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Steel Mill Roll-Neck Bearings: Lithium Complex or Calcium Sulfonate?
Roll-neck bearings see roll-cooling water, abrasive scale, shock at the bite and heat. Lithium complex is the familiar pumpable default. Calcium sulfonate usually holds up better once water arrives. Aluminium complex is a third option, not a tie-breaker you skip.
Direct answer
Roll-neck bearings see water, scale, shock load and heat. Lithium complex is the familiar Indian default because it pumps; calcium sulfonate complex usually holds its structure and extreme-pressure response better once roll-cooling water arrives, at a cost in pumpability. Aluminium complex is the option when sprayability and water resistance matter and you do not want a sulfonate. The wrong call shows up as washed-out grease and scored necks, not as a missed dropping point.
- Separate grease-lubricated roll-neck bearings from oil-film backup rolls. They are not the same fill.
- Water washout and spray-off decide more steel-mill arguments than dropping point.
- Lithium complex often needs added EP that can wash away. Calcium sulfonate carries more of that response in the thickener.
- NLGI 1 and NLGI 2 can be the same chemistry for different relube hardware. Do not mix families to get there.
- Build a small SKU set for the stand, the table and the auxiliaries instead of one mill drum.
Duty cycle of a typical rolling mill
A rolling-mill stand is wet, dirty and sudden. Work-roll and some backup chock bearings that are grease lubricated see roll-cooling water, mill scale, shock when the bar enters the bite, and heat conducted out of the roll. Many large backup rolls are not on grease at all: they sit in circulating oil-film bearings. Putting a roll-neck grease into an oil-film bearing, or judging the grease by Morgoil practice, is a category error. Confirm which bearings are anti-friction and grease-fed before you open a thickener debate.
The cycle that matters is not average load. It is water on the chock, scale in the seal, a relube pulse from a centralised system, and long stops where wet grease sits and rusts. ISO 12924 can classify the product afterwards. It will not tell you whether this stand is a water problem or a heat problem. Write both, with a measured temperature if the stand runs hot, and say whether relube is a gun, a single-line system or a dual-line system.
LiX vs CaSX vs aluminium complex for mill stands
Lithium complex is the default because plants already pump it. Properly made, it has a high dropping point by ASTM D2265 and a workable consistency across NLGI 1 and NLGI 2. Its extreme-pressure response is mostly added sulfur-phosphorus chemistry, not the soap. That package can be good on a fresh ASTM D2596 weld and still be the part that leaves when roll coolant washes the bearing. Calcium sulfonate complex is built differently: the overbased sulfonate and its calcite structure carry load and rust protection inside the thickener, which is why it is the usual candidate once D1264 washout and D4049 spray-off become the argument. It is also more viscous under the shear of a long line. Apparent viscosity, ASTM D1092, belongs in the brief if the pump is already marginal.
Aluminium complex is the third family, not a footnote. It has a long history in wet, sprayable industrial greases, including mill duties where water resistance and a high drop point are wanted without a sulfonate thickener. It is not a lithium complex with a different label, and it is not automatically food-grade because some aluminium-complex products are. Industrial EP versions and incidental-food-contact versions are different formulas. Manufacturing routes for the first two families are on the lithium complex and calcium sulfonate complex pages. Choose here; cook there.
Water, scale and relube interval as the real spec
Scored necks are usually a film that was washed out, starved or packed with scale. A higher dropping point does not fix any of those. Specify water with ASTM D1264 and, if the stand is deluged, ASTM D4049. Specify rust with ASTM D1743 or ASTM D6138, because mills stop and wet grease sits. Specify load with ASTM D2596 and wear with ASTM D2266, and write them as screens. A four-ball weld is not a campaign on a hot mill. DIN 51819 FE8 is the more serious mechanical-wear method when the buyer will pay for it; DIN 51821 FE9 is the hot-life method when temperature, not water, is the claim.
Scale is an abrasive solid. Adding graphite or molybdenum disulfide because a cement gear uses them can make a wet rolling bearing worse. Solids belong only if the contact truly frets or slides and the seal can tolerate them. The relube interval is a specification line: volume per pulse, how many bearings one injector feeds, and whether dirty grease can leave. If fresh grease cannot purge scale, no thickener upgrade survives the shift.
Centralised NLGI 1 vs NLGI 2 at the bearing
NLGI grade is consistency, measured by ASTM D217 worked penetration at 25 °C, not quality. NLGI 2 sits in a hand-packed housing. NLGI 1, and sometimes NLGI 0, is what a long centralised line in a cool cellar will still move. Using NLGI 2 because the TDS looks more serious is how injectors skip and necks run dry. Using a soft grade in a hot, leaky chock is how the floor is lubricated instead of the race.
Keep one thickener family across the grades you dual-stock. A lithium-complex NLGI 1 on the line and a calcium-sulfonate NLGI 2 in the gun is a mixture, and mixture charts are screens, not permission. Pumpability still needs a low-temperature number: ASTM D1092, DIN 51805 flow pressure, or the system OEM’s own ventmeter limit. Do not invent a “winter grade” by stirring oil into NLGI 2 on the stand. That destroys both the grade and the additive balance.
Building a mill SKU set instead of one drum
A practical set is small. One water-resistant grease for the wet roll necks, in the NLGI grade the centralised system can pump. One general industrial grease for dry tables, cranes and fans that never see roll coolant. An open-gear product only where there is an open gear, formulated as a gear lubricant rather than spooned from the bearing drum. Oil-film bearings stay on their circulating oil, specified as an oil, with demulsibility and cleanliness, not as a grease project.
Lubechem does not sell these as stocked mill drums. The practice formulates them under a brief: water or not, line length, ambient, metal temperature, current TDS, and a photograph of a scored neck or a washed cage. Plant practice and audit language, as distinct from the kettle recipe, sits under industrial lubrication management. No steel producer is named here as a client, and no bearing-life extension is claimed.
What Lubechem will and will not claim
We will not claim a mill reference, a BIS licence or an OEM approval that is not on a certificate you can read. Formulating toward a method is not the same as holding an approval. The hero image is a conceptual illustration of mill duty, not a photograph of a Lubechem site.
We will claim the decision rule. If the failure is white, emulsified grease and rust, start with washout, spray-off and rust methods and look hard at calcium sulfonate or a proven aluminium complex. If the failure is a dead injector in January, start with NLGI grade and D1092, not with a new thickener. If the failure is a brown, oxidised soap in a hot, dry neck, then temperature methods earn the conversation. Compatibility of whatever you displace is a purge plan. A chart is a screen, not a guarantee.
What actually separates mill greases
| Question | Lithium complex | Calcium sulfonate complex | Aluminium complex |
|---|---|---|---|
| Dropping point, ASTM D2265 | High; still not the service limit | Often very high or none observed | High; still not the service limit |
| Roll-cooling water | EP additive can be the part that leaves | Structure and inherent EP usually hold better | Historically used where water and sprayability both matter |
| Long centralised lines | Often the easier pump | Check ASTM D1092 before you commit | Depends on oil viscosity and grade, not on the name |
| Scale and shock | Needs a real EP screen, D2596 / D2266 | Calcite thickener is part of the load response | Do not assume solids; test the duty you have |
People-first note: this is a selection article for roll-neck duty. It names no mill as a client and reports no life extension. Kettle practice stays on the lithium-complex and calcium-sulfonate pages.
Questions plants actually ask
Is calcium sulfonate automatically the right roll-neck grease?
It is the usual candidate when water washout and inherent EP are the failure. It still has to pass pumpability on your line, ASTM D1092 or the OEM’s limit, and it is the wrong conversation if the bearing is actually an oil-film backup roll.
Can we keep lithium complex in the gun and switch only the centralised system to calcium sulfonate?
Not safely. Different thickener families in the same housing are a mixture. Charts are screens, not guarantees. Purge, or stay inside one family and change only the NLGI grade.
Which methods should a mill TDS show for water and load?
ASTM D1264 washout, ASTM D4049 if the stand is heavily deluged, ASTM D1743 or D6138 for rust, ASTM D2596 and D2266 as load and wear screens. FE8 or FE9 only if you actually run them.
Does Lubechem supply mill grease from stock?
No. Lubechem is a formulation practice, not a store. A mill SKU is developed against your water, scale, relube hardware and target methods, and ownership follows the contract.
Literature and prior art
Citations below are orientation, not a freedom-to-operate opinion. Lubechem does not copy claimed compositions and does not treat a patent as a product endorsement.
- ASTM D217, D1092, D1264, D4049, D1743, D6138, D2266, D2596, D2265 — Grade, pumpability, water, rust, wear, EP and drop point. None of these is a mill campaign by itself.
- DIN 51819 FE8 and DIN 51821 FE9 — Mechanical wear and high-temperature bearing life when the buyer needs more than a four-ball screen.
- ISO 12924 and ISO 6743-9 — How to classify the grease after the duty is chosen, not before.