Rabbling
Working with a rabble, that is, the tool provided for stirring the molten metal bath in a puddling furnace with cinder to assist purification.

Ragging
A series of grooves usually horizontal, made in the surface of a roll in order to assist the roll to bite the steel and to prevent skidding between the roll and the work. Ragging is usually found in roughing and forming passes.

Rare Earth Metals
The lanthanide metals of the periodic table (atomic nos. 57 to 71) are also known as rare earth metals.

Reaming
The removal of the ragged inside edge at the ends of cut tubes.

Recarburisation
The adjustment of carbon content of molten steel by addition of carbonaceous material, high-carbon pig iron or a high-carbon alloy.

Recrystallization
1. A change from one crystal structure to another, such as that occurring upon heating or cooling through a critical temperature.
2. Formation of a new, strain-free grain structure from the structure existing in cold-worked metal.

Recrystallization Annealing
Annealing cold-worked metal to produce a new grain structure without a phase change.

Recrystallization Temperature
The approximate minimum temperature at which recrystallization of a cold-worked metal occurs within a specified time.

Recuperator
The waste flue gases from high temperature processes contain the sensible heat of vapourisation of water (apart from the latent heat, which is not practical to recover) which is recovered in a recuperator by transfer of heat continuously from one fluid to another.

Red Hardness
The relatively high hardness retained by certain special steels (for example, high speed tool steels) even when heated up to a low red heat.

Red Rust
A reddish brittle coating of iron oxide which develops on an uncoated or coated steel surface when oxygen in the atmosphere mixes with iron.

Reducing Agent
Either natural gas or coal can be used to remove the oxygen from iron ore in order to produce a scrap substitute. In gas-based processes, the iron ore is heated in a vessel as reformed natural gas passes through. In coal-based processes, iron ore is combined with gasified or ground coal and heated. The oxygen in the ore combines with carbon and hydrogen in the gas or coal, producing reduced, or metallic, iron.

Reed
An internal discontinuity originating from a subcutaneous blow-hole which has become oxidised and has been elongated during rolling.

Reel Breaks
Fractured base metal normally caused by poor leveling. It is indicated by light kinks across the width of the winding coil.

Reeking
Ingot mould dressing with soot deposition, derived from tar burning.

Reeling
Straightening (and planishing) a round bar by feeding it between contoured steel rolls in a direction approximately parallel to the principal axis of the rolls.

Refining
The removal, by slag or other reactions, of undesirable elements and of metallic oxides and gases from molten steel.

Refining Slag
The finishing slag employed for refining the heat.

Refractory Brick
Heat-resistant (normally non-metallic) brick. Because its melting point is well above the operating temperatures of the process, refractory bricks line most steel making vessels that come in contact with molten metal and slag, like the walls of the blast furnace, sides of the ladles, and inside of the BOF apart from the flues or stacks through which hot gases are conducted. These are made of materials such as dolomite (double calcium and magnesium carbonate), magnesite (magnesium carbonate), silica (SiO2), silicates of aluminium, chromic oxides, etc. and are able to withstand temperatures from 260o to 1760oC.

Reflowed Surface
A shiny tin plate product surface which is achieved by heating the tin coating up to its melting point (thereby melting the tin) and cooling it back to room temperature.

Refractory Creep
Like most structural materials, refractories experience creep behaviour when exposed to high temperatures. Most refractories show two characteristic stages of creep. In the first stage, called primary creep, rate of subsidence declines gradually with time. In the second stage, called steady stage, the rate of subsidence is constant. At very high temperatures, steady stage creep is sometimes followed by tertiary creep region where the rate of subsidence accelerates and leads to catastrophic failure or creep rupture. Primary creep is generally short in duration, while secondary creep can occur over a long term.

Regenerator
Arrangement (chambers filled with a checkwork of refractory bricks) for receiving and then utilizing heat from hot spent gas from a furnace. They are used alternately to absorb heat from one fluid and then transfer it to another fluid.

Reheating
Heating steel to a uniform temperature in readiness for hot working.

Reheating Furnaces
These are divided into two general classes :
1. Batch Type : Here, the charged material remains in a fixed position on the hearth until heated to rolling temperature.
2. Continuous Type : Here, the charged material moves through the furnace and is heated to rolling temperature as it progresses through the furnace. These include pusher-type, rotary-hearth-type, walking-beam-type, walking-hearth-type and roller-hearth-type furnaces.

Reinforcing Bar (Rebar)
A commodity-grade steel used to strengthen concrete in highway and building construction.

Reline
The process of replacing the refractory lining of a liquid steel vessel. Once it wears out, the brick lining of a furnace must be cooled, stripped and replaced. This maintenance can be significant because a blast furnace reline may require up to three months to complete.

R Enamel
An unpigmented enamel used to increase resistance to corrosion, or decrease bleaching effect of tinplate on food can interiors.

Rephosphorisation
Reversion of or addition of phosphorus into steel under steel making practice.

Reshearing (Resquaring)
Shearing sheets to desired finished dimensions with right-angled edges.

Residuals
The impurities in mini-mill steel as the result of the mix of metals entering the process dissolved in obsolete scrap. Residuals are key concerns regarding the mini-mills' recent entry into the flat-rolled market, where high residuals can leave sheet steel too brittle for customer use.

Resilience
The ability of a material to absorb energy when deformed elastically and return to its original shape upon release of load.

Resistance Heating
Heating of steel by passing current through solid conductors and using the heat generated as a result of the conductors’ inherent resistance to the flow of current. It can be applied through three methods :
1. The indirect method, in which the steel is heated by radiation and convection from resistors through which the current is passed.
2. The direct method in which the current is passed directly from a power source through the metal.
3. The induction method in which the current is induced in the steel by an induction coil connected to the power supply.
Neither the indirect nor the direct method of resistance heating is practical for steel-making operations. However, the induction method is employed successfully in special steel-melting operations.

Reversing Mill
The stand of rolls used to reduce steel sheet or plate by passing the steel back and forth between the rolls; the gap between the rolls is reduced after each pass.

RH Degassing
Ruhrsthal-Heraeus process developed in the early 1960's with the objective of degassing a ladle of steel without total enclosure of the ladle in a vacuum chamber. The argon gas is injected into one leg or extension of the refractory-lined vacuum vessel, which is dipped into the steel containing ladle. This causes the molten steel from the ladle to rise into the evacuated chamber with a boiling action that releases gases from the steel that then flows back into the ladle through the second leg. The recirculation of steel is continued until the desired degree of degassing is attained.

Ribbing
A coating defect consisting of a flow mark defect with an appearance similar to corduroy fabric. Ribbing usually occurs when the flow marks (ribs), from application on the coater, do not flow out and level the surface of the coating.

Ridge
A hump across the width of the surface of the coil.

Rimming
When molten steel cools to the temperature range in which it begins to solidify as ingot, the solubility of gases dissolved in the steel decreases and the excess gases are expelled from the metal. The amount of gases, chiefly oxygen, dissolved in liquid steel and the amount of gases released during the solidification determine the type of ingots : killed, semi-killed, capped and rimmed.

Sometimes, the amount of gases evolved during solidification are so much that the top ingot surface does not solidify immediately after pouring. Instead, numerous honeycomb blowholes form very close to the side surface of the ingot, extending from top to bottom. The evolution of gas causes the steel to rise after pouring and produces a boiling action that is commonly called rimming action. This action is stopped by a metal cap secured to the top of the mould.

Rimming Steel
A steel possessing a rim of purer material (with maximum freedom from surface blemishes), and is associated with evolution of carbon monoxide gas occurring due to the interaction of dissolved iron oxide and carbon during the solidification of low carbon and low manganese steel made under controlled deoxidation. The composition and extent of the rim can be varied and, if required, the rimming action can be arrested after sometime.

Rockwell Hardness Test
An indentation hardness test using a calibrated instrument that utilizes the depth of indentation, under constant load, as a measure of the hardness of the material. Either a 120o diamond cone with a slightly rounded point, or a 1/16-or 1/8-inch diameter steel ball is used as the indenter.

Rod (Wire Rod)
Generally round, square, half-round, rectangular or polygonal semi-finished steel length that is rolled from a billet and coiled for further processing. Rod is commonly drawn into wire products or used to make bolts and nails. Rod trains (rolling facilities) can run as fast as 20,000 feet per minute (more than 200 miles an hour).

Roke (Roak)
A longitudinal surface defect (an elongated fissure) caused by a blow which is not welded up during rolling and has perforated the surface and become oxidised.

Rolled Edge
Edge which is finished accurately to desired shape by using rolls at the edges.

Rolled-in-Scale
Local areas of scale, formed during a previous heating, which has failed to be eliminated during the rolling operations and has got pressed into the surface of the stock during rolling.

Roller Levelling (Mangling)
A staggered system of rolls used to flatten the steel without any appreciable reduction in gauge.

Roller Table
During the complete rolling cycle, the hot steel is transported by reversible, live rollers in the mill tables, called roller tables. Front and back roller tables alternately feed and receive the piece during each pass through the rolling mill, and mechanical units called manipulators rotate the piece through 90o as required and move it from pass to pass.

Roll Force Cylinder
See A.G.C. Cylinder.

Roll Force Systems
Mill stands place considerable pressure on slabs, blooms and coils to further process the material. There are two general ways of applying the force to the steel‹screw and hydraulic systems.
Screw (Incline Plane) This older method used the basic principle of the screw to adjust the space between the mill rolls. Because metal touches metal, these configurations will wear down over time and can cause quality problems.
Hydraulic (Pancake Cylinder) This modern system uses fluid pressure to rapidly adjust the roll spacing several times per second. These minute, instantaneous adjustments allow for superior gauge tracking and higher-quality products.

Roll Forming
1. An operation used in forming sheet. Strips of sheet are passed between rolls of definite settings that bend the sheet progressively into structural members of various contours, sometimes called "moulded sections." 2. A process of coiling sheet into open cylinders.

Roll Marks
Periodic surface defects due to some imperfection on the surface of a roll or due to particles of matter picked up by rolls.

Rolling Mill
1. Any of the mills in which metal undergoes a rolling process. These include the Slabbing Mill, Hot Roll Mills, Cold Roll Mills, Single Reduction Mills, and Double Reduction Mills. 2. Any operating unit that reduces gauge by application of loads through revolving cylindrical rolls; operation can be hot or cold. The elevated temperature rolling mill is the Hot Mill and is capable of reducing the gauge of a slab 92-99%.

Roll Pass (Pass)
Openings of definite shapes formed between a set of rolls through which hot steel passes for taking up the given shape or undergoing a desired amount of reduction in sectional area. This term also applies to a single passage through a pair of rolls for the purpose of altering the shape and / or reducing the cross-sectional area.

Rolls
The rolls control the reduction and shaping of the metal. There are three parts to a roll; namely, the body, or the part on which the rolling is done, the necks which support the body and take the rolling pressure, and the wobblers, where the driving force is applied through loose-fitting spindles and boxes which together form a sort of ingenious universal coupling.

Roll Scale
Oxide of iron which forms on the surface of steel while it is being heated and rolled. Much of the scale is cracked and loosened during the rolling operation and may fall off the piece naturally or be blown off by high-pressure water sprays or other means.

Roughing Stand
The first rolling stand through which metal passes during hot rolling imparting very high reduction. Once reduced by the roughing stands, the metal continues on to the finishing stands where smoother rolls with a smaller gap are used to complete the hot roll process.

Runner
The refractory channel through which the molten steel enters the mould.