A significant share of technical drawings from Europe show a stainless steel grade on the material line: 1.4301, 1.4404, 1.4571 or 1.4305. These grades look similar from the outside, but differ markedly in corrosion resistance, machining time, surface quality and price. Choosing the wrong grade means either unnecessary cost or a corrosion problem in the field. This guide compares the stainless grades that purchasers and designers encounter most often from a CNC contract manufacturing perspective; it can be read as the stainless-steel sequel to our aluminium guide.
The Most Commonly Used Grades
| EN number | Short name / AISI | Type | Corrosion resistance | Machinability | Price (304 = 100) | Typical use |
|---|---|---|---|---|---|---|
| 1.4301 | X5CrNi18-10 / 304 | Austenitic | Good (general atmosphere, food) | Medium-difficult | 100 | General machinery, food equipment, architecture |
| 1.4307 | X2CrNi18-9 / 304L | Austenitic, low C | Good; better after welding | Medium-difficult | 100–105 | Welded structures |
| 1.4404 | X2CrNiMo17-12-2 / 316L | Austenitic, Mo | Very good (chlorides, marine, chemical) | Difficult | 130–150 | Medical, pharmaceutical, marine, chemical, offshore |
| 1.4571 | X6CrNiMoTi17-12-2 / 316Ti | Austenitic, Mo + Ti | Very good; stable at high temperature | Difficult (Ti carbides wear tools) | 135–155 | Common on German drawings; chemical, process equipment |
| 1.4305 | X8CrNiS18-9 / 303 | Austenitic, S-added | Medium (lower than 304) | Very good (free-machining) | 105–115 | Series turned parts, Swiss-type turning, fasteners |
| 1.4104 | X14CrMoS17 / 430F | Ferritic, S-added | Medium-low | Very good | 85–95 | Magnetic, series turned parts, shafts |
| 1.4057 | X17CrNi16-2 / 431 | Martensitic | Medium-good | Medium | 110–125 | Hardenable shafts, pump shafts |
| 1.4462 | X2CrNiMoN22-5-3 / Duplex | Austenitic-ferritic | Excellent (chlorides, stress corrosion) | Difficult | 170–220 | Offshore, oil and gas, seawater |
The price index is approximate for bar material and varies over time with nickel and molybdenum prices.
304 or 316L?
This is the most frequently asked question. Thanks to its molybdenum content, 1.4404 (316L) is markedly more resistant than 1.4301 (304) to pitting corrosion in chloride environments (seawater, salt, cleaning chemicals, body fluids). However, its price is 30–50% higher and it is harder to machine. The rule: if the part does not come into contact with chloride, acidic or medical environments, 304 is sufficient; 316L is chosen for marine, chemical, pharmaceutical and medical applications. The "316L just in case" approach adds 30–50% material cost and 10–20% machining cost unnecessarily.
1.4571 (316Ti): The Classic of German Drawings
1.4571 is very common on German-sourced drawings; the titanium addition was introduced in older production methods to prevent intergranular corrosion after welding. Modern low-carbon 1.4404 provides the same corrosion resistance and gives a better surface; titanium carbides shorten tool life and can cause streaking on polished surfaces. For this reason many German standards accept 1.4404 as equivalent to 1.4571. If the drawing specifies 1.4571 and the customer approves, the wording "1.4404 or 1.4571" simplifies sourcing; in certified applications the grade on the drawing is used exactly.
1.4305 (303): The Material for Series Turned Parts
The sulphur addition makes chip breaking easier; 1.4305 machines 30–50% faster than 304 and runs much more stably on Swiss-type lathes. The price is slightly lower corrosion resistance and non-weldability. It is the first choice for high-volume stainless fasteners, pins, connector parts and valve needles. In our article on series production on Swiss-type lathes we explain this material's effect on cycle time.
Machining Challenges of Stainless Steel
- Work hardening: austenitic stainless steels harden as they are cut; insufficient feed or a dull tool hardens the surface and makes the next pass more difficult. Consistent feed and sharp, coated tools are required.
- Low thermal conductivity: heat accumulates in the tool; high-pressure coolant and a suitable cutting speed (typically 120–200 m/min for 304) are essential.
- Long, stringy chips: especially with 304 and 316L, this is where chip-breaker geometry and free-machining grades (303) show their advantage.
- Thermal expansion and elastic spring-back: on thin-walled parts, passes and clamping are planned carefully for dimensional stability.
- Cycle time: the same part takes 30–60% longer than in steel and 3–5 times longer than in aluminium; because the labour share is high, Turkey's hourly rate advantage is pronounced with stainless steel.
Surface and Finishing Operations
Typical finishing operations for stainless parts: passivation (removes free iron residue from the surface and restores corrosion resistance; standard for medical and food parts), electropolishing (below Ra 0.2, smooth hygienic surface), bead blasting and brushing (matt appearance), polishing. Surface requirements of Ra 0.8 or 0.4 are common in food and pharmaceutical equipment; these values must be stated clearly on the drawing. An EN 10204 3.1 certificate and PMI (portable alloy analysis) verification eliminate the risk of mix-ups.
Availability in Turkey
1.4301, 1.4404, 1.4305 and 1.4571 are available from stock in Turkey as bar and plate; European-origin (Italy, Spain, Germany) and domestic material is supplied with 3.1 certificates. 1.4462 duplex and special grades may require a lead time of 1–3 weeks. For other items that affect the price, see our article on the 12 factors.
Choices That Lower Cost
- Use 304 instead of 316L in chloride-free environments.
- Choose 303 (1.4305) for series turned parts if the corrosion requirement allows; machining time is shortened by 30–50%.
- If the drawing specifies 1.4571, consider the 1.4404 equivalent.
- Keep surface roughness tight only on the surfaces where it is needed; requesting Ra 0.4 on the whole part increases cost significantly.
- Design to standard bar diameters; ground h9 bar is only necessary for Swiss-type parts.
Frequently Asked Questions
What is the difference between 316 and 316L?
316L is low-carbon (≤0.03% C); it resists intergranular corrosion after welding. For machined parts the two are mostly considered equivalent; 1.4404 is the standard in Europe.
Which tolerance is realistic on stainless parts?
±0.01 mm on turned parts, ±0.005 mm on Swiss-type parts and ±0.02–0.05 mm on milled housings is standard.
Is stainless steel magnetic?
Austenitic grades (304, 316) are non-magnetic; ferritic (1.4104) and martensitic (1.4057) grades are magnetic. Cold working can create slight magnetism in austenitic grades.
Is passivation mandatory?
Generally yes for medical, food and pharmaceutical parts; optional for general machine parts. It must be stated on the drawing or in the order.
Conclusion
Choosing the right stainless grade is a deliberate balance between the corrosion environment, machinability and cost. 304 is sufficient for most general applications, 316L is necessary in chloride and medical environments, and 303 delivers clear savings on series turned parts. Send the technical drawings of your stainless parts via our quote form; we will provide a price together with grade and surface treatment recommendations. For information on our CNC turning and Swiss-type machining capacity, please see our service pages.
