Rolling mill stand frame · Mill modulus and housing stretch, gauge sensitivity, monoblock versus split and prestressed housings
A rolling mill housing is the heavy frame, built as a pair of posts, a split housing or a single monoblock, that holds the roll chocks or roll saddles and carries the roll separating force while strip or plate is rolled. Its stretch under load adds directly to the gauge error of the stand. Ask three things first: what rolling force and stiffness the housing is designed for, how its stretch combines with roll and bearing deflections in the mill modulus, and whether the design is monoblock, split or prestressed and how it opens for roll changes and strip wrecks.
Housings (frames) of flat and bar rolling mill stands, including post-type 2-high and 4-high housings and monoblock or split cluster-mill housings. Roll chocks, bearings, rolls, screw-downs and complete rolling mills are outside this page, as are ball mill and crusher housings.
CNFX editorial research · Sources checked October 11, 2026 · 4 sources
Read the mill modulus and the housing's share of stretch
US patent 3,546,913 compares mills of the same 30 in work roll and 84 in roll length. For its "A Standard Mill" with a 1,000 in² housing post area at a nominal 3.0 × 10⁶ lb rolling load, it lists deflections including 0.0029 in at the housing top, 0.0039 in at the housing bottom and 0.0051 in in the housing post, a total rolling deflection of 0.0885 in, a mill modulus of 16,960 tons/in, and a 1.15% change in rolling load to produce a one mil (0.001 in) gauge variation at the strip centre line. [1]
The patent states that "rolling loads normally vary only 5 to 10%". Its heavier "B Standard Mill" with a 1,200 in² housing post area and larger backup rolls reached 19,820 tons/in, 17% stiffer, while its fully prestressed stand reached 417,000 tons/in. [1]
Editorial calculation from the patent's table: the housing top, bottom and post together stretch 0.0029 + 0.0039 + 0.0051 = 0.0119 in, about 13% of the 0.0885 in total; the rest comes from screws, nuts, breaker block, bearings, roll bending and flattening. With 1 mil per 1.15% of load, a 5% load swing moves gauge about 4.3 mil (about 0.11 mm). 16,960 short tons/in is about 5,940 kN/mm. [1]
Editorial note: a stiffer housing alone cannot fix gauge if roll and bearing deflections dominate; ask the supplier for the calculated stretch of the housing under rated force and how it fits in the stand's total mill modulus.
Give the supplier the mill type (2-high, 4-high, cluster), rated rolling (roll separating) force, required housing stretch or stiffness, window dimensions and chock or saddle interfaces, material and casting or fabrication route, inspection (ultrasonic, magnetic particle), machining tolerances on window and liner faces, weight limits for transport and lifting, and the drawings or 3D model the housing must match.
02
Choose monoblock, split or prestressed construction
Sendzimir measures mill housing stiffness, or mill modulus, in metric tons per millimetre of stretch, and states that a stiffer mill gives tighter gauge tolerance and flatter strip. Its monoblock housing for a ZR 21 cluster mill reaches 496 t/mm; its split housing approximates that because the two halves are prestressed together before rolling to more than the maximum roll separating force, so it behaves like a monoblock. [3]
The split design can be opened for roll changes and strip wreck clearing, accepts spacers between the halves for slightly larger work rolls, and can carry load cells between the halves to calculate the actual roll separating force. [3] Sendzimir's Zero Crown housing is designed to stretch uniformly under load through side frame and transverse slab deflection, and Sendzimir states that "Most of the mill flexibility is within the mill rolls, not the housing". [4]
US patent 7,765,844 notes the trade-offs of monoblock cluster-mill housings: high housing stiffness and simple gauge control, but a very small roll gap opening after a strip break, difficulty clearing broken strip from the block, a limited range of work roll diameters, and difficulty measuring rolling force because "the vertical rolling force is dispersed into the mono block by several rolls". [2] Editorial calculation: 496 metric t/mm is about 4,860 kN/mm. [3]
03
Plan manufacture and inspection of the housing
The reviewed sources describe stiffness and construction, not foundry practice; the questions below follow from what the housing must do and are editorial guidance to put to the supplier.
Editorial note: because the housing post and window faces carry the roll force and locate the chocks or saddles, ask for the steel grade and casting or welding route, the mechanical test results, the volumetric inspection method and acceptance level for highly stressed zones, and the flatness and parallelism of machined window and liner faces. Agree whether the housing is finish-machined as a pair, and what measurement report comes with it.
04
Cast steel housings poured and machined to customer drawings
Both suppliers reviewed are heavy steel casting makers producing housings and other mill parts to customer drawings; ask each for the largest housing poured and machined, and for inspection reports from a comparable job.
05
Posts, cap and base, window liners, saddle bores and split joint
Rated force, housing stretch, window tolerances and weight for a mill-housing order
Only the force and stretch rows carry published numbers, both from US patent 3,546,913's 1970 standard mill; section modulus, hardness and tolerances have to come from the supplier's calculation and drawings for your stand.
Field
What it means and published values
Ask the supplier for
Rated Rolling Force (kN)
Roll separating force; patent example 3.0 × 10⁶ lb. [1]
Design and test force.
Frame Section Modulus (cm³)
Bending stiffness of top and bottom.
Calculated value.
Elastic Deformation (mm)
Patent example housing stretch 0.0119 in total. [1]
Stretch at rated force.
Material Grade
Cast or rolled steel grade.
Grade and test certificates.
Operating Temperature (°C)
Ambient or hot-mill exposure.
Range.
Surface Hardness (HBW)
Window and liner faces.
Hardness.
Machining Tolerance (mm)
Window, bores, faces.
Tolerances and report.
Weight (t)
Transport and lifting.
Weight per housing.
Footprint (L×W×H) (mm)
Stand envelope.
Drawing.
07
Send the stand, force and inspection data together
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
2 companies list this product among what they make. Company figures are quoted from each
company's own website; every card states where the relationship came from.
Anshan Metal Co., Ltd.
Manufacturing site to be confirmed for the order
Lists rolling mill housings with bearing chocks, couplings and other steel plant parts.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What is mill modulus?
The stand's stiffness: rolling force per unit of stretch, e.g. tons per inch or metric tons per millimetre; a stiffer mill gives tighter gauge. [1][3]
How much of a mill's stretch comes from the housing?
In US patent 3,546,913's standard mill, housing top, bottom and post stretched 0.0119 in of a 0.0885 in total rolling deflection. [1]
Why are split housings prestressed?
Sendzimir prestresses the two halves above the maximum roll separating force so the housing behaves like a monoblock. [3]
Sources and what still needs a direct check
Sources checked 2026-10-11. US patents 3,546,913 and 7,765,844 describe the inventors' own mills against prior designs; Sendzimir is a cluster-mill maker describing its own housings. Stiffness for your stand must come from its own calculation.
