Exera® Finemac™ free-cutting wire Wire

Exera® Finemac™ is a lead-free, hardenable, free-cutting carbon steel characterized by excellent machinability and high hardness, high wear resistance and exceptional dimensional stability after hardening.

Hardening operations are very much simplified compared to Sandvik 20AP, owing to the wider temperature and time range available using Exera® Finemac™. This results in significantly reduced failure rates during hardening. Exera® Finemac™ also exhibits very good cold heading properties. The material is suitable for long, narrow components with tight tolerances.

Service temperature -50 to 100°C (-55 to 210^oF). Prolonged service at elevated temperatures causes decreased hardness when used in the hardened and tempered condition.

Chemical composition (nominal) %

Forms of supply

Ovality: For D1 and D2, max. 50% of the tolerance width: for D3 max. 25% of the tolerance width: D4 ovality in accordance with the tolerance table below.

Mechanical properties

1) Nominal values. Other properties on request.

Impact strength

Observe that the quenching time and temperature are dependent on dimension. Specimens for the Charpy-V impact strength test are larger than standard wire dimensions.

Table of impact strength for Sandvik Finemac™, hardened and quenched condition. See Figure 1.

Soaking temperature 810°C (1490^oF), soaking time 4 min, tempering time 30 min.

Figure 1. Impact strength after recommended hardening procedures, valid for all dimensions.

Soaking time 30 minutes. Standard Charpy-V specimens at 20^oC (68^oF).

Physical properties

1) Mean values in temperature ranges (x10^-6)

Exera® Finemac™ is a magnetic material.

Heat treatment

Soft-annealing

When required, soft-annealing should be conducted for a period of one hour at a temperature of 650 - 680^oC (1200-1250^oF).

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 vacuum. Contact Sandvik for advice.

Prolonged service at elevated temperatures causes decreased hardness when used in the hardened and tempered condition. See also Impact strength under Mechanical properties.

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.

Hardness

Figure 2. Hardness after quenching in oil at 50^oC (120^oF), valid for all dimensions.

Figure 3. Hardness after recommended hardening and tempering procedures, valid for all dimensions.

Tempering time 30 minutes.

Hardening operations

Hardening operations will be very much simplified compared to Sandvik 20AP, owing to the wider temperature and time range available using Exera® Finemac™. Scrapping rates during hardening will be greatly reduced.

Figure 4. The cooling rate of Exera® Finemac™ vs. that of Exera® 20AP.

Machining

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 assume the use of a suitable cutting fluid. In 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 2.5 mm has a Cu/Sn surface layer. This layer enables components to be machined with very high demands on dimensions due to the fact that the guide bushing can be set with very tight tolerances, thereby achieving high accuracy on the finished dimensions.

Turning

The charts below give guidance on 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 Figures 5 - 8 have been brazed, cemented carbide tools. Brazed tools used: Sandvik Coromant tool 310 L197-1212-200 grade H10F, rake angle 0°, clearance angle 6° and entering angle 90°.

Figure 5. Wire diameter 1.20 mm, high tensile strength, drawn condition, depth of cut between 0.2-0.3 mm. Brazed cemented carbide.

Figure 6. Wire diameter 1.20 mm, medium tensile strength, drawn condition depth of cut between 0.2-03 mm. Brazed cemented carbide.

Figure 7. Wire diameter 3.00 mm, drawn condition, depth of cut between 0.4-0.6 mm. Brazed cemented carbide.

Figure 8. Wire diameter 3.50 mm, ground condition, depth of cut between 0.5-0.9 mm. Brazed cemented carbide.

Bar automatics

Diameter > approx. 2 mm

¹⁾ For parts requiring high precision.
²⁾ For parts with moderate tolerance requirements and parts that subsequently must be finish machined.

Reaming

Cutting speed for diameters > about 2 mm

All data are nominal. Values refer to 20°C (68^oF) unless otherwise stated.

For other requirements and further information please contact your Sandvik office.