TPT-January-2015

Article

Shandong SiFang Technical Development Co Ltd

pieces of the same material and the same heat treatment processing demonstrates that the die has quenched fully, and the hardness range is 55 ~ 65HRC. The mechanical property comparison of new high chromium die steel and German die steel is listed in Table 3. (Radial samples) 3.4 Microstructure of new crimping die steel The carbide of high chromium die steel is mainly of M­ 7 C 3 type, and these carbides appears in incontinuous strip, block, grain and chrysanthemum-like shapes; their microhardness can reach 1,800HV and these carbides account for 20 per cent or so. Certainly, the matrix can been designed as austenite, bainite or martensite and so on according to the die service condition of different material types, and their macrohardness can reach HRC55 ~ 65. The microstructure of new high chromium die steel is shown in Figure 5 and Figure 6. The matrix of German die steel is martensite, and the carbides take up about 15 per cent, which are mainly of M­ 7 C 3 type. Its microstructure is shown in Figure 7. 3.5 Wear-resisting property comparison of crimping die steel in laboratory The MM-200 ring-block wear testing machine has been adopted in the experiment, and the homemade water system has been cooling the samples through the testing process. There are the same testing parameters adopted, including loading force, spindle speed, testing time, cooling water rate,

Figure 4: Field hardness testing picture of experimental cylindrical sample profile

The high casting quality of dies has been verified in ultrasonic testing and performance testing. Ultrasonic testing results show: a) good ultrasonic penetrability and detestability, few noise waves, so the microstructure is uniform, compact b) the part from the work surface to the depth of 100mm meets the Level 1 requirement of DIN EN-12680-2 c) the internal space meets the Level 2 requirement of DIN EN-12680-2 at least 3.3 Hardness and performance of new crimping dies Developed high chromium die steel is of excellent hardenability; the cross-sectional anatomy of large test

Figure 5: Microstructure of new high chromium die steel Austenite + Carbide, × 200

Figure 6: Microstructure of new high chromium die steel Martensite + Carbide, × 500

Figure 7: Microstructure of new high German die steel Martensite + Carbide, × 100

Impact toughness /kJ•m -2

Material and heat treatment method

Tensile strength /MPa

Average /kJ•m -2

Material and heat treatment method

Average/MPa

705 725 695 635 695 720 732 717 683

40 35 40 40 40 40 40 21 30

High chromium die steel Quenching and tempering

High chromium die steel Quenching and tempering

695.8

39.2

German die steel Quenching and tempering

German die steel Quenching and tempering

710.7

30

Table 3: Mechanical property comparison of new high chromium die steel and German die steel

90

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J anuary 2015