Introduction: 40Cr belongs to medium carbon alloy steel, which is widely used in machinery manufacturing. After heat treatment such as modulation and quenching, different performance advantages are obtained. The application fields are also different, the hardness is different, and the selected processing inserts are also different. Then What insert is good for processing 40Cr?

40Cr corresponds to foreign standard steel type:

American AISI/SAE/ASTM standard steel type 5140;

Japanese JIS standard steel type SCr440(H)/SCr440;

International Organization for Standardization ISO standard steel type 41Cr4.

German DIN standard material number 1.7035/1.704 German DIN standard steel type 41Cr4/42Gr4;

British EN standard steel No. 18, British BS standard steel type. 41Cr4;

French AFNOR standard steel type 42C4, French NF standard steel type 38Cr4/41Cr4;

Italian UNI standard steel 40Cr corresponds to foreign standard steel type:

Belgian NBN standard steel type 42Cr4;

Swedish SS standard steel type 2245;

What parts is 40Cr used to produce ?

After modulation and heat treatment, 40Cr has good comprehensive mechanical properties, so it is often made into shaft parts, and which are one of the typical parts  in machines, such as worms, spline shafts, gears, crankshafts, Mandrels, connecting rods, main shafts, half-shaft casings, collars, sleeves, etc. are all types of shaft parts.

Hardness after 40Cr heat treatment

The commonly used heat treatment methods of 40Cr include modulation and quenching, and the quenching includes surface quenching and flame quenching.

The hardness after quenching of 40Cr is about 32-36HRC, and the hardness after quenching is between 48-60HRC. For example, the hardness after flame quenching reaches HRC48-55, and the hardness reaches HRC52-60 after surface quenching. According to different parts needs to be dealt with accordingly.

Selected inserts for of machining 40Cr

After modulation, the hardness of 40Cr is 32-36HRC, the hardness is not high, and it can be completed by selecting carbide tools. For the quenched workpiece with HRC48-60 degrees, it can be completed with CBN inserts

Why choose CBN inserts for high hardness and carbide inserts for low hardness? See the performance comparison of the following two tools:

(1) In terms of hardness: the hardness of carbide inserts is more than HRC70, while the hardness of CBN inserts is more than HRC90. CBN inserts are more suitable for processing ultra-high hardness materials.

(2) High temperature resistance: carbide inserts can withstand high temperatures of 1000°C, while CBN inserts can withstand high temperatures of 1500°C without affecting their performance, so CBN inserts are often used for dry cutting without adding cutting fluid.

Case parameters of CBN inserts processing 40Cr

Workpiece Name: Half Shaft Sleeve

Workpiece material: 40Cr

Workpiece hardness: HRC47-55

Processing parts: outer circle, end face

Processing size: φ110*82/φ120*110

Tolerance requirement: 0.02

Roughness requirement: Ra: 1.6

Processing condition: continuous processing

insert model: BN-H05 C25 CNGA120408

Tool life: 48 pieces/cutting edge

Result: Compared with the international famous brand coated CBN inserts, the life is increased by 20%.