Salt Spray Test
An accelerated corrosion test in which metal specimens are exposed either continuously or intermittently to a fine mist of sal- water solution. An accelerated salt-spray test used by automotive is the CASS test.
An imperfection consisting of a thin, flat piece of metal attached to the surface of a sand casting or ingot. A scab usually is separated from the casting proper by a thin layer of sand or refractory and is attached to the casting along one edge. An erosion scab is similar in appearance to a cut or wash.
Scale is a layer of oxide that forms on the surface of steel when it is exposed to oxygen at elevated temperatures. Scale can form on the steel in the reheat furnace, the soaking pits, in the hot mill, and in the annealing furnaces.
Resistance to corrosion by air at elevated temperatures. In stainless steels Chromium is the most important element for increasing the scaling resistance particularly at temperatures above 1000°F.
Machining the surface layers from ingots, billets and slabs before fabrication.
Cutting surface areas of metal objects, ordinarily by using a gas torch. The operation permits surface defects to be cut from ingots, billets, or the edges of plate that is to be beveled for butt welding. See Chipping.
Mechanical finish produced by applying scotch brite (registered trademark of 3M Co.) to the surface of the metal to give a fine scratch pattern appearance. It is also useful in reducing tool wear (i.e. removal of abrasive surface oxides).
On the surface of metal, an unwelded ford or lap which appears as a crack, usually resulting from a defect obtained in casting or in working.
Steel that is incompletely deoxidized and contains sufficient dissolved oxygen to react with the carbon to form carbon monoxide and thus offset solidification shrinkage.
Sendzimir Cold Rolling Mill
Frequently referred to as Z mill which features 1-2-3-4 top and bottom roll arrangement; each work roll is supported throughout its entire length by two first intermediate rolls, that are, in turn, supported by three second intermediate rolls which transfer the roll separating forces to a rigid one piece cast steel housing through four backing assemblies. A Z-mill operates with very small diameter work rolls. The roll setup facilities exertion of high forces on the coil which in turn accomplishes rolling to very thin gauges and tight tolerance.
- Sheets. Less than .1876″ thick, and more than 23-15/19″ wide, and cut to length.
- Sheet coil. Sheet not cut to a length, but coiled.
- Strip. Less than .1876″ thick, and under 24″ wide.
- Plate. Over .1875″ thick, over 10″ wide, and cut to length.
- Slab. Semi finished steel block; width at least twice its thickness.
- Sheet. Sheet is material which measures under 3/16 inch (4.76 mm) in thickness and 24 inches (609.6 mm) and over in width.
A type of cutting operation in which the metal object is cut by means of a moving blade and fixed edge or by a pair of moving blades that may be either flat or curved.
Shot blasting consists of attacking the surface of a material with one of many types of shots. Normally this is done to remove something on the surface such as scale, but it is also done sometimes to impart a particular surface to the object being shot blasted, such as the rolls used to make a 2D finish. The shot can be sand, small steel balls of various diameters, granules of silicon carbide, etc. The device that throws the shot is either a large air gun or spinning paddles which hurl the shot off their blades.
Bonding of adjacent surfaces of particles in a mass of metal powders, or in a compact, by heating.
A piece or strip of metal produced to a suitable thickness, width, and edge configuration, from which pipe or tubing is made.
Skid & Shroud
Skids are platforms upon which material is placed for shipment. These platforms are normally of wooden boards nailed to 2 x 4’s or 4 x 4’s so that a fork truck can get its forks underneath the platform. The material being shipped is usually fastened to this platform by narrow strips of thin metal called banding. To shroud means to cover the steel being shipped with heavy, water-proof paper to protect it from moisture and handling damage during transit.
To skin pass material is to give it a very light pass on a rolling mill after final annealing. There is essentially a minimum reduction in thickness during this last pass. It is usually done for one of these three reasons
- to flatten the material
- to impart a particular surface to the steel from the rolls
- to cold-work the material to slightly increase its mechanical strength.
Edging process on flat-rolled metal and alloy strip. After metal removal, a #5 square edge is produced.
Slab describes the size and shape of material at an early stage of processing. A slab is typically 6 inches thick, 51 inches wide, and around 200 inches long. It will be processed to become a hot roll band or a plate. Slabs may come directly from the continuous caster or be formed from ingots via the blooming mill.
To slit steel is simply to cut it. The most common slitter available is a pair of scissors. The slitters used in the mill have circular blades that resemble washers. These rotate as the steel passes through them. The slitters have a payoff reel and a take-up reel which pass the steel through the slitter knives. Between these two reels are two shafts, one above the steel and one below the steel. The round slitter knives are placed on the shafts and adjusted so that they cut off the edges of the steel to produce a good edge and/or cut the steel into narrow strips of the width the customer wants.
Slitting stock is produced with the knowledge that the product will be further processed by mill customer. Mill produces the final gauge but not the final width. The customer will do additional slitting/shearing.
Defects in the nature of irregularly shaped pieces of steel clinging loosely to finished steel. Slivers may result from defective composition (over-oxidized, high sulfur); defective teeming of molten steel; defective heating (burning); tearing of corners in early stages of rolling; etc.
A metallurgical thermal processing operation in which the metal or matte is separated in fused form from nonmetallic materials or other undesired metals with which it is associated.
Any crooked surface defect in a plate, resembling a snake.
Prolonged heating of a metal at selected temperature.
Reduction in ductility of a metal or alloy associated with local penetration by molten solder along grain boundaries.
Solution annealing is a process performed on steels. In our case, these are primarily the 300 series stainless. The process consists of heating the material up to a temperature above 1950°F and holding it long enough for the carbon to go into solution. After this, the material is quickly cooled to prevent the carbon from coming out of solution.
Solution-annealed material is in its most corrosion-resistant and ductile (farmable) condition.
Solution Heat Treatment
A process in which an alloy or metal is heated to a suitable temperature, is held at that temperature long enough to allow a certain constituent to enter into solid solution, and is then cooled rapidly to hold that constituent in solution. Most solution heat treatments soften or anneal.
Designates all alloys and metals produced at USSM other than stainless steels and precipitation hardenable stainless steels. Categories of special metals would include nickel, nickel base alloys, cobalt base alloys, titanium and titanium base alloys, glass sealing alloys (iron-nickel), etc.
An instrument using an extended surface — a photographic plate or film, or a fluorescent screen — for receiving the X-ray diffraction pattern. Spinning
An electric-resistance welding process in which the fusion is limited to a small area. The pieces being welded are pressed together between a pair of water-cooled electrodes through which an electical current is passed during a very short interval so that fusion occurs over a small area at the interface between the pieces.
Normally refers to full hard and extra full hard condition depending on the alloy, specification and customer. In the case of type 301, customer’s expectations should be made clear to avoid error.
Condition that occurs when a flat-rolled metal or alloy is cold-worked; upon release of the forming force, the material has a tendency to partially return to its original shape because of the elastic recovery of the material. This is called Springback and influenced not only by the tensile and yield strengths, but also by thickness, bend radius and bend angle.
Additions of elements to 300 series stainless steel which are stronger carbide formers than Chromium. These carbide forming elements (Titanium in type 321 and Columbium in type 347) essentially “tie up” all of the Carbon present preventing Chromium from reacting with Carbon and thus avoiding sensitization and serious loss of corrosion-resistance.
The broad classification of iron-base alloys (50% minimum iron) containing at least 10% chromium that are known for their excellent corrosion- and heat- resistance. Other elements are also added to form alloys for special purposes in addition to the corrosion-resistance imparted by the chromium. Some of these elements are
An alloy of Carbon and Iron.
Straight Chrome (Martensitic/Ferritic)
As the name indicates, the straight chromes essentially contain only chromium as their major alloying element. To become a stainless steel a material must have a minimum chromium of 10.5% with chromium in the mid 20’s being the normal highest chromium. All of the straight chromes have a ferritic structure in the annealed condition. This ferritic structure is quite soft and, accordingly, not exceedingly strong. However, the martensitic stainless with their higher carbons have the ability to be made very hard by heat treatment. Typical of the non-hardenable ferrites are types 409, 430, 434, and 436, while martensitics are types 410, 420, and 440.
An increase in hardness and strength caused by plastic deformation at temperatures lower than the recrystallization range.
(see Continuous Casting) Strand casting is the direct casting of steel from the ladle into slabs. When two or more heats are cast without interruption, the process is called continuous strand casting. In strand casting, a heat of steel is tapped into a ladle in the conventional manner. The liquid steel is then teemed into a tundish which acts as a reservoir to provide for a constant casting rate. The steel flows from the tundish into the casting machine and rapid solidification begins in the open ended molds. The partially solidified slab is continuously extracted from the mold. Solidification is completed by cooling the moving steel surface. More than one strand may be cast simultaneously, depending upon the heat and slab size. A reduction in size may be carried out by hot-working the product as it exists from the strand prior to cutting the cast section to length. Chemical segregation is minimized due to the rapid solidification rate of strand cast product. Steel produced from a strand-casting operation is always fully killed steel, thus is generally considered to have excellent surface quality. Approximately 50% of the steel used in producing plate products is from strand castings.
The ability of a material to resist applied forces.
Material criteria used primarily in the transportation industry. High ratios for Titanium and Aluminum alloys stress the need to develop higher strength inducing process for heavier Iron, Nickel and Cobalt base alloys to improve their strength-to-weight ratios.
A process of reducing residual stresses in a metal or alloy by heating to a suitable temperature and holding for a sufficient length of time.
Stress Rupture Test
A method of evaluating elevated-temperature durability in which a tension-test specimen is stressed under constant load until it breaks. Data recorded commonly include
Failure by cracking from the combined effects of corrosion and stress. One of the important characteristics is the absence of visual overall attack. The metal or alloy appears to be satisfactory except where it is cracked.
A hydraulic stretching of material past its yield point to impart permanent deformation to obtain better-than-rolled flatness.
Strip is material which measures 3/16 inch (4.76 mm) and under in thickness and under 24 inches (609.6 mm) in width.
An annealing treatment in which a steel is heated to a temperature below the A1 temperature and then cooled slowly to room temperature.
The layer of metal underlying a coating, regardless of whether the layer is base metal.
A generic term covering several processes applicable to a suitable ferrous alloy that produce, by quench hardening only, a surface layer that is harder or more wear resistant than the core. There is no significant alteration of the chemical composition of the surface layer. The processes commonly used are induction hardening, flame hardening and shell hardening. Use of the applicable specific process name is preferred.
The surface quality of flat-rolled stainless products may vary according to manufacturing practices. It is important to both producer and purchaser that surface-quality requirements be clearly established. It must be recognized, however, that some degree of variation in surface quality may exist from lot to lot. It is customary to visually inspect products in the “as-rolled” condition to ensure their freedom from injurious imperfections such as gross slivers, snakes, cracks, blisters, and gouges. Minor pits, seams and scratches are not considered injurious and are not customarily removed in plate only. It should be recognized that when surfaces are subjected to descaling operations subsequent to mill inspection, imperfections may be disclosed that were not visible in the “as-rolled” condition. Therefore, products that will be inspected after descaling necessitate special surface conditioning and closer inspection than customarily employed, and the surface requirements should be established in each instance. Flat roll product for certain cold-drawing or cold- pressing operations may require a high degree of surface finish, even to the need for a surface-ground finish.
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