LAAN-A-HN-E002

No.251Mater ia l Test ing System

Hardness Test on Propelling Pencil Lead Core by Shimadzu DUH-W201S Dynamic Ultra Micro Hardness Tester

Propelling (or mechanical) pencil lead cores are made by mixing black lead with polymer resin. The hardness symbols HB and B are evaluated by a density measurement tester according to the density obtained by drawing on line drawing paper; however, hardness

is not yet scientifically defined.The following introduces an example of a hardness test performed on propelling pencil lead cores using the Shimadzu Dynamic Ultra Micro Hardness Tester.

Propelling pencil lead core

Propelling pencil

Standard vise

Test force

Fig. 2 Conceptual diagram

Fig. 1 Overview of DUH-W201S

1. Specimen

1) Specimen name Propelling pencil lead coreHB B 2B

2) Specimen No. No.1 No.2 No.33) Specimen size (mm) φ0.5 × 70

2. Test conditions

1) Testing machine Shimadzu DUH-W201S Dynamic Ultra Micro Hardness Tester (See Fig. 1)

2) Indenter Triangular pyramid indenter with tip angle of 115° (made of diamond)

3) Test type Load-unload test4) Test force (mN) 495) Loading rate

(mN/sec) 4.413

6) Holding time (sec) 157) Test method The lead core was inserted

into the propelling pencil and the tip of the core that was worn to a flat surface by drawing a line on paper was fixed in place by the standard vise and tested. (See Fig. 2)

SHIMADZU CORPORATION. International Marketing Division3. Kanda-Nishikicho 1-chome, Chiyoda-ku, Tokyo 101-8448, Japan Phone: 81(3)3219-5641 Fax. 81(3)3219-5710Cable Add.:SHIMADZU TOKYO

No.251

1) Table 1 summarizes the results (mean values) of testing by the test conditions in section 2.

2) Fig. 3 shows the force-depth graph after testing.

3. Test results

Fig. 3 Force-Depth Graph

Fig. 4 Indentation in HB Core Fig. 5 Indentation in B Core Fig. 6 Indentation in 2B Core

Specimen Name Specimen No. Maximum Force[mN]

Maximum Depth[μm]

Dynamic Hardness[DHT115-1]

Propelling pencil lead core

HB No.1 49.32 2.803 24.213

B No.2 49.28 3.394 16.509

2B No.3 49.26 3.615 14.543

Remarks) The calculation expression for dynamic indentation hardness is as follows:DHT115-1 = 3.8584P/h2

where, DHT115-1 : Dynamic hardness of triangular pyramid indenter at load end P : Maximum Force (mN) h : Maximum Depth (μm)

Table 1 Hardness Measurement Results (Mean Values)

Force-Depth Graph

Maximum Depth (μm)

Max

imum

For

ce (m

N)

The Shimadzu DUH-W Dynamic Ultra Micro Hardness Tester allows the hardness of propelling pencil lead cores to be evaluated by hardness value and not density.

4. Summary

3) The order of specimen hardness in 1) is as follows : HB > B > 2BThis means that HB is about 1.5 times harder than B and B is about 1.1 times harder than 2B.

4) Figs. 4 to 6 show images of the indentation.

2B B HB

50.00

0.000.00 5.00