Important technical terms

Deburring
In production engineering, a burr (= sharp-edged notch) is formed at edges and borders of work-pieces in most of the procedures: for cast components at the seam line of upper and lower part of the mould, for die components at the seam line of upper and lower die, at the cutting edges of shears and saw blanks, at welding seams, etc. These have to be removed for reasons of functional fulfillment or safety, too. There are numerous possibilities for that: e.g. grinding, brushing as well as chemical, electrochemical and electric removing procedures or also combinations of these procedures.

Deep etching
A chemical testing method applied for the verification of material in-homogeneities (e.g.: segregations, contaminations, ...). With stronger acid impact, the contaminated and therefore easier attackable areas are extracted and thus made visible.

Degreasing
That means the removal of carbon containing boring oil, lubricating oil and/or grease residues from the surface in a degreasing plant, to avoid carbonizing of the seamless tubes in subsequent annealing. In case oil and grease residues are not removed completely, carbonizing will occur during annealing and thus decrease the corrosion resistance of the finished tube.

Degree of purity
That means the quantification of inclusions in the steel by amount and chemical composition. Also the shape of the inclusions can be of importance.

Delivered quantity tolerance
The delivered quantity tolerance describes the admissible deviation of the delivered quantity from the confirmed nominal quantity of an order. An order is therefore considered executed and fulfilled in an orderly manner, when the delivery quantity does not undercut the admissible minimum quantity and not exceed the admissible maximum quantity.

Delivery loyalty
The delivery loyalty in general describes the compliance with the quantity, the required quality and the agreed delivery deadline of ordered products and/or in the narrower sense the deviation from the promised (confirmed) delivery deadline of the customer to the actual delivery deadline (delivery of the goods) in days and/or weeks.

Delivery standard
A delivery standard is a uniform delivery specification for certain products, which defines the designation and the order, the requirements to the manufacturing process, the chemical composition, the mechanical and technological properties, the thermal treatment, the appearance of the surface, the number and type of tests, etc.

Delta ferrite
Depending on the alloying element content as well as the cooling conditions, small amounts of delta ferrite can occur in austenitic non-corrosive stainless steels. At higher temperatures (approx. 750 °C), this delta ferrite disintegrates in various phases, which can deteriorate corrosion resistance, stability and/or formability.

Deoxidization
Procedure for the removal of excess oxygen (refining process) from steel melts. The oxygen content is to be decreased that far, that solidification takes place without blistering. Deoxidization is executed in the ladle or in the electric arc furnace. There is a differentiation between deoxidization via the gas phase, precipitation deoxidization (by addition of elements, whose oxygen affinity is larger than that of iron; this includes Mg, Mn, Si, AI, C, Ca) and diffusion deoxidization as well as their combination.

Desalting plant
Desalting plants serve the treatment of drinking water and/or feed water for machines and plants from saline water (seawater). The salt is removed from the water in various manners, among others by means of osmosis, evaporation + condensation, ion exchanger, ...

Destructive testing
Generic term for all material tests, which result in destruction of the component. These test methods include the mechanic-technologic tests as well as the corrosion test methods.

Die
A die is a tool, through which the hollow/billet is drawn/pressed for tube drawing/extrusion. Therefore, the die determines the outside diameter of the formed tube.

Die scars
More or less deep and visible scars, which result on the surface of the work-piece by the tools. For cold drawing, so-called die scratches can be produced outside (for tube also inside).

Dimension test
For the dimension test of seamless stainless steel tubes, outside diameter, wall thickness and tube length are examined for compliance with the customer requirements (standards). In case the customer requirements are exceeded or undercut, the respective tube has to be taken out of the production lot and scrapped.

Document
Certificate, document for the proof of a fact.

Drawing
Drawing includes four variants. For plug drawing, the hollow is drawn over an inner tool (plug), which is set firmly to the drawing die. Thus outside and inner diameter as well as the wall thickness is reduced. Drawing with the drawing mandrel is characterized by the fact, that the hollow is drawn through the drawing die together with the inner tool, the so-called drawing mandrel. Because after drawing the tube sticks firmly to the mandrel, a detaching mill and a mandrel removal device are required. For plug drawing with flying plug, the inner tool is designed that way that it is supported by the internal wall of the tube and is thus kept in the drawing position. Sinking, there is no inner tool. Basically only the outside and inner diameter is reduced, whereat the wall thickness can increase or decrease slightly according to the reduction ratio. Reductions of the cross section of up to 50 % are achieved.

Drawing mandrel
Is the designation of the tool for mandrel drawing, which determines the inner diameter of the finished tube.

Drawing point
Drawing point is the designation for the reduction of the diameter at the hollow end, so that it can be passed through the die and held by the drawing dogs.

Drawing soap
Serves as a lubricant for mandrel drawing. The soaping of the tube surface is executed by immersion in a soap (stearate) bath at 70 °C. Before soaping of the tube surface, however, a substrate, the so-called "drawing bonder" (oxalic acid) has to be applied.

Dressing and straightening
(=finishing department) This includes all facilities and operations, which give the steel products the desired finish after shaping. In the finishing department, essentially the following tasks are executed: straightening, sampling for destructive testing methods, non-destructive testing, cutting, deburring, mix up testing, surface and dimension check, marking, determination of weight, length and/or number of pieces, packaging.

Ductility
That means the ability of a material, to change its form without the occurrence of material separations.

Duplex steel
This steel has a two-phase structure consisting of approx. 50 % ferrite and approx. 50 % austenite and has a high corrosion resistance and stability. The ratio ferrite/austenite to a large extend depends on the content of the respective alloying element like chromium, nickel, carbon, molybdenum and nitrogen and the thermal treatment/cooling executed.

Dye penetration test
The component is immersed into a special liquid or sprayed with it, whereat this penetrates deeply into cleavages, pores or cracks due to the capillary effect. A very low-viscosity, mostly red color is applied for that most frequently. After immersion, the liquid adhering to the surface is rinsed off and the component is cladded with a chalk film. Again due to the capillary effect, the dried chalk film is penetrated by dye, which is still stored in the flaws. The flaws emerge clearly and strongly enlarged on the white surface, so that even ultra-fine cracks become detectable. Naturally, only those flaws can be detected with the capillary procedures, which are on the surface of the work-piece.