Steel Mill Bronze Bearings for Casters, Mills and Furnaces: Above the Grease Limit
Manufacture and application of bronze rings, particularly in machinery and equipment.
Steel Mill Bronze Bearings for Casters, Mills and Furnaces: Above the Grease Limit
At 300 °C the grease is gone long before the bearing is. That single fact reorganises how steel mill bronze bearings should be specified, because the component that fails first in a caster, a reheat furnace or a ladle turret is almost never the bronze — it is the lubricant, and then the alloy that was chosen on the assumption that a lubricant would be there. Three separate limits govern these positions: the limit of the grease or oil, the limit of the bronze matrix, and the limit of the solid lubricant. This page sets out each one, maps the bearing positions through an integrated plant from caster to coil, and gives the alloy and counterface figures that belong on the drawing. One clarification at the outset: solid bronze on its own is a low-friction bearing material, not a self-lubricating one. Self-lubrication in the strict sense requires a solid lubricant embedded in the sliding surface.
Three limits, not one temperature rating
The most common specification error on steel mill bronze bearings is to ask for a temperature rating. There is no single number to give, because three independent mechanisms are in play and the lowest one governs.
The lubricant limit — and it is the first one reached
Grease is a soap-thickened oil. Heat attacks it three ways: the base oil evaporates, what remains oxidises into a varnish or a coke-like deposit, and the thickener is left behind as a hard residue that can block the very clearance it was meant to protect. Circulating oil fails differently — it thins, it is washed out by cooling water, or it burns at the contact. In either case the lubricant is gone well before the metal is affected. A furnace car wheel that reads 300 °C at the rim does not have a grease with a 300 °C rating; it has no grease.
The alloy limit — strength and hardness decay with temperature
Bronze loses strength and hardness as temperature rises, and the published room-temperature figures do not hold. More importantly for this industry, the ceiling differs enormously between alloy families:
- Lead melts at 327 °C. That is a hard physical boundary, and it is well below the metal temperature at many plant positions.
- For leaded tin bronzes of the C93700 and C93800 classes, the published maximum mechanical service temperature is approximately 140 °C.
- For C93800, published data gives an incipient melting point of 316 °C — below the melting point of pure lead, because the lead-rich phase is not pure lead.
- For CuSn12, the commonly used upper band is approximately 250 °C.
Read those in order and one conclusion follows: the comparison is made grade by grade, against the published maximum mechanical service temperature of the grade actually being considered, and not against a figure borrowed from another family. A leaded tin bronze of the C93700 or C93800 class leaves the list at approximately 140 °C, which is nowhere near the roughly 250 °C at which CuSn12 is still a candidate — the two are not on the same scale, and a specification that puts them in one band will be wrong at one end or the other. Above approximately 250 °C the answer is an aluminium bronze, because only a change of matrix raises the ceiling. A tin bronze with embedded solid lubricant answers a different question: it is for a position whose temperature already sits inside the tin bronze ceiling but where no grease or oil supply can be maintained. Embedded graphite removes the lubrication limit, not the temperature limit.
The solid-lubricant limit — and why it sits highest
Graphite shears between the planes of its crystal structure. It does not evaporate, and it does not oxidise rapidly or carbonise in the temperature range where organic lubricants have already failed. Its practical ceiling is far above the grease limit, which is precisely why plugged bronze is the standard answer at furnace and caster positions. The published dry coefficient of friction for graphite-plugged bronze — 0.08 to 0.20 — applies across that regime rather than only at room temperature.
Working above the grease limit? Send the measured metal temperature, the load, the motion and the access interval, and we will come back with an alloy, a plug pattern and a counterface specification — or a note that the position needs the alloy family changed.
See graphite-plugged bearing designs
Where they sit in an integrated plant
The positions below run from the caster to the coil, grouped by area. The alloy implication is noted where the temperature or the load removes candidates from the list.
Continuous casting
Mould foot rollers support the strand where the shell is thinnest and the temperature is highest, under water spray and against scale. They are the position where the temperature limit does the most selection work. Segment rollers run the length of the containment section at lower temperature but under ferrostatic load and continuous rotation, with the bearing in a hot, wet, scale-laden environment. Dummy bar heads carry the starting chain and its pivots take shock load at start-up. Mould oscillation linkages run at a few hertz through small amplitudes — a duty that produces fretting in a rolling bearing and that suits a sliding one. Withdrawal and straightening roll supports take high radial load with slow, continuous rotation and heavy water exposure.
Hot and cold rolling
Chock liners and wear plates slide against the housing window under roll separating force. The motion is small, slow and intermittent, and the load is high — a sliding-bearing duty by any definition. Screw-down nuts and spindles convert motor rotation into roll gap adjustment: low speed, very high axial load, and a position where a nut material with good sliding behaviour against a steel screw matters more than tensile strength. Looper supports hold strip tension between stands and oscillate through a limited arc. Pusher and skid mechanisms in the reheat furnace area slide hot billets along skid rails, with the bearing close to the heat source.
Reheat and heat-treatment furnaces
Furnace car and bogie wheels are the classic high-temperature bushing position: high static load, slow rolling with sliding at the flange, direct radiant heat from the charge, and no realistic relubrication during a campaign. Walking beam pivots lift and advance the charge through the furnace in a rectangular cycle — a small-amplitude oscillating duty at temperature. Furnace door and flue damper linkages are lower-load but sit in the hot gas path, and they are the positions most often found seized at an outage.
Ladle and torpedo car
Ladle trunnion bushings carry the full weight of a filled ladle and rotate only when the ladle is tilted for pouring: very high load, very small angular travel, long dwell between movements, and radiant heat from the vessel shell. Turret pivots on a ladle turret see the same combination with the added factor of a rotating superstructure. Ingot and charging crane pivots carry high load at low speed with intermittent operation.
Coiling and strip processing
Coiler mandrel bushings work inside the mandrel where the temperature is moderate but access is poor and the duty is a repeated expansion-and-collapse cycle. Hot strip guides position the strip between stands and are adjusted under load. Pinch roll pivots oscillate through small arcs as the roll gap opens and closes, and they sit in the spray zone.
Material handling
Conveyor rollers, scrap grab hinges and transfer car wheels are the positions where the temperature constraint is relaxed but the contamination one is not. A scrap grab hinge is a high-shock, low-speed joint that rarely receives lubrication attention; away from the furnace it is a legitimate place for a leaded bearing bronze with its published machinability rating of 70 (free-cutting brass = 100) and a regular greasing routine. Put the same hinge next to a reheat furnace door and it is not.
Temperature map of a steel plant by zone
The alloy table that follows answers the question “what can this grade take?”. This table answers the one that arrives first on a plant: “roughly how hot is this position, and what does that remove from the list?” It is a triage tool, not a design method — the bands are general industry practice for estimating duty, and the figure that governs any specific bearing is the measured metal temperature at that bearing.
| Zone | Approx. metal temperature band | Lubrication failure mode | Candidate material system |
|---|---|---|---|
| Continuous caster — mould foot rolls, segment rolls, oscillation linkages | High. Strand surface is well above 900 °C; bearing temperature depends entirely on the cooling circuit | Grease cokes; cooling water and scale then wash out or abrade whatever remains | CuAl10Fe5Ni5-C (CC333G) with embedded graphite. CuSn12-C with graphite only where the measured metal temperature stays below approximately 250 °C. No leaded grade at any point in this zone. |
| Reheat furnace — car and bogie wheels, walking beam pivots, skid pushers | High. Several hundred °C at the wheel rim over a campaign | Grease is gone within hours; there is no relubrication during a campaign | Aluminium bronze with embedded graphite. No leaded grade. CuZn25Al5 is excluded on its published 260 °C ceiling, and separately on dezincification where the position is wetted. |
| Heat-treatment and annealing furnaces — bogie wheels, door and damper linkages | Moderate to high, and highly position-dependent | Lower load than a reheat furnace, but these are the positions most often found seized at an outage | Aluminium bronze with graphite for wheels and beams. CuSn12-C with graphite is admissible at door and damper linkages where the measured metal temperature stays below approximately 250 °C. |
| Hot rolling mill — chock liners, screw-down nuts, looper pivots | Moderate, with radiant spikes during delays and cobble clearance | Oil thins and is displaced by cooling water; scale enters with it | CuZn25Al5 (CC762S) for screw-down nuts and large wear plates where the wetted duty has been checked for dezincification. CuAl10Fe5Ni5-C where the measured temperature rules the brass out. |
| Ladle and torpedo car — trunnion bushings, turret pivots, charging crane pivots | Moderate to high, driven by radiant heat from the vessel shell rather than by contact | Very high load, very small angular travel and long dwell: starvation rather than wash-out | CuAl10Fe5Ni5-C with graphite. CuSn12-C or CuSn12Ni2-C with graphite where the measured metal temperature stays below approximately 250 °C. No leaded grade. |
| Cooling bed and run-out table — transfer pivots, apron guides | Falls along the bed: high at the hot end, near ambient at the discharge end | Water spray and scale, with the temperature falling along the machine | Aluminium bronze with graphite at the hot end; CuSn12-C or CuSn12Ni2-C with graphite once the measured temperature is below approximately 250 °C. One bed can legitimately carry two specifications. |
| Coiling, shear and descaling — coiler mandrel bushings, pinch roll pivots, shear linkages | Low to moderate, with poor access the governing problem | Grease survives thermally but the greasing round does not reach the position | CuSn12-C or CuSn12Ni2-C with graphite, for access reasons rather than thermal ones. A leaded grade is admissible here only where the measured temperature stays low and a greasing routine is genuinely maintained. |
Temperature bands are general industry practice for estimating duty, not a design code, and they are stated for triage rather than for dimensioning. The governing figure is the measured metal temperature at the bearing itself. Where that cannot be measured, treat the position as hot until proven otherwise.
Two exclusion rules that apply across the whole map. First, leaded grades — CuSn7Zn4Pb7 and the C93700 and C93800 classes — are not candidates at caster mould foot rolls, segment rolls, furnace car wheels, walking beam pivots, ladle trunnions or furnace door linkages, all of which run above the approximately 140 °C published maximum mechanical service temperature for the class either continuously or during an upset. Second, CuZn25Al5 is not a leaded alloy and is therefore not excluded by the first rule, but its published maximum operating temperature of approximately 260 °C keeps it out of the furnace interior, and it is separately susceptible to dezincification wherever the position is wetted.
Where the map stops being useful. Above roughly 450–500 °C, oxidation of graphite in air becomes appreciable, and the solid-lubricant limit stops being an already-solved part of the problem and becomes a design question in its own right. At those temperatures the plug material, the atmosphere at the contact and the duty cycle all have to be considered together, and the envelope set out later on this page no longer applies by default.
Customization Bronze rings
The rings are manufactured to meet exact client specifications, with precise measurements and tailored designs.
Bronze rings Specific Uses
Alloy selection for high-temperature bronze bearings
The table below covers the alloys that carry most of this work. Values are published specification figures. Rows are ordered by published maximum service temperature, with the grades for which no single published figure could be established placed last.
| Designation (EN / DIN) | UNS (comparable) | Rm MPa | Rp0.2 MPa | A5 % | Hardness (min. unless stated) | Density g/cm³ | Published max. service temperature | Machinability |
|---|---|---|---|---|---|---|---|---|
| CuSn12-C CC483K / 2.1052 |
comparable to C90800 | 300 min. | 150 min. | 6 min. | 90 HBW min. | ≈8.8 | ≈250 °C | — |
| CuZn25Al5 CC762S comparable |
comparable to C86300 / SAE 430B | 780 typical |
— | — | 210 HB typical |
7.83 | ≈260 °C published manufacturer data, 500 °F |
— |
| CuSn10-C CC480K |
comparable to C90500 | 280 min. continuous |
170 min. | 10 min. | 80 HBW min. | ≈8.8 | — | 30 |
| CuAl10Fe5Ni5-C CC333G |
comparable to C95800 / C95500 | 650 · 600 min. | 280 · 250 min. | 13 min. | 150 · 140 HBW min. | 7.6–7.64 | — | 50 |
| CuAl10Ni5Fe4 CW307G / 2.0966 |
comparable to C63000 | 620–760 typical 640–690 |
270–380 typical |
15 typical |
180–248 HBW typical 180 |
≈7.6 | — | no published rating |
| CuAl11Ni5Fe5 CW308G / 2.0978 |
comparable to C63020 | ≈896–931 | — | — | ≤255 HB | ≈7.5 | — | no published rating |
A dash in the temperature column means published values for that grade conflict across the sources consulted; the figure must be established from the governing specification and the material test certificate rather than taken from a secondary source. Values compiled from published EN, DIN, ASTM and SAE data sources, cited here solely as published material property data. Cross-system designations are comparable to, or similar but not identical to, one another — verify before substitution. Machinability is the published rating against free-cutting brass = 100; aluminium bronzes carry no such rating and are described in published sources as comparable to steel of the same hardness. Two notes apply to every row. (1) Section-size effect: properties are bound to the test-bar or casting section size in the governing specification; large sections generally show lower strength and hardness, particularly in yield, and the outer skin of a casting is harder than its core, so a component machined heavily from one face no longer retains as-cast surface values. (2) Figures quoted as min. are specification floors, not expected production values — do not design to the minimum. The two figures separated by · are continuous, centrifugal or permanent-mould casting, and sand casting, respectively. Separately, all published values are room-temperature values and decay as temperature rises.
Reading the table for plant duty
CuAl10Fe5Ni5-C (CC333G) is the workhorse for hot, wet, scale-laden positions. At 650 MPa minimum in continuous, centrifugal or permanent-mould castings it carries the load, the aluminium oxide surface film gives it the corrosion and oxidation behaviour that a furnace-area position needs, and its published machinability rating of 50 keeps it practical to finish. Foot rollers, segment roller bearings, chock liners and furnace car wheel bushings all start here.
CuAl10Ni5Fe4 and CuAl11Ni5Fe5 move the strength up. CW307G at 620–760 MPa and typically 640–690 MPa, with 180 HBW typical, is the choice where section strength and wear resistance govern over castability. CW308G at approximately 896–931 MPa and up to 255 HB is the upper end of the range, used where a smaller section has to carry the same load — and it should be specified with the section-size caveat firmly in mind, because those figures come with a hardness ceiling rather than a floor.
CuSn12-C and CuSn10-C belong in the cooler bands. Where the measured metal temperature stays below approximately 250 °C, CuSn12-C at 300 MPa minimum remains a sound choice: good sliding behaviour, tolerance of a less-than-perfect counterface, and it embeds small particles rather than scoring. CuSn10-C at 280 MPa minimum in continuous castings brings better elongation at 10 % and a published machinability rating for C90500 of 30 — which is the practical point to remember, because 30 against free-cutting brass at 100 means longer cycle times and a different tooling approach than a leaded bronze at 70.
CuZn25Al5 at 780 MPa typical and 210 HB typical is the high-load choice for screw-down nuts, large wear plates and slow heavily loaded sliding surfaces. Its published tensile figure is a typical value rather than a specification minimum, so it should not be quoted as a floor. On temperature, published manufacturer data sheets for this alloy give a maximum operating temperature of approximately 260 °C (500 °F); that figure, and not the strength, is what decides whether the grade can be placed in a hot position. The same sources record that the alloy is susceptible to dezincification, which is a separate constraint from temperature and one that has to be checked wherever the position is wetted. As with every alloy here, the measured metal temperature comes first.
Where leaded alloys can and cannot be used. This is the paragraph that gets specified wrongly most often in this industry, so it is stated in full. Leaded bronzes are used because lead improves machinability and provides a smear of soft phase that helps boundary lubrication. Both advantages depend on the lead staying solid. Lead melts at 327 °C; the published maximum mechanical service temperature is approximately 140 °C for the C93700 and C93800 classes; and C93800 has a published incipient melting point of 316 °C. Therefore: a leaded tin bronze is not a candidate at any position above approximately 140 °C — not at caster mould foot rollers, segment rollers, furnace car wheels, walking beam pivots, ladle trunnions or furnace door linkages, all of which run above that figure either continuously or during an upset. What replaces it depends on the measured metal temperature. Where that temperature is above approximately 250 °C, specify an aluminium bronze from the table above, because only a change of matrix raises the ceiling. Where it sits below the tin bronze ceiling and the difficulty is that no grease or oil supply can be maintained at the position, a tin bronze with embedded solid lubricant is the answer — embedded graphite removes the lubrication limit, not the temperature limit. Where measurement is not possible, treat the position as hot until proven otherwise. State the reason on the drawing so the next person to revise it does not undo the decision. Leaded alloys remain entirely appropriate at cool positions with a regular lubrication routine — a scrap grab hinge away from the furnace, a transfer car wheel in a clean bay, a general-purpose machine bearing. The test is the measured metal temperature, not the area of the plant.
The following is a composite description of representative duty, not a measured installation. Where two positions carry the same part number and one of them fails early, the cause is frequently the metal temperature rather than the load, the fit or the installation. A furnace car wheel position runs at a metal temperature far above ambient for the length of a campaign; the same part number on a transfer car in the same building stays close to ambient. Specified in a leaded bronze, the first is outside the published service temperature for the class and the second is well inside it. Nothing about the load, the fit or the installation needs to be wrong for that to happen — the drawing simply omitted the one input that mattered.
Solid lubrication design at temperature
Where a position cannot be lubricated during a campaign, the lubricant has to be part of the bearing. The published design envelope for graphite-plugged bronze in dry running is:
Graphite-plugged bronze — published engineering envelope (dry running)
- Allowable surface pressure, dry running: ≈100 N/mm² (aluminium-bronze matrix up to 120)
- Sliding speed, dry running: ≤0.5 m/s
- PV ceiling, dry running: ≈1.0–2.5 N/mm²·m/s (oil-lubricated up to 5.0)
- Counterface hardness: ≥40–45 HRC, surface finish Ra ≤0.8 µm
- Coefficient of friction, dry: 0.08–0.20
These figures apply to dry running. Where a PV or load value is quoted, the lubrication regime — dry, boundary or full-fluid — and whether the duty is continuous or intermittent must be stated alongside it. Published plug coverage is 20–30 % of the sliding surface (some standards specify 25–35 %) at φ3–10 mm. The same envelope applies across all bronze bushing applications; what separates one path from another is the operating condition that governs, not the numbers themselves.
Three consequences follow for plant duty. First, at 0.5 m/s the speed ceiling is not usually the binding constraint at a caster or furnace position, because the motion is slow — the pressure ceiling of approximately 100 N/mm² is what sizes the projected area. A ladle trunnion carrying a filled vessel turns that into a substantial bearing length. Second, coverage matters more than plug diameter at high load: the transfer film has to be continuous across the load zone, and 20 % coverage on a wide, heavily loaded trunnion behaves differently from 30 % coverage on a narrow one. Third, at an aluminium-bronze matrix the pressure ceiling rises to 120 N/mm², which is often the deciding argument for CC333G at a hot, heavily loaded position.
Wear plates and slide plates
The same principle applies where the geometry is flat rather than cylindrical. Chock liners and housing window wear plates slide under roll separating force at very low speed — the pressure ceiling governs, the speed ceiling never does. Expansion joint slide plates under furnace structures and ductwork accommodate thermal growth of the structure: the sliding distance is small, the duty is intermittent, and the position is essentially inaccessible once the plant is hot. Both are natural applications for graphite-plugged bronze wear plates, and in both cases the counterface — 40–45 HRC or harder at Ra 0.8 µm or finer — is the specification most often left off the drawing.
Scale, cooling water and exclusion
Mill scale is a hard, sharp abrasive. Cooling water is a lubricant displacer. In a caster or a rolling stand they arrive together, and they are the reason two specifications on the counterface are not optional.
Counterface hardness: 40–45 HRC or harder. A soft shaft or pin lets hard scale particles embed in it, and an embedded particle then machines the bushing bore on every pass. Hardening the counterface is the single cheapest measure available against this mechanism.
Surface finish: Ra 0.8 µm or finer. A rough counterface abrades the transfer film faster than the plugs can replace it, and it holds water against the surface. Both effects shorten life, and neither is visible from outside the housing.
Exclusion before retention. At a caster or spray-zone position, the more useful sealing question is not how to keep grease in but how to keep water and scale out. A labyrinth on the outboard side, a lip or felt element, or a simple scraper in front of the bearing all reduce ingress; a seal fitted only to retain grease will usually be defeated by the spray pressure anyway. Where exclusion cannot be made to work, a plugged bronze with embedded solid lubricant removes the question — it does not matter that water washes the interface if there is no fluid lubricant there to wash out.
Clearance allowance for ingress as well as growth. The fitted clearance has to accommodate thermal growth (next section) and a working allowance for particles that get past the exclusion. A bushing sized on growth alone will seize in a scale-laden position.
Thermal expansion and clearance
Bronze expands more than steel. Where a bronze bushing is fitted into a steel housing on a steel shaft, the outside diameter is constrained while the bore grows faster than the shaft — so the running clearance increases with temperature, and the cold clearance must be chosen accordingly. Reverse the materials and the opposite happens.
Three checks are worth doing on the drawing rather than on the floor. First, calculate the bore growth at maximum metal temperature from the coefficient of expansion and the bore size, and confirm the hot clearance is still within what the application tolerates. Second, confirm the bushing can grow at the outside diameter without extruding at the housing — a retained bushing in a hot housing needs the retention designed for the hot condition, not the cold one. Third, confirm the cold clearance at start-up, which in a furnace car that begins its campaign at ambient is a genuinely different condition from the running one.
There is no universal allowance to quote here, which is the point: the number comes from the bore, the temperature rise and the material pairing. Our fits and clearances reference sets out the method; the designer remains responsible for the result.
Steel Plant Bronze Bearings: Bushing and Wear-Plate Selection
plain bearings, wear plates and nuts in steel and metallurgy plant — ladles, rotary kilns, furnaces, rolling mills, casting and metal-forming equipment.
Shapes of Bronze Rings:
High-precision machining for tight tolerances and smooth finishes, tailored to specific shapes, sizes, and features. Common bronze alloys like phosphor bronze, aluminum bronze, and silicon bronze offer unique properties, including strength, corrosion resistance, and electrical conductivity.
Manufacturing Capabilities
Customization and Support
A steel plant is one of the hardest environments for a plain bearing outside a mine: high and often near-continuous load, radiant and conducted heat, abrasive scale and dust, and hydraulic and process fluids. Ladle trunnions, rotary kilns, furnaces, rolling mills and casting and metal-forming lines all depend on bushings and wear parts that carry enormous load, tolerate heat and contamination, and protect the pin or structure. This page sets out these applications, the alloys that fit each, and where graphite-plugged or self-lubricating bronze is the workable answer.
Why steel plant duty is extreme
Steel and metallurgy bearings fail in ways that combine the worst of several worlds. Load is carried heavily and often continuously, so there is little unloaded dwell for an oil film to re-form. Motion is a slow oscillation, a low-speed partial rotation, or an intermittent slide under full load and frequent shock. And the environment — heat, abrasive scale, dust, water sprays and process fluids — attacks both the bearing and any lubricant.
Three consequences follow. First, boundary or mixed lubrication is the normal running state at many positions, so the bearing material must tolerate brief metal contact and embedded hard scale. Second, a seized ladle trunnion or a failed kiln support bushing can stop a whole production line or a heat, at high cost. Third, because the duty is so severe, the bearing is usually the deliberately replaceable part: it is designed to wear before the pin or the expensive structural member does.
This is the context in which bronze is specified rather than steel-on-steel or a rolling bearing. Bronze tolerates contamination and shock, protects the pin, holds load at elevated temperature better than most polymers, and — in the graphite-plugged and self-lubricating forms — keeps a slow-moving joint working where grease cannot survive.
Ladle and furnace positions
Ladle trunnions carry the full weight of a ladle and its molten metal through a slow oscillation as the ladle is lifted and tilted, under enormous static load and radiant heat from the hot shell. EAF and BOF tilt and electrode positions add similar heavy, slow, hot duty. The bushing must carry the load, tolerate heat and scale, and — because the ladle is tilted only occasionally — must not seize after long idle periods.
High-strength cast bronze is the usual choice for the trunnion bushing, sized so that wear goes to the bushing rather than to the trunnion pin, which is far more costly to replace. Where the position cannot be greased reliably, or where heat and scale defeat grease between tilts, a graphite-plugged bronze carries the load dry and keeps the joint free; see the graphite-plugged bronze bearings page. The aluminium bronze and high-tensile brass material pages cover the grades for this heavy, hot duty.
Selection note
Ladle and furnace structures carry molten metal and are governed by plant safety codes and the responsible engineer. A trunnion bearing is not a component whose allowable load a supplier fixes from material alone: the sizing, material approval and inspection regime for a load-bearing or safety-relevant structure must be established against the applicable code and the plant specification.
Rotary kilns and dryers
Rotary kilns rotate continuously at low speed under the full weight of the shell and its charge, supported on tyres and rollers. The support-roller and thrust bushings carry this load around the clock, at elevated temperature and in an environment of dust and heat where a grease system is difficult to keep clean.
Tin bronze and aluminium bronze are both used in kiln support positions, chosen for load capacity, wear resistance and behaviour at temperature. Where access is limited or heat defeats routine greasing, a self-lubricating bronze keeps the roller running. The tin bronze material page covers the grades commonly selected for kiln bushings.
Rolling mills and screw-down positions
Rolling mills apply enormous force to reduce metal, and the screw-down and adjusting positions carry this force through slow rotation or reciprocation. Bronze nuts and bushings are widely used here: the nut is the deliberately replaceable, thread-protecting part that takes the wear of the screw so the costly screw can be renewed far less often.
High-strength aluminium bronze is commonly used for heavy mill screw-down and guide bushings for its strength and wear resistance, often with a solid lubricant where the position runs dry or is hard to service. The high-tensile brass and aluminium bronze pages cover the grades for mill duty. Guide, table-roller and auxiliary bushings across the line use the same alloy logic matched to load and access.
Casting and metal-forming lines
Ingot casting and metal-forming lines add reciprocation, slide and intermittent rotation under heavy load, in heat, scale and water spray. Uncoiler mandrels carry the weight of a coil through slow rotation, and forming presses and slides add shock. These positions are hard on a grease film, so bronze with an embedded solid lubricant is common.
For a dry, heavy slide or reciprocating position, graphite-plugged or solid-lubricant bronze tolerates the scale and heat that destroy grease and keeps the part moving until a planned service. The solid lubricants material page explains how graphite and similar plugs work and how coverage is set for the motion.
Wear plates and slide surfaces
Where a surface slides rather than pivots, the bearing appears as a wear plate or slide block — on forming presses, guides and moving machinery parts. These carry high surface pressure with slow, intermittent motion in heat, scale and dust.
Plate geometry and bed-in matter as much as the alloy. A plate allowed to rock or edge-load concentrates the whole load at a corner and fails quickly; the counterface must be flat and smooth, and the plate needs enough length for the load to spread. Mounting must stop rotation and creep. Where the plate runs dry, graphite coverage is set by the motion so a film is maintained across the whole stroke. See the bronze wear plates page for design guidance.
Specification checklist
Seven items, and the temperature ones are the ones most often missing on a plant drawing:
- Alloy designation and casting method — the mechanical figures differ between continuous, centrifugal, permanent-mould and sand casting.
- Maximum metal temperature — measured or estimated at the bearing, not the furnace or strand temperature.
- Load and motion — peak and mean load, amplitude, speed, and whether the duty is continuous or intermittent.
- Counterface specification — 40–45 HRC or harder, Ra 0.8 µm or finer, stated for the shaft or pin.
- Fitted clearance and thermal growth allowance — both figures, with the calculation attached.
- Lubrication regime — dry, boundary or full-fluid, and the plug coverage and diameter where the design is dry-running.
- Inspection interval and wear limit — expressed as a measurable dimension, not a judgement.
Have the metal temperature and the load? Send those two plus the motion and the access interval and we will return an alloy, a plug pattern, a clearance and a counterface specification for the position.
Compare published bronze material properties
Frequently asked questions
What is the maximum service temperature for a bronze bushing in a steel plant?
There is no single figure, because three separate limits apply and the lowest one governs. The lubricant limit comes first: grease cokes or loses its base oil by evaporation, and oil is washed out or burns, in each case long before the metal is affected. The alloy limit follows: published figures are approximately 250 °C for CuSn12 and approximately 260 °C (500 °F) for the C86300-class high-tensile brasses, while leaded tin bronzes of the C93700 and C93800 classes sit at approximately 140 °C. Aluminium bronzes extend the range substantially, because a change of matrix is what raises the alloy limit; embedding a solid lubricant does not raise it, since the plugs address the lubrication limit rather than the strength of the metal holding them. The solid-lubricant limit is the highest of the three, because graphite remains effective at temperatures far above the point at which any organic lubricant has gone. State all three on the drawing rather than one rating.
Can leaded bronze alloys be used at caster or furnace temperatures?
Not at those temperatures. Lead melts at 327 °C, and the published maximum mechanical service temperatures for the common leaded tin bronzes sit well below that — approximately 140 °C for the C93700 and C93800 classes. Caster mould foot rollers, segment rollers, furnace car wheels and ladle trunnions all run above that figure, either continuously or during an upset. What replaces it depends on the measured metal temperature. Where that temperature is above approximately 250 °C, specify an aluminium bronze from the table above, because only a change of matrix raises the ceiling. Where it sits below the tin bronze ceiling and the difficulty is that no grease or oil supply can be maintained at the position, a tin bronze with embedded solid lubricant is the answer — embedded graphite removes the lubrication limit, not the temperature limit. Where measurement is not possible, treat the position as hot until proven otherwise. Leaded alloys remain appropriate for cool, regularly lubricated positions away from the heat.
Why does graphite keep lubricating after the grease has cooked?
The two fail by different mechanisms. Grease is a soap-thickened oil: heat drives off the base oil by evaporation, oxidises what remains into a varnish or a coke-like residue, and leaves the thickener behind as a hard deposit that can block the clearance. Graphite is a crystalline solid whose layered structure shears between its planes, and it does not evaporate, oxidise rapidly or carbonise in the same temperature range. In a plugged bushing the graphite sits in holes in the bronze rather than in the clearance, so it keeps being fed to the surface as the bronze wears. The published dry coefficient of friction of 0.08–0.20 applies to that regime.
Which grade is used for continuous caster mould foot rollers?
Start from the measured metal temperature at the roll surface and work downwards, because temperature is the input that removes most candidates from the list. Foot rollers run hot, are sprayed or internally cooled with water, and carry the ferrostatic pressure of the strand, so leaded alloys are excluded on temperature grounds. The usual starting points are CuAl10Fe5Ni5-C (CC333G, comparable to C95800) at 650 MPa minimum in continuous, centrifugal or permanent-mould castings, and CuAl10Ni5Fe4 (CW307G, comparable to C63000) at 620–760 MPa where section strength governs. Where measured metal temperature stays below approximately 250 °C and the water circuit keeps it there, CuSn12-C remains an option. Confirm every value against the material test certificate.
How do you deal with mill scale and cooling water at the bearing interface?
Treat scale as an abrasive and water as a lubricant displacer, because that is what they are, and address both at the same time. Three measures work together: a counterface at 40–45 HRC or harder finished to Ra 0.8 µm or finer, so that hard scale particles are less able to embed and score; an exclusion arrangement on the outboard side of the bearing — a labyrinth, a lip or a scraper — since a feature that keeps water out is more useful here than one that keeps grease in; and a clearance allowance sized for particle ingress as well as for thermal growth. Where the bearing is directly sprayed, a bronze with embedded solid lubricant removes the washout mechanism altogether.
How much clearance allowance is needed for thermal expansion?
There is no universal allowance, because it depends on the bore size, the temperature rise above the fitting temperature, and the difference between the expansion of the bronze and the expansion of the shaft and the housing. The calculation is not optional: a bushing that cannot grow will either seize on the shaft or extrude at the housing bore. Work from the coefficient of expansion of each material, the maximum metal temperature and the fitted clearance, and check the result against both the seizure case and the ovality case. Where the housing is steel and the shaft is steel, the bronze grows more than either, so the bore clearance increases with temperature while the outside diameter is constrained.
Can graphite-plugged wear plates be used as rolling mill chock liners?
They suit that duty where the motion is sliding rather than rolling and the published envelope is respected. A chock liner slides against the housing window under load, at very low speed, and intermittently — which is what graphite-plugged bronze is designed for. The published allowable surface pressure for dry running is approximately 100 N/mm², rising to 120 for an aluminium-bronze matrix, with a sliding speed ceiling of 0.5 m/s and a PV ceiling of approximately 1.0–2.5 N/mm²·m/s. These figures apply to dry running; where a PV or load value is quoted, the lubrication regime and whether the duty is continuous or intermittent must be stated alongside it. The counterface must also be 40–45 HRC or harder at Ra 0.8 µm or finer.
What goes on the drawing for a high-temperature furnace car wheel bushing?
Seven items, and the temperature ones are the ones usually missing. The alloy designation together with the casting method, because mechanical figures differ between continuous, centrifugal, permanent-mould and sand casting. The maximum metal temperature, not the furnace air temperature. The counterface specification: 40–45 HRC or harder, Ra 0.8 µm or finer. The fitted clearance together with the thermal growth allowance. Where the design is dry-running, the solid-lubricant coverage and plug diameter — 20–30 % coverage at φ3–10 mm is the published range. Whether the duty is continuous or intermittent. And the inspection interval with the wear limit expressed as a measurable dimension rather than as a judgement call.
Bushing applications by equipment
The table below maps the common bearing and wear positions across steel and metallurgy plant to the bearing form normally used. Individual plants differ, and the list is a starting point for a drawing review rather than a fixed recipe.
| Equipment | Application / position | Motion | Typical bearing form |
|---|---|---|---|
| Ladles & furnaces | Trunnion and tilt bushings on ladles, EAF and BOF | Slow oscillation / partial rotation under very heavy load | High-strength cast bushing; graphite-plugged for dry or hot duty |
| Rotary kilns | Support-roller and thrust bushings, kiln drive positions | Low-speed continuous rotation, heavy load, heat | Tin-bronze bushing; self-lubricating where access is limited |
| Rolling mills | Screw-down nuts, guide and table-roller bushings | Slow rotation / reciprocation under high screw load | Bronze nut / bushing, high-strength alloy; graphited where dry |
| Casting & forming | Ingot-casting and metal-forming wear parts | Reciprocation / slide under load | Bronze wear plate or bushing with solid lubricant |
| Coil processing | Uncoiler mandrel and payoff bushings | Slow rotation, heavy coil load | Cast bushing; bronze with plugs where dry |
| Furnace auxiliaries | Door, electrode and mechanical bushings near heat | Oscillation / slide, heat exposure | Cast bushing; graphite-plugged where heat defeats grease |
Application mapping is based on common steel-plant layouts and is for selection orientation. The governing drawing and the plant specification take precedence for any specific equipment. Bushing forms and materials are covered on the bronze bushings and self-lubricating bearings pages.
Alloy selection for steel plant duty
Where grease can be applied on a reliable schedule, plain cast bronze is the conventional choice. In heat and scale, the same alloy body is used with solid graphite plugs. The main alloys in steel plant bushings are summarised below; full composition and property tables live on the material pages rather than being repeated here.
| Alloy | Strong points | Typical steel-plant role |
|---|---|---|
| C95400 aluminium bronze | High strength, fatigue and wear resistance; good hot hardness | Ladle trunnions, mill screw-downs and heavy bushings |
| C86300 (manganese bronze / high-tensile brass) | Very high strength for extreme static and shock load | Heavy mill and press bushings under extreme load |
| C93200 (SAE 660) leaded tin bronze | Good embeddability and conformity; tolerant of dirt and scale | General greased bushings across the plant |
| High-tin / phosphor bronze | Good strength and wear; stable behaviour at temperature | Kiln and continuous-rotation support bushings |
Cross-standard equivalents and composition limits are on the alloy grade page and the aluminium bronze, high-tensile brass, leaded tin bronze and tin bronze material pages.
Two points recur in steel-plant enquiries. The first is that the bushing or nut is usually the sacrificial part: it wears before the pin, screw or structural member does, which is why a mill screw-down nut is specified as the replaceable element that protects the screw. The second is that aluminium bronze and high-tensile brass need a counterface hard enough and smooth enough to avoid galling, which is why they are specified with a hardened, ground pin or screw.
