High copper low alloy steel sheet
Inactive Publication Date: 2005-09-22
ALWIN MARY
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AI Technical Summary
Benefits of technology
[0005] The problem of hot shortness also has increased the costs in making low alloy steel using electric arc furnaces to form the molten carbon steel. Approximately 75% of the cost of making steel by electric arc furnace is the cost of the scrap used as the starting material for charging the electric arc furnace. Steel scrap has been traditionally separated by copper content to less than 0.15% by weight copper, greater than or equal to 0.15% to up to 0.5% by weight copper, and above 0.5% by weight. Scrap with copper content above 0.5% copper could be mixed with scrap with low copper levels to make an acceptable scrap, which also added to the cost of the scrap commercially available. In any event, the scrap which was low copper below 0.15% by weight is the highest cost scrap, with the other two grades of scrap being of less cost. In making steel sheet by traditional commercial processes, such as by continuous thick slab or thin slab casting, only scrap with less than 0.15% copper is generally useful in electric arc furnaces. This adds considerably to the cost of the steel sheet produced. Scrap grades with copper content up to 0.5% were useful in electric arc furnaces servicing bar mills, or at considerable expense by mixing with scrap of lower copper content to reduce the overall copper content of the scrap to less than 0.15%.
[0006] Applic
Problems solved by technology
Previously high copper low-alloy steel sheet was known and was known to provide corrosion resistance; however, such low alloy steel containing about 0.50% or more of copper frequently exhibited “hot shortness” during hot working, so that cracks or extremely roughened surfaces, sometimes referred to as “checking,” may develop during hot deformation.
Hot shortness occurs by copper separating during surface oxidation from the oxidizing layer to a layer adjacent the surface of the produced sheet resulting in a commercially unacceptable steel.
However, these procedures and alloying additions were expensive and caused the resulting corrosion resistant steels to be expensive.
Notably, nickel is an expensive alloy additi
Method used
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DETAILED DESCRIPTION OF THE DRAWINGS
[0029]FIGS. 3 and 4 illustrate a twin roll continuous strip caster which has been operated in making high copper low alloy steel strip in accordance with the present invention. The following description of the described embodiments is in the context of continuous casting steel strip using a twin roll caster. The present invention is not limited, however, to the use of twin roll casters and extends to other types of continuous strip casters and other ways of making steel sheet.
[0030]FIG. 3 shows successive parts of an illustrative production line whereby steel sheet (or strip) can be produced in accordance with a twin roll caster. FIGS. 3 and 4 illustrate a twin roll caster denoted generally as 11 which produces a cast steel strip 12 that passes in a transit path 10 across a guide table 13 to a pinch roll stand 14 comprising pinch rolls 14A. Immediately after exiting the pinch roll stand 14, the strip optionally may be passed into a hot rolling m...
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Abstract
A high copper low alloy steel sheet made by the steps comprising preparing a molten melt producing an as-cast low alloy steel comprising by weight, between 0.02% and 0.3% carbon, between 0.10% and 1.5% manganese, between 0.01% and 0.5% silicon, between 0.002 and 0.0095% sulfur, greater than 0.01% and less than or equal to 0.15% phosphorus, less than 0.05% aluminum, more than 0.20% copper, less than 0.03% tin, and less than 0.10% nickel, and the remainder iron and impurities resulting from melting, and solidifying the molten melt into sheet less than 10 mm in thickness in a non-oxidizing atmosphere to below 1080° C. The copper content may be between 0.2% and 2.0% by weight. The high copper low alloy steel may also have a corrosion index (I) of at least 6.0 in accordance with ASTM G101 where: I=26.01 (% Cu)+3.88 (% Ni)+1.20 (% Cr)+1.49 (% Si)+17.28 (% P)−7.29 (% Cu)(% Ni)−9.10 (% Ni)(% P)−33.39 (% Cu)2. The high copper low alloy steel may be produced by twin roll casting, and may have thickness less than 5 mm or less than 2 mm in thickness.
Description
RELATED APPLICATION [0001] The present application is a continuation-in-part of application Ser. No. 10 / 805,831, filed Mar. 22, 2004.BACKGROUND AND SUMMARY OF THE INVENTION [0002] Previously high copper low-alloy steel sheet was known and was known to provide corrosion resistance; however, such low alloy steel containing about 0.50% or more of copper frequently exhibited “hot shortness” during hot working, so that cracks or extremely roughened surfaces, sometimes referred to as “checking,” may develop during hot deformation. See, The Making, Shaping and Treating of Steel (9th edition) at page 1154. Hot shortness occurs by copper separating during surface oxidation from the oxidizing layer to a layer adjacent the surface of the produced sheet resulting in a commercially unacceptable steel. The occurrence of these undesirable surface conditions could be minimized by careful control of oxidation during heating and taking care not to overheat during hot working. Also, the addition of ni...
Claims
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Login to View More IPC IPC(8): B22D11/00B22D11/06C22C38/02C22C38/04C22C38/06C22C38/10C22C38/16
CPCB22D11/001B22D11/0622C22C38/16C22C38/04C22C38/02C22C38/06C22C38/10
InventorALWIN, MARY
OwnerALWIN MARY