JPH0770576A - Lubricant composition for hot rolling - Google Patents

Abstract

PURPOSE:To obtain a lubricant compsn. which does not cause slipping, prevents seizure to a roll, and greatly reduces the abrasion of a rolling roll on hot-rolling steel materials including stainless steel. CONSTITUTION:The compsn. for metal is obtd. by incorporating 1-30wt.% (based on the compsn.) fine solid particles (e.g. a carbonate, an oxide, silica, a carbide, a nitride, a sulfide, or a fluoride) having particle sizes of 20-1,000Angstrom , pref. 20-500Angstrom , into a lubricant base oil.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lubricant composition for hot working of steel materials, particularly steel sheet rolling, shaped steel rolling, wire rolling,
The present invention relates to a lubricant composition for hot rolling, which exhibits a lubricating effect such as seizure prevention and wear reduction without causing slippage in hole rolling such as pipe making.

[0002]

2. Description of the Related Art When various materials are hot-rolled and the material to be rolled is baked on a rolling roll, various surface roughness occurs on the surface of the rolling roll, which is printed on the surface of the steel and causes surface defects.
To deal with the occurrence of surface flaws, we are dealing with flaws such as polishing work of steel materials that requires a significant increase in man-hours and setting severe rolling restrictions. This leads to high costs. As a method of preventing such seizure, use of hot rolling oil, optimization of roll cooling, review of rolling operation conditions, and the like have been conventionally considered.

A flaw on the surface of a steel material caused by seizure is a serious problem particularly in hot rolling of stainless steel. Stainless steel is generally 13% or more by weight
It has a chemical composition containing Cr, and thereby exhibits excellent corrosion resistance and oxidation resistance, but has a thin oxide scale on the surface and high resistance to hot deformation. Therefore, during hot rolling, it is easy to make contact between the rolling roll and the metal, resulting in seizure and surface flaws in the steel material.

However, the problem of seizure is not limited to hot rolling of stainless steel, but may occur in hot rolling of ordinary steel or special steel. That is,
In recent years, while high productivity, high quality, and low cost have been aimed at, high-speed and high-pressure rolling has been carried out more than ever. For this reason, the rolling load increases, and seizure easily occurs. Further, recently, due to the development of schedule-free rolling, new hot rolling mills, new wear-resistant rolls, etc., seizure prevention has become more important than ever.

In order to deal with this problem, a rolling roll or its reinforcing roll is used for the purpose of reducing the frictional force between the rolling roll and the steel material to be rolled, preventing the surface of the roll from being roughened or worn, and improving the quality of the rolled product. The supply of lubricant has been proposed and has been practiced.

As an anti-seizure lubricant used in the hot rolling of ordinary steel, a lubricant containing a solid lubricating substance such as graphite, MoS ₂ or mica has been proposed. However, although this lubricant certainly reduces wear, it does not allow the amount of lubricant applied per unit time to increase because slippage occurs when a large amount is applied to the rolls, and seizure is still prevented. It was difficult.

As a lubricant for hot rolling of stainless steel, one in which iron oxide powder is dispersed in lubricating oil is disclosed in JP-A-63-254195, and graphite powder is disclosed in JP-A-1-167396. Those dispersed in a viscous aqueous solution have been proposed.

Further, as a lubricant for hot rolling commonly used for stainless steel and ordinary steel, JP-A-4-130194 and JP-A-4-13194 have been used.
[0195] Each of the publications discloses a lubricant for hot rolling in which inorganic fine particles having an average particle size of about 1 µm are dispersed in a viscous aqueous solution of 1 to 30% by weight. Further, JP-A-4-277595 discloses a lubricant for hot rolling containing 5 to 50% by weight of ceramic powder having an average particle size of 1 to 5 μm and a Vickers hardness of 1500 or more.

However, even these cannot completely prevent the direct metal contact between the rolling roll and the steel material to be rolled, so that the effect of sufficiently preventing the seizure on the roll and the abrasion of the roll cannot be obtained. Was the actual situation.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the material to be rolled from seizing on the surface of a rolling roll without causing slip in hot rolling of various steel materials including stainless steel, and at the same time, to prevent the material from rolling. It is an object of the present invention to provide a lubricant composition capable of significantly reducing wear, thereby improving rolled product quality and working efficiency.

[0011]

Means for Solving the Problems As a result of earnest studies for achieving the above object, the present inventor has found that the particle size is 20 to 1000Å
A lubricant composition containing a high proportion of ultrafine particles (that is, 0.002 to 0.1 μm) is effective for preventing a direct contact state between a rolling roll and a steel material to be rolled in a hot rolling process. We have found that we can achieve the purpose.

According to the present invention, solid fine particles occupying 80% by weight or more of particles having a particle size of 20 to 1000Å are added based on the total weight of the composition.
A lubricant composition for hot rolling of metals, characterized in that the lubricant composition is contained in an amount of ˜30 wt%.

The lubricant composition of the present invention can be applied to hot rolling of both stainless steel and plain steel, thereby preventing seizure of the steel material on the rolling roll without causing slip and Wear is greatly reduced. As a result, good rolled product quality can be obtained and at the same time,
There is no need to increase man-hours due to flaw maintenance or restrictions on rolling conditions, and the rolling frequency is significantly reduced due to the reduced roll change frequency due to extended roll life.

[0014]

First, the lubricant composition of the present invention is characterized in that it contains 1 to 30% by weight of solid fine particles having a particle size of 20 to 1000Å, which are colloidal particles, based on the total weight of the composition. is there. The particle size of such colloidal particles is, for example, Brownian motion / dispersed state in a liquid medium (eg, base oil).
It can be measured by photon correlation molecular spectroscopy. In addition, it is not necessary to make all the fine particles have a particle size in the range of 20 to 1000Å, and the effect of the present invention can be obtained if 80% by weight or more of the whole particles are in this particle size range. Hereinafter, although not particularly mentioned, the description regarding the particle diameter is intended for 80% by weight or more of all particles.

The smaller the particle size of solid particles, the more
It is introduced into the fine surface irregularities of the friction interface between the roll and the steel material, but when the particle size becomes 1000 Å or less, direct contact between the metal of the roll and the steel material is prevented to the level of surface roughness. It turned out to be possible. Thereby,
It is considered that unlike a conventional lubricant composition using particles having an average particle size of about 1 μm, seizure of a steel material on a roll and reduction of roll wear can be sufficiently prevented.

Moreover, since the state of direct contact between metals is prevented by introducing fine particles to the interface to prevent seizure, slippage, etc. is different from seizure prevention due to a decrease in friction coefficient using a solid lubricant. No solid biting is involved, so that the solid fine particles can be blended in the lubricant composition in an amount such that a sufficient seizure prevention effect and roll wear reduction effect can be obtained.

If the particle size of the particles exceeds 1000 Å, direct contact between the metals occurs at least at the surface roughness level, seizure cannot be sufficiently prevented, and roll wear also increases. On the other hand, when the particle size is less than 20Å, the solid fine particles tend to aggregate. When coarse secondary particles are formed due to aggregation, it becomes difficult to prevent direct contact between metals by fine particles, and the seizure prevention effect is insufficient. The preferable particle size range of the solid fine particles is 20 to 500 Å.

When the content of solid fine particles is less than 1% by weight,
The amount of fine particles is too small to obtain the desired effect, while
If the content exceeds 30% by weight, problems will occur in uniform dispersibility in the lubricant base oil and the effect will be saturated. The content of the solid fine particles is preferably 5 to 25% by weight.

The type of solid ultrafine particles is not particularly limited as long as it can exist as a solid at the hot rolling temperature. Examples of suitable solid ultrafine particles include inorganic substances such as carbonates, silicates, oxides, carbides, nitrides, sulfides and fluorides, and it is preferable to use one or more of these. it can.

Examples of carbonates are alkali metal and alkaline earth metal carbonates such as Na ₂ CO ₃ , CaCO ₃ , MgCO ₃ . Examples of silicates are MxO ・ ySiO ₂ (M: alkali metal,
Alkaline earth metal). Examples of oxides include Al ₂ O ₃ , T
iO ₂ , NiO, Cr ₂ O ₃ , CaO, ZnO, SnO, CdO, PdO, Bi ₂ O ₃ , Li
₂ O, K ₂ O, Na ₂ O, B ₂ O ₃ , SiO ₂ , MnO ₂ , ZrO ₂ and the like.
Examples of carbides include SiC and TiC, and examples of nitrides include TiN and B
Examples of N, AlN, Si ₃ N _{4 and the} like, examples of sulfides include MoS ₂ and PbS, and examples of fluorides include CaF ₂ .

The surface of these solid fine particles is preferably treated with an organic substance (eg, petroleum sulfonic acid) to form a modified colloidal dispersion whose surface is lipophilically modified.
Accordingly, a large amount of solid fine particles can be contained in the base oil with good dispersibility even if the viscosity of the base oil is low by simply dispersing the lubricant in the base oil. Examples of such solid particles which have been surface-modified include commercially available basic and highly basic metal salt sulfonates, highly basic metal salt phenates, and modified silica colloids.

Other types of solid fine particles are commercially available as, for example, colloids, or those obtained by a known fine particle production method such as a gas phase method are surface-modified as necessary as described above. It can be used by doing.

When the lubricant composition of the present invention is basic, the effects of preventing seizure and reducing roll wear are further enhanced.
When the total base number (value determined by potentiometric JIS K2501) of the lubricant composition is 40 mgKOH / g or more, particularly 100 mgKOH / g or more, the seizure prevention effect becomes very remarkable. It is presumed that if the lubricant has a basic property, the reactivity with the oxide scale that is likely to be generated on the surface of the steel material during hot working is enhanced, and the lubricating effect is further enhanced.

However, even if the lubricant composition is acidic, the particle size is
If the content of the fine particles of 20 to 1000Å is 1 to 30% by weight, the effect of preventing seizure and the effect of reducing roll wear can be sufficiently obtained, though it is lower than that of the basic composition.

Therefore, the basicity or acidity of the lubricant composition can be selected according to the likelihood of seizure of the hot rolling applied. For example, when seizure is very likely to occur, such as hot rolling of stainless steel under high load conditions, by using a highly basic lubricant composition having a base number of 100 mgKOH / g or more, It is possible to effectively prevent seizure. On the contrary, in hot rolling of ordinary steel and hot rolling of stainless steel where the rolling load is not severe, even with a basic lubricant composition or acidic lubricant composition with a lower base number, seizure prevention and roll wear reduction The effect of is fully obtained.

The lubricant composition of the present invention can be produced by dispersing fine particles having a particle size of 20 to 1000Å in the lubricant base oil in a proportion of 1 to 30% by weight based on the total weight.

The lubricant base oil may be one commonly used as a hot rolling oil, and is one of fats and oils such as mineral oil, synthetic lubricating oil, rapeseed oil and lard oil, and higher fats and esters thereof. Alternatively, two or more kinds can be used. Alternatively, a commercially available hot rolling oil may be used as it is. Further, instead of the lubricant base oil, a viscous aqueous solution containing a thickener may be used.

The lubricant composition of the present invention comprises, in addition to the above-mentioned solid fine particles and base oil, one kind or two kinds if necessary.
It may contain one or more additives. Such additives can be selected from those commonly added to lubricant compositions. Suitable additives include extreme pressure additives, antioxidants, pour point depressants, viscosity index improvers and the like.

Examples of extreme pressure additives include sulfur-based extreme pressure additives such as sulfurized fats and oils, sulfurized mineral oils, dinonyl polysulfide, and tricresyl phosphate, dioctyl phosphate, and phosphoric acid extreme pressure additives. . Examples of antioxidants include bisphenols such as methylene-4,4'-bis (2,6-di-tert-butylphenol), alkylphenols such as di-tert-butylcresol, naphthylamines and the like. Examples of pour point depressants and viscosity index improvers include polyacrylates, olefin polymers, polymethacrylates, polyolefins and the like.

These additives may be added within the range of conventionally known blending amounts, but it is generally preferable that the amount of each additive is as small as 5% by weight or less based on the total weight of the lubricant composition. Also, all solid particles have a particle size of 20 to 1000Å
It is most desirable to use solid fine particles, but as mentioned above, other particle sizes (particle size less than 20Å or more than 1000Å)
The solid particles may be coexistent in a small amount of 20% by weight or less of the whole.

The lubricant composition of the present invention contains not only ordinary stainless steel represented by JIS SUS304 but also 20% by weight of Cr.
Even in the hot rolling of the high-corrosion high-purity ferritic stainless steel containing the above, the effect is remarkably exhibited. Needless to say, the same effect can be obtained by using it as a lubricant for hot rolling of metal materials such as carbon steel, Ti and Al. Also, the type of hot rolling is not limited to plate rolling such as thick plate and thin plate, but steel pipes with hole type rolls,
The lubricant composition of the present invention can be applied to rolling of shaped steel, rolling of H-shaped steel with a universal mill, and hot rolling into various forms such as bar steel and wire rod.

The lubricant composition of the present invention can be supplied by various conventionally known methods. That is, depending on the viscosity and concentration required, an air atomization method that mixes with compressed air and supplies in the form of a spray, a water injection method that mixes with water and supplies, and steam that atomizes with heated steam and supplies. An atomizing method or the like is possible, and any method can obtain the remarkable lubricating effect of the present invention. Of course, a method of supplying the undiluted solution as it is may be used, or a general oil supply method other than the above may be used. Further, the supply of the lubricant composition may be carried out directly on the rolling roll or may be carried out via the reinforcing roll. Further, the lubricant composition does not necessarily have to be supplied to the entire surface of the rolling roll, and may be supplied only to a portion where seizure is likely to occur.

[0033]

EXAMPLE Next, a specific example will be described. The particle size of the solid particles in the examples is measured by the centrifugal sedimentation method, and then the particles having a particle size of 1 μm or less are sub-micron particle size analyzer by Brownian motion / photon correlation molecular spectroscopy. (Made by Couter Electronics, Inc.
COUTER N4 type) and larger particles were measured with a Shimadzu laser diffraction particle size distribution analyzer (SALD-3000).

The lubricant composition used in each example is shown in Table 1.
Inventive Example Nos. 1 to 10 having the composition shown in Comparative Example No. 11 to
There were 14 compositions of 14 kinds. These were prepared by mixing solid particles and liquid components (both are commercial products blended) with a homomixer. No other additives were blended.

The liquid components used are as follows. Commercial hot rolling oil: paraffinic mineral oil + fats and oils (beef tallow) +
Sulfurized fats and oils (viscosity 100 cSt / 40 ℃) High viscosity mineral oil: Paraffinic mineral oil (viscosity 230 cSt /
40 ° C) Polymer compound-added oil: Synthetic ester oil + polyacrylate Viscous aqueous solution: Water containing acrylic acid polymer as a thickener

[0036]

[Table 1]

(Example 1) High-Cr cast iron (main component: 2.8% C-18% Cr) roll used in a four-stage hot rolling mill of No. 2 stand of a finishing tandem mill in a hot steel plate rolling mill line On the other hand, by using a water injection type lubricant supply device, the 14 types of lubricant compositions shown in Table 1 were each treated with high corrosion resistance ferritic stainless steel (22% Cr-2% M
o, 500 tons) was supplied at a concentration of 0.5% by weight at the time of rolling (supply rate: 200 cc / min), and seizure and wear of the rolling rolls were examined. The results are shown in Table 2.

[0038]

[Table 2]

When the lubricant composition of the comparative example containing the solid particles having a coarser particle size of 1 μm or more according to the prior art was used, the seizure of the steel material on the rolling rolls was remarkable, and the solid particles were all produced. Depending on the type, the friction coefficient was too low and slippage occurred. On the other hand, particle size
When the lubricant composition of the present invention containing fine particles of 20 to 1000Å in a proportion of 1 to 30% by weight is used, neither slip occurs, and seizure of the rolling roll is prevented or significantly reduced. As a result, the amount of wear of the roll was reduced as compared with the comparative example. That is, by making the particle size of the solid particles as fine as 1000Å or less, the seizure prevention effect was dramatically improved.

The effect of preventing seizure and reducing roll wear according to the present invention is that when the particle size of solid fine particles is as small as 500 Å or less, it is more basic than acidic ones, especially 40 mgKOH / g or more in total base number. It is understood from the results in Table 2 that the above becomes more remarkable when the basicity of is shown.

It was also confirmed that even if the concentration at the time of supplying the lubricant was increased to 1.0% by weight, stable rolling could be performed without causing slip during rolling. Furthermore, when using a roll of other material such as high carbon high speed steel (high speed steel) roll, high alloy grain cast iron roll, adamite roll, etc. as the rolling roll, the same as when using the high Cr cast iron roll It was also confirmed that the effect could be obtained.

(Example 2) During hot rolling of a steel pipe (SUS304, ordinary steel, etc.) in a mandrel mill line, the above-mentioned lubrication was applied to the hole-type rolls (sizer roll, mandrel mill roll, etc.) of all rolling stands. The agent composition was supplied as a stock solution (supply amount: 2 to 4 l / min). Similar to Example 1, when the lubricant composition of the present invention was supplied, no seizure occurred on the high Cr cast iron roll and no flaw was observed in the product. On the other hand, when the lubricant composition of the comparative example was supplied, severe seizure and large wear of the roll occurred.
As a matter of course, the product was flawed.

(Example 3) During the H-shaped hot rolling of stainless steel (SUS304, SUS430, etc.) and plain steel in the shaped steel rolling line, the horizontal rolls and vertical rolls of the finish universal rolling mill were each lubricated as described above. The agent composition was supplied at a concentration of 1.0 wt% by a water injection type oil supply device.
(Supply amount: 100 cc / min). Similar to Example 1, when the lubricant composition of the present invention was supplied, seizure did not occur on any of the rolls, wear was small, and no flaw was observed on the product. On the other hand, when the lubricant composition of Comparative Example was supplied, severe seizure and large wear occurred on all the rolls. Many rolled products also had severe defects that required maintenance with a coil grinder.

[0044]

As described above, the lubricant composition containing the solid fine particles having a particle size of 20 to 1000Å according to the present invention in the lubricant base oil in a proportion of 1 to 30% by weight has a Even in hot rolling of stainless steel, which is likely to occur, it exhibits excellent effects in preventing seizure on hot rolling rolls, significantly reducing wear of rolling rolls, and preventing slip during rolling. As a result, the quality of rolled products is improved and work efficiency is improved.

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Claims (1)

[Claims] 1. A hot-rolling process for a metal, which comprises solid fine particles having a particle size of 20 to 1000Å in an amount of 80% by weight or more in a proportion of 1 to 30% by weight based on the total weight of the composition. Lubricant composition.