Part 1 High chromium cast iron machining and cutting tool selection
High chromium cast iron is a kind of high hardness and high strength alloy white cast iron with high corrosion resistance wear-resistant , high chrome cast iron in the case without any heat treatment, the generally hardness of HRC45 or more, the tensile strength 650 ~ 850MPa.
High chromium cast iron is a kind of difficult to cut material, carbide insert is difficult to machine, and due to the brittleness, it generally used only for fine finishing. With the advent of new cutting tool materials, high chromium cast iron machining cutting tool industry experienced cemented carbide inserts- ceramic insert – cbn inserts, to a certain extent, changed the high chromium cast iron machining processes and equipment investment.
Before 2003, due to restrictions by the cutting tool material, carbide inserts and ceramic cutters is the main stream of machining high chromium cast iron, high chromium cast iron process generally: blank-softened processing (lower hardness)--- roughing --- heat treatment (to increase the hardness) --- finishing.
It can be seen from the above machining process, not only increase the workload, impact machining efficiency, but also increase the machining costs. Halnn superhard developed BN-K1 solid cbn inserts in 2003, due to the hardness higher than carbide and ceramic and fracture resistance and resistance higher than ceramic insert, BN-K1 solid cbn insert is used for processing high hardness cast iron, which hardness is HRC35-HRC68 with roughing, intermittent machining and finishing.
Compared with ceramic cutters, BN-K1 solid cbn insert hardness generally about HV3500, which is 2 times of ceramic insert and 4 times of carbide insert. BN-K1 solid cbn inserts heat resistance up to 1400~ l500℃. When BN-K1 solid cbn inserts process high cast iron, its hardness at 1000 ℃ even higher than that of ceramic and carbide. The wear resistance of BN-K1 solid cbn insert is 25 times of silicon nitride ceramic. Impact resistant is 2000 times of silicon nitride ceramic, cutting tool life can reach the silicon nitride ceramic 22 to 30 times. And BN-K1 solid cbn insert parameters 3-5 times higher than the carbide insert. BN-K1 solid cbn insert is widely used for high-alloy cast iron rolls, pump parts, high chromium cast iron linears and other wear-resistant castings machining.
Part 2 Halnn Tool machine high chromium cast iron cutting parameters and case
In the machining process, in addition to reasonable selection of cutting tools, selection of cutting tool parameter is also an important factor in high-efficiency machining high chromium cast iron. These three factors of in the depth of cut, feeds, cutting linear speed, the increase in the depth of cut is undoubtedly one of the effective means to improve processing efficiency, but also for some large pump parts, metallurgy, mining machinery wear-resistant castings, cutting the large amount, to improve processing efficiency, the depth of cut to be increased. Since BN-K1 solid cbn insert anti-break strength and resistance to chipping damage advantage, compared with the ceramic cutting tool, BN-K1 solid cbn insert is more suitable for the use of large depth of cut to reduce the number of feed to improve processing efficiency. BN-K1 solid cbn insert due to the high hardness and excellent high temperature wear resistance, can be used 3-5 times for high-speed cutting higher than cemented carbide and ceramic cutting tools.
The following is the Halnn tool machining high hardness cast iron industry typical cases:
1. BN-K1 solid cbn insert interrupted turning slurry pump outer circle machining case,
Cutting parameters: Vc = 75m/min, ap=2.5~5mm, Fr= 0.1mm/r.
The results show: BN-K1 solid cbn insert intermittent process did not produce fractured, each blade is equivalent 25 pieces ceramic blade, it reduces the cost of the cutting tool, processing efficiency is increased by 5 times.
2. BN-K1 grade cutting tool milling processing high chromium cast iron liner：
Cutting parameters: Vc = 55m/min, ap=2.5mm, fr = 0.25mm/r.
Measured both ends the same size, no retract and cutting tool wear and tear. The use of ceramic cutting tool milling takes 5 to 7 blades to complete, and the insert edge when the insert cutting wear faster, leading to increased cutting resistance, resulting in retraction, seriously affecting the quality and efficiency of the processing surface.