Chemical composition (nominal) %

Dimensions

Sandvik 15LM is available in a wide range of sizes. The following chart indicates the approximate stand-ard size range.

Figure 1: Standard size range

Tolerances

The thickness and width tolerances are +/- tolerances to the nominal size. The normal tolerance classes for most of our strip products are T2 and B1. Tighter tolerances as well as other tolerance limits can be offered upon request.

Finishes and forms of supply

The strip steel can be supplied in coils or lengths with various edges and surfaces.

Mechanical properties

Nominal values at 20°C.

Physical properties

The physical properties of a steel are related to a number of factors, including alloying elements, heat treatment and manufacturing route, but the data presented below can generally be used for rough calculations.

Density, g/cm³: 7.85
lb/in^3: 0.28

Thermal expansion per °C, x10 –6:
from 20°C to 100°C: 10.4
to 200°C: 11.6
to 300°C: 12.4
per °F, x 10 –6 ,
from 68°F to 210°F: 5.8
to 390°F: 6.4
to 570°F: 6.9
Thermal conductivity
at 20°C, W/(m · °C): 49
68°F, Btu/(ft · h · °F): 28

Tolerances

In the standard finish, the tolerances is symmetrical, half above and half below the nominal size. Other tolerances can be discussed. The tolerances are based on the Swedish Standards SS 21 21 10 and 21 21 11 respectively.

Thickness tolerance

The standard tolerance is T1 according to table 3. Closer tolerances can be agreed upon.

Width tolerance

The standard tolerance is B1 according to table 4. Closer tolerances can be agreed upon.

Table 4. Width tolerances, B1

Blanking & Bending

Blanking

In order to achieve optimal blanking results tools and presses must be accurate and stable in dealing with hardened and tempered strip. A lubricant is recommended to minimize tool wear.

Clearance between punch and die

A radial clearance of 4–10% of the strip thickness is recommended. This will give low burr height in combination with long tool life and a sheared edge with a narrow shear zone and a wide break zone.

Tools

Tool steels of type AISI D2 or D4 with hardness about 63 HRC can be used except where thick gauges, slender tool sections and small corner radii are involved. In that case we recommend high-speed steel, type AISI M2 hardened and tempered to about 63 HRC. Carbide tools are recommended for blanking in very long runs, unless the strip is too hard and thick or the shape of the items is unsuitable. More detailed recommendations will be furnished on request. The corner radii should be min. 0.25 x the strip thickness, but not smaller than 0.25 mm (0.010 in.), and the diameter of the punch not smaller than 2 x the strip thickness. The risk of the hole slug or the blanked item being carried along with the punch on its return stroke can be lessened by using a die without a taper, i.e. with a straight section starting from the edge of the tool. The straight section should be at least 5 x the strip thickness or at least 3 mm (0.118 in.) in length.

Bending

Table 6 shows average values for the least bending radius, r min . These figures refer to strip with a nominal tensile strength as per table 5. The bending tests were carried out according to Swedish Standard SS 11 26 26 method 3, i.e.in a 90° vee block with a 25 mm (1 in.) die opening, the blanked test pieces being 35 mm (1.38 in.) wide and turned so that their burr edge was facing inwards in the bend.

Applications

• Springs in general
• Spring washers in cars
• Scraper blades for the pulp and paper industry