Metal Cutting of Forging Grade Steel and Nodular Iron - Cutting Process in the Microstructure; Comparison of the Materials Ck 45 V, Ck 45 N, Ck 45 BY; 49 MnVS 3 BY and GGG-60

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Video in TIB AV-Portal: Metal Cutting of Forging Grade Steel and Nodular Iron - Cutting Process in the Microstructure; Comparison of the Materials Ck 45 V, Ck 45 N, Ck 45 BY; 49 MnVS 3 BY and GGG-60

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Metal Cutting of Forging Grade Steel and Nodular Iron - Cutting Process in the Microstructure; Comparison of the Materials Ck 45 V, Ck 45 N, Ck 45 BY; 49 MnVS 3 BY and GGG-60
Alternative Title
Zerspanen von Schmiedestahl und Kugelgraphitguß - Schnittvorgang im Feingefüge; Vergleich der Werkstoffe Ck 45 V, Ck 45 N, Ck 45 BY; 49 MnVS 3 BY und GGG-60
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E 2697
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Technical Metadata

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Film, 16 mm, LT, 124 m ; SW, 11 1/2 min

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Subject Area
The influence of three different thermal treatments on the machinability of steel Ck 45 and also a comparison of machinability between a microalloyed steel and nodular iron. Flow chips, shear chips, shear plane, flow zone, shear angle, chip thickness ratio, built-up edge, plastic deformation. (Microcinematography, slow-motion.)
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To investigate the influence of heat treatment on its machinability, three types of the steel Ck 45 were produced from one melt. The left picture shows the polished and etched microstructure of the quenched and tempered Ck 45. In the middle there is the structure of the normalized Ck 45 - and right a structure which results from controlled cooling down from forging heat. The quenched and tempered Ck 45 V has a homogeneous, fine-grained ferritic-pearlitic structure. The normalized structure of Ck 45 N has a regular net of ferrite with pearlite inclusions. In the case of the control-cooled Ck 45 BY the net of ferrite is coarser. The net of ferrite corresponds to the former austenite grain boundaries.These
microcinematographic shots show the process of orthogonal cutting. From the left, the cutting wedge enters forcibly into the workpiece, upsets the material and, because of the tension, the structure of the material is cleft open. The shear angle equals 35 degrees. As a result of mainlyplastic deformation, a flow chip arises in the case of steel Ck 45 V. The chip runs over the face to the left. Between the tool and the chip there is a clearly delineated, bright flowing layer.
A regular flow chip is also formed while cutting the normalized structure of the steel Ck 45 N. The upper surface of the chip is more strongly deformed than in the case of the quenched and tempered structure. The net of ferrite is ductile and softer than the matrix. This facilitates the cutting operation. The bright stripes parallel to the shear zone correspond to the former net of ferrite in the structure of the steel. The shear angle equals 40 degree. During this investigation, the cutting geometry was constant with a rake angle of 0 degree and a tool orthogonal clearance of 80.
steel Ck 45 BY is control-cooled down from forging heat and has a coarse which is favourable shearing. The shear angle of 40 degree is greater than in the case of the Ck 45 V. This results from a low chip thickness ratio. The upper surface of the chip is cleft and irregularly shaped.
The microalloyed steel 49 MnVS 3 BY and the nodular iron GGG-60 are used, for example in making crankshafts and other passenger car engine components. The control-cooled steel (left) has a consistent net of ferrite with a mainly pearlite matrix. To improve the machinability the steel has an increased sulphur content. The bright ferrite contains manganese sulphide in the form of dark, round and elongated inclusions. The ferritic-pearlitic matrix of the nodular iron (right) is characterized by the spheroidal graphite inclusions. Due to the globular form of the graphite, the casting shows good resistance to stress peaks.
At a cutting speed of 0.01 m/min the cutting process is consistent. The flow chip has a bright flowing layer on its lower side. In the shear zone, the net of ferrite and the ferrite in the pearlitic matrix is deformed at an angle of 35 degree. After the deformation the ferrite forms parallel bright stripes in the chip.
The cutting speed was raised from 0.01 m/min to 1.25 m/min. By a proportional increase of the picture frequency the process seems to run at the same speed. The curved flow chip runs continuously. The flowing layers between chip and tool are more clearly marked than at the lower speed.
The wedge of the tool penetrates into the workpiece and compresses the graphite inclusions out of the matrix. As a result of plastic deformation with following cracking, individual elements of continuous chips are formed. After the shearing of a chip element, the cutting pressure is abruptly relieved and the wedge of the tool again penetrates into the workpiece. The continuous chip is interrupted when a spheroidal graphite inclusion arrives at the shear zone and thus the connections between the chip elements are broken. The upper surface of the chip looks very rough.
At a cutting speed of 1.25 m/min a stable built-up edge of 70 micrometer in height is formed. This is an indication of the tendency for sticking in the case of this cast iron. The built-up edge is characterized by a positive tool
The orthogonal rake of about 35 degree. This causes only small shearing and facilitates chip coherence.
The pictures are turned through 90 degree. This contrasts very clearly the differences between the cutting of steel and cast iron. In the case of the steel (left) the shear zone runs continuously and the discharge of crops is consistent, while the cutting of nodular iron (right) produces individual and partly continuous chips which are tom off the surface.