Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1988-12-15
1991-04-09
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
72 41, 72 42, H01F 104
Patent
active
050061810
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of lubricating parts to be rolled in a warm rolling of high silicon steels.
BACKGROUND OF THE INVENTION
Recently, from standpoint of saving natural sources and energy, small sizings and high efficiency of electromagnetic or electronic parts have been demanded, and soft magnetic property, especially Si steel sheets having excellent iron loss have been also required. It is known that soft magnetic properties of Si steel sheets are improved with increasing of addition of Si and exhibit the maximum permeability at about 6.5 wt %, and since natural electric resistance is high, the iron loss is made small. In this kind of steel sheets, if Si content is greater than 4.0 wt %, workablity is abruptly worsened, and therefore it has been impossible to produce high Si steel sheets in industrial scales by the rolling process, but it has been found that the warm rolling could be performed on the thin steel sheets.
For warm rolling (200.degree. to 600.degree. C.) this kind of steel sheets, it is important to perform rolling and lubricating as keeping the above mentioned temperatures for following purposes;
The warm rolling is carried out on nonferrous metals as Al. In this rolling, an oil is much applied to lubricate and cool the sheet. However it is very important that the high Si sheet should not be cooled. Surface pressure is very high in comparison with rolling on the nonferrous metals and the above mentioned lubrication is not suited to the warm rolling of the high Si steel sheet.
The lubrication of water soluble coolant is employed to hot rolling, but since this is to cool the steel materials and the rolls, such a lubrication could not be used to the warm rolling of the high Si steel. In cold rolling, the lubricant mixed with an oil and a water is sprayed, but such a lubrication cannot be used to the warm rolling, either, because the temperature of the steel is lowered thereby.
These conventional rolling lubrications could not be adopted to the warm rolling of the high Si steel sheet with less workablility, and a new lubricating way has been demanded for smooth warm rolling.
DISCLOSURE OF THE INVENTION
In view of such circumstances, the inventors have made many studies on warm rolling lubrication of the high Si steel sheets, and they have found that the warm rolling was carried out on the high Si steels at temperatures between 200.degree. and 600.degree. C., while a lubricant was sprayed to working rolls or assistant rolls, the lubricant having been produced by mixing a solid lubricant endurable to rolling temperatures into a heat resistant grease, whereby the rolling is available at low rolling load, not decreasing the rolling temperatures.
In the lubricating practice, the lubricant can be more sprayed to rolls against edges of the sheet than to rolls against the center, thereby to roll the high Si steel by effectively preventing cracks at the sheet edges by applying the lubricant to the edges.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing warm rolling loads on 6.5% Si steel with different lubricants;
FIG. 2 is a graph showing expansions in width by the warm rolling with different lubricants and non lubricant;
FIG. 3 shows one of embodiments of the invention;
FIG. 4 is a graph showing the warm rolling on 6.5% Si steel by the invention in comparison with non lubricant rolling; and
FIG. 5 is a graph showing limits of cracks when the warm rollings were carried out by the present method, the comparison method and non lubricant rolling.
MOST PREFERRED EMBODIMENT FOR PRACTISING THE INVENTION
The present invention performs the warm rolling, while a lubricant is sprayed to working rolls or assistant rolls, the lubricant having been produced by mixing a solid lubricant endurable to rolling temperatures into a heat resistant grease. Molybdenum disulfide or graphite are used for the solid lubricant powders.
Known liquid lubricants to be used at high temperatures are lubricating composite oils such as silicone oil (available temper ature: to
REFERENCES:
patent: 3575858 (1971-04-01), Adair et al.
Fujita Fumio
Kamata Masamoto
Masuda Sadakazu
Murakami Tadayoshi
Yagi Ryuichi
Nields Henry C.
Nippon Kokan Kabushiki Kaisha
Sheehan John P.
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