JIS G3441 ERW Pipe
JIS G3441 ERW pipe is alloy steel tubing made to the Japanese Industrial Standard for alloy steel tubes for machine structural purposes. The standard explicitly permits two manufacturing routes - weldless (seamless) or electric-resistance-welded (resistance welding) - so an ERW tube is a legitimate form of JIS G3441, not a deviation from it. It is supplied in chromium and chromium-molybdenum grades such as SCr420TK, SCM420TK and SCM440TK, in outside diameters from 38 to 426 mm (1.50–16.77 in).
The single most important point for specifiers: JIS G3441 is a mechanical-tubing standard for machined and stressed components, not a pressure-pipe or boiler-tube standard. It is the correct choice for shafts, pins, gears, hydraulic bodies and bearing seats, and the wrong choice for fluid, gas or boiler duty.
GNEE supplies JIS G3441 as both seamless and ERW tube, with heat treatment (as-manufactured, annealed, or quenched and tempered on request) matched to the part. Send your OD × wall, grade and heat-treatment requirement to get a quote with lead time.
Technical Specifications
| Parameter | Capability |
|---|---|
| Standard | JIS G3441 (alloy steel tubes for machine structural purposes) |
| Manufacturing method | Electric-resistance-welded (ERW) or seamless (weldless), as ordered |
| Grades | SCr420TK, SCM415TK, SCM418TK, SCM420TK, SCM430TK, SCM435TK, SCM440TK (SNC815TK, SNCM420TK, SCM822TK in the full list) |
| Outside diameter | 38–426 mm (1.50–16.77 in); ERW is most economical up to roughly 219 mm OD |
| Wall thickness | 5–60 mm (0.197–2.362 in) |
| Length | 3,000–12,000 mm (118–472 in), fixed or random |
| Ends | Plain ends or beveled ends; plastic caps (small OD) or steel protectors (large OD) |
| Surface | Black, oiled, varnished or galvanized |
| Heat treatment | As-manufactured / annealed; quenched and tempered on request |
| Certification | Mill test certificate to EN 10204 3.1; third-party inspection (SGS, BV, TÜV) available |
The JIS G3441 outside diameter spans 38 to 426 mm (1.50–16.77 in), and the JIS G3441 tolerance classes (Class 1, 2 and 3) let the buyer trade precision against cost - tighter classes suit hydraulic bodies and bearing seats.
Chemical Composition
The JIS G3441 chemical composition is specified as ranges for each grade (not as upper limits) - a frequent point of error on supplier pages that print "C max". Nickel and copper are controlled as residual impurities (Ni ≤0.25%, Cu ≤0.30%).
| Grade | C | Si | Mn | P max | S max | Cr | Mo |
|---|---|---|---|---|---|---|---|
| SCr420TK | 0.18–0.23 | 0.15–0.35 | 0.60–0.85 | 0.030 | 0.030 | 0.90–1.20 | - |
| SCM415TK | 0.13–0.18 | 0.15–0.35 | 0.60–0.85 | 0.030 | 0.030 | 0.90–1.20 | 0.15–0.30 |
| SCM418TK | 0.16–0.21 | 0.15–0.35 | 0.60–0.85 | 0.030 | 0.030 | 0.90–1.20 | 0.15–0.30 |
| SCM420TK | 0.18–0.23 | 0.15–0.35 | 0.60–0.85 | 0.030 | 0.030 | 0.90–1.20 | 0.15–0.30 |
| SCM430TK | 0.28–0.33 | 0.15–0.35 | 0.60–0.85 | 0.030 | 0.030 | 0.90–1.20 | - |
| SCM435TK | 0.33–0.38 | 0.15–0.35 | 0.60–0.85 | 0.030 | 0.030 | 0.90–1.20 | - |
| SCM440TK | 0.38–0.43 | 0.15–0.35 | 0.60–0.85 | 0.030 | 0.030 | 0.90–1.20 | - |
The chromium and molybdenum are what separate G3441 from carbon machine tube: Cr builds hardenability and wear resistance, Mo suppresses temper brittleness and lets the part hold strength after quenching and tempering.
Mechanical Properties
The JIS G3441 mechanical properties depend on grade and heat treatment, so a single number is misleading. The table below shows the representative minimum for the chromium and lower Cr-Mo grades in the as-manufactured or annealed condition, against the upper range reached when the order specifies quenching and tempering for the SCM4xx grades.
| Property | As-manufactured / annealed (SCr420TK, SCM420TK) | Quenched & tempered, order-specified (SCM420TK → SCM440TK) |
|---|---|---|
| Tensile strength Rm | ≥480 MPa (70,000 psi) | 885–1,080 MPa (128,000–157,000 psi) |
| Yield strength ReL | ≥330 MPa (48,000 psi) | 685–930 MPa (99,000–135,000 psi) |
| Elongation A | ≥22% | ≥12% |
| Impact toughness | Charpy on request (e.g. −20 °C) | Higher, grade-dependent |
| Test standards | JIS Z 2241 (tension), JIS Z 2242 (impact) | JIS Z 2241, JIS Z 2242 |
Read the values against the actual certificate: the same grade can sit at the annealed minimum or the quenched-and-tempered maximum depending on what the order called for, and the high-strength figures above are grade-specific (SCM440TK reaches the top of the range).
JIS G3441 vs G3445 vs G3454 vs G3462
Four JIS tube standards are routinely confused. Reading JIS G3441 vs JIS G3445 is about alloy versus carbon for the same machine-structural job; reading JIS G3441 vs JIS G3454 is about machine-structural versus pressure service - a different family entirely. They are not interchangeable.
| Standard | Product family | Typical grades | Service |
|---|---|---|---|
| JIS G3441 | Alloy steel tubes for machine structural purposes | SCr420TK, SCM420TK, SCM440TK | Machine parts - not pressure |
| JIS G3445 | Carbon steel tubes for machine structural purposes | STKM11A–STKM17C | Machine parts - not pressure |
| JIS G3454 | Carbon steel pipes for pressure service | STPG38, STPG42 | Pressure piping |
| JIS G3462 | Alloy steel tubes for boiler and heat exchanger | STBA20–STBA26 | Boiler / heat exchanger |
The practical rule: if the duty is fluid, gas or boiler, G3441 is the wrong standard - use G3454/G3455/G3456 (pressure) or G3462 (boiler alloy) instead.
JIS G3441 grade ladder
| Grade | Character | Typical use |
|---|---|---|
| SCr420TK | 1.0% Cr, no Mo; economical alloy | General machined parts, shafts |
| SCM420TK | 1.0% Cr, 0.2% Mo | Case-hardened gears, pins, hydraulic bodies |
| SCM440TK | 1.0% Cr, high C; highest strength when QT | High-strength shafts, heavy stressed parts |
Choose by what the part must survive: a plain machined bracket needs only SCr420TK, while a hardened gear or high-strength shaft calls for SCM420TK or SCM440TK with quenching and tempering.
Seamless vs ERW for JIS G3441
| Route | Size suitability | Strength of the route |
|---|---|---|
| ERW | Smaller OD and thinner walls (economical to ~219 mm OD) | Lower cost, consistent weld, good for general machine parts |
| Seamless | Full 38–426 mm range, heavy walls | No weld line; preferred where the buyer's spec forbids a longitudinal weld |
Both routes meet the same JIS G3441 chemistry and property requirements; the choice is economic and dictated by size and any weld-line restriction in the part drawing.
Quality Control and Testing
Chemistry verification. Ladle analysis per grade; product analysis tolerance per JIS G0321 on request.
Tensile and flattening tests. Tension per JIS Z 2241; flattening where specified, confirming the weld and parent metal behave together.
Non-destructive examination. Eddy current or ultrasonic inspection of the weld/body; 100% on thin walls.
Hardness and decarburization check. Confirmed where hardening or machining to a finished surface is involved.
Third-party inspection. SGS, BV or TÜV witness and certificate available against the purchase order.
Send your grade, OD × wall, manufacturing route and heat-treatment requirement - our technical team will confirm the specification against the current JIS G3441 edition and return a quotation with lead time. Contact GNEE today.
Why Source JIS G3441 from GNEE
Both routes in one package. GNEE supplies JIS G3441 as ERW or seamless, matched to your size and weld-line requirement.
Grade and heat-treatment control. SCr420TK through SCM440TK, as-manufactured/annealed or quenched and tempered, with verified chemistry.
Inspection and documents. EN 10204 3.1 mill certificate as standard; SGS/BV/TÜV third-party inspection on request.
Export experience. 160+ customers served, shipped from Tianjin with consolidated documentation.
FAQ
What is JIS G3441 ERW pipe used for?
JIS G3441 is alloy steel tubing for machine structural purposes: crankshafts, piston pins, gears, axles, sprockets, hydraulic components and other machined or stressed machine parts. It is a mechanical-tubing product, not a pressure or boiler tube.
Is JIS G3441 seamless or welded?
The JIS G3441 standard permits both. Tubes may be weldless (seamless) or electric-resistance-welded (resistance welding). So an ERW JIS G3441 tube is a legitimate form of the standard, and a supplier that claims G3441 is 'seamless only' is reading the standard incorrectly.
What grades are covered by JIS G3441?
The chromium and chromium-molybdenum grades are SCr420TK, SCM415TK, SCM418TK, SCM420TK, SCM430TK, SCM435TK and SCM440TK. The fuller standard also lists nickel-chromium grades SNC815TK and SNCM420TK and the higher-alloy SCM822TK. Carbon is specified as a range, not a maximum, for each grade.
What is the chemical composition of JIS G3441 SCM420TK?
SCM420TK (wt%): C 0.18–0.23, Si 0.15–0.35, Mn 0.60–0.85, P max 0.030, S max 0.030, Cr 0.90–1.20, Mo 0.15–0.30. Note the carbon is a range (0.18–0.23), not a 'C max' value as some supplier pages write.
Is JIS G3441 suitable for pressure service?
No. JIS G3441 is for machine structural purposes and is not a pressure-pipe or boiler-tube standard. Pressure duties in the JIS system belong to JIS G3454 (carbon steel pressure pipe, STPG), JIS G3455/G3456 (high-pressure/high-temperature), JIS G3458 (alloy pressure pipe) and JIS G3462 (alloy boiler tube). Do not specify G3441 for fluid, gas or boiler service.
What is JIS G3441 equivalent to?
It is commonly cross-referenced to ASTM A519 and EN 10297-1, both alloy mechanical-tubing standards. The important caveat is that A519 and EN 10297-1 are seamless-only, whereas JIS G3441 also permits electric-resistance-welded tube, so it is the broader specification.
What is the difference between JIS G3441 and JIS G3445?
JIS G3441 is alloy steel (Cr and Cr-Mo grades such as SCM420TK) for machine structural purposes; JIS G3445 is carbon steel (STKM grades) for the same machine-structural use. G3441 carries tighter dimensional tolerances and finer grain for precision-fit applications such as hydraulic bodies and bearing seats, and its strength ceiling is higher.
How do I specify a JIS G3441 ERW pipe order?
State the standard and grade (for example JIS G3441 SCM420TK), the manufacturing method (ERW), outside diameter and wall thickness with quantity and length, the heat treatment (as-manufactured/annealed, or quenched and tempered if required), end condition, any Charpy impact or third-party inspection, and destination port. Confirm the current JIS G3441 edition at order.
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