂ O, K ₂ O, Na ₂ O, Ca
By supplying one or more kinds of solid powders of O, B ₂ O ₃ , CaF ₂ , SiO ₂ , and MnO ₂ to the surface of hot-worked steel, and reacting the supplied solid powder with the scale on the surface of the steel, The scale of the surface is modified into a molten oxide having a low melting point, and this molten oxide is used as a lubricating film.

Since the scale melt thus formed has a higher heat resistance than conventional lubricants, it does not burn out and disappear. The solid powder supplied here depends on the type of oxide formed on the surface of the hot-worked steel,
The kind of powder to be supplied and the proper value of the mixing ratio change. The scale layer formed on the surface of iron-based (including stainless steel) hot-worked steel is mainly composed of iron oxide. Depending on the type and amount of added elements, the oxide composition and film The thickness is different. For example, stainless steel is often a mixture of iron oxides and chromium oxides, or a complex oxide of iron and chromium.In carbon steel, the value of iron oxides depends on the carbon content. The number and film thickness are different.

As a solid powder which reacts with such an oxide and is melted, an oxide of an alkali metal works effectively,
The material is not limited to that, and boron oxide, fluoride, or salt may be used depending on the case. In any case, it may be a combination of solid powders that reacts with the oxides forming the scale to form a compound having a melting point equal to or lower than the temperature at which hot working is to be performed. The type and blending ratio can be arbitrarily selected. As a method of selection, the kind and blending ratio of elements that react with the scale constituent on the surface of the material to be processed can be determined with reference to the phase diagram of a binary system or a ternary system. Further, the solid powder does not have to be directly supplied to the surface of the steel material, but may be supplied in a state of being mixed with the liquid lubricant so as to be easily supplied.

On the other hand, in order to stably form a molten lubricating film that reacts with the scale by supplying such a lubricant to the surface of the hot-worked steel material, it is necessary to react the scale and the supplied solid powder completely. Must be processed. That is, the present invention cannot exert its sufficient effect unless the time required for the solid powder and the scale to completely react and melt is secured between the supply and the processing.
Further, even if the amount of the solid powder supplied is too small, it cannot react with the scale on the surface of the hot-worked steel material to form a sufficient lubricating film. Therefore, the relationship between the degree of reaction between the scale of the surface of the hot-worked steel and the solid powder and the reaction / melting time and the supply amount of the solid powder was investigated.

FIG. 1 shows the relationship between the amount of reaction between the excessively supplied solid powder and the scale (thickness of the scale corresponding to the amount of the solid powder reacted and melted) and the time after the supply. Shows the relationship between the scale film thickness on the surface of hot-worked steel and the supply amount of solid powder required to completely melt it. As is clear from FIG. 1, if the reaction time with the scale is 1 second, a molten coating sufficient to function as a lubricating coating can be obtained. Further, as is clear from FIG. 2, when 0.5 g or more of solid powder per 1 cm ^{2 of the} surface of the steel material is supplied, the required lubricating film can be obtained. Therefore, the moving speed of the hot-worked steel material and the supply location of the lubricant are specified so that processing is performed after 1 second or more has elapsed after the supply of the lubricant containing solid powder as the main component. For example, in the case of a hot-working steel material moving at a speed v (m / sec), the lubricant of the present invention (solid powder or a liquid lubricant containing a mixture of solid powders) is located v (m) before the processing location. )
The supply device may be installed to supply the lubricant. Alternatively, a method may be used in which after the lubricant is supplied, the movement is stopped for 1 second or more before the steel material is processed, and then the steel material is fed to the processed portion.

The lubricating film formed by the method according to the present invention has a reactivity and adhesion with a new surface generated when a hot-worked steel material is processed more than a lubricating film formed by a conventional method. As the new surface is generated, the lubricating film supplied to the working friction area is preferentially filled in the newly generated area at the same time as the new surface is generated, and it is possible to effectively prevent direct contact between the processing tool and the hot-worked steel material. It can be effectively prevented.

[0012]

[Example] 4Hi rolling mill (work roll diameter: φ150 m
m, cylinder length: 300 mm), SUS 430 steel material was rolled at 900 ° C. The steel material is 200m wide
A m, a length of 500 mm, and a thickness of 15 mm were used. This was placed in a heating furnace and held until the uniform temperature reached the center of the material. Then, this material was taken out of the heating furnace, and a powder (average particle size: 50 μm) in which Li ₂ O and B ₂ O ₃ were mixed in a weight ratio of 1: 1 on the surface (both front and back surfaces) of this material.
m), Na ₂ O (average particle size: 100 μm), Na ₂
Polybutene (viscosity 70 cSt) prepared by mixing O and SiO ₂ in a weight ratio of 3: 1 (average particle size: 40 μm)
Three kinds of lubricants, liquid lubricants dispersed by forced agitation, were supplied in an amount of ² g per 1 cm ² of the hot steel material, and rolling was carried out 3 seconds after the supply. Also,
For comparison, rolling was performed using the same material when a conventional mineral oil-based lubricant and a lubricant mixed with iron oxide were supplied during processing.

As a result, in the lubrication method using three kinds of lubricants according to the present invention, seizure on the roll and flaws on the surface of the material were not found even with a large reduction ratio, but with conventional lubricants. The seizure of the roll occurred, and the flaws on the surface of the material also occurred. Also, comparing rolling loads, compared to when rolling with conventional lubricant,
The rolling load is 15 when the rolling according to the present invention is performed.
%, And the rolling torque was reduced by 10% or more.

[0014]

EFFECTS OF THE INVENTION By using the present invention, the seizure between the working tool and the hot-worked steel material, the flaws of the product that occur with the seizure, and the load required for working are reduced as compared with the conventional lubrication method. By doing so, the wear of the working tool can be reduced.

[Brief description of drawings]

FIG. 1 shows the relationship between the amount of reaction between the excessively supplied solid powder and the scale (the film thickness of the scale corresponding to the amount reacted and melted with the solid powder) and the amount of time after the supply.

FIG. 2 shows the relationship between the scale film thickness on the surface of hot-worked steel and the supply amount of solid powder required to completely melt it.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display part // C10N 10:02 10:04 10:14 30:06 30:08 40:24 Z 8217-4H 50:08 80:00 (72) Inventor Fuyasu Yamamoto 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Central Research Division

Claims (4)

[Claims] 1. In a process of hot working a steel material, a solid powder or a liquid lubricant containing the solid powder is supplied to the surface of the hot worked steel material, and a scale (existing on the surface of the hot worked steel material ( A hot-lubrication method characterized by reacting with and melting an oxide) to form a lubricating film on the surface of hot-worked steel. 2. Li ₂ O, K ₂ as a solid powder to be supplied
O, Na ₂ O, CaO, B ₂ O ₃ , CaF ₂ , Si
The hot lubrication method according to claim 1, wherein one kind or a mixture of two or more kinds of O ₂ and MnO ₂ is used. 3. The hot lubrication according to claim 1, wherein the amount of solid powder supplied to the surface of the hot worked steel material is 0.5 g or more per 1 cm ^{2 of the} surface of the hot worked steel material. Method. 4. The method according to claim 1, wherein a time from supplying the solid powder to the surface of the hot worked steel material to performing hot working is 1 second or more. Hot lubrication method.