Halnn CBN cutting tools advantages for machining chilled cast iron compared with carbide and Ceramic cutting tools

Part 1 Introduction of Chilled cast iron

Chilled cast iron is that placed cold iron in the mold to accelerate the cooling rate of the casting obtained. Due to cooling speed of the cast iron surface layer which contact with the chilled cast iron, so cast iron belong to white in a certain part of the thickness, and this part has a higher hardness and better wear resistance; while the deeper part cast iron which away from the chilled, has a lower cooling rate and belong to gray cast iron; the transition region between the white and gray showed a mottled. Typical chemical composition of chilled cast iron: content :C3%~3.5%, Si0.5%~0.7%, Mn0.5%~0.7%, P<0.4%, S<0.07%.

The characteristic of chilled cast iron: a hard outer and tough inner outer, surface portion occurrent of white, hardness and wear resistance were greatly improved, the inside still remained the gray tissue to prevent overall embrittlement. Chilled cast iron used for be the part which there is non-abrasive under friction condition, in addition to the sliding parts also included varying degrees of rolling movement. The parts surface not only requested high hardness, good wear resistance, but also requires the work piece which machined has a sufficiently high strength and toughness, Generally, chilled was usually used in the manufacture rollers, wheels and other parts.

Such as the rolls which made of chilled cast iron rolls, based on the base structure of the white layer. Rolls can be divided into ordinary chilled cast iron rolls and alloy chilled cast iron rolls, alloy chilled cast iron roll also includes low-alloy chilled cast iron casting rolls , alloy rolls and high-alloy’s. The following is the cast iron images

Part 2 The reason which why it is difficult to machine the Chilled cast iron:

(1)Chilled cast iron is a typical materials which was hard and brittle, it has a high surface hardness. The unit cutting force can reach 3000MPa during roughing, the strong impact can easily cause vibration, increasing the tool’s wear.

(2) Chilled cast iron has high hardness and high thermal strength. Especially when machine the large parts , the cutting tool costs long working hours, the tools will have a high temperature, and cutter body prone to deformation or welding inserts met the phenomenon which welding opened. Make the tools broken.

(3) The surface structure of chilled cast iron is white, it was hard and brittle , when the tool cut in or cut out, easily prone to chipping, resulting in tools wasted or damaged.

(4)The chilled cast iron is often used to make a variety of rolls, the structure’s size was large , allowance is also large, a larger depth of cut and feed rate needed when turning, has a higher requirements of the tools strength and rigidity of the process system.

Part 3 How to choose the tool material to machine the chilled cast iron:
The surface layer’s hardness of the chilled cast iron can reach about HRC60, high hardness, brittleness, and there are many surface hard spots and sand, which is why the material is required for tool have a high red hardness, impact resistance, wear resistance, high bending strength, thermal conductivity Big.

The analysis of the tool material:

(1)Carbide Tool: Due to the characteristics of the material, carbide tools body has a hardness around HSD100, the workpiece can be machine when there is certain gap between the workpiece and the tools, so the range of suitable for machining ductile iron with low hardness (HSD70 less ). It is almost impossible to machine the chilled cast iron which hardness reached about HSD85 .

(2)ceramic tool: Because ceramic tools has brittleness nature, low transverse rupture strength, weak ability to withstand impact loads, so we can choose ceramic tools when machining hardness less than HRC55 or using a small amount of feed, but rough castings accompanied by trachoma generally, including sand casting defects, chipping easily happened when using ceramic tool. 

(3)Halnn cubic boron nitride cutting tools BN-K1 Brand

BN-K1 grades CBN tool has a better Cutting performance, hardness, fracture resistance and abrasion resistance, the tool can greatly improve the cutting efficiency of surface of chilled cast iron, this tools cutting effect is significantly higher than other cutting tool materials. BN-K1 grades cubic boron nitride cutting tools has a higher hardness, a better wear resistance than carbide tools. CBN tools has the same disadvantage of brittleness like ceramic tools, While BN-K1 grades tools using non-metallic binder and cubic boron nitride powder production, the tool adds toughness, impact strength performance, compared to ceramic tools, has a excellent chipping resistance to damage. Your can get the BN-K1 grades tools advantage and which material can be machined from the following table.

BN-K1 grades tools advantage and which material can be machined

Tools Grade	Material Machined	Performance advantages	Application industry
BN-K1	Chilled Cast iron, High alloy Cast iron, heat-resistant alloy, high manganese steel	Good crash damage resistance and excellent high temperature resistance to fracture	High hardness alloy cast iron roll, industrial pump parts, alloy wear resistant castings

The effect comparison between BN-K1 brand tool and ceramic tool(as followed table)   

Except for machining the chilled cast iron roll,BN-K1 can also machine chilled cast iron parts ,such as: valve lifters, valve tappet, etc; but also for other high-alloy cast iron flywheel parts, industrial pumps, cylinder and so on; also suitable heat-resistant high manganese steel and other steel parts processing. When machining those high hardness casting parts, BN-K1 tools can exhibit excellent than Carbide cutting tool material and ceramic tools material on chipping damage resistance and high temperature fracture resistance.
Part 4 The case of Halnn superhard materials company’s BN-K1 brand tools process the chilled cast iron rolls:
When turning the chilled cast iron rolls, the rolls has a higher hardness, roughing roll usually has pores, trachoma, including sand casting, defects the tools impact resistance, heat resistance, wear resistance demanding. We should choose BN-K1 to process this type rolls. This brand maintaining excellent wear resistance and hardness like CBN tools, it also has a better impact toughness, not collapse damage, can pull roll shortage roughing,BN-K1 is the most high-impact hardness of superhard cutting tool grades currently. This tools can withstand a greater depth of cut and metal removal rate.
Application Case as follows:

Processing the cast iron roll
Rolls Hardness	HSD80
Cutting Parameters	ap=4mm;Fr =1mm/r; Vc =55m/min
insert Grade	Halnn BN-K1	Other Ceramic insert
Tools material Feed rate	1mm/r	0.5 mm/r
Lifetime per Tip	3piece/point	0.5piece/point

From the table, We can get:

With the same cutting speed and back engagement of BN-K1 grades CBN cutting tools and a European brand of ceramic inserts,BN-K1 CBN tools feed rate is twice higher than the ceramic tools and six times lifetime than ceramic tools,BN-K1 improve processing efficiency, saving processing time.

If you would like to know more details ,please feel free to contact with us halnntools@gmail.com ,whatapp:+8618695866134