If an enquiry says only “20 mm Grade 23 titanium square bar for a medical device,” I would not quote it yet. I would ask for the drawing.
There is a simple reason. Square stock can be a sensible starting shape for a block-like part, but the word square tells me nothing about implant suitability. It does not improve fatigue strength, corrosion behaviour or biocompatibility. Those questions belong to the alloy, standard, processing history, finished surface and the device maker’s validated process.
What square stock may change is the machining job. Sometimes it reduces rough cutting and chip volume. Sometimes it merely replaces a readily available round bar with a special, slower and more expensive shape.
I start with the finished part
The first comparison I make is visual. If most of the part is turned around a centreline, round bar is normally the better starting point. Pins, shafts and screws are obvious examples.
A housing, fixture or instrument block is different. Four broad finished faces may fit inside a square or rectangular blank with less stock removal. Even here, I do not compare nominal dimensions alone. I compare purchased weight, usable allowance, production route and lead time.
This is the useful, narrow claim for titanium square bar in medical manufacturing: its outline may sit closer to the finished outline. It is not a better medical material because it has four sides.
Then I ask how the square will be produced
A calliper cannot tell you the manufacturing route. The section might be rolled close to size. It might be forged and finished. It might be machined from qualified round bar. A blank cut from plate can look similar too.
Those routes should not be mixed casually on the purchase order. With rolled square stock, I want to know the available section, corner condition, straightness, twist and surface. For a forging, I ask about the input stock, heat treatment, test location and machining allowance. If the supplier machines a square from round bar, the parent-bar specification and heat identity still have to follow the new pieces. The certificate must continue to describe the parent product form truthfully; machining it square does not create a separately certified rolled or forged square bar.
I treat plate-cut blanks separately. Their certificate and reported properties relate to the parent plate and its governing standard. Machining four sides does not turn a plate blank into certified bar. If that route is acceptable, say so. If it is not, prohibit it on the drawing or PO.
The ASTM line comes before the Grade 23 nickname
For implant material I look for the controlling standard and revision, not just a grade number. ASTM F67 covers unalloyed titanium Grades 1, 2, 3 and 4 for surgical-implant manufacture. Bar is included in its product forms. ASTM F136 covers wrought annealed Ti-6Al-4V ELI, UNS R56401, and also includes bar.
“Grade 23” is useful workshop shorthand, but it is not enough for this order. ASTM B348/B348M uses Grade 23 for bar and billet. ASTM B265 uses the same grade number for sheet and plate. ASTM F136 identifies the implant alloy as Ti-6Al-4V ELI and UNS R56401 rather than calling it Grade 23.
For that reason, I would rather see “ASTM F136, UNS R56401, wrought annealed bar” followed by the revision and order requirements. For commercially pure implant material, specify ASTM F67 and the required grade. Before ordering a square section to either standard, confirm that the invoked revision accepts the ordered product form and that the agreed route can be certified accordingly. The ASTM F67 vs ASTM F136 guide covers this choice in more detail.
ASTM B348/B348M still belongs on industrial titanium-bar orders when the drawing invokes it. It is not a substitute for ASTM F67 or ASTM F136.
What the Beiyu size range does, and does not, mean
Beiyu reviews square titanium bar enquiries from 3 × 3 mm to 500 × 500 mm. The stated length limit is up to 6000 mm. I keep those figures separate on purpose.
They do not mean that a 500 × 500 mm section is available at 6000 mm length. That combination is not a standard stock promise. Heavy cross-sections often need a forged or machined route, and their workable lengths may be much shorter. The size range available to an implant-material standard will also be narrower than the full industrial range.
In practice, I need the grade, standard, section, length, condition, quantity, tests and acceptable route before I can confirm a workable combination. Think of the published figures as the boundary for an enquiry, not a warehouse inventory.
I would not leave “20 mm square” on the drawing
I would write 20 × 20 mm, followed by the tolerance for both dimensions. I would add the cut length and its tolerance. Then I would check the features that are easy to overlook:
- straightness and twist for long feed lengths;
- corner radius and edge condition;
- removable allowance on every machined face;
- mill, peeled, ground or machined surface;
- the Ra limit and measurement area, if roughness is controlled;
- the production stage at which the final section is inspected.
A round-bar diameter tolerance does not solve these points. Square stock has its own section and form controls. If the drawing relies on a general tolerance block, call out anything that must be inspected separately.
The paperwork must stay with the cut pieces
My first certificate check is against the PO: standard, revision, product form, grade or UNS designation, condition and ordered tests. My next question is physical. How will the heat identity stay connected after one long length is cut into blanks or repacked into smaller bundles?
The RFQ should answer that question. State whether heats must remain separate and what marking each piece or bundle needs. If the order requires EN 10204 3.1 documentation, ultrasonic examination or grain-size reporting, define the method, coverage, acceptance basis and report format before production. It is too late to add them when the material is ready to ship.
For the two medical routes discussed above, see the ASTM F67 titanium bar page und den ASTM F136 Ti-6Al-4V ELI bar page.
What I need to review the route
Send the finished-part drawing and intended use. Include the ASTM standard and revision, grade or UNS number, both section dimensions, cut length, tolerances, acceptable route and quantity. Add the required certificates, inspections, marking and packing.
The medical titanium bar RFQ checklist covers the fields shared by round and square material. Mark the square-stock details directly on the drawing, then send the package to Beiyu. We can review the material route and workable size before issuing a quotation.