Structural Steel
42CrM04 - HB 217 - HR 280 - HV 290
Chromium-molybdenum alloy steel 42CrMo4 (AISI 4140 in the US) is a strong and durable steel that meets European requirements. Additionally, it has good wear resistance and hardness, both of which can be further improved by heat treatment techniques including quenching and tempering. 42CrMo4 steel is widely used in automotive, aerospace, oil and gas, heavy machinery, and power generation industries for manufacturing critical components like gears, shafts, and axles due to its high strength, toughness, and good hardenability.
Construction steel 42CrMo4
Used for machine parts and automotive
GET SOME THEORY FROM THE BOOKS
Wet abrasive cutting stands out as the most suitable method for materialographic cutting due to its minimal impact on the specimen in relation to the processing time. This technique involves the use of a cut-off wheel comprising abrasive particles and a binder.
DURING THE PROCEDURE
-
The sample should accurately reflect the characteristics of the original piece or component from which it is derived.
-
The cut-off wheel should experience minimal wear and tear.
-
The cut-off wheel should not face obstruction during the cutting process.
-
There should be no occurrence of thermal damage or burning on the surface of the specimen.
-
The specimen should be cool to the touch upon extraction from the machine.
-
The presence of burrs should be minimized.
-
The resulting surface should exhibit a uniform and smooth appearance with consistent scratches.
RECOMMENDED
We recommend you to mount your samples the most convenient way, giving attention to the heat resistance of the sample material, although, if a mounting press is unavailable, cold mounting becomes the sole viable option. Conversely, with access to a mounting press, the selection of mounting material can be refined based on specific attributes.
A crucial factor to consider is the abrasion rate, which denotes the speed at which material is ground or polished away. Ideally, the chosen mounting material should closely match the abrasion rate of the sample material. It is essential to recognize that the abrasion rate differs from the hardness of the sample.
As for the resin needs, we recommend the use of Epoxy resin as Epoxies offer a robust mounting solution with high resistance to chemicals and abrasion. Although they typically require a longer setup time compared to other castable materials, they exhibit superior flow and minimal shrinkage properties. For mounting challenging samples, long-cure epoxies are employed, and they can be introduced into a vacuum environment to eliminate trapped air and address voids.
IN THE END
If necessary, calibrate the sample with a coarser grit to make sure flat surface is achieved. The workpiece should be perfectly flat.
Time used 6 min
Rotation (sample holder) Clockwise
Speed 150 RPM
Pressure (30mm samples) 2 DaN
Achieved surface roughness at this step 0.084 Ra
Fluid Water
In the grinding steps for Structural Steel 42CrM04, when dealing with a flat sample, the process commences with a 40 µm. In case the sample is not flat, a coarser grit should be initially employed to achieve a flat surface (54 µm).
It's important to note that the applied force during grinding depends on the diameter of the sample, and in this instance, the sample has a diameter of 30mm. Additionally, to prevent excessive damage to the sample, it is recommended to rotate the sample clockwise.
Pre-polishing is not neccessairy in this step for this material.
Time used 4 min
Rotation (disc-workpiece) Clockwise at polishing step. Counterclockwise at fine polishing step
Speed 150 RPM
Pressure (30mm samples) 2 DaN
Achieved surface roughness at this step 0.018 Ra
Fluid Water
In the polishing steps for Construction Steel 42CrM04, the process initiates with a 9 µm abrasive. Subsequently, following the 9 µm, a 2 µm abrasive is employed. The applied force during polishing is contingent on the diameter of the sample, with the current sample having a diameter of 30mm. During the 9 µm abrasive phase, it is recommended to rotate the sample in a counter-clockwise direction to eliminate scratches from coarser grits. Conversely, for the 2 µm abrasive, a clockwise rotation is advised to prevent excessive damage to the sample. It is crucial that all scratches align in the same direction, and if not, repeating the preceding step becomes necessary.
1 5000g 10x
Time used 5 min
Rotation (sample holder) Counterclockwise
Speed 150 RPM
Pressure (30mm samples) 2 DaN
Achieved surface roughness at this point 0.061 Ra
Fluid Colloidal Silica
Finally, a suitable pad with a colloidal silica solution is utilized to clean and execute the last polishing step, providing a mirror-like finish to the Structural Steel 42CrM04 sample.
2 Colloidal Silica 10x