Killed steels

For temperatures above 4S0 C (900 F) consider die advantages of killed steel. 

Carbon steels heated for prolonged periods at temperatures above 455°C (8.50°F) may be subject to the segregation of carbon, which is transformed into graphite. When this occurs, the structural strength of the steel will be affected. Killed steels or low-alloy steels of chromium and molybdenum or chromium and nickel should be considered for elevated-temperature seivices. 

Low-carbon plate and sheet are made in three qualities fully killed with silicon and aluminum, semikiUed (or balanced), and rimmed steel. Fully killed steels are used for pressure vessels. Most general-purpose structural mild steels are semikiUed steels. Rimming steels have minimum amounts of deoxidation and are used mainly as thin sheet for consumer applications. 

The copi>er contenis of the Ueels, which were supplied through the courtesy of TOffice Technique pour rUiilisaiion de TAcier (France), varied from 0-03 to 0-11. The killed steels contained about 0O4<7 Al and 0- l o Si. 

The conditions which affect the type of reaction are bath temperature and the composition of iron or steel which is being coated. At 480-520°C the reaction between iron and zinc can be linear with time so that the thickness of the alloy layers will increase in direct proportion to the immersion time and the reaction will continue to be relatively rapid. With some steels (e.g. some silicon-killed steels), the reaction can be linear at the normal galvanising temperature of about 450 C. 

Aluminum iodide pentadecahydrate, 2 386 Aluminum-iron alloys, 2 308-309 Aluminum-iron-silicon alloys, 2 316-317 a-Aluminum-iron-silicon alloys, 2 317 intermetallic phases, 2 316t P-Aluminum-iron-silicon alloys, 2 317 intermetallic phases, 2 316t Aluminum-killed steel, continuous-cast,... 

Continuous carbon dioxide foaming, 24 21 Continuous-cast aluminum-killed steel, 23 270... 

Figure 5. Elongated manganese sulfide inclusion in aluminum killed steel after hot...

These steels account for over 90% of all steel production, There are numerous varieties, depending upon carbon content and method of production. In one classification, there are killed steels, semikilled steels, rimmed steels, and capped steels, These are described in considerable detail under Iron Metals, Alloys, and Steels. 

Boron. Tlii element is added to increase hardenability, hut is effective only when added to fully killed steels. Since only a few thousandths of lfr ol boron usually remains in the steel, evaluation of boron steels is by increased hardennbility rather than chemical content. The hardenahilily chariLcleristtcs ol elements already present in the steel are intensified by boron, making possible alloy ingredient conservation. Although effective with low-carbon sieels, ihe effectiveness of the element decreases as the earhon content increases. 

One can prevent the formation of hydrogen blisters by using a clean steel without voids such as killed steels instead of rimmed ones. Manufacturing processes and... 

For temperatures above 480°C (900°F) consider the advantages of killed steel. 

Steel 202 was treated with rare earth metals to modify the sulphide inclusions. The manganese and silicon concentrations are typical for silicon killed steels. 

Doherty R. D. Melford D. A., Solidification and microsegregation in killed steel ingots with particular reference to 1% C 1.5% Cr-steel. JISI, (1966) 1131-1143... 

Common specifications such as ASTM A53 permit killed steel. (3) Because silicon killed and unkilled steels have different fracture toughness and also different design strengths, unintentional mix ups could cause fabrication, commissioning and/or operating problems. 

National standards for carbon steel pipe used at higher temperatures and pressures commonly require killed steel. For normal duties the deoxidation practice is not normally specified. Nevertheless, most seamless pipe is either killed or semikilled, except where specially ordered. An exception to this generalization is Germany, where... 

Sweden SIS 1233-06 SIS 1233 Killed steel Electric resistance weld Required... 

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