Sandvik Coromant has launched two new ISO P steel turning insert grades, GC4415 and GC4425.Click image to enlargeby Rolf Olofsson

What do an ancient Roman war strategy and ISO P steel turning grades have in common, and how can this help increase your machine shop’s output? Here, Rolf Olofsson, product manager at Sandvik Coromant explores how the coating and substrate of carbide grades can make a huge difference in the efficiency and productivity of steel turning processes.

A common misconception in the metalworking industry is that machining steel is simple. Experienced machinists know that turning ISO P steel is anything but. First among many concerns is the breadth of materials in the ISO P classification, which range from ductile low-carbon steels to high-alloyed. 

Secondly, the hardness of different steels ranges significantly from one end of the spectrum to the other. The type of application varies – as do machining conditions in workshops. 

Clearly, steel turning is challenging and given all the variables, the task of selecting a grade to cater to the wide range of properties exhibited by ISO P steels is even more daunting. 

Grade of all trades
For any such grade, fracture resistance is paramount. So too is a cutting edge capable of delivering the hardness needed to resist plastic deformation induced by the extreme temperatures present in the cutting zones. 

What’s more, the grade must be equipped with a coating that can prevent flank wear, crater wear and edge buildup. It’s also vital that the coating adhere to the substrate; if it doesn’t stick, the substrate is exposed, leading to rapid failure.

All carbide grades contain a cemented carbide core, or substrate, which defines the toughness and strength of the grade.Click image to enlargeGiven this array of demands, it’s crucial to understand the structure of a steel turning grade in order to make an informed decision when picking one for your application.


Structure of a carbide insert
All carbide grades contain a cemented carbide core, also known as a substrate. The substrate defines the toughness and strength of the grade. It also determines the grade’s resistance to plastic deformation. 

The cemented carbide substrate is usually covered by a few layers of coating such as titanium carbonitride (TiCN), alumina (Al2O3), or titanium nitride (TiN), which give the insert its edge toughness, adhesion and wear resistance properties. The recipe for superior resistance to different kind of wears, flank, crater and edge buildup, adhesion to substrate and improved tool life also lies in the microscopic details that go into designing the coating layer. 

Figure 1a: Conventional CVD alumina coating with random crystal orientation.Click image to enlargeRoman shield wall 
In conventional alumina coating, crystal growth direction is random, as depicted in Figure 1a. If the growth in the coating layer can be controlled to ensure all crystals line up in the same direction, as depicted by yellow in Figure 1b, superior wear resistance is the result. 

Figure 1b: With Inveio, every crystal in the alumina coating is lined up in the same direction, towards the top surface.Click image to enlargeClick image to enlargeTo help you understand the power of crystal alignment, let’s consider an example from Roman history. When Roman legions conducted a siege, they frequently deployed a shield wall — the testudo (“tortoise”) formation. In this formation all shields were aligned and tightly packed, eliminating vulnerable gaps. The shield wall helped the Romans resist attack while advancing. 

The alignment of crystals in a coating layer works similarly. The closely packed unidirectional crystals act as a shield and provide better resistance against difficult conditions at the cutting zone.

Unidirectional crystals
Sandvik Coromant’s R&D experts have found a way to control the crystal growth in the alumina coating to ensure all crystals line up in the same direction, with the strongest part towards the top surface. This patented technology, known as Inveio coating, gives inserts a new level of wear resistance and tool life.

The tightly packed unidirectional crystals create a strong barrier oriented towards the cutting zone and chip. This helps Inveio equipped grades greatly improve resistance to crater wear and flank wear. Another benefit is that heat is more rapidly led​ away from the cutting zone, helping the cutting edge retain its shape for longer times in cut. Overall, what you get is a predictable tool with a long tool life.

With the introduction of second-generation Inveio technology — featured in Sandvik Coromant’s latest ISO P steel turning grades GC4415 and GC4425 — the benefits of unidirectional coating have been enhanced. Improved crystal orientation makes for more consistent performance and significantly improved wear resistance.

Intermittent cutting operations
Now that we’ve discussed the first two considerations for selecting an insert grade, namely the substrate and the coating, let’s briefly look at the third: performance during intermittent cutting operations. This is an important requireFigure 1b: With Inveio, every crystal in the alumina coating is lined up in the same direction, towards the top surface.Click image to enlargeClick image to enlargement as it helps avoid any sudden insert breakages. 

Look for inserts that have undergone post-treatment: a process in which very fine, sharp ceramic particles are bombarded onto the insert coating. Imagine a hammer striking on the coating to reinforce and strengthen it. Inserts that have undergone effective post-treatment perform well during intermittent cutting.

The new GC4415 and GC4425 ISO P steel turning grades are ideal for manufacturers operating in mass and batch production setups. Equipped with a new substrate at their heart that is reinforced by Inveio technology, the two grades offer reliable performance and superior wear resistance. In addition, their new post-treatment boosts performance in intermittent cutting operations, avoiding sudden breakages and enabling both insert grades to outperform over a broad application range.

Customers have been able to implement higher cutting speeds (Vc) and multiplied feed rates (Fn) with these grades. A general engineering manufacturer subjected a 4140 pre-heat treated steel workpiece to multidirectional external roughing with the GC4425 insert. Compared with using a competitor’s ISO insert for the same process, the customer was able to achieve a 100 per cent productivity increase, with a reduced cycle time of 50 per cent – plus a 30 per cent cost reduction. 

Machining ISO P steel is tricky. By keeping a few considerations in mind when selecting a grade – such as substrate toughness and new advances in the area of material science and tooling technology – you can make a huge difference in your steel turning efficiency and your machine shop’s overall productivity. SMT

Cutting Tools Tech Tips: Centering your machining centre processes

By Tim Fara, Bilz Tool Co.

Machining centre manufacturers spend effort, design, and cost to make sure the spindle in the machine will operate on centreline. Spindle rotational accuracy as well as spindle alignment play an important role in cutting tool performance and productivity.

Cutting tools in the Cloud: Iscar, CGTech partnership

Users of CGTech's Vericut software for simulating CNC machine tools can now download directly Iscar tool assemblies because of a partnership between CGTech-MachiningCloud and Iscar.

Turning inserts for cost reduction

Tungaloy Corp.'s new range of turning inserts, EcoTurn, are dimensionally smaller than standard ISO insert ranges making these inserts eco-friendly because they need less resourse than standard inserts, claims the company. Tungaloy also claims that despite the smaller size, the performance of the EcoTurn inserts is equal to standard size inserts.

Automotive Enablers

by Kip Hanson

Competing in today’s automotive market requires high performance tooling

Swiss-type quick-change tooling

Seco Tools has introduced a modular toolholder system for manufacturers seeking to improve their productivity with Swiss-type machining. The system enables fast, easy and repeatable insert indexing and tool changes outside of tight machine work spaces.

Beating Vibration

By Jim Barnes

Dampening vibration in extended reach toolholders boosts productivity

Extended-reach tooling can provide significant  productivity benefits through reductions in setup times.

Skills Training: The Missing Sizzle

If Brian Philip could change education in manufacturing in secondary and post secondary institutions, he would add the missing “sizzle” to the steak.

Toolholding for high performance machining

 A toolholding system for high performance machining developed by German tooling manufacturer Haimer is gaining in popularity in North America.

Organizational changes at Seco

Todd Miller is the manager of product marketing at Seco Tools, Troy, MI. He is part of a series of organization changes at the cutting tool company.

OSG Canada adds to tooling lineup

OSG Canada has added two new tooling lines to its product offering.

Parting-off techniques

CoroCut QD is a new generation of cutting tools from Sandvik Coromant for parting and grooving of larger diameter bars. The company says these new tools optimize cuts that require longer tool overhang.

Balance Matters

by Drew Strauchen

4 ways proper tooling balance saves time and eliminates problems

Cutting tools: Drilling Dilemma

by Kip Hanson

The choice between solid carbide and indexable drills is often a perplexing one  

ATI Stellram acquires Greenfield threading line

ATI Stellram has acquired the Assembled Threading Tools product lines of Greenfield Industries Inc.

Ontario: The Spice of Life

by Andrew Brooks

Precision metal fabrication is rewarding work, but governments could be helping a lot more

Stay In Touch

twitter facebook linkedIn