SM570
High-strength weldable structural steel · JIS G 3106:2024 — Rolled steels for welded structure
SM570 is the highest-strength grade in JIS G 3106:2024, specified primarily by 570–720 MPa tensile strength, thickness-dependent yield strength, controlled weldability and 47 J longitudinal Charpy toughness at −5 °C. It is not defined by a single mandatory production route: the ordered product form, thickness, delivery condition, toughness testing and actual heat chemistry must all be confirmed before design, welding or substitution.
- JIS G 3106:2024Governing specification · The current standard was issued on February 20, 2024.
- 570–720 MPaTensile strength · Specified through the normal thickness range.
- 460 to 420 MPaMinimum yield or proof strength · Decreases by thickness category from ≤16 mm to >75–100 mm.
- 47 J minimum at −5 °CNotch toughness · Mean of three longitudinal V-notch specimens; mandatory under the standard for product thickness over 12 mm.
- Up to 100 mmNormal thickness range · For plate/sheet, strip and sections; flats are normally limited to 40 mm.
- Ceq or Pcm limits apply as specifiedWeldability controls · The applicable control depends on delivery route and purchaser–manufacturer agreement; actual heat chemistry remains essential for welding decisions.
Overview
- Designation system
- JIS grade designation under JIS G 3106
- Product forms
- Hot-rolled steel plate and sheet, Hot-rolled strip in coil and cut lengths, Rolled structural sections, Hot-rolled flats
- Condition
- Final delivery condition producing the specified properties, N — normalized by agreement, T — tempered by agreement, Q — quenched and tempered, TMC — thermomechanically controlled by agreement
- Density
- 7850 kg/m³ (Conventional nominal density used for steel mass calculations; not a distinguishing SM570 grade requirement.)
What the designation covers
JIS G 3106 covers hot-rolled steels intended for welded structures such as bridges, ships, rolling stock, storage tanks and fabricated containers. In SM570, “570” identifies the lower limit of the specified tensile-strength range in N/mm². Unlike lower-strength SM grades, SM570 has no A, B or C toughness suffix: the complete current JIS grade symbol is simply SM570. References to “SM570C” in some commercial databases should not be treated as the official JIS designation.
| Product form | Standard thickness applicability | Important qualification |
|---|---|---|
| Plate and sheet | ≤100 mm | Plate/sheet over 100 mm through 150 mm may be supplied only under the special purchaser–manufacturer agreement provisions of Annex JA. |
| Strip in coil and cut lengths | ≤100 mm | Mechanical testing and lot formation follow the strip provisions of JIS G 3106. |
| Rolled structural sections | ≤100 mm | Thickness is taken at the test-piece location. Separate annex requirements apply to small sections. |
| Hot-rolled flats | ≤40 mm | Separate annex requirements apply where width is below 40 mm; special provisions may be used for widths from 40 mm to below 50 mm. |
SM570 plate above 100 mm is not ordinary catalogue-compliance material. The Annex JA route requires explicit agreement and has separate chemistry and tensile requirements; it should be identified clearly in the purchase specification and inspection document.
Chemical composition and weldability controls
| Applicable thickness | C | Si | Mn | P | S |
|---|---|---|---|---|---|
| ≤100 mm | ≤0.18% | ≤0.55% | ≤1.70% | ≤0.035% | ≤0.035% |
These are heat-analysis requirements. Other alloying elements may be added as necessary and must not be assumed absent.
The five-element composition table does not fully describe the metallurgical design of an SM570 heat. Producers may use Ni, Cr, Mo, Cu, V, Nb, Ti, B or other additions to obtain strength, toughness and process control. The complete analysis is therefore more useful for welding assessment than the basic C–Si–Mn–P–S limits alone.
| Thickness | Maximum Ceq |
|---|---|
| ≤50 mm | 0.44% |
| >50 to 100 mm | 0.47% |
| >100 mm | By purchaser–manufacturer agreement |
| Thickness | Maximum Pcm |
|---|---|
| ≤50 mm | 0.28% |
| >50 to 100 mm | 0.30% |
| >100 mm | By purchaser–manufacturer agreement |
The specification maxima are acceptance limits, not welding-procedure instructions. Preheat and heat-input decisions must use the actual reported composition together with thickness, joint restraint, consumable hydrogen level, ambient conditions and the qualified welding procedure.
Mechanical-property requirements
| Nominal thickness | Minimum yield point or proof stress | Tensile strength |
|---|---|---|
| ≤16 mm | 460 MPa | 570–720 MPa |
| >16 to 40 mm | 450 MPa | 570–720 MPa |
| >40 to 75 mm | 430 MPa | 570–720 MPa |
| >75 to 100 mm | 420 MPa | 570–720 MPa |
For sections, nominal thickness is the thickness at the test-piece location.
| Thickness | JIS tensile specimen | Minimum elongation |
|---|---|---|
| ≤16 mm | No. 5 | 19% |
| >16 to 100 mm | No. 5 | 26% |
| >20 to 100 mm | No. 4 | 20% |
The applicable specimen is determined by the product geometry and JIS testing provisions. Values obtained from different specimen types should not be compared as though they were the same test.
| Applicable material | Temperature | Minimum absorbed energy | Direction and acceptance basis |
|---|---|---|---|
| SM570 with thickness >12 mm | −5 °C | 47 J | Mean of three specimens taken in the rolling direction |
A lower test temperature may be specified by purchaser–manufacturer agreement. The standard requirement does not establish toughness at temperatures below the ordered test temperature.
Sections with a leg length below 40 mm and flats below 40 mm wide are governed by the separate mechanical-property requirements of Annex JB. Annex JB may also be applied within specified intermediate size ranges. Do not certify these products solely against the general plate-property table.
Delivery condition and fabrication significance
| Suffix | Condition | Commercial significance |
|---|---|---|
| N | Normalized by agreement | Heat treatment must be stated as part of the grade marking. |
| T | Tempered by agreement | Confirm the preceding production route and producer documentation. |
| Q | Quenched and tempered | Ceq requirements are directly relevant; uncontrolled reheating can alter the developed properties. |
| TMC | Thermomechanically controlled by agreement | Confirm producer restrictions on hot forming, flame straightening and heat input. |
| Agreed symbol | Other agreed heat treatment | The condition and acceptance basis must be defined in the order. |
SM570 is a strength-and-toughness specification, not a unique alloy recipe or mandatory microstructure. Material supplied as Q and material supplied as TMC may meet the same room-temperature tensile requirements while responding differently to welding, hot forming, stress relief or local heating. The delivery condition shown on the inspection certificate is therefore part of the engineering identity of the product.
Welding procedures should control hydrogen, interpass temperature, heat input and hardness or toughness where required by the fabrication code. Consumables must be selected for the required deposited-metal strength and toughness rather than solely by matching the number 570. Procedure qualification should represent the actual product thickness and delivery condition. Repair welding of SM570 plate or sheet requires prior agreement between purchaser and manufacturer under JIS G 3106.
Cold forming, hot forming, flame straightening, post-weld heat treatment and thermal cutting can affect the properties developed by quenching and tempering or thermomechanical processing. Limits should come from the steel producer, applicable fabrication standard and qualified procedure; they are not universal properties of the SM570 designation.
Specifying and accepting an order
| Item | What to state or check | Why it matters |
|---|---|---|
| Standard edition | JIS G 3106:2024 | Requirements and annex provisions can change between editions. |
| Designation and condition | SM570 plus N, T, Q, TMC or other applicable condition suffix | SM570 alone does not identify the production route. |
| Product form and dimensions | Plate, sheet, coil, section or flat; nominal thickness and relevant section dimensions | Thickness controls yield strength, weldability limits, testing and whether an annex applies. |
| Impact requirement | Standard −5 °C requirement or an agreed lower test temperature | The standard 47 J value does not demonstrate low-temperature performance below the test temperature. |
| Chemistry reporting | Full heat analysis and the applicable Ceq or Pcm result | Required for traceability and practical welding assessment. |
| Inspection document | Document type, heat number, mechanical tests, impact results and delivery condition | Confirms that the delivered product—not merely the grade name—meets the order. |
| Additional testing | Ultrasonic examination, through-thickness properties, transverse impact tests or tighter chemistry where required | These are not automatically provided by the basic SM570 designation. |
| Dimensions and tolerances | Applicable provisions of JIS G 3192, JIS G 3193 or JIS G 3194 | The correct supporting standard depends on product form. |
For fracture-critical, highly restrained, thick-section or low-temperature service, the base designation may be insufficient. Project requirements may need a lower Charpy temperature, minimum individual impact value, transverse testing, maximum Pcm below the JIS limit, ultrasonic quality, through-thickness ductility or producer-specific processing controls. Such requirements must be ordered explicitly rather than inferred from SM570.
Substitution and design interpretation
SM570 should not be substituted solely by matching nominal yield strength. A valid comparison must include product standard, thickness-dependent yield requirement, tensile range, impact temperature and specimen direction, delivery condition, chemistry and weldability controls, dimensional tolerances, testing frequency and certification. European S460 grades and North American 65 ksi-class structural steels may occupy a broadly similar strength range, but none is automatically equivalent to JIS SM570.
The 570 designation is a tensile-strength classification. It should not be interpreted as 570 MPa yield strength or used directly as a design resistance without the applicable structural design standard and thickness category.
Sources
- JIS G 3106:2024 — Rolled steels for welded structureJapanese Standards Association
- JIS G 3106:2024 English previewJapanese Standards Association
- Hot-Rolled Steel Products Specifications — JIS G 3106:2024 tablesChina Steel Corporation
- High Performance Steel for Bridge ConstructionThe Japan Iron and Steel Federation
- Arc Welding of High-Strength SteelKobe Steel, Welding Business
Ask MetalMate about SM570
Discussing: SM570
AI assistant · Responses are generated and can contain errors; verify specifications before acting.