ELECTRIC FURNACE STEEL

都市 · 发表于 2007-4-12 16:39

Electric Furnace Steelfficeffice" />

Definition: Steel made in any furnace where heat is generated electrically, almost always by arc. Because of relatively high cost, only tool steels and other high-value steels are made by the electric furnace process.

Electric Steel Process

In the electric steel process, the heat required is obtained not by oxygen combustion of the accompanying elements in the pig iron, but from electrical energy. The conversion of electrical energy into heat can be achieved by an electric or, induction, or plasma furnace. Electric steel processes are based on the use of scrap, with small amounts. Of solid pig iron. Over 90 % of all electric steel produced is by the use of the a.c. electric are furnace. Three graphite electrodes carry the current through the furnace roof into the charge of metal. The electric arc formed melts the charge at temperatures up to 3500 °C. The Furnace has the following essential components: the vessel or shell with a furnace door and a tapping hole; the roof which can be removed for charging; electrode arms which support the electrodes; tilting equipment for emptying the furnace; the furnace transformer; and the measuring and control equipment.

The melting procedure for the electric is furnace comprises the following stages:

1) Charging

2) Melting

3) Oxidization (decarburization), with an increase in temperature

4) Tapping

The raw materials (scrap, sponge iron, pig iron, alloying elements, etc.) together with the required additives (lime, coal, ore, etc.) are loaded into special charging buckets which are then emptied into the furnace through a bottom opening. To fill the furnace, two or three charging operations are required, between which the scrap is partially melted. In some installations the scrap is pre-heated prior to the melting process.

The melting process begins with switching on the current and striking the arc. A

supplementary blow with oxygen and fuel-oxygen mixtures accelerates melting and reduces current consumption. The duration of the melting period is determined by the electric power limit and the maximum heat load of the furnace shell.

The very rapid development of the ffice:smarttags" />d.c. electric are furnace began in the middle of 1985

Important advantages are:

1) Lower electrode consumption

2) Savings in electrical energy

3) Smaller effect on the electricity supply system

4) Symmetrical distribution of heating in the melt

5) Stirring effect on the melt

The central electrode becomes the cathode, and the melt the anode, the bottom of the furnace vessel being insulated from the wall. Current-carrying elements are built into the hearth, and provide an electrical connection to the melt. The d.c. arc acts as a jet pump, directing the gases in and around the electric arc plasma toward the melt, causing efficient heat transfer from the electrode to the melt.

http://en.wikipedia.org/wiki/Electric_arc_furnace (other reference)

都市 · 发表于 2007-5-29 10:13

The grade of steel to be used is, in general, related to the thickness of the material and the stress pattern associated with its location.

Thickness, t, in mm	Material class
	I		II		III
	Mild steel	H.T. steel	Mild steel	H.T. steel	Mild steel	H.T. steel
t ≤ 15 15 < t ≤ 20 20 < t ≤ 25 25 < t ≤ 30 30 < t ≤ 35 35 < t ≤ 40 t > 40	A A A A B B D	AH AH AH AH AH AH DH	A A B D D D E	AH AH AH DH DH DH EH	A B D D E E E	AH AH DH DH EH EH EH

Structural member category	Within 0,4L amidships	Outside 0,4L amidships
SECONDARY: Lower strake in longitudinal bulkhead Deck plating exposed to weather, in general Side plating	I	A/AH
PRIMARY: Bottom plating, including keel plate Strength deck plating, excluding those belonging to the special category Continuous longitudinal members above strength deck, excluding longitudinal hatch coamings Upper strake in longitudinal bulkhead Vertical strake (hatch side girder) and upper sloped strake in top wing tank	II	A/AH
SPECIAL: Sheerstrake or rounded gunwale, see Note 1 Stringer plate at strength deck, see Note 1 Strength deck plating at outboard corners of cargo hatch openings in container carriers and other ships with similar hatch opening configurations, see Note 2 Strength deck plating at corners of cargo hatch openings in bulk carriers, or carriers, combination carriers and other ships with similar hatch opening configuration, see Note 3 Deck strake at longitudinal bulkhead, see Note 4 Bilge strake, see Notes 5 and 6 Longitudinal hatch coaming of length greater than 0,15L, see Note 7 End brackets and deckhouse transition of longitudinal cargo hatch coamings, see Note 7	III	II, in general I, outside 0,6L
NOTES 1. In ships with length exceeding 250 m, sheerstrake or rounded gunwale and stringer plate at strength deck are not to be less than Grade E/EH within 0,4L amidships. 2. Plating at outboard corners of cargo hatch opening and plating intersections of the longitudinal underdeck girders and the cross-deck strips are not to be less than Class III within the length of the cargo region. 3. Not to be less than Class III within 0,6L amidships and Class II within the remaining length of the cargo region. 4. Excluding deck plating in way of inner-skin bulkhead of double hull ships. 5. In ships with a double bottom over the full breadth and with length less than 150 m, bilge strake may be of Class II within 0,4L amidships. 6. In ships with length exceeding 250 m, bilge strake is not to be less than Grade D/DH within 0,6L amidships 7. Grade is not to be less than D/DH. 8. Corner inserts in way of any complex openings such as for lifts and side doors which may impinge on the deck plating or stringer plate are to be of Grade D/DH for t ≤ 20 mm and Grade E/EH for t > 20 mm. 9. For strength members not mentioned, Grade A/AH may generally be used. 10. Within 0,4L amidships, single strakes required to be of Class III or of Grade E/EH are to have breadths not less than 800 + 5L mm, but need not be greater than 1800 mm. 11. The material class used for reinforcement and the quality of material (i.e. whether mild or higher tensile steel) used for welded attachments, such as waterway bars and bilge keels, is to be similar to that of the hull envelope plating in way. Where attachments are made to rounded gunwale plates, special consideration will be given to the required grade of steel, taking account of the intended structural arrangements and attachment details. 12. The material class for deck plating, sheerstrake and upper strake of longitudinal bulkhead within 0,4L amidships is also to be applied at structural breaks of the superstructure, irrespective of position. 13. Engine seat top plates outside 0,6L amidships may be Grade A/AH. Steel grade requirement for top plates within 0,6L amidships will be specially considered. 14. Steel grade is to correspond to the as-fitted thickness. 15. Plating materials for sternframes, rudders, rudder horns and shaft brackets are, in general, not to be of lower Grades than corresponding to Class II. For rudder and rudder body plates subjected to stress concentrations (e.g. in way of lower support of semi-spade rudders or at upper part of spade rudders) Class III is to be applied.

xiaoningfly · 发表于 2007-9-11 14:42

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[ 本帖最后由 xiaoningfly 于 2007-9-11 14:43 编辑 ]

xiaoningfly · 发表于 2007-9-11 14:42

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xiaoningfly · 发表于 2007-9-11 14:44

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SpecNIE · 发表于 2007-9-12 16:15

晕这有什么好发的

hl · 发表于 2007-10-11 16:53

不过我觉得挺不错的。可惜只能大概了解一下，没有时间仔细看透。

-龙船调- · 发表于 2009-10-9 17:47

呵呵，又是一项技术工艺啊。谢谢。顶一下。

[船体] ELECTRIC FURNACE STEEL

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