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PCBN inserts for Machining High Speed Steels


High speed steel simply written HSS, is a tool steel with high hardness, high wear resistance and high heat resistance, also known as High Speed tool Steel, commonly known as white Steel. It is mainly used for making metal cutting tools, super hard material tool handle matrix, cold extrusion die and cold block press die, roll etc.

High speed steel has played an important role in the development of modern industry since it was born. In high speed cutting, it can still maintain high hardness which is in above HRC60 even the temperature reaches 500℃.

Application of high speed steel

Common typical components:Since its appearance in 1903, HSS has been famous for manufacturing metal cutting tools. With the rapid development of science and technology, HSS has been widely used. Since 1960s, Japan,centered on the automobile and bicycle industries, has successfully experimented with high speed steel for molds, and now produces about 15% of the high speed steel for molds.

Other components:In recent years, as a kind of roll material, semi-high speed steel has the same high hardness, high wear resistance and excellent high temperature resistances as high speed steel, so both high speed steel and semi-high speed steel are great materials for roll manufacturing. High speed steel roller with high hardness, high temperature resistance, good wear resistance and harden ability of high speed steel as the working layer of the roller, with toughness can meet the requirements of forging steel, cast steel or ductile iron as the core of the roller material, and the two in metallurgy or set of high performance roll.

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Cutting tool material for processing high speed steel

High speed steel itself can be used as cutting tool material, therefore only the hardness of cutting tools is higher than the hardness of HSS, it can process the workpiece made by HSS material, and that is PCBN insert, the following is the research and development of high speed steel tool material specific as the following table:

Grade Suitable material for processing Processing way Recommended operating conditions
BT-(S)2800 High speed steel Rough machining Intermittent
BT-(S)2800A Hardened steel, heat and abrasion resistant steel, high manganese steel Rough finish, semi – finishing Intermittent – Continuous
BT-6000 Hardened steel, high speed steel finishing Continuous
BT-6000A Hardened steel, high strength alloy finishing Continuous -medium intermittent
BT-9000 Hardened steel, high speed steel finishing Intermittent – strongly intermittent

High speed steel processing case I
Workpiece material: powder high speed tool steel (M2, M4, M5, M6)
Hard degree: HRC65 – HRC68

Processing difficulties
The insert of an imported brand was tried at first, but the effect was not ideal, which was mainly reflected in the short service life of the insert during rough machining. The reason was that after the vacuum heat treatment, the inner hole wall was slightly deformed, which led to intermittent turning and cutting tools during processing, and the insert loss was very great.

High speed steel processing case II
Processing material: HRC67 degree high – speed steel

Processing sequence

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Processing difficulties

a.Due to the high cutting temperature, the current PCBN insert in use, cutting edge often off the head.

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b.Tool life is too low, in the case of 600 RPM, precision 0.02mm, the smoothness quickly becomes poor, high frequency of tool change, the maximum service life of the tool is 37 pieces.The cutting speed is changed to 1000 RPM for better finish but lower tool life.

Tool plan

1.Tool structure redesign: due to the high hardness of high-speed steel processing, in view of the customer’s previous use of non-standard groove tool processing, rigidity is insufficient, the tool is often hot off the head phenomenon, so changed to the standard groove blade structure;
2. Tool material: the tool grade is BT-6000, which is more resistant to high temperature and higher cutting hardness. The customer USES it normally, without any instability of cutting size and roughness;The customer is very satisfied with the durability and cost of the tool.

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High speed steel roll processing case

Processing difficulties: High hardness, large machining allowance, cutting resistance, and part of the intermittent cutting impact, insert easy to break.
Trial cutting cases: The BT-S2800A material is made by Huachen Superhard Co.Ltd, whose tool life is one times that of a certain brand CBN insert.

Processing materials: high speed steel roller, HSD90

hardness

Insert: bn-s20 RCMX120700

Cutting parameters: Fr=0.2mm/r, Vc=35m/min

 

Brand Per edge life Final failure form
HC BT-S2800A 25/per edge Normal abrasion
Some brand CBN insert 12/per edge Broken

High speed steel die processing case:

Processing difficulties: Ultra high hardness parts, large machining allowance, and there are serious intermittent cutting conditions, the insert is easy to collapse damage can not be processed normally.
Trial cutting cases compound CBN insert BT-9000 material can withstand strong intermittent cutting, no collapse phenomenon.

Processing condition: strong intermittent cutting outer circle

Processing materials: high wear resistant powder high speed steel, HRC65;

Insert: bt-h21 CNGA120408

Cutting parameters: ap=0.15mm, Fr=0.1mm/r, Vc=35-60m/min, wet cutting

Brand Per edge life Final failure form
HC BT-9000 5 Normal abrasion
Some Japanese CBN insert <1 Broken
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