Exera® 20AP is a hardenable, free-cutting carbon steel medical wire characterized by excellent machinability. The grade has high hardness, high wear resistance and exceptional dimensional stability after hardening.
Exera® 20AP is used for dental applications such as dental burrs and drills.
Chemical composition (nominal) %
Forms of supply
|Forms of supply/ finishes||Diameter
||Cu-Sn coating||Standard tolerance||Length|
|Wire in coils|
Other sizes on request.
Ovality: For D1 and D2, max. 50% of the tolerance width, for D3 max. 25% of the tolerance width.
|Forms of supply/Finishes||Diameter||Tensile strength||Proof strength||Elongation|
|mm||Rm1)||Rp0.21) 2)||A 1)3)|
|Wire in coils||0.80-1.60||770|
1) Nominal values. Other properties on request.
2) Rp0.2 and elongation values are given for information only.
Quenching time and temperature is dependent on material size, the specimens for impact strength are larger than standard wire.
Table of impact strength for Exera® 20AP, hardened and quenched condition (soaking temperature 800°C and soaking time 10 min, tempering time is 30 min)
|Tempering temperature, °C||Impact strength, J|
Figure 1. Impact strength after recommended hardening procedures, valid for all dimensions.
Soaking time 30 minutes. Standard Charpy-V specimens at 20oC.
Density annealed 7.8 g/cm3, 0.28 lb/in3
Cold drawn, 0.18 µΩm
Heat treated, 0.21 µΩm
1) Mean values in temperature ranges (x10-6)
Exera® 20AP is a magnetic material.
When required, soft-annealing should be conducted for a period of one hour at a temperature of 650 - 680oC.
|≤5||800 - 820||3 - 6||in oil at 50oC|
|> 5||790 - 810||6 - 10||in water|
The smaller the diameter, the shorter the soaking time. To avoid oxidation and decarburization, hardening should be conducted in a protective gas atmosphere using nitrogen, argon or a vacuum.
Contact Sandvik for further advice.
Prolonged service at elevated temperatures causes decreased hardness when used in the hardened and tempered condition. See also "Impact strength".
|Temperature, oC||100 - 600|
|Tempering time, min||30 - 60|
The core of the material needs a tempering time of at least 30 minutes. To reduce the risk of cracking, tempering should be conducted immediately after hardening. The heating rate should not be too high, particularly in the case of intricately shaped components.
Figure 2. Hardness after recommended hardening procedures, valid for all dimensions.
Soaking time 30 minutes.
The recommended values, based on Sandvik Coromant cemented carbide cutting tools or high speed steel tools from Sandvik, are to be regarded as starting data. To obtain the optimal combination of finishes, tolerances and productivity the values should be adjusted for each individual operation. The data assumes the use of a suitable cutting fluid. If machining without a cutting fluid, the values should be reduced by about 10%.
Detailed recommendations can be obtained from your nearest Sandvik Coromant or Sandvik office.
In the manufacture of sophisticated precision components, the material's highly uniform and very good machinability offers reliable production with high productivity. This is of major importance since component processing costs can be several hundred times greater than the cost of the raw material.
Material in the drawn condition up to Ø 3 mm has a Cu/Sn surface layer. The layer enables components to be machined by lathes equipped with guide bushing.
The charts below give guidance of how speed and feed affect diameter tolerances and surface roughness of turned components. The charts are based on longitudinal turning. The tolerances are given by using the ISO-system, i.e. IT7 could mean h7, k7 or js7.
The tools used in Figure 3 - 6 were brazed cemented carbide tools and in Figure 7 indexable cemented carbide inserts. Brazed tools used: Sandvik Coromant tool 310 L197-1212-200 grade H10F, rake angle 0°, clearance angle 6° and entering angle 90°. Indexable tools used: Sandvik Coromant insert TCMT 110202-UF GC415 and tool holder STGCL 1212F 11.
Figure 3. Wire diameter 1.20 mm, high tensile strength, drawn condition, depth of cut between 0.2-0.3 mm. Brazed cemented carbide
Figure 4. Wire diameter 1.20 mm, medium tensile strength, drawn condition depth of cut between 0.2-03 mm. Brazed cemented carbide.
Figure 5. Wire diameter 3.00 mm, drawn condition, depth of cut between 0.4-0.6 mm. Brazed cemented carbide.
Figure 6. Wire diameter 3.50 mm, ground condition, depth of cut between 0.5-0.9 mm. Brazed cemented carbide.
Figure 7. Wire diameter 6.0 mm, ground condition, depth of cut between 0.2-0.5 mm. Indexable cemented carbide inserts.
CNC lathes and similar
Indexable insert tools. For diameters d < approx. 20 mm lower cutting speeds should be used.
|GC 4015||CT525||GC 235|
|CT 5015||GC 4025||GC 4035|
Diameter > approx. 2 mm
Single and multiple spindle automatic lathes
Diameter > approx. 10 mm
|Operation||Finish turning||Rough turning|
|Plunge cutting and parting off||0.02-0.05||0.05-0.10|
|Diameter < approx. 10 mm||Cutting depth||Finish turning1)||Medium||Rough turning2)|
|Single point turning||<1||0.005-0.01||0.01-0.015||0.025|
|Plunge cutting and parting off||>3||0.005
1) For parts requiring high precision.
2) For parts with moderate tolerance requirements and parts that subsequently must be finish machined.
Parting off and grooving
|GC 235, 4025||0.05-0.15||55-110|
|Self-opening die heads||HSS||5-10|
1)Cemented carbide drills of Delta type with the following data can also be used:
Grade GC1020, speed 60-100 m/min.
|Finish milling with high cutting speed under
favorable working conditions
|Finish and medium-rough milling under normal to
difficult working conditions
Medium-rough to rough milling under difficult conditions
|Tool type||Grade||Cutting speed|
|Solid carbide end mills||4030
Brazed helical fluted end mills
Cutting speed for diameters > about 2 mm
Gun drill geometry
All data is nominal. Values refer to 20°C unless otherwise stated.
For other requirements and further information please contact Sandvik.