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High-performing inserts for steel turning

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article image A comparison in wear patterns after 300 components were machined.

SANDVIK Coromant’s GC4225 represents the next generation of P25 grades to enhance machining performance in the general steel turning area.

Over the past few years, Sandvik Coromant has carried out extensive R&D to establish the new P25 grade, which is the next insert generation to make the general steel-turning area even broader, more productive and more reliable.

Improving on the form of previously introduced P25-inserts has been achieved through years of analysis and development at Sandvik Coromant.

Several grade properties have been improved – this was a formidable task, with currently a third more P25 applications than for P15 finishing and P35 roughing.

The GC4225 extends the application and capabilities of its predecessor GC4025, allowing use of a P25 grade in a far wider area. For example, in the automotive industry, P25-grades are often required to withstand the initial cut of forged skin with varying stock removal, followed by additional cuts at high cutting speed.

In general steel turning everything varies. The material can vary from un-alloyed to high-alloyed bar-material through to various forgings and castings. The type of operation varies from rough to finish turning with conditions ranging from good to difficult.

GC4225 has an improved capacity to adapt to variations in workpiece material and operational demands towards the tougher end of applications, thus providing more versatility.

The new black and yellow grade provides new potential for increasing productivity through higher cutting data, backed up by improved reliability.

Production types include single part to mass-production, of micro parts to giant rolls, short to very long edge engagements and with and without coolant.

Optimisation requirements may be from the highest cutting data for maximum productivity to extended tool-life for security and tool-changing considerations.

No other machining area makes the volume of demand on a cutting tool as the large P25 turning area, according to Sandvik.

For rough machining, it might typically take two medium-roughing passes of up to 8mm in depth of cut, with a subsequent intermediate finishing pass of 1mm to hold the next process tolerance. The insert has to stand up to the different demands of both operations while maintaining good chip control and sustained tool life to complete the cutting operation.

Upgrading to the new GC4225 will be a great hit for the whole steel machining industry, says Pat Ryan, General Manager of Sandvik Coromant, Australia.

“Thanks to its broad application area, from low-carbon steel to high-alloy steel, its strength and its predictability, it will become the number one choice for steel turning,” he said.

The new grade is also more durable, partly through an increased ability to withstand thermal demands. It is suitable for various optimisation requirements within the very broad area of general steel turning.

A combination of improved insert toughness and wear resistance has contributed to the GC4225 grade becoming a better all round grade.

It is a multi-talented solution and through improved coating adherence has considerably elevated the edge-line security of inserts. This makes it possible to use a P25 grade throughout an even wider area than before, which is especially advantageous for machine shops with varying one-off component production - but without losing the ability for higher metal-removal-rate optimisation for large-volume machining.

The breadth of the P25 turning-area means there are several different wear patterns that can develop. The ideal is for all inserts in all operations to only develop controlled flank wear, as this is the more "natural", abrasive way an edge should wear out and is thus the more predictable wear-rate of a cutting edge. The reality today is that wear patterns combine to form premature edge breakdown.

With the development of GC4225, a major step has been taken towards the reduction of unwanted wear types developing rapidly or, in some cases, even at all.

Both resistances to edge-deformation and to crater wear have been improved in the GC4225.

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