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                          Heat Treatment Requirements

DC (Direct Chill) Casting
A continuous method of making ingots or billets for sheet or extrusion by pouring the metal into a short mold. The base of the mold is a platform that is gradually lowered while the metal solidifies, the frozen shell of metal acting as a retainer for the liquid metal below the wall of the mold. The ingot is usually cooled by the impingement of water directly on the mold or on the walls of the solid metal as it is lowered. The length of the ingot is limited by the depth to which the platform can be lowered; therefore, it is often called semicontinuous casting.

Dead Flat
Perfectly flat. As pertaining to sheet, strip or plate. Refer to Stretcher Leveling.

Dead Soft Annealing
Heating metal to above the critical range and appropriately cooling to develop the greatest possible commercial softness or ductility.

Dead Soft Steel
Steel, normally made in the basic open-hearth furnace or by the basic oxygen process with carbon less than 0.10% and manganese in the 0.20-0.50% range, completely annealed.

Dead Soft Temper
Condition of maximum softness commercially attainable in wire, strip, or sheet metal in the annealed state.

Deburring
A method whereby the raw slit edge of metal is removed by rolling or filing.

Decarburization
Removal of carbon from the outer surface of iron or steel, usually by heating in an oxidizing or reducing atmosphere. Water vapor, oxygen and carbon dioxide are strong decarburizers. Reheating with adhering scale is also strongly decarburizing in action.

Decarburization
Loss of carbon from the surface of a ferrous alloy as a result of heating in a medium that reacts with carbon.

Decarburization
The loss of carbon from the surface of a ferrous alloy as a result of heating in a medium that reacts with the carbon at the surface.

Decoration (of dislocations)
Segregation of solute atoms to the line of a dislocation in a crystal. In ferrite, the dislocations may be decorated with carbon or nitrogen atoms.

Deep Drawing
The process of cold working or drawing sheet or strip metal blanks by means of dies on a press into shapes which are usually more or less cup-like in character involving considerable plastic deformation of the metal. Deep-drawing quality sheet or strip steel, ordered or sold on the basis of suitability for deep-drawing

Deformative Bands
Generally, bands in which deformation has been concentrated inhomogeneously.

Degassing Process (In steel making)
Removing gases from the molten metal by means of a vacuum process in combination with mechanical action.

Degenerate Structure
Usually refers to pearlite that does not have an ideally lamellar structure. The degree of degeneracy may vary from slight perturbations in the lamellar arrangement to structures that are not recognizably lamellar.

Delta Iron
Allotropic modification of iron, stable above 2552 (degrees) F. to melting point. It is of body-centered cubic crystal structure.

Dendrite
A crystal that has grown in treelike branching mode.

Dendrite
A crystal that has a tree-like branching pattern, being most evident in cast metals slowly cooled through the solidification range.

Dendritic Segregation
Inhomogeneous distribution of alloying elements through the arms of dendrites.

Deoxidation
(1) Removal of oxygen from molten metals by use of suitable chemical agents. (2) Sometimes refers to removal of undesirable elements other than oxygen by the introduction of elements or compounds that readily react with them.

Deoxidizing
Removal of oxygen. In steel sheet, strip, and wire technology, the term refers to heat treatment in a reducing atmosphere, to lessen the amount of scale.

Die Sinking
Forming or machining a depressed pattern in a die.

Die-Lines
Lines of markings daused on drawn or extruded products by minor imperfections in the surface of the die.

Diffusion
(1) Spreading of a constituent in a gas, liquid or solid, tending to make the composition of all parts uniform. (2) The spontaneous movement of atoms or molecules to new sites within a material.

Dilatometer
An instrument for measuring the expansion or contraction of a solid metal resulting from heating, cooling, polymorphic changes, etc.

Dish
A concave surface departing from a straight line edge to edge. Indicates transverse or across the width.

Dislocation
A linear defect in the structure of a crystal.

Doctor Blade Steel Strip
A hardened and tempered spring steel strip, usually blued, produced from approximately .85 carbon cold rolled spring steel strip specially selected for straightness and good edges. Sometimes hand straightened or straightened by grinding and cur to desired lengths. This product is used in the printing trade as a blade to uniformly remove excess ink (dope) from the rolls; hence its name.

Drawing
(1) Forming recessed parts by forcing the plastic flow of metal in dies. (2) Reducing the cross section of wire or tubing by pulling it through a die. (3) A misnomer for tempering.

Drawing Back
Reheating after hardening to a temperature below the critical for the purpose of changing the hardness of the steel.

Drill Rod
A term given to an annealed and polished high carbon tool steel rod usually round and centerless ground. The sizes range in round stock from .013 to 1 1/2 diameter. Commercial qualities embrace water and oil hardening grades. A less popular but nevertheless standard grade is a non-deforming quality. Drill Rods are used principally by machinists and tool and die makers for punches, drills, taps, dowel pins, screw machine parts, small tools, etc.

Drop Forging
A forging made with a drop hammer.

Drop Hammer
A forging hammer than depends on gravity for its force.

Dry Rolled Finish
Finish obtained by cold rolling on polished rolls without the use of any coolant or metal lubricant, of material previously plain pickled, giving a burnished appearance.

Ductile Crack Propagation
Slow crack propagation that is accompanied by noticeable plastic deformation and requires energy to be supplied from outside the body.

Ductility
The ability of a material to deform plastically without fracturing, being measured by elongation or reduction of area in a tensile test, by height of cupping in an Erichsen test or by other means.

Ductility
The capacity of a material to deform plastically without fracturing.

Ductility
The property of metals that enables them to be mechanically deformed when cold, without fracture. In steel, ductility is usually measured by elongation and reduction of area as determined in a tensile test.

Duralumin
The trade name applied to the first aluminum-copper-magnesium type of age-hardenable alloy (17S), which contains nominally 4% Cu, 1/2% Mg. The term is sometimes used to include the class of wrought aluminum-copper-magnesium alloys that harden during aging at room temperature.

Duralumin (obsolete)
A term formerly applied to the class of age-hardenable aluminum-copper alloys containing manganese, magnesium, or silicon.