Forging steel, and forged products obtainable therefrom
a technology of forging steel and products, which is applied in the direction of engine components, mechanical equipment, etc., can solve the problems that the patent documents do not go as far as to disclose concrete, and achieve the effect of excellent fatigue characteristics and excellent fatigue characteristics
Inactive Publication Date: 2009-07-23
KOBE STEEL LTD
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Benefits of technology
[0014]This invention has been made in view of the forgoing circumstances and has the object of providing forging steel with refined inclusions so as to make available forged products (including parts) having excellent fatigue characteristics and also providing forged products (including parts) (crankshafts in particular) that is obtainable from the use of the above-mentioned forging steel and can exhibit excellent fatigue characteristics.
[0031]The aspect of the present invention is configured as described above, and by adjusting the amount of the dissolved Ca and the dissolved Mg in the steel, it has become possible to control the morphology of the inclusions formed and thereby to provide forging steel with refined inclusions. The forged products available from the use of such forging steel can be expected to show excellent fatigue characteristics and prove particularly useful for large-size forged products such as crankshafts for ships and vessels.
Problems solved by technology
However, the above Non-patent Documents do not go as far as to disclose concrete means about how to realize globalizing the shape of the inclusion and making it smaller.
However, the morphology control technology for these inclusions described above is not targeting at forged products used under such severe environmental conditions as the power transmission member in the marine driving source is subjected to.
Method used
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embodiments
[0119]In an electric furnace, 20-100 tons of scrap material was melted and tapped to fill the ladle. Then, by using the ladle-heating type refining equipment with a bottom-blowing agitator, molten steel processing was carried out. In this molten steel processing, the first course of heating and composition adjustment (LF-I) was conducted to the molten steel tapped out of the converter or electric furnace; the degassing treatment (VD) was applied to the molten steel after completion of the first heating and composition adjustment; and the second heating and composition adjustment (LF-II) was carried out to the molten steel after completion of the degassing treatment.
[0120]At the time of the above first course of heating and composition adjustment, such slag formation agents as CaO, Al2O3, and MgO were added to the surface of the molten steel for formation of top slag including CaO and MgO in the amounts shown in Table 1. In the next place, Al was added to deoxidize the molten steel, ...
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Abstract
Disclosed is a forging steel characterized in that prescribed composition of components must be satisfied. In particular, any one of the below-mentioned (I)-(IV) need be complied with in regard to dissolved Ca and dissolved Mg. (I) Dissolved Ca: 2-500 ppb (meaning “mass ppb” hereafter) and dissolved Mg: 0.04-5 ppm (meaning “mass ppm” hereafter); (II) Dissolved Ca: 2-100 ppb and dissolved Mg: 5-ppm; (III) Dissolved Ca: 2 ppb or less (0% not included) and dissolved Mg: 0.04-5 ppm; (IV) Dissolved Ca: 2-500 ppb and dissolved Mg: 0.04 ppm or less (0% not included).
Description
BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to forging steel and forged products obtainable from the use of the above forging steel. While the forged products manufactured from the forging steel of the present invention are being utilized usefully and widely in such industrial fields as machinery, ships and vessels, electrical equipment, etc., explanation hereunder is going to be made centering on an application to the crankshaft used for a power transmission member in a marine driving source as an example of typical application.[0003]2. Description of the Related Art[0004]The large-size crankshaft used as a power transmission member in a marine driving source requires superior fatigue characteristics that rarely cause fatigue breakdown even under a very severe use environment.[0005]As a method of improving fatigue characteristics of the crankshaft, the Non-patent Document 1 describes that improvement in fatigue characteristics was tried by...
Claims
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Patent Timeline
Login to View More IPC IPC(8): C22C38/42C22C38/20
CPCC21C7/072C21C7/10C22C38/00C22C38/44C22C38/02C22C38/04C22C38/06C22C38/002C22C38/18B21K1/08
InventorDEURA, TETSUSHINAGAO, MOTOHIROABIKO, TAKASHI
OwnerKOBE STEEL LTD