S31675 stainless steel for high nitrogen surgical implants
In recent years, the demand for high-end medical stainless steel
has been increasing, and due to the high cost of imported medical
stainless steel, long delivery cycles, and high communication
costs, the call for the localization of high-end medical stainless
steel has also been increasing. The domestically produced S31675
high nitrogen stainless steel was born in this context.
S31675 (ASTMF1586) is a nitrogen reinforced stainless steel for
surgical implants, mainly used for hip and knee joints and fracture
fixation devices. Its special use requires the material to be very
"pure", which means that the content of non-metallic inclusions
such as sulfides, alumina, silicates, and spherical oxides is low.
This grade of stainless steel is usually produced using the
electroslag remelting (ESR) smelting process. ESR is a super
refining process that enables stainless steel to have excellent
micro cleaning levels that meet regulatory requirements. It can
also meet other special requirements of these ASTM standards for
implant materials, such as having fine grain structure. The
domestically produced S31675 adopts the same production process as
Europe and America, and its quality is not inferior to imported
products. And it has significant advantages in terms of price,
delivery cycle, and minimum order quantity.
Relevant standards
ASTMF1586
ISO5832-9
YY0605.9-2007- Metallic Materials for Surgical Implants - Part 9:
Forged High Nitrogen Stainless Steel
EN10088-309/05X4CrNiMnMo21-9-4
2.4772
M30NW
chemical composition
| element | C | Mn | P | S | Si | Cr | Ni | Mo | N | Nb | Cu | Fe |
proportion (Mass%) | 0.08 max | 2.00-4.25 | 0.025 max | 0.01 max | 0.75 max | 19.50-22.00 | 9.00-11.00 | 2.0-3.0 | 0.25-0.50 | 0.25-0.80 | 0.25 max | Bal |
mechanical property
| Delivery status | Diameter or thickness/mm | Tensile strength Rm/MPa | Prescribed non proportional elongation strength Rp0.2/MPa | Elongation after fracture (A/%) |
| Annealed state | Full size | 740 | 430 | 35 |
| Semi hard state | 1.59-19.1 | 1000 | 700 | 20 |
| Hard state | 1.59-19.1 | 1100 | 1000 | 10 |
Grain size
Determine the grain size of austenite according to the prescribed
method, and the result should not be coarser than level 5.
No foreign phase
According to the specified method, there should be no presence in
the microstructure of the steel δ Ferrite χ Xianghe σ Phase.
Inclusion content
According to the prescribed method, the content of non-metallic
inclusions in steel measured on a section of billet or bar with a
thickness not exceeding 150mm should not exceed the provisions in
the following table
Note: Generally, electroslag remelting steel is used to meet purity
requirements and gain other advantages.
| Inclusion type | Reference level for inclusion content |
| Fine series | Coarse series |
sulfide alumina silicate Spherical oxide | 1.5 2 2 2.5 | 1.5 1.5 1.5 1.5 |
characteristic
S31675 stainless steel has good corrosion resistance and good
mechanical properties.
Strict raw material selection and smelting process ensure the
extremely high quality required for the production of stainless
steel for surgical implants.
Due to its composition and absence of ferrite, the steel is
completely non magnetic and exhibits excellent resistance to
pitting and crevice corrosion in physiological media
(Cr%+3.3Mo%+15N%>32).
The stabilizing effect of niobium can generate excellent
intergranular corrosion resistance.
The combination of smelting and processing processes ensures that
the product can obtain uniform, fine-grained materials with very
low inclusion levels. This ensures that the product has excellent
fatigue resistance, which is ideal for producing parts that
withstand high stress.
Product form
Wire, bar, plate, strip, seamless tube, capillary tube
