Cold work tool steel

Abstract

Cold work tool steel of the present invention comprises 0.4<=K value<=2.6 (K value Cr(wt %)-6.8C (wt %)), 15.5<=L value<=21.0 (L value=Cr(wt %)+15.5C (wt %), 0.60 wt %<=Si<=2.0 wt %, 0.10 wt %<=Mn<=1.0 wt %, 0.03 wt %<S<=0.2 wt %, 1.25 wt %<Mo+0.5 W<3.0 wt %, 0.05 wt %<=V<=1.0 wt %, and the balance Fe and inevitable impurities, in which the highest hardness obtained by tempering at 450 DEG C. or higher after quenching is HRC 61 or more.

Description

technical field [0001] The present invention relates to cold work tool steel (cold work tool steel), in particular to cold work tool steel suitable for various cold dies, such as cold forging punching dies, forming dies for high tensile strength steel plates, bending dies, Cold forging dies, satin dies, thread rolling (making) dies, punch components, slotting tools, lead frame blanking dies, gauges, deep drawing punches, bending die punches, shearing edges, stainless steel bending dies, drawing Dies, plastic processing tools for cold pressing, punches for gears, cam wheel parts, blanking stamping dies, progressive blanking dies, sealing plates for mud and sand feeders, threaded members, rotary discs for concrete spraying machines, IC seals Dies, precision stamping dies requiring high dimensional accuracy, and the above-mentioned cold dies used after surface treatment (such as CVD treatment, PVD treatment or TD treatment). Background technique [0002] By dispersing a large ...

AI Technical Summary

Problems solved by technology

[0002] By dispersing a large amount of high-hardness carbides through crystallization or precipitation, the wear resistance of cold tool steel represented by JIS steel SKD 11 can be enhanced, and it can be used in various applications requiring wear resistance or rubbing resistance (such as cold forging punching dies, cold forging dies, etc.); however, known cold work tool steels still have the following problems: (1) insufficient toughness; (2) hardening of the forming conditions, etc. will weaken the hardness of the die; and ( 3) Possibility of breakage in wire-cut electric discharge machining

[0014] However, the known cold work tool steel represented by SKD 11 has a problem of extremely poor workability even in the annealed state, because crystalline carbides are dispersed in large quantities in order to ensure predetermined wear resistance; During machining, crystalline carbides often cause wire breakage

[0015] Materials in which the amount of crystalline carbides are reduced to improve their machinability are also known in the prior art; however, in this known material, it is difficult to ensure an attainable hardness of HRC 60 or more during high temperature tempering

On the other hand, when the material is tempered at low temperature to obtain high hardness, the stress generated in the material during quenching cannot be removed. Therefore, when we perform EDM or wire-cut EDM on the obtained material, the remaining Stresses may be out of balance resulting in fracture or damage to the material

[0016] In the cold work tool steel disclosed in Cited Patent 1, the reduction of crystalline carbides is greater than that of SKD 11, and the composition will be adjusted, so that the hardness of HRC 60 or greater can be ensured, and the machinability can be improved to some degree; however, even in the cold work tool steel disclosed in Cited Patent 1, the improvement of machinability is still insufficient

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