Metal Glossary
Stainless Steel: C
Camber, Straightness Tolerance
The permitted deviation from a true straight line, or bow, within a specified length of a product. The usual methods to determine such a deviation are with a straight edge and dial gauge or a flat plate and feeler gauges.
Carbide Precipitation
This occurs in an alloy when the thermal conditions and processing allow one or more of the constituents react with any available Carbon to form discrete particles within the microstructure. Usually this is undesirable in austenitic and ferritic stainless steels as chromium carbide is formed preferentially and compromises the corrosion resistance.
Carbide
A compound formed when an element, usually a metal, combines with Carbon. The carbides of metals are usually very hard. Both Iron and Chromium readily form carbides – Chromium has the greater affinity so will form its carbide in preference to Iron. This is a significant disadvantage in stainless steels as any carbide formation depletes the amount of chromium available to form the protective oxide layer. This is one reason why stainless steels have very low Carbon content (maximum 0.03% in low Carbon grades).
Related terms: Carbide, Inter-granular Corrosion, Sensitisation, Stabilised Grades
Cast, Heat, Melt
These terms are used interchangeably for the product of a single melting or refining furnace charge. Occasionally, if the furnace contents are cast into a number of different forms, these may be called separate casts.
Cathode
The electrode in an electrochemical cell, through which positive electric current leaves an electrolyte. The electrode reaction at a cathode is a reduction of ions or molecules in the electrolyte by electrons emitted from the cathode. In corrosion processes, reduction of dissolved oxygen and emission of hydrogen are two common reactions. The current flow causes positive ions to migrate towards the cathode.
Cathodic Protection
Electrochemical corrosion protection achieved by lowering the electrode potential.
Cold Drawing
Drawing hollow or solid products through a hardened steel or tungsten carbide die at room temperature. Cold drawing reduces the O.D. or wall thickness, or both. It produces smooth surface finishes and develops closer tolerances. Cold drawing increases hardness and mechanical properties. In welded hollow products it promotes weld area recrystallisation during subsequent annealing. Cold drawing of hollow sections is usually done with a mandrel in the bore (drawn over mandrel).
Cold Rolling
Passing sheet or strip at room temperature between a pair of rotating rolls. The reduction in thickness may be very light, as in the finishing process applied to hot rolled sheets, or heavy as in the cold rolling of narrow strip. Cold rolling improves surface finish, increases hardness and mechanical properties and develops tighter dimensional tolerances.
Cold Working
Changing the shape, dimensions, mechanical properties and surface finish of a work-piece by mechanical deformation at room temperature. It may be accomplished by rolling, forging drawing, pressing, forming, bending, swaging, etc.
Concentricity
In tubular products this describes how closely the centres of the two circles that respectively describe the outside diameter and bore coincide. The separation of these two centres causes variation in wall thickness around the tube and eccentricity.
Related terms: Eccentricity
Corrosion Fatigue
Cracking, possibly initiated and certainly accelerated, in a work-piece subjected to alternating or cyclic stresses in the presence of a corrosive medium. It will cause premature, often unexpected, failure.
Related terms: Fatigue
Corrosion
Degradation of a material by chemical or electrochemical reaction with its immediate environment.
CPP Plate
CPP is short for Continuously Product Plate - CPP is hot rolled plate up to 12mm thick and will have been coiled up during the production by hot rolling as compared to Quarto Plate over 12mm thick that will not have been coiled during production by hot rolling. For more information and the stock range please click on the link below.
Related terms: Quarto Plate
Creep
The tendency of a metal to flow or deform permanently under an applied load that is lower than its yield point. It is time and temperature dependent, the rate always increases with temperature.
Crevice Corrosion
Localised corrosion that occurs in narrow crevices where stagnant, non-aerated, liquid can accumulate. It is a particular problem with alloys, such as stainless steels, that rely on a passive film to protect them as these films are unstable in the presence of high concentrations of Chloride Cl- and Hydrogen H+ ions. The lack of aeration prevents the passive film from regenerating so attack can proceed. Good design is the key to preventing crevice corrosion.