Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
634 is a chromium-nickel-molybdenum semi-austenitic precipitation-hardening (PH) stainless steel. This datasheet presents the material within the American (ASTM / ASME / AMS / UNS) standard system.
With about 15.5% chromium, 4.3% nickel, 2.75% molybdenum and a controlled nitrogen and carbon content, AM-355 is a higher-carbon variant of AM-350 that develops higher strength while retaining good weldability and corrosion resistance comparable to type 316. It is supplied in the soft austenitic condition (Condition A), formed, then transformed to martensite and precipitation-hardened by a multi-step heat treatment. The low-temperature hardening gives minimum distortion, and the alloy is well suited to flat-rolled and extensively formed components.
Typical applications include aerospace structural and engine components, gas-turbine parts, missile and frame structures, fasteners, and high-strength corrosion-resistant hardware.
Typical values, SCT850 condition.
| Property | Value | Unit |
|---|---|---|
| Density | 7.91 | g/cm³ |
| Melting range | 1400–1440 | °C |
| Elastic modulus | 200 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 11.7 | µm/m·°C |
| Thermal conductivity (20 °C) | 14.2 | W/m·K |
| Specific heat (20 °C) | 480 | J/kg·K |
| Structure | Semi-austenitic (precipitation-hardening) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 15.0 | 16.0 | Corrosion resistance |
| Nickel | Ni | 4.0 | 5.0 | Austenite stability |
| Molybdenum | Mo | 2.50 | 3.25 | Strength; pitting resistance |
| Nitrogen | N | 0.07 | 0.13 | Strengthening element |
| Carbon | C | 0.10 | 0.15 | Strengthening element (higher than AM-350) |
| Manganese | Mn | 0.50 | 1.25 | Deoxidiser; austenite former |
| Silicon | Si | — | 0.50 | Deoxidiser |
| Phosphorus | P | — | 0.040 | Residual impurity |
| Sulphur | S | — | 0.030 | Residual impurity |
Typical values by heat-treatment condition, per ASTM A693 / AMS 5547 for UNS S35500.
| Condition | Tensile strength | 0.2% Yield | Hardness |
|---|---|---|---|
| SCT850 | ≥1480 MPa (215 ksi) | ≥1240 MPa (180 ksi) | ~49 HRC |
| SCT1000 | ≥1280 MPa (185 ksi) | ≥1140 MPa (165 ksi) | ~44 HRC |
| DA (double-aged) | ≥1210 MPa (175 ksi) | ≥1070 MPa (155 ksi) | ~42 HRC |
| Condition A (annealed) | ~1170 MPa (170 ksi) | ~415 MPa (60 ksi) | ~B98 HRB |
Confirm against the mill test report. Elongation typically ≥8–12% depending on condition.
| Environment | Performance | Notes |
|---|---|---|
| Atmospheric / general | Very Good | Comparable to type 316 |
| Mild acids | Good | Molybdenum addition aids resistance |
| Chloride pitting | Good | Better than other PH grades (Mo) |
| Oxidation | Good | At elevated temperature |
| Seawater | Limited | Not recommended for prolonged exposure |
Corrosion resistance is comparable to type 316 in most media and superior to the hardenable 400-series grades; the higher carbon gives higher strength than AM-350 with broadly similar corrosion behaviour.
A semi-austenitic precipitation-hardening alloy; supplied in Condition A (soft, austenitic) and hardened by a multi-step transformation-plus-ageing sequence.
Solution Treatment (Condition A) Supplied solution-treated (~1040 °C) in the soft austenitic condition for forming.
Transformation and Precipitation Hardening SCT (sub-zero cooling and tempering): condition at ~930 °C, refrigerate (~−75 °C) to transform austenite to martensite, then temper — SCT850 (~455 °C) for maximum strength, SCT1000 (~540 °C) for higher toughness. DA (double ageing): age at ~735 °C then ~455 °C for components where refrigeration is impractical. Air cool after tempering.
Good weldability for a high-strength PH grade; matching filler is used. Heat treatment after welding develops full properties.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching AM-355-type filler |
| Resistance / seam | Good | — |
| GMAW / MIG | Good | Matching filler |
Weld in Condition A; heat-treat after welding to develop strength.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Preferred condition | Condition A for best formability and machinability |
| Work hardening | Moderate-to-high rate; positive feeds, rigid setup |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Good in Condition A (formable semi-austenitic PH) |
| Hot forming | ~1150–950 °C; solution treat + harden afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Aerospace | Structural parts, frames, fittings | High strength + corrosion resistance |
| Gas turbine | Engine and turbine components | Strength at temperature |
| Missile / defence | Frame and structural components | Strength-to-weight |
| General industrial | High-strength formed components | Strength + corrosion resistance |
| Product Form | ASTM Standard | ASME / AMS |
|---|---|---|
| Plate, sheet and strip | ASTM A693 grade 634 | ASME SA-693 / AMS 5547 |
| Bar and wire | ASTM A564 (634) | AMS 5743 |
| Forgings | ASTM A705 (capability) | — |
| Welding consumables | Matching AM-355-type filler | — |
Chromium-nickel-molybdenum semi-austenitic precipitation-hardening stainless steel. UNS S35500.
| AISI Type | Cr % | Ni % | Mo % | Other | Best Used For |
|---|---|---|---|---|---|
| 634 | 15–16 | 4–5 | 2.5–3.25 | N, high C | Semi-austenitic PH; highest strength of the AM grades |
| 633 | 16–17 | 4–5 | 2.5–3.25 | N | Semi-austenitic PH; bellows, weldability (AM-350) |
| 631 | 16–18 | 6.5–7.75 | — | Al | Semi-austenitic PH; springs, formability (17-7PH) |
| 632 | 14–16 | 6.5–7.75 | 2.0–3.0 | Al | Semi-austenitic PH; high strength at temperature (PH15-7Mo) |
| 630 | 15–17.5 | 3–5 | — | Cu, Nb | Martensitic PH; general high strength (17-4PH) |
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