Table of Contents
What Is Sintered Steel?
Sintered steel is a steel part made by powder metallurgy (PM): iron or steel powder is blended with alloying elements and lubricant, compacted in a precision die at 400–800 MPa, and then sintered in a controlled-atmosphere furnace at 1,120–1,300°C. During sintering, atomic diffusion bonds the powder particles into a solid metal part — without melting the material.
The result is a near-net-shape steel component, typically 85–95% of theoretical density, with:
- Dimensional repeatability of IT7–IT8 as-sintered (IT5–IT6 after sizing)
- Material utilization above 95%, versus 40–60% for many machined-from-bar routes
- Unit costs that undercut machining, casting, and forging at medium-to-high volumes
Sintered steel is the workhorse of the PM industry: gears, sprockets, structural brackets, bearing housings, synchronizer hubs, and pump components are produced by the hundreds of millions each year.
If you are sourcing sintered steel parts, send your drawing for a DFM review and quote — engineering responds within 24–48 hours.
How Sintered Steel Is Made
1. Powder Preparation
Base iron powder (atomized or reduced) is blended with alloying additions — copper, nickel, graphite (carbon), and sometimes molybdenum — plus 0.5–1% lubricant for die compaction. Powder selection largely determines the final grade's strength and cost.
2. Compaction
The blend is pressed in a rigid die at 400–800 MPa into a "green" compact with 75–85% density. Our press lines cover 6T–400T, supporting multi-level parts with complex geometries formed in a single stroke.
3. Sintering
Green parts travel through continuous mesh-belt furnaces at 1,120–1,300°C in a protective atmosphere (typically N₂/H₂). Particles bond, alloying elements diffuse into the iron matrix, and the part reaches its final mechanical properties — typically 90%+ of theoretical density.
4. Secondary Operations (Optional)
- Sizing/coining — re-pressing for tighter tolerances (down to IT5–IT6)
- Heat treatment / sinter hardening — for wear and load-bearing surfaces
- Steam treatment — seals surface porosity, improves wear and corrosion resistance
- Copper infiltration — near-full density for pressure-tight or high-strength parts
- CNC machining — features that cannot be pressed (threads, cross-holes, undercuts)
See the complete powder metallurgy process and our sintering and heat treatment capabilities.
Common Sintered Steel Grades (MPIF Standard 35)
| Grade | Alloy System | Density (g/cm³) | Tensile Strength (MPa) | Typical Use |
|---|---|---|---|---|
| F-0008 | Iron + 0.8% C | 6.4–6.8 | 240–340 | Low-load structural parts, bearing seats |
| FC-0205 | Fe + 2% Cu + 0.5% C | 6.6–7.0 | 340–480 | General structural, automotive brackets |
| FC-0208 | Fe + 2% Cu + 0.8% C | 6.8–7.1 | 380–550 | Most widely used PM steel — gears, hubs, sprockets |
| FN-0205 | Fe + 2% Ni + 0.5% C | 6.8–7.1 | 380–520 | Toughness-critical parts, impact loads |
| FN-0405 | Fe + 4% Ni + 0.5% C | 7.1–7.3 | 480–690 | High-strength gears, heat-treatable |
| FL-4405 | Copper-infiltrated steel | 7.2–7.6 | 700+ | Near-full density, connecting rods, hydraulic parts |
| Sinter-hardened grades | Fe + Ni + Cu + Mo | 6.8–7.2 | 800–1,100 (as-sintered) | High-load gears without secondary heat treatment |
Values are typical as-sintered ranges per MPIF Standard 35; exact properties depend on density, sintering practice, and heat treatment. Compare grades interactively in our material comparison tool or browse the full materials hub.
Key Properties of Sintered Steel
Density and Porosity
Standard sintered steel runs 6.6–7.3 g/cm³ — about 85–93% of wrought steel's 7.85 g/cm³. The residual porosity is a designed characteristic:
- Beneficial for oil-impregnated self-lubricating bearings (18–25% connected porosity stores lubricant)
- Acceptable for most structural parts (strength scales with density)
- A problem for pressure-tight walls — solved by copper infiltration or higher-density compaction routes
Tolerances
- As-sintered: IT7–IT8 on pressing-direction dimensions; IT8–IT9 perpendicular
- After sizing: IT5–IT6 achievable on critical features
- See powder metallurgy tolerance planning for design guidance
Surface Finish
Ra 0.8–3.2 μm as-sintered; Ra 0.2–0.8 μm after sizing or machining. Details in surface finish expectations.
Where Sintered Steel Parts Are Used
- Automotive (largest share): transmission gears, synchronizer hubs, sprockets, connecting rods, ABS rings, shock absorber components, seat recliner mechanisms
- Power tools: gearbox planetary gears, bevel gears, clutch components — see power tool gearbox gears
- Home appliances: washing machine gears, compressor parts
- Industrial equipment: hydraulic pump gears, actuators, sprockets and chain components
- Locks and hardware: lock cylinders, latch components
Sintered Steel vs Machined, Cast, and Forged Steel
| Factor | Sintered Steel (PM) | Machined from Bar | Casting | Forging |
|---|---|---|---|---|
| Best volume | 10,000+ pcs/year | Prototype–low volume | Medium–high | Medium–high |
| Material utilization | 95%+ | 40–60% | 70–85% | 70–90% |
| Geometry | Complex in pressing axis | Any | Free-form 3D | Limited |
| Strength | 85–95% of wrought | 100% | 70–90% | 100%+ (grain flow) |
| Tolerance | IT7–IT8 (IT5–6 sized) | IT6–IT9 | IT10–IT13 | IT10–IT14 |
| Tooling cost | Moderate (die) | None | Moderate | High |
| Unit cost at volume | Lowest for small complex parts | High | Medium | Medium–high |
Deep dives: PM vs CNC machining · PM vs casting · PM vs forging · when not to use PM
Sourcing Sintered Steel Parts
SinterWorks produces sintered steel components on 36 presses (6T–400T) with 4 continuous sintering lines and 2,600T annual capacity. Every program includes:
- DFM review against PM design rules before tooling
- Material certification per MPIF Standard 35
- CMM dimensional reports, full inspection lab
- PPAP Level 3 documentation for automotive programs
Submit your drawing for a 24–48 hour quote, or contact engineering to review feasibility first.
Frequently Asked Questions
Is sintered steel as strong as regular steel?
Standard sintered steel reaches roughly 85–93% of theoretical density, so as-sintered tensile and fatigue values run below wrought equivalents of the same chemistry. Higher-density routes — sizing, copper infiltration, double-press/double-sinter, or heat treatment — close most of the gap, and sinter-hardened grades exceed 1,000 MPa tensile without secondary heat treatment.
What is the most common sintered steel grade?
FC-0208 (iron + 2% copper + 0.8% carbon) is the most widely used sintered steel grade worldwide. It offers the best balance of strength, machinability, and cost for gears, hubs, and structural parts. See the FC-0208 material guide for full property data.
Can sintered steel parts be welded or machined?
Yes, with precautions. Sintered steel machines well with standard tooling, though porosity reduces tool life slightly versus wrought steel. Welding is possible but porosity can cause defects in the weld zone; brazing and sinter-bonding are often better joining routes. Details are in our welding, brazing, and bonding guide.
Does sintered steel rust?
Yes — like any carbon steel, unprotected sintered steel corrodes, and its surface porosity can accelerate it. Common protections include steam treatment (black Fe₃O₄ layer), zinc or nickel plating, oil dipping, and painting. Stainless sintered grades (304L, 316L) are used when corrosion resistance is structural to the application.
What tolerances can sintered steel hold?
IT7–IT8 as-sintered is standard on pressing-direction dimensions; perpendicular dimensions typically hold IT8–IT9. After a sizing (coining) operation, IT5–IT6 is achievable on critical features such as bearing bores and gear bores.
What is the minimum order quantity for sintered steel parts?
Because each part requires dedicated compaction tooling, PM economics start making sense around 1,000–5,000 pieces for simple parts and 10,000+ pieces per year for most programs. Tooling cost and lead time are reviewed case by case in the DFM stage.
Related Resources
Use these internal links to keep moving through the most relevant guides, service pages, and technical references for this topic.
Materials Hub
Compare sintered steel grades (FC-0208, FN-0405, FL-4405) with stainless and specialty PM materials.
FC-0208 Material Guide
The most widely used sintered steel grade — full property data and application guidance.
PM vs CNC Machining
Cost and capability comparison between sintered steel parts and machined-from-bar routes.
Request a Quote
Send drawings, annual volume, and target grade for a 24–48 hour DFM review and quotation.
Need Sintered Steel Parts for a Production Program?
Share your drawing, annual volume, and target grade. Our engineering team will confirm PM feasibility, recommend a grade, and return a quotation with tooling cost within 24–48 hours.
- DFM review support
- Material and process guidance
- Quotation feedback within 24-48 hours