What a QU70 Rail Is and Where It Is Used
QU70 is a crane rail profile in the QU series. It is specified where a compact rail section has to carry concentrated wheel loads from overhead travelling cranes, gantry cranes, transfer cars and rail-mounted yard equipment. The head is narrow in relation to the section height and the web is thick, which suits the largely vertical wheel load of a crane trolley running on a short wheel base.
Typical installations are crane runways in steel processing plants, mining and quarry sites, heavy manufacturing bays, storage yards and light rail track inside industrial complexes. In these duties the rail is usually fixed to a continuous steel girder or to a concrete foundation beam with welded or bolted clips, so the profile has to combine bending stiffness with a base that can be clamped without distortion.
Section selection should not be driven by mass alone. Wheel load, wheel diameter, wheel base, crane span, travel speed and the support spacing of the runway all influence bending stress at the rail base and at the head. A QU70 section is normally adequate for moderate wheel loads; larger trolley loads call for QU80, QU100 or QU120.
Dimensional and Mass Specification
| Profile | Height (mm) | Base width (mm) | Head width (mm) | Web thickness (mm) | Mass (kg/m) |
|---|---|---|---|---|---|
| QU70 | 120 | 120 | 70 | 28 | 52.8 |
| QU80 | 130 | 130 | 80 | 32 | 63.69 |
| QU100 | 150 | 150 | 100 | 38 | 88.96 |
| QU120 | 170 | 170 | 120 | 44 | 118.1 |
Because the four QU profiles share the same geometric logic, one section can be substituted for another on the same runway only after the bending stress, the clip spacing and the crane wheel load have been recalculated. Increasing the section raises the rail line, so the clip height and the crane buffer setting must be adjusted as well.
Steel Grades and Mechanical Requirements
Crane rails in the QU series are normally produced in U71Mn rail steel, the grade family also used for heavy railway rails. The grade combines a pearlitic structure with good wear resistance at the running surface and sufficient toughness in the web and base to resist the repeated impact of a passing wheel. For railway rail profiles of 43 kg/m to 75 kg/m, U71Mn is specified in GB/T 2585, and a tensile strength of not less than 880 MPa is a normal acceptance level for that grade. Crane rail sections themselves are covered by GB/T 3426.
Purchasers who need a harder running surface for high wheel loads or for rail that will stay in service without head replacement should state the requirement on the order, because heat treatment of the head changes both hardness and the permissible straightness after straightening.
Lengths, Drilling and Tolerances
QU70 rail is commonly supplied in 6 m, 9 m, 12 m and 12.5 m lengths, with longer lengths or short cut pieces available to order. Ends are sawn or milled square, free of burrs, and the rail is delivered undrilled unless the buyer provides a joint bar drawing. Drilling is done on a radial drill or a CNC line to the hole diameter, pitch and edge distance on that drawing; holes are deburred and the hole edges are chamfered to reduce stress concentration under the joint bar.
Straightness is the tolerance that most often decides whether a rail is accepted for a crane runway. Rails are roller straightened in the vertical and horizontal planes, then checked against a straightedge with a feeler gauge over a defined length. The permissible deviation, together with the tolerances on height, base width and head width, should be stated in the order drawing so that mill and inspector work to the same number.
Inspection, Handling and Storage
Dimensional check of height, base width, head width, web thickness and camber on a sampling basis.
Visual examination for cracks, laps, scabs, rolled-in scale, deep grooves and mechanical damage at the ends.
Verification of the heat number against the inspection certificate and the marking on the rail web.
Lifting with slings or magnets that do not score the head; rails stacked on timber bearers, clear of the ground, with the layers aligned.
Storage under cover where the rail will not be installed for a long period, especially in coastal or humid environments.
Frequently Asked Questions
Q: What is the mass of a QU70 rail per metre?
A: 52.8 kg/m. The section is 120 mm high, 120 mm wide at the base and 70 mm wide at the head, with a 28 mm web.
Q: How does QU70 differ from QU80?
A: QU80 is 130 mm high with a 130 mm base, an 80 mm head and a 32 mm web, giving 63.69 kg/m. It carries a higher wheel load and needs matching clip and buffer settings.
Q: Which steel grade is normally used for QU70?
A: U71Mn rail steel is the standard choice. Tensile strength of not less than 880 MPa is a normal acceptance value for this grade under GB/T 2585.
Q: Can QU70 rail be drilled for fishplates?
A: Yes. Holes are drilled to the buyer drawing, with the pitch, diameter and edge distance taken from the joint bar used. Holes are deburred and chamfered after drilling.
Q: What lengths are available?
A: 6 m, 9 m, 12 m and 12.5 m are standard, and other lengths can be cut to order. Length tolerance and end squareness are agreed on the order.
Q: How is straightness checked before dispatch?
A: After roller straightening, the rail is checked against a straightedge with a feeler gauge in both planes. The accepted deviation is the value written into the order drawing.