High-alloyed steel

Plain Carbon and Low Alloy Steels. For the purposes herein plain carbon and low alloy steels include those containing up to 10% chromium and 1.5% molybdenum, plus small amounts of other alloying elements. These steels are generally cheaper and easier to fabricate than the more highly alloyed steels, and are the most widely used class of alloys within their serviceable temperature range. Figure 7 shows relaxation strengths of these steels and some nickel-base alloys at elevated temperatures (34). 

An important iadustrial use of NaH involves its in situ formation ia molten NaOH or ia fused eutectic salt baths. At concentrations of 1—2% NaH, these compositions are powerful reducing systems for metal salts and oxides (5). They have been used industrially for descaling metals such as high alloy steels, titanium, zirconium, etc. 

Calcium hydride is prepared on a commercial scale by heating calcium metal to about 300°C in a high alloy steel, covered cmcible under 101 kPa (1 atm) of hydrogen gas. Hydrogen is rapidly absorbed at this temperature and the reaction is exothermic. 

Subsection C This subsection contains requirements pertaining to classes of materials. Carbon and low-alloy steels are governed by Part UCS, nonferrous materials by Part UNF, high-alloy steels by Part UHA, and steels with tensile properties enhanced by heat treatment by Part UHT. Each of these parts includes tables of maximum allowable stress values for all code materials for a range of metal temperatures. These stress values include appropriate safety fac tors. Rules governing the apphcation, fabrication, and heat treatment of the vessels are included in each part. 

The simple analytieal proeedure of tungsten determination in high alloy steel and niekel base alloys by atomie emission speetrometry with induetively eoupled plasma (AES-ICP) was developed. Proposed teehnique ineludes the dissolution of 0.1-0.5 g of material in mixed aeids (25 ml HCl, 3 ml HNO, 5 ml HF), eomplexation of tungsten by 9 % solution of oxalie aeid and measurement of tungsten emission intensity (k = 207.911 nm). 

A simple ealibration eurve based on distilled water is suitable for tungsten determination (linearity range is 1-50 mg/dm of W), no interferenee from Fe, Co, Cr, Ni was found. The aeeuraey of the method is eonfirmedby analysis of eertified referenee materials of high alloy steels and niekel based alloys (in range of 0.3 to 15 % W). The analyzed values are agreeing well with the eertified values. 

The same results were gained for Cr analysis in high alloyed steels. The error of linear calibration in this case is 0.28%. The application of theoretical corrections decreases this error to 0.07%. The standard error of the linear calibration on the base of the analytical pai ameter Ici.j,yipj,j,p is 0.23% and the application of the theoretical corrections in this case gives error 0.04%. 

High-alloy steels with >16% Cr" (e.g. 1.4301, AISI 304) Neutral waters and soils (25°C) <0.2 <-0.1 Protection against pitting and crevice corrosion... 

High-alloy steels with >16%Cr = Halide-free cold acids 0.2/1.1 -0.1/0.8 Protection against active and transpassive corrosion... 

In all cases partial or total hulls of aluminum or stainless steel must be provided with cathodic protection. This also applies to high-alloy steels with over 20% chromium and 3% molybdenum since they are prone to crevice corrosion underneath the coatings. The design of cathodic protection must involve the particular conditions and is not gone into further here. 

Cures, the equipment is made of vei y expensive high-alloy steels. Energy and hydrogen costs result in high operating costs, much higher per barrel of feed than the FCC unit. 

Tube O.D. Carbon Steel High Alloy Steel (750) Low Alloy Steel (850) Nickel-Cooper (600) Nickel (850) Nickel-Chromium-Iron (1000) Alum mum Almninmn Alloys, Copper Copper Alloys, Titanimn Alloys at Code Maximmn Allowable Temperature... 

Finally, a book has recently been published covering corrosion problems related to nuclear waste disposal" . It discusses a variety of subjects including corrosion behaviour and SCC of copper, carbon steels and high alloy steels under conditions related to nuclear waste disposal. Special attention is paid to pitting and problems associated with hydrogen gas generation from corrosion processes. 

A collaborative test programme covering low-alloy and high-alloy steels was carried out by the Central Electricity Generating Board and various steelmakers. Samples were exposed in specially constructed chambers held at 566°C, 593°C and 621 °C fed with power-station steam at a pressure of 3-45 MN/m for times of up to 16 286 h. In the assessment of the results both metal lost from the surface and subsurface penetration were measured. The results have been reported by King, Robinson, Howarth and Perry in a C.E.G.B. report. Selected data are shown in Fig. 7.32, in which the broken lines have been obtained by extrapolation of the experimental results. 

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