1Introduction & scope
Hot rolling is the metal-forming operation in which steel is plastically deformed between rotating cylindrical rolls at a temperature above its recrystallisation point — for plain carbon and most low-alloy steels, that means somewhere between 850 °C and 1,250 °C, deep within the austenite phase field[2]. At these temperatures the yield strength of steel falls to less than one-tenth of its room-temperature value, dynamic and post-dynamic recrystallisation continuously regenerate the grain structure during deformation, and the workpiece can be reduced in cross-sectional area by 95% or more between casting and finished product without ever cracking. Essentially every long product, structural section, plate, hot strip, rail, wire rod, and reinforcing bar manufactured today begins its working life in a hot rolling mill[1].
The companion paper on this site, Rolling Mills: Principles, Components, Processes, and Products[3], places hot rolling within the broader context of metal forming and traces the historical development of the rolling concept from Leonardo da Vinci’s sketches to Henry Cort’s 1783 grooved-roll patent to the modern continuous mill. The present paper concentrates on hot rolling itself: the metallurgical events that take place inside a slab as it travels from reheating furnace charging door to coiler, the equipment that orchestrates those events, the parameters an operator controls, and the design choices that distinguish a structural section mill from a hot strip mill, a TMT bar mill, or a heavy plate mill.
The treatment is organised in three layers. Sections 2–3 cover the physics and metallurgy — what happens inside the steel and how engineers describe it mathematically. Sections 4–8 cover the equipment and process — the furnace, descaler, mill stands, pass schedule, and run-out table. Sections 9–11 cover the engineering choices — mill configurations for different products, defect modes and tolerances, and the standards that govern the finished material.
(Schematic placeholder. The five subsystems shown are common to long-product, flat-product, and structural mills, though the specific arrangement varies by product type as discussed in Section 9.)
2What hot rolling does, metallurgically
To understand why hot rolling exists at all — and why it cannot simply be replaced by cold rolling for primary shape conversion — one has to start with what happens inside the steel when it is heated and squeezed.
2.1The austenite window
Plain carbon steel exists in two principal crystal structures at atmospheric pressure: ferrite (body-centred cubic, the room-temperature phase) and austenite (face-centred cubic, the high-temperature phase). The transition between them occurs at about 723 °C for low-carbon steel and shifts upward with carbon content along the iron–carbon equilibrium boundary. Above the upper critical temperature (typically 850–920 °C for structural grades), steel is fully austenitic. Hot rolling is conducted in this austenite window, usually with a comfortable margin — reheating temperatures of 1,200–1,250 °C are typical for slab and bloom stock[4], and rolling continues down to a finishing temperature that may be as low as 850 °C for thermomechanically processed grades or as high as 1,050 °C for conventional structural sections.
Two reasons make austenite the right phase for primary forming. First, the FCC structure has more independent slip systems than ferrite’s BCC structure, so it deforms more uniformly without cracking. Second, the flow stress of austenite at 1,100 °C is roughly 50–80 MPa — about one-fifth of the flow stress of the same steel at room temperature — meaning a given mill can produce far greater reductions per pass with far smaller forces.
2.2Dynamic recrystallisation
The defining metallurgical event of hot rolling is dynamic recrystallisation (DRX). When austenite is deformed at elevated temperature, dislocations multiply and rearrange themselves into low-angle subgrain boundaries. If the temperature is high enough and the strain is large enough, new strain-free grains nucleate at these boundaries during the deformation itself and consume the deformed matrix. The result is a continuously refreshed, fine-grained microstructure that can absorb arbitrarily large total reductions without cracking[5].
Dynamic recrystallisation is contrasted with two related phenomena that occur between rolling passes: static recrystallisation (SRX), where new grains nucleate during the interpass dwell after deformation has stopped, and metadynamic recrystallisation (MDRX), where nuclei formed during deformation continue to grow after the pass ends. In a modern multi-stand finishing mill, the interpass time is short (often less than one second), so all three mechanisms operate simultaneously and the controlling parameter shifts from one to the next as the strip moves down the train.
The window for DRX is described mathematically by the Zener–Hollomon parameter Z, which combines strain rate and temperature into a single dimensionless number[6]:
where ε̇ is the strain rate (s−1), Q is the activation energy for hot deformation (typically 280–380 kJ/mol for plain carbon steels), R is the universal gas constant (8.314 J/mol·K), and T is the absolute temperature (K). At low Z (high temperature, low strain rate — conditions typical of the roughing mill) DRX dominates, the steel softens dramatically, and very large reductions are possible. At high Z (low temperature, high strain rate — conditions typical of the last finishing stand) DRX is suppressed and the steel work-hardens. Engineers choose pass schedules to keep the early passes well within the DRX window for grain refinement and the last passes outside it when fine, retained-strain microstructures are wanted.
2.3Grain refinement and properties
The cumulative effect of repeated DRX cycles is dramatic grain refinement. A continuously cast slab leaves the caster with an austenite grain size of 1–5 mm; after roughing in a typical structural mill the grain size may be 100–300 µm; after finishing it can be as fine as 10–20 µm. When the steel finally cools through its transformation temperature on the run-out table, the prior austenite grains transform to ferrite, pearlite, bainite, or martensite depending on cooling rate — but the new phases inherit the small prior austenite grain size. The Hall–Petch relationship dictates that yield strength varies inversely with the square root of grain diameter, so the fine grains produced by hot rolling translate directly into higher strength in the finished product. This is the underlying reason hot rolled structural steel can meet a 250 MPa yield strength specification with simple ferrite-pearlite microstructures, where unworked steel of the same composition would barely reach 180 MPa.
3Process parameters & equations
Three quantities define a single rolling pass: the entry thickness h0, the exit thickness h1, and the work-roll diameter D. From these, every other process parameter follows.
3.1Reduction, draft, and elongation
The absolute draft Δh = h0 − h1, the reduction ratio r = Δh / h0, and the elongation λ = h0 / h1 are related by simple constancy of volume (assuming negligible spread):
A pass that reduces thickness by 50% (r = 0.5) doubles the length (λ = 2). Practical hot rolling reductions are constrained at the upper end by the bite condition (the workpiece must actually grip the rolls and not slip backward) and at the lower end by mill productivity (very small reductions waste passes). For a steel-on-steel friction coefficient of 0.3–0.4 typical of hot rolling, the maximum draft per pass is approximately:
where R is the work-roll radius. This gives, for example, a maximum draft of about 18 mm in a 200 mm radius work roll, or 36 mm with 400 mm rolls — explaining why heavy roughing mills use very large work rolls.
3.2Bite angle and the contact arc
When the bar enters the gap, it touches the rolls along a contact arc whose angular extent α (the bite angle) is governed by:
The contact arc length is Lp = R·α for small angles, or more precisely Lp ≈ √(R·Δh). This length matters because the rolling force and the rolling torque are computed by integrating the contact pressure over it.
3.3Rolling force
The total separating force F that the rolls must exert on the workpiece — and that the mill stand must resist — can be estimated to first order by the simple slab-method expression:
where σ̄ is the mean flow stress over the pass, w is the bar width, Lp is the projected contact length, and Qp is a geometry-and-friction multiplier (the “pressure factor” or “Sims factor”) that accounts for the difference between the actual non-uniform contact pressure and a uniform mean pressure equal to σ̄[7]. In hot rolling Qp typically lies between 1.0 and 1.6. For a 1,500-mm-wide hot strip mill rolling a 25-mm-thick coil down to 18 mm at 1,000 °C with a 600 mm-radius work roll, equation (5) gives a separating force on the order of 25–30 MN per stand — the reason mill housings are massive cast steel structures with bolted tie rods.
3.4Torque and power
The mill motor must supply the torque to overcome the tangential friction force at the roll surface plus the work of plastic deformation. To a first approximation:
where a is the lever-arm coefficient (typically 0.4–0.5 for hot rolling). Power follows from torque and angular velocity: P = T · ω. A mid-sized hot strip finishing stand operating at 5 m/s with the force above might draw 6–10 MW per stand — six or seven such stands therefore demand a total connected motor capacity of 50–70 MW for the finishing train alone, before adding roughing, descaling pumps, run-out table cooling, and auxiliaries.
4The reheating furnace
Every hot rolling line begins at the reheating furnace: a long, gas-fired or oil-fired chamber where slabs, blooms, or billets are brought up to rolling temperature and held for long enough that the temperature is uniform from surface to core[8]. The furnace is the single largest energy consumer on most hot rolling lines — specific energy consumption for reheating alone is typically 1.2–1.6 GJ per tonne of finished steel, or roughly 350–450 kWh of equivalent fuel energy per tonne. Modern mills with flue-gas recuperators and walking-beam designs achieve the lower end of that range; older pusher furnaces sit at the upper end.
4.1Furnace types
Three main furnace types are used in long-product and flat-product hot rolling. Pusher furnaces are the simplest: billets or slabs are pushed end-to-end through a tunnel by a hydraulic ram at the charging door. They are cheap, mechanically robust, and well-suited to long runs of identical stock. Their drawbacks are limited length flexibility, the fact that the bottom face of every charge contacts the hearth and develops “skid marks” (cooler stripes that become visible after rolling), and the difficulty of removing a partial charge for grade changes.
Walking-beam furnaces overcome these limitations. The hearth is divided into fixed beams and movable beams that periodically lift, advance, and lower the stock so that no piece slides. Skid marks are eliminated, partial charges can be evacuated easily, and stock of different lengths can be mixed. Walking-beam designs dominate new construction for slab reheating in flat-product mills and are increasingly common in heavy section mills.
Rotary hearth furnaces use an annular hearth that rotates past fixed burners; the charge enters at one point and exits roughly 270° later after a complete pass through the heating, soaking, and discharge zones. Rotary hearths are favoured for round billets used in seamless tube production and for short batches in specialty mills.
4.2Heating zones, soak time, and uniformity
Whatever the type, every modern furnace is divided into at least three temperature zones: a preheat zone where waste heat from the flue gas brings the cold charge up to roughly 700 °C; a heating zone where the temperature climbs to within 50 °C of the target; and a soaking zone where the charge is held at the target temperature for long enough to equalise core and surface temperatures[9]. The soaking time depends on charge thickness and on the thermal diffusivity of the steel, but a useful rule of thumb for plain carbon steel is one minute of soak per millimetre of half-thickness — so a 250 mm slab needs about two hours in the soak zone after reaching temperature.
Excessive soaking is wasteful and metallurgically harmful: above 1,250 °C austenite grains coarsen rapidly (the kinetics roughly follow an Arrhenius relationship) and the slab develops a thick oxide scale that consumes 1–2% of the charge weight as “scale loss”[8]. Insufficient soaking is worse: a cold core means uneven flow stress through the thickness, asymmetric reductions, edge cracking, and rolled-in surface defects from skid marks that never had time to homogenise. Modern furnaces close this loop with optical pyrometers reading surface temperature at the discharge door and model-predictive control systems that calculate the implied core temperature and pull only fully soaked stock.
5Descaling
The instant a hot slab leaves the furnace, two things start happening to its surface. First, the bright steel oxidises rapidly — a layer of iron oxide scale (a mixture of FeO, Fe3O4, and Fe2O3) thickens at a rate that doubles for every 100 °C above 1,000 °C. Second, the surface begins to cool, particularly along the edges and the bottom face, faster than the core. By the time the slab reaches the first roll stand it may carry a 1–2 mm thick scale layer over an essentially uniform-temperature substrate.
If this scale is not removed before rolling, it gets pressed into the surface of the steel by the rolls, leaving permanent rolled-in defects that downgrade the finished material. High-pressure water descaling is the standard solution: arrays of nozzles deliver 100–420 bar water jets perpendicular to the slab surface, simultaneously cracking the brittle scale by thermal shock and physically washing it away. The water consumption is significant — 2–4 m³ per tonne of steel for a typical hot strip mill, though most of this is recycled through clarifiers and cooling towers.
Primary descaling (immediately after the furnace) is mandatory. Secondary descaling stations are commonly installed before each major mill section to remove the thinner scale that re-grows during the interpass dwell — secondary scale forms much more slowly because the surface temperature has dropped and the air is partially excluded by water sprays, but it still reaches 50–100 µm thicknesses on a slab travelling 50 m between roughing and finishing stations. In TMT bar mills the descaling is typically done with a single primary station and roller-type mechanical scale breakers that engage the bar between roughing passes.
6Roughing, intermediate & finishing trains
After descaling, the slab enters the rolling line proper. Modern hot rolling lines almost universally divide the deformation work into three sequential stages, each optimised for a different combination of reduction, speed, and shape control.
6.1The roughing train
The roughing train is where the bulk of the area reduction takes place. A 250 mm-thick slab might be reduced to a 30 mm transfer bar in five to seven roughing passes; a 150 mm bloom for structural shapes might be reduced to a 70 mm intermediate stock in four passes. Roughing stands are characterised by very large work rolls (often 1,000 mm diameter or more), short, infrequently varied roll gaps, and operating speeds of only 1–3 m/s. The temperature drops gradually through the roughing train, but it remains comfortably inside the dynamic recrystallisation window so each pass produces a refined, equiaxed grain structure as it deforms.
Two roughing layouts are common. Reversing roughing mills use a single stand (or two stands working as a tandem pair) and pass the workpiece back and forth through the rolls until the target intermediate thickness is reached; between passes the rolls are screwed down by a hydraulic system and edger rolls maintain the width. Reversing mills are mechanically simple, cheap, and well-suited to plate mills and small section mills, but the throughput is limited because the workpiece must decelerate, reverse, and accelerate between every pass. Continuous roughing mills place several stands in a line, each delivering one pass; the workpiece moves continuously forward and never reverses. Continuous roughing achieves dramatically higher throughput (a single line can deliver more than a million tonnes per year of finished plate or strip) at the cost of greater capital investment and more complex tension control between stands.
6.2The intermediate train
An intermediate train is interposed between roughing and finishing in long-product mills (bar, rod, and section mills) but is generally absent from flat-product mills. The intermediate stands take the relatively large transfer bar from the roughing train and progressively reduce both its cross-section and its temperature in preparation for finishing. The grooves cut into intermediate-mill rolls combine reduction with shaping — a square section is rolled into an oval, then the oval is rotated 90° and rolled back into a smaller square, alternating in successive passes (the “oval–square” pass schedule). Each pass may reduce the cross-sectional area by 20–30%, and a typical intermediate train has six to ten stands. Intermediate stands run at higher speeds than roughing (5–15 m/s) and use smaller work rolls (300–600 mm diameter).
6.3The finishing train
The finishing train performs the final shape and dimension control. In a hot strip mill it consists of six or seven four-high stands tandem-coupled with very tight interstand spacing and continuous tension control; the strip enters the first stand at perhaps 1,050 °C and 25 mm thickness and exits the last stand at 880 °C and 2 mm thickness, travelling at 18 m/s or more[10]. In a structural section mill the finishing train consists of a few specialised stands (universal stands for I-beams, double-duo stands for channels) that produce the exact final cross-section in one or two passes after the intermediate train has produced an approximation of the right shape. In a TMT bar mill the finishing train ends in a high-speed block (eight or ten stands of small-diameter tungsten-carbide rolls operating at 100 m/s exit speed) immediately followed by the quenching boxes that give TMT bars their characteristic dual-phase structure.
The finishing train is the part of the mill where the final mechanical properties are decided. The temperature profile through the finishing stands, the total reduction, the strain rate per pass, and the time between successive passes all directly control the prior austenite grain size that the steel carries when it arrives on the run-out table — and that grain size, combined with the cooling rate that follows, determines the strength, ductility, and toughness of the finished product.
7Pass design & the rolling schedule
Pass design is the engineering activity of choosing the shape and size of every roll groove on every stand of a long-product mill so that the bar progresses from input billet to output section in the smallest reasonable number of passes, with each pass producing a workable amount of reduction, no edge cracking, predictable grain refinement, and a final product within tolerance. Pass design is to long-product mills what the gauge schedule is to flat-product mills, and it is the area in which the most experienced rolling mill engineers add the most value.
The basic principles are mechanical: each pass must (a) keep the cross-sectional reduction within bite limits, typically 18–25% area reduction in roughing and 12–18% in finishing for plain carbon steel; (b) maintain the strain rate within the DRX window so the steel does not work-harden; (c) avoid cross-sectional shapes whose corners would cool too fast and become brittle; and (d) leave the bar in a shape that the next pass can grip without slipping. The classical schedules — box pass, oval-square, oval-round, diamond-square, false-round-finishing-round — are catalogued in a handful of textbooks[7] and have been refined empirically by every section mill operator for more than a century.
For flat products the equivalent activity is the gauge schedule or draft schedule, which specifies the entry and exit thickness at each finishing stand. Modern hot strip mills compute the gauge schedule online using a process model that starts from the target finishing temperature and gauge and works backward, balancing roll force, motor power, and inter-stand tension constraints. The model is recalibrated after every coil from measured rolling forces, exit thicknesses, and temperatures, so by the end of a day the predictions are usually within 1–2% of actual.
(Schematic placeholder showing the cross-sections at the entry and exit of three roughing stands.)
8Controlled cooling & TMCP
What happens after the last finishing pass is as important as anything that happens before it. The hot bar or strip leaves the mill at perhaps 900 °C carrying a freshly recrystallised austenite microstructure. As it cools, the austenite must transform to one or more of ferrite, pearlite, bainite, or martensite. The cooling rate determines which transformation products form, in what proportions, and with what grain size — and therefore determines the strength, ductility, and toughness of the finished material.
8.1The run-out table
The run-out table is the long roller table downstream of the last finishing stand. In hot strip mills it can be 100 m or more long, fitted with banks of laminar-flow water headers that spray the top and bottom of the strip from a controlled height. The cooling rate is set by switching individual header banks on and off, allowing rates of 5–100 °C per second to be applied selectively along the length of the strip. The strip exits the run-out table at a precisely controlled coiling temperature and is wound into a coil at the downcoiler.
For long products such as structural sections, the equivalent device is the cooling bed: a wide rake of moving fingers that walks the bars sideways across an open-air zone, allowing them to cool naturally at a rate of perhaps 0.5–2 °C per second over five to fifteen minutes, depending on size. For TMT bars the equivalent is the quenching box — a high-pressure water jacket that wraps the bar for a few seconds immediately after the last rolling pass, forming a martensitic case while the core remains hot enough to self-temper.
8.2Thermomechanical controlled processing (TMCP)
Thermomechanical controlled processing — TMCP — is the umbrella term for hot rolling schedules that deliberately combine controlled rolling with controlled cooling to achieve specific microstructures. A typical TMCP route for a high-strength low-alloy (HSLA) plate steel uses three control levers in combination[11]:
- Microalloying with niobium, vanadium, or titanium (typically 0.02–0.10% combined) to retard recrystallisation and pin grain boundaries.
- Finishing in the unrecrystallised austenite region — below the temperature at which static recrystallisation would otherwise occur between passes — so that the austenite grains become heavily flattened (“pancaked”) and accumulated strain is retained.
- Accelerated cooling on the run-out table to a coiling temperature in the bainite range, so that the pancaked austenite transforms to a fine ferrite-bainite mixture rather than coarse ferrite-pearlite.
The result is a material with yield strengths of 460–700 MPa from leaner chemistry than would otherwise be needed, lower carbon content (and therefore better weldability), and better low-temperature toughness. TMCP is now standard practice for line-pipe steel, ship plate, and high-rise structural plates — products where every kilogram saved by a stronger material translates directly into capital cost savings or fuel efficiency.
(Two curves on the same axes: conventional finishing at higher temperature with slow air cooling; TMCP with low finishing temperature and accelerated cooling crossing the bainite nose of the CCT diagram.)
9Mill configurations by product
The same five-stage architecture — furnace, descaler, roughing, finishing, cooling — takes very different physical forms depending on what is being produced. Five product families dominate the world’s hot rolling output[12].
9.1Hot strip mills
The largest and most capital-intensive hot rolling lines are hot strip mills, which convert continuously cast slabs (typically 200–250 mm thick, 1,000–2,100 mm wide) into coiled hot strip 1.5–25 mm thick. A modern hot strip mill consists of a walking-beam reheating furnace, a hydraulic primary descaler, a roughing train of two to five stands (sometimes one reversing rougher plus a continuous coil-box arrangement), a flying crop shear, a secondary descaler, a six- or seven-stand finishing train, a 100 m run-out table with laminar-flow cooling, and one or two downcoilers. Annual production for a single line is typically 3–5 million tonnes; the capital cost is in the hundreds of millions of dollars. Hot strip is the input feedstock for cold rolling (passenger cars, appliances), pipe and tube manufacture, and the construction industry where it is sold as plate and sheet.
9.2Plate mills
Plate mills produce flat product in discrete pieces rather than coils — typically 5–200 mm thick, 1,500–5,500 mm wide, and 5–20 m long. The classic plate mill is a single reversing four-high stand: the slab is rolled back and forth through the same stand, with each pass reducing the thickness and (alternately) lengthening or widening the plate. A modern plate mill adds a stand-alone primary descaler, an edger for width control, an accelerated-cooling system, a hot leveller, and crop and dividing shears. Plate mills produce shipbuilding plate, pressure-vessel plate, line pipe stock, and the heaviest structural plates for skyscrapers and bridges. Production is more flexible but lower-volume than a hot strip mill — a million tonnes a year is a respectable plate mill output.
9.3Section mills
Section mills (also called structural mills) produce I-beams, H-beams, channels, angles, tees, and rails. The input is a bloom (typically 250×350 mm to 400×500 mm) from continuous casting; the output is a long, complex cross-section bar that must be rolled, cooled, straightened, and cut to length. Section mills use specialised stands — universal beam stands for I- and H-sections (with horizontal rolls for the flanges and vertical rolls for the web in a single integrated housing), and conventional two- or three-high stands with grooved rolls for channels and angles. The largest section mills produce 800 mm-deep universal column sections in single rolls; a typical Indian section mill making ISMB I-beams up to ISMB 600 produces 600,000–1,000,000 tonnes per year.
9.4Bar & rod mills
Bar mills produce round bar, square bar, hex bar, flat bar, and reinforcement rebar in lengths of 6–18 m. The input is typically a 100×100 mm to 160×160 mm billet from continuous casting. The mill is a long, low-profile train of two-high stands using grooved rolls in the roughing and intermediate sections and four-high cantilever stands or compact pre-finishing/finishing blocks in the finishing section. Wire rod mills are an extreme variant: the input is the same billet, but the output is a 5–30 mm-diameter coil running at exit speeds of 100 m/s or more, achieved by a high-speed finishing block of eight to ten miniature stands using tungsten-carbide rolls[13]. TMT rebar mills are a specialised variant of the bar mill, with a quenching box immediately after the finishing stand; the TMT process is covered in detail in our TMT Bar Manufacturing Process reference paper.
9.5Specialised mills
Beyond the four main families above, several specialised hot rolling mill types serve narrower markets. Rail mills produce 60–80 kg/m railway rail in lengths up to 120 m using universal stands tailored to the asymmetric rail profile. Seamless tube mills use a piercing process (Mannesmann mill) followed by a plug or mandrel mill to produce hollow tubes from solid round billets; technically these are hot rolling mills although the geometry is unusual. Skin-pass mills apply a very small final reduction to hot-rolled coil to improve flatness and surface appearance, sitting at the boundary between hot rolling and cold rolling.
10Defects, tolerances & quality
Hot rolled material is sold against published tolerance standards (IS 1852 in India, EN 10029 for plate in Europe, ASTM A6 for structural sections in the US) that bound the acceptable variation in thickness, width, length, straightness, flatness, and weight per metre. A modern mill operating with hydraulic gauge control and online thickness measurement can hold thickness within ±1% on hot strip and ±2.5% on heavy plate. Section mills hold weight-per-metre within ±2.5% for medium sections and ±4% for heavy sections per IS 808.
The recurring defect modes are well understood and largely manageable through process control. Surface defects include rolled-in scale (failed descaling), seams and laps (subsurface inclusions or improper roll clearance), slivers (overground or torn surfaces from earlier processes), and skid marks (cooler stripes from furnace beam contact). Internal defects include central segregation inherited from the slab caster, hydrogen flakes (cracks induced by trapped hydrogen during cooling), and ghost lines from non-metallic inclusions. Geometric defects include camber (sideways curvature), edge waves and centre buckles (residual flatness errors after coiling), out-of-square sections, twisted bars, and missing fillets in structural shapes. Each defect mode can be traced to a specific failure of furnace control, descaling, pass design, mill maintenance, or cooling control, and the operator’s job is to keep all of them inside the limits set by the customer specification.
11Standards & further reading
Hot rolling activities in India and Indian-aligned export markets are governed by a small set of Bureau of Indian Standards documents that specify dimensional requirements, mechanical properties, and tolerances. The most relevant are summarised in the table below.
| Standard | Title | Scope |
|---|---|---|
| IS 808 : 1989 | Dimensions for hot rolled steel beam, column, channel and angle sections | Section dimensions, weight per metre, tolerances for ISMB, ISHB, ISMC, ISA |
| IS 1786 : 2008 | High strength deformed steel bars and wires for concrete reinforcement | TMT and CTD rebar grades Fe 415, Fe 500, Fe 550, Fe 600 and ductility variants |
| IS 2062 : 2011 | Hot rolled medium and high tensile structural steel | Chemistry, tensile, impact, and bend properties for grades E 250, E 275, E 350, E 410, E 450 |
| IS 1852 | Rolling and cutting tolerances for hot rolled steel products | Allowable dimensional variation on hot rolled bars, sections, and plate |
| IS 11587 | Structural weather resistant steels | Cor-Ten-equivalent grades for exposed bridge and architectural use |
| IS 10748 | Hot rolled steel strip for welded tubes and pipes | HR strip grades feeding ERW pipe mills |
For deeper treatment of any single topic in this paper, the following sources are recommended:
- For the metallurgy and microstructural evolution: Honeycombe & Bhadeshia, Steels: Microstructure and Properties[14], particularly chapters on austenite decomposition and thermomechanical treatment.
- For pass design and rolling force calculations: Roberts, Hot Rolling of Steel[7], the standard reference work.
- For TMCP and accelerated cooling: Tamura et al., Thermomechanical Processing of High-Strength Low-Alloy Steels[11].
- For mill equipment and process layouts: the technical reference papers published by SMS group, Danieli, and Primetals Technologies, available from their respective websites.
- For Indian plant practice and the IS standards themselves: the Bureau of Indian Standards portal at standardsbis.bsbedge.com, where current IS documents can be purchased and downloaded.
Topic-specific companion papers on this site cover the products of hot rolling in detail: the ISMB I-beam encyclopedia, the ISHB H-beam encyclopedia, the ISMC channel encyclopedia, the ISA angle encyclopedia, and the TMT rebar encyclopedia. The cold rolling counterpart of this paper covers what happens to hot strip after it leaves the coiler: Cold Rolling Mills. The TMT-specific process is covered in TMT Bar Manufacturing Process. Pricing and project enquiries for hot rolling mill equipment and rolls can be directed to G.P. Roll Makers India through the Ask an Expert page; corrections, content suggestions, or general feedback about this paper are welcome at the RollingMill.in feedback page.