Steel concepts

C. A. Siebert, D. V. Doane, and D. H. Breen, The Hardenability of Steels—Concepts, Metallurgical Influences andindustrialApplications, American Society for Metals, Metals Park, Ohio, 1977. 

In addition to the necessary quality features, another relevant criterion for evaluating the usual steel concepts for plastic molds is the efficiency of the mold manufacturing process. Throughout the added value chain through to the finished plastic mold, the following evaluation criteria apply ... 

FIGURE 3.1 Comparison of the production stages involved in the steel concepts for manufacturing molds and tools for plastics processing... 

These requirements inevitably translate into different properties profiles for plastic mold steels. The different steel concepts can be grouped as follows ... 

To meet the special requirements the tools and molds have to satisfy in terms of functional properties such as wear resistance, corrosion resistance, or high hardness combined with adequate toughness, a range of special steels are available tailored to the particular criteria, some of them high-alloyed. Depending on the steel concept, these may require more or less complex heat treatment after pre-machining in the annealed state. 

Rotating cone viscometers are among the most commonly used rheometry devices. These instruments essentially consist of a steel cone which rotates in a chamber filled with the fluid generating a Couette flow regime. Based on the same fundamental concept various types of single and double cone devices are developed. The schematic diagram of a double cone viscometer is shown in... 

This concept is explained by Figure 12 which shows the uniaxial stress— strain curve for a ductile material such as carbon steel. If the stress level is at the yield stress B or above, the problem is no longer a linear one. 

D. V. Doane and J. S. Kirkaldy, Hardenability Concepts with Applications to Steel, TMS-AIME, Warrendale, Pa., 1978. 

The principal cathodic reaction on the upper surface of the membrane is the reduction of Cu " that is formed by the reaction of Cu with dissolved oxygen in the water these Cu ions are provided partly from the diffusion through the pores in the oxide membrane from within the pit and partly from those produced by cathodic reduction (equation 1.154). Lucey s theory thus rejects the conventional large cathode small anode relationship that is invoked to explain localised attack, and this concept of an electronically conducting membrane has also been used by Evans to explain localised attack on steel due to a discontinuous film of magnetite. 

This concept may be invoked to account for electrolyte formation in microcracks in a metal surface or in the re-entrant angle formed by a dust particle and the metal surface. More importantly, it can also explain electrolyte formation in the pores of corrosion product and hence the secondary critical humidity discussed earlier. Ferric oxide gel is known to exhibit capillary condensation characteristic and pore sizes deduced from measurements of its adsorptive capacity are of the right order of magnitude to explain a secondary critical relative humidity as70 7o for rusted steel . 

The above simple concepts need to be modified and expanded to allow discussion of stress-corrosion cracking of stainless steels in general, especially as the role of hydrogen in assisting crack growth must be accounted for. 

A consideration of the costs of the protective Schemes 1 and 3 given in Table 9.2 indicates that the latter is significantly more expensive than the former, and it is of interest, therefore, to apply the concept of the time value of money to these two schemes for 11 of steel processed. 

A number of industrial applications have been described including successful subsea installation . Double layer activation has been used in the laboratory for estimation of both shape and growth of pits in stainless steel. Advantages of TLA are that (a) the concept is easily understood, (b) interpretation is relatively easy and (c) the system installation can be non-invasive. 

The alkaline version of the Mn02 / zinc cell follows a different concept because it turns the construction of the Leclanche cell completely around now the cathode (Mn02 + carbon) forms a hollow cylinder contacting the inner wall of the cell container (steel) along its outer surface. The inner cavity has to accommodate anode, electrolyte, separator, and current collector. Usually, the separator forms a basket, which is automatically inserted and pre-... 

The concept of a ductile-to-brittle transition temperature in plastics is likewise well known in metals, notched metal products being more prone to brittle failure than unnotched specimens. Of course there are major differences, such as the short time moduli of many plastics compared with those in steel, that may be 30 x 106 psi (207 x 106 kPa). Although the ductile metals often undergo local necking during a tensile test, followed by failure in the neck, many ductile plastics exhibit the phenomenon called a propagating neck. Tliese different engineering characteristics also have important effects on certain aspects of impact resistance. 

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