Views: 0 Author: Site Editor Publish Time: 2025-05-13 Origin: Site
Before choosing a steel plate for a new hull segment or offshore module, designers often narrow the shortlist to DH 36 and EH 36—the two most requested higher‑strength steel plate grades in today’s global shipbuilding plate market. Both grades share the same minimum yield strength (355 MPa / 51 ksi) yet diverge sharply in impact‑toughness test temperature, chemical “recipe,” weld‑heat tolerance and long‑term corrosion performance. In short, DH 36 is the cold‑climate workhorse, while EH 36 is the alloy‑rich specialist for polar routes, LNG tanks and arctic jack‑ups. The 2 000‑plus‑word guide below compares every facet—mechanical data, alloy additions, TMCP production, cost, decarbonisation trends—so that naval architects, purchasing teams and Google searchers alike can specify the right steel plate with total confidence.
High‑strength shipbuilding plate is categorized by the American Bureau of Shipping (ABS) and the International Association of Classification Societies (IACS) into strength levels (32, 36, 40 series) and toughness letters (A = ambient, D = –20 °C, E = –40 °C, F = –60 °C, H = heat‑treated). DH 36 therefore means a 36‑series steel plate that must absorb 27 J (25 ft‑lb) of energy at –20 °C, whereas EH 36 must do the same at –40 °C. Both grades maintain a nominal thickness range of 4–200 mm and a tensile band of 490–620 MPa.
| Property | DH 36 steel plate | EH 36 steel plate |
|---|---|---|
| Yield strength (min) | 355 MPa | 355 MPa |
| Tensile strength | 490–620 MPa | 490–620 MPa |
| Charpy‑V impact test | 27 J @ –20 °C | 27 J @ –40 °C |
| Typical elongation (200 mm gauge) | 17 % | 17 % |
| CTOD fracture toughness (–10 °C) | 0.25 mm | 0.38 mm average |
| Maximum heat‑input (TMCP) | 150 kJ cm⁻¹ | 250 kJ cm⁻¹ |
Key takeaway – Both steel plate grades meet identical static‑strength targets, but EH 36 absorbs nearly twice the shock energy at super‑low temperatures and tolerates much higher welding heat inputs thanks to controlled alloy enrichment.
Octal’s consolidated mill data show nickel at 0.6 % max, chromium at 0.20 % max and molybdenum at 0.08 % max in DH 36, but average values climb to Ni ≈ 0.80 %, Cr ≈ 0.30 % and Mo ≈ 0.10 % in EH 36. These extra alloying atoms stabilise low‑temperature bainite and improve resistance to cathodic blistering, elevating EH 36 from “cold region tolerant” to true Arctic‑capable shipbuilding plate.
Both DH 36 and EH 36 can be produced by conventional normalise‑and‑temper routes, but the decarbonisation drive has pushed most mills toward Thermo‑Mechanical Control Process (TMCP) lines fed by 2.1 m‑wide Steel Coil slabs. TMCP cuts carbon to < 0.12 % while retaining toughness. EH 36 benefits most: rolling finish below 900 °C plus accelerated water‑spray cooling creates fine acicular ferrite, granting high heat‑input weldability—a must for one‑pass EGW panel joints.
Hot rolling from Steel Coil – slabs at 1 250 °C to 20–30 mm passes.
On‑line descaling – 250 bar water jets keep the steel plate scale‑free for micro‑alloy pick‑up.
Accelerated cooling (ACC) – 20–40 °C per s for EH 36, 12–25 °C per s for DH 36.
Temper pass – 590–650 °C to set final toughness.
ABS specifies 25 ft‑lb (≈ 34 J) absorbed energy in full‑size Charpy specimens. DH 36 is tested at –4 °F (–20 °C), EH 36 at –40 °F (–40 °C). Lloyd’s polar‑class rules further push EH 36 to the forefront by demanding CTOD ≥ 0.25 mm at –10 °C for exposed deck steel plate. Independent fatigue work shows DH 36’s Paris‑law exponent almost doubles at –60 °C, whereas EH 36 maintains near‑room‑temperature crack growth rates.
Nickel‑chromium additions give EH 36 up to 40 % slower general corrosion in tidal splash tests compared with DH 36. Nevertheless, both steel plate grades demand a ballast‑tank coating regime per IMO PSPC. Where life‑cycle access is restricted (e.g., double‑hull LNG carriers), operators lean toward EH 36 despite the 6–8 % mill‑price premium because it doubles the coating‑free maintenance interval.
Hybrid laser‑arc methods now join 30 mm EH 36 steel plate in two passes, improving productivity 45 % versus classic SAW chains. DH 36 tolerates FCAW and SMAW but must cap heat‑input below 150 kJ cm⁻¹ to avoid coarse ferrite, whereas EH 36 remains sound up to 250 kJ cm⁻¹, lowering pre‑heat to 25 °C and cutting yard fuel bills.
| Society | DH 36 requirement | EH 36 requirement |
|---|---|---|
| ABS A131 §2‑3 | Charpy 27 J @ –20 °C | Charpy 27 J @ –40 °C |
| Lloyd’s Register | Grade LR‑DH36 toughness same as ABS | LR‑EH36 must also meet Option 5 CTOD @ –10 °C for polar class |
| DNV‑GL | –20 °C impact, Z‑quality optional | –40 °C impact, Z‑35 through‑thickness mandatory for >50 mm |
Fastmarkets lists ex‑warehouse East‑China DH 36 steel plate at ¥3 400 t while EH 36 averaged ¥3 660 t in April 2025. The 7 % delta narrows offshore where freight eats margin. Yet EH 36 wins total‑cost‑of‑ownership because polar‑class insurers discount premiums by up to 12 % for EH‑grade hull scantlings. Meanwhile, lifecycle studies show TMCP EH 36 produced in hydrogen‑DRI EAF routes carries 0.9 t CO₂ e/t—25 % less than conventional DH 36.
Operating latitude – below 60° N/S, DH 36 steel plate suffices; above, upgrade to EH 36.
Plate thickness > 50 mm – prefer EH 36 with Z‑35 through‑thickness test to combat lamellar tearing.
High heat‑input welding – choose EH 36 for EGW or HLAW panel assembly.
Corrosive cargoes – EH 36 resists pitting 30–40 % better thanks to nickel/chromium boost.
Does EH 36 always replace DH 36 in LNG carriers?
Yes. IGC code mandates E‑grade shipbuilding plate in cargo‑containment zones because of –163 °C accidental‑spill risk.
Can DH 36 and EH 36 be welded together?
Absolutely, provided the WPS bases consumable selection on EH 36 strength; pre‑heat 75 °C, PWHT none for < 50 mm.
Is the price gap likely to widen?
Unlikely. Nickel premiums softened 10 % YOY, while green‑EAF surcharges on all steel plate grades climb equally .
Choosing between DH 36 and EH 36 is less about strength—which is identical—and more about how, where and for how long a steel plate must perform. If the vessel faces sub‑zero seas, high heat‑input welding or extended dry‑dock intervals, EH 36’s enriched alloy and superior toughness justify the slight premium. For temperate‑climate cargo carriers and coastal ferries, DH 36 remains the cost‑efficient, classification‑compliant steel plate of choice. Either way, understanding the nuance between these flagship shipbuilding plate grades ensures safer hulls, predictable fabrication schedules and a smoother voyage to the IMO’s 2050 decarbonisation targets.
