SPV355
Weldable carbon-manganese pressure-vessel steel plate · JIS G 3115:2022 — Steel plates for pressure vessels for intermediate temperature service · JIS G 3193 — Dimensions, mass and permissible variations of hot-rolled steel plates, sheets and strip
SPV355 is a weldable, killed carbon-manganese steel plate specified by JIS G 3115 for pressure vessels and high-pressure equipment outside explicitly high- or low-temperature service. Its defining features are a 520–640 MPa tensile-strength range, thickness-dependent minimum yield strength, mandatory Charpy requirements above 12 mm, and condition-dependent weldability controls. The delivery condition, impact-test options and any simulated fabrication heat treatment must be specified rather than inferred from the grade name alone.
- JIS G 3115:2022Current governing edition · Published March 22, 2022 and confirmed as active on June 22, 2026.
- 6–150 mmStandard thickness range · Actual mill availability may be narrower.
- 355 / 335 / 315 MPaMinimum yield point or proof strength · For thicknesses 6–50 mm, over 50–100 mm, and over 100–150 mm respectively.
- 520–640 MPaTensile strength · Applies throughout the specified 6–150 mm thickness range.
- 47 J average; 27 J individual at 0 °CStandard Charpy requirement · Longitudinal V-notch specimens; normally applicable when plate thickness exceeds 12 mm.
- As-rolled is permittedDelivery route · Normalizing may be applied; TMC or quench-and-temper supply requires agreement and condition identification.
Overview
- Designation system
- Japanese Industrial Standards (JIS) grade designation
- Product forms
- Hot-rolled steel plate
- Condition
- As-rolled, Normalized, when applied, Thermo-mechanically controlled (TMC), by agreement, Quenched and tempered, by agreement, Test-piece conditions simulating normalizing and/or post-weld heat treatment, when specified
- Density
- 7.85 g/cm³ (Nominal engineering value for carbon steel; density is not a defining SPV355 requirement in JIS G 3115.)
What the designation defines
JIS G 3115 covers hot-rolled steel plates having improved weldability for pressure vessels and other high-pressure equipment. It expressly excludes plates intended for high-temperature and low-temperature service. “Intermediate temperature” is therefore a product-standard scope description, not a numerical design-temperature rating.
The number 355 corresponds to the minimum yield point or proof strength, in MPa, for plate up to and including 50 mm thick. The minimum decreases for thicker plate. SPV355 does not by itself establish pressure-design allowable stresses, elevated-temperature strength, corrosion allowance or acceptance under a particular vessel code; those matters must be established under the applicable construction code.
Manufacture, delivery condition and suffixes
SPV355 is manufactured from killed steel. The standard permits as-rolled delivery, with normalizing applied when needed. Thermo-mechanical controlled processing or quenching and tempering may be used by agreement between purchaser and manufacturer. These routes can produce materially different microstructures and fabrication responses even though the finished plate satisfies the same grade-level mechanical requirements.
| Symbol | Meaning | Practical significance |
|---|---|---|
| No suffix | Normally as-rolled | Do not assume normalized or TMCP supply from the bare SPV355 designation. |
| N | Plate normalized by agreement | The plate itself receives the normalizing treatment. |
| TMC | Thermo-mechanically controlled plate | Relevant carbon-equivalent or Pcm limits apply; the condition should be preserved in procurement and traceability. |
| Q | Plate quenched and tempered | Permitted by agreement; weldability limits are also subject to agreement for SPV355Q. |
| TN | Test material normalized | The plate can be shipped as-rolled for subsequent purchaser heat treatment; certified properties are based on normalized test material. |
| SR | Test material receives treatment corresponding to post-weld heat treatment | The intended thermal cycle and number of cycles must be stated where fabrication will include PWHT. |
| TQ | Test material quenched and tempered | Used where the purchaser will perform the corresponding plate treatment. |
A test-piece suffix does not mean that the delivered plate received that heat treatment. This distinction is critical when reviewing certificates or purchasing plate for heat treatment by the fabricator.
Chemical composition and weldability controls
| Element | Maximum, mass % |
|---|---|
| C | 0.20 |
| Si | 0.55 |
| Mn | 1.60 |
| P | 0.020 |
| S | 0.020 |
The standard permits addition of alloying elements not shown in this basic table. A certificate review should therefore consider the full reported analysis rather than only these five elements.
For TMC plate, JIS G 3115 controls weldability using carbon equivalent. By agreement, the weld-cracking susceptibility composition Pcm may be used instead. The calculations use cast-analysis values and include each element appearing in the equation whether or not it was intentionally added. For quenched-and-tempered SPV355, the applicable Ceq or Pcm limit is established by agreement.
| Plate thickness | Ceq maximum | Pcm maximum when substituted by agreement |
|---|---|---|
| 6–50 mm | 0.40 % | 0.26 % |
| Over 50–100 mm | 0.42 % | 0.27 % |
| Over 100–150 mm | 0.44 % | 0.29 % |
Ceq is the default weldability index; use of Pcm in its place requires purchaser-manufacturer agreement.
Room-temperature mechanical requirements
| Nominal thickness | Minimum yield point or proof strength | Tensile strength |
|---|---|---|
| 6–50 mm | 355 MPa | 520–640 MPa |
| Over 50–100 mm | 335 MPa | 520–640 MPa |
| Over 100–150 mm | 315 MPa | 520–640 MPa |
The 355 in the designation must not be applied as the minimum yield strength of plate thicker than 50 mm.
| Plate thickness | JIS tensile specimen | Minimum elongation |
|---|---|---|
| 6–16 mm | No. 1A | 14 % |
| Over 16–40 mm | No. 1A | 18 % |
| Over 40–150 mm | No. 1A | 18 % |
| Over 40–150 mm | No. 4 | 21 % |
Elongation values are specimen-dependent and should not be compared directly without accounting for gauge geometry.
The tensile specimen is taken transverse to the final rolling direction. The specified bend performance is 180° around an inside radius equal to 1.5 times the specimen thickness, using a JIS No. 1 bend specimen, without cracking on the outside of the bend. The manufacturer may omit actually conducting the bend test unless the purchaser specifically requests it, but the plate remains required to possess the specified bendability.
Notch toughness and test orientation
| Applicability | Test temperature | Specimen orientation | Three-specimen average | Minimum individual result |
|---|---|---|---|---|
| Plate thickness over 12 mm | 0 °C | Longitudinal, parallel to final rolling direction | 47 J | 27 J |
Standard-size or permitted subsize V-notch specimens are taken near quarter thickness and quarter width. The notch-length direction is perpendicular to the plate surface.
For plate 12 mm thick or less, impact testing is performed with subsize specimens when specified at ordering. JIS G 3115 provides reduced acceptance energies according to specimen size and the difference between plate thickness and full-size specimen thickness. The required specimen size and acceptance criterion should therefore be stated explicitly for thin plate.
A lower test temperature may replace the standard temperature by agreement. Transverse impact testing may also be agreed; with purchaser approval, it can replace the default longitudinal test. For SPV355TMC, an optional agreed requirement of 47 J average and 27 J individual at −20 °C is provided. This stronger toughness option is not automatic merely because the plate is TMC.
Fabrication implications
SPV355 is designed as a weldable pressure-purpose plate, but the grade designation is not a welding procedure. Welding consumables are generally selected from the 490 MPa-class high-tensile-steel range, with final matching based on required weld-metal strength, toughness, service environment and construction code. Welding procedure qualification remains necessary.
Preheat and interpass temperature should be established from the actual heat analysis, Ceq or Pcm, plate thickness, restraint, hydrogen level, heat input and applicable code. Low-hydrogen consumables and proper electrode or flux drying are important for delayed-cracking control. Processes involving high dilution require particular attention because the plate chemistry can significantly influence weld-metal properties.
PWHT can alter strength and toughness, especially when several fabrication heat cycles are involved. If PWHT is anticipated, order testing in the appropriate SR simulation, stating the temperature-time cycle and number of repetitions. For TMC plate, uncontrolled hot forming or subsequent heat treatment can negate the metallurgical benefits of controlled rolling; the plate producer and governing construction code should be consulted before such processing.
Ordering, inspection and substitution
| Item | What to state or verify |
|---|---|
| Standard and grade | JIS G 3115:2022, SPV355, including the required condition suffix. |
| Dimensions | Thickness, width and length; confirm that the mill's available range covers the order. |
| Thickness tolerance | JIS G 3115 uses a normal minus tolerance of 0.25 mm with width- and thickness-dependent plus tolerances. Zero minus tolerance may be agreed, with the plus tolerance increased accordingly. |
| Impact testing | Temperature, longitudinal or transverse orientation, full-size or subsize specimen and acceptance energy. |
| Fabrication heat treatment | Any normalizing, quench-and-temper treatment or PWHT simulation, including the number of SR cycles. |
| Weldability reporting | Applicable Ceq or agreed Pcm requirement and complete analysis of elements used in the calculation. |
| Nondestructive examination | Any ultrasonic testing under JIS G 0801 or another agreed method, including examination level and acceptance criteria. |
| Documentation | Unless otherwise specified, JIS G 3115 calls for a JIS G 0415 inspection certificate 3.1. |
| Code acceptance | Confirm that SPV355, its condition, thickness and certification are accepted by the governing pressure-vessel or statutory code. |
Dimensions and general permissible variations are linked to JIS G 3193, with specific thickness tolerances stated in JIS G 3115. Weld repair of plate surface imperfections requires prior purchaser approval. Additional nondestructive testing is not automatic and must be agreed before manufacture.
Do not substitute another nominally 355 MPa pressure-vessel grade on strength alone. Chemistry, delivery condition, impact-test temperature and orientation, thickness effects, PWHT response, dimensional tolerances, inspection documents and construction-code recognition can all differ.
Sources
- JIS G 3115:2022 — Steel plates for pressure vessels for intermediate temperature serviceJapanese Standards Association
- JIS G 3115:2022 English previewJapanese Standards Association
- JIS G 3115 revision committee documentJapan Iron and Steel Federation
- SPV steel welding consumable selection and welding precautionsJapan Welding Engineering Society, Welding Information Center
- Steel Plates — reference tables of pressure-vessel standardsNippon Steel Corporation
- Steel Plate Product Specifications — JIS G 3115:2022China Steel Corporation
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