Tianjin Brisk Metalwork Co., Ltd. is one of the leading manufacturers and suppliers of s420mh structural hollow section in China. We have world-leading production equipment and strong manufacturing capabilities. Please feel free to buy bulk durable s420mh structural hollow section from our factory.
Why Doesn't S420 Use the Same J0/J2 Naming System as S275 and S355?
Each character in the designation is a production instruction:
- S = structural steel
- 420 = 420 MPa minimum yield class
- M = thermomechanically rolled delivery condition, so strength comes from controlled rolling rather than from extra carbon and alloy
- H = hollow section
We form and weld the section from TM coil. It is not normalized and not hot-finished. If your project needs a hot-finished route, the EN 10210 family (for example S420NH) is a different product, and we can quote that separately.
What Do We Supply in S420MH?
| Item | Our supply range |
|---|---|
| Standard | EN 10219-1 (dimensions and tolerances to EN 10219-2) |
| Grade | S420MH (S420MLH available on request for low-temperature service) |
| Process | Cold-formed, welded (ERW/HFW) from TM coil |
| SHS | 20 x 20 mm to 500 x 500 mm |
| RHS | 20 x 10 mm to 600 x 400 mm |
| CHS | 21.3 mm to 610 mm OD |
| Wall thickness | 2 mm to 20 mm |
| Length | 6 m and 12 m standard, cut-to-length on request |
| Surface | Black oiled, painted, hot-dip galvanized |
| Certificate | EN 10204 3.1 as standard, 3.2 with third-party witness on request |
Not every size is available in every wall thickness. Send us your list and we will confirm what runs in S420MH.
How Much Weight Can S420MH Save Compared With S355?
Because yield is about 18% higher than S355 (420 vs 355 MPa), a strength-governed member can often carry the same load with a thinner wall. Reference calculation for a 250 x 150 RHS in tension:
| Section | Approx. weight | Yield tension capacity |
|---|---|---|
| 250 x 150 x 10, S355 | ~57.0 kg/m | ~2,580 kN |
| 250 x 150 x 8, S420MH | ~46.5 kg/m | ~2,490 kN |
That is about 18% less steel per metre for a capacity difference under 4%. This is an illustration for comparison. Your engineer must run the real design check to EN 1993.
Real project case: An overseas fabricator was building roof-truss chords from 120 tonnes of 250 x 150 x 10 S355J2H RHS. After a design review they moved the strength-governed chords to 250 x 150 x 8 S420MH. The result:
- Steel quantity dropped from 120 t to about 98 t, roughly 22 tonnes saved
- Shipment fell from 5 x 40 ft containers to 4
- Fillet weld volume at every node fell with the thinner wall
- Chords that were deflection-governed stayed in S355 (see below)
Why Do Fabricators Find S420MH Easier to Weld Than You Would Expect at 420 MPa?
TM rolling achieves strength through grain refinement, not high carbon. The carbon equivalent stays low, so preheat demands are usually lighter than for a conventional 420 MPa steel and heat-affected zones are less prone to hardening. For your welding team, this means:
- Welding procedure qualification must follow S420, not S355. Do not reuse an S355 WPS without checking.
- Use matching filler metal. Your WPS specifies it.
- Corner welding is a design and fabrication decision for your engineer, not a blanket permission.
Where Does S420MH Not Help?
We would rather tell you now than after your order arrives:
- Stiffness-governed members. Higher yield does not raise the modulus of elasticity. If deflection, vibration or buckling controls, a thinner S420MH wall may deflect more than the S355 section it replaced.
- Hot bending or stress relieving above about 580 degC. TM strength can be lost when the steel is heated well above its rolling temperature. Ask us before you plan any hot work. Hot-dip galvanizing at around 450 degC is not a concern.
- Mixed-grade assemblies. Keep S355 and S420MH clearly marked in the shop.
How Do We Control Quality on Every S420MH Lot?
- Coil incoming check: every coil is traced by heat number and TM delivery condition, and coil certificate values are checked against our order specification.
- Forming and sizing: in-line dimensional control on width, height, wall, squareness and twist.
- Weld seam testing: non-destructive testing of the weld seam on the production line.
- Mechanical testing by lot: yield, tensile and elongation on samples from the finished section. Charpy V-notch tests are carried out on walls of 6 mm and above.
- Flattening and visual check: weld integrity and surface condition at the ends and along the length.
- Documentation: mill certificate tied to heat and lot, with third-party witness available.
Where Is S420MH Used?
- Long-span roof and bridge trusses where chord weight decides freight and crane cost
- Crane, lifting and handling frames where dead weight counts against payload
- Stadium and canopy structures with slender, exposed sections
- Telecom and lattice towers where a lighter member reduces foundation load
- Trailer and equipment frames where weight reduction increases payload
How Do We Finish and Pack S420MH?
- Black oiled for painting at your site
- Painted in the colour and system you specify
- Hot-dip galvanized for exposed structures
- Packing: strapped bundles with dunnage, end protection for painted and galvanized sections, marking with grade, size, heat number and lot
FAQ
Q: Can I replace S355J2H with S420MH directly?
A: No, not without a design check. Yield goes up but stiffness does not, and your welding procedure has to be requalified for the higher grade.
Q: Do you supply S420MH in seamless?
A: No. S420MH under EN 10219 is a cold-formed welded product. For a seamless or hot-finished route, please ask about EN 10210 grades.
Q: Can you supply S420MLH for low-temperature service?
A: Yes, on request. Tell us the minimum design temperature so we can quote the correct grade.
Q: Can you cut sample pieces for testing?
A: Yes. We can send cut test pieces so you can verify grade before releasing a full order.
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