SSAB Strenx Tube 700MLH
Product identity, mechanical-property conditions and fabrication limits for SSAB's thermomechanically rolled high-strength structural hollow sections.
Tags: materials, steel, hollow-sections, producer-products
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Identity and supplied condition
SSAB lists 27 J at −50°C for Strenx Tube 700MLH, transverse Charpy V on a 10 × 10 mm basis, with impact testing from 6 mm wall. Its welding guide lists 100°C maximum recommended preheat/interpass for 700MLH, versus 300°C for 700QLH. Determine minimum preheat and heat input for the actual joint separately. SSAB 700MLH impact footnote, SSAB tube welding guidance
Strenx Tube 700MLH is SSAB's cold-formed, high-frequency-welded structural hollow section made from thermomechanically rolled steel. The current product page identifies EN 10219-3 (2020). It is a tube product: a flat Strenx grade or a differently suffixed tube must not be substituted on the strength number alone. SSAB product data
SSAB describes the tube family for transportation, lifting and agricultural structures. Its workshop guidance notes that cold forming leaves residual stresses and that cutting can cause distortion. These application descriptions identify candidate uses; they do not establish the capacity or fatigue life of a finished assembly. SSAB tube product group
Read the property footnotes
The current product data give the following limits:
| Property | Published value |
|---|---|
| Minimum proof strength, Rp0.2 | 700 MPa |
| Tensile strength | 750–950 MPa |
| Minimum elongation, A5 | 10% |
| Transverse Charpy V energy | 27 J at −50°C |
Elongation decreases by two percentage points when D/T < 15 for circular sections or (B + H)/(2T) < 12.5 for square/rectangular sections. Rectangular-section mechanical testing uses the longer side. Impact testing applies at wall thickness ≥6 mm; the stated energy corresponds to a full-size 10 × 10 mm specimen. These conditions belong with the numbers whenever they are copied into a comparison. SSAB mechanical properties and footnotes
Welding: qualify the joint and thermal cycle
SSAB's Welding of Strenx, V1 US Letter 2026, lists 100°C as the maximum recommended preheat/interpass temperature for Tube 700MLH. Its separate Tube 700QLH entry is 300°C: copying that row would change the fabrication limit substantially. The guide recommends low-alloy consumables with hydrogen content no higher than 5 ml/100 g weld metal. Minimum preheat selection depends on the material, consumable, thickness and welding conditions; the maximum is not an instruction to preheat every joint to 100°C. SSAB welding guide, temperature and consumable sections
The same guide gives a recommended t8/5 cooling interval of 1–20 seconds for the group containing Tube 700MLH, in a table framed around minimum 27 J at −40°C. That welding recommendation has different conditions from the base-product Charpy entry above. The guide also explains that heat-affected-zone hardness depends on grade, thickness and heat input. Treat it as procedure-development guidance, with the welding specification and required qualification controlling the actual joint. SSAB welding guide, cooling-time and HAZ sections
For a fabrication record, retain the joint configuration, consumable classification, heat input, measured temperatures and inspection acceptance criteria. Check whether a repair, attachment weld or local straightening operation falls within the qualified procedure; it changes the delivered tube just as a production weld does.
Cutting, coatings and dimensional control
SSAB warns that hot-dip galvanizing may cause cracking and directs users to consult its technical support before galvanization. SSAB fabrication and chemistry notes
The tube-family page discusses machining with stable equipment and thermal cutting, including distortion from residual stresses. This supports checking the process on representative stock; it does not supply a universal cutting speed, straightening temperature or stress-relief recipe for 700MLH. SSAB tube workshop guidance
Inspect dimensions at the stage that matters to the assembly. A nominal section size does not describe its actual corner radii, seam location, straightness or the fit of a welded attachment. Establish which dimensions are incoming-stock checks and which are finished-part requirements. Plan cutting and clamping so that released distortion is detected before the part reaches final assembly.
Bounded application example
SSAB's rear-underrun-protection page names 120 × 120 × 4 mm square Tube 700MLH among candidate sections. It explicitly says performance depends on material, section shape, thickness, support spacing and connections, and calls for an engineering study. The example therefore demonstrates a producer-named configuration, not approval of every guard built from that section. SSAB rear impact guard application guidance
For that nominal square, the elongation-footnote ratio is (120 + 120)/(2 × 4) = 30. This is above 12.5, so that particular geometry condition does not trigger the two-point reduction. Its 4 mm wall is below the product page's ≥6 mm impact-testing threshold. Neither calculation supplies a guard load rating or an impact-test certificate; those require the actual product documents and assembly qualification.
Selection and source control
The linked product and application pages show no explicit technical revision date. The welding PDF's footer identifies 420-UK, V1 US Letter 2026. This draft uses those sources as reviewed on 2026-11-01; obtain the current order-specific documentation rather than treating this summary as a purchase specification.