Blanking is a cutting process used to produce flat pieces from sheet metal. In this case, a blanking operation needs to be performed on a 2 m thick steel to obtain 75 mm diameter pieces. The shear strength of the material is given as 450 MPa. We need to determine the blanking force required.

1. Understanding the Blanking Process:
- Blanking is a shearing process where a punch and die are used to cut out a desired shape from a sheet of material.
- The punch is a tool with the desired shape, while the die is a tool with a hole that matches the shape of the punch.
- When the punch and die come together, the material is sheared and the desired shape is obtained.

2. Calculation of Shear Stress:
- Shear stress is the force per unit area acting parallel to the face of the material.
- The shear strength of the material is given as 450 MPa, which represents the maximum shear stress the material can withstand before failure.

3. Calculation of Shear Area:
- The shear area is the area of the material that is subjected to the shearing force during the blanking process.
- In this case, the shear area can be calculated as the product of the thickness (2 m) and the circumference of the blank (75 mm).
- The circumference can be calculated using the formula: C = πd, where d is the diameter of the blank.

4. Calculation of Blanking Force:
- The blanking force can be calculated using the formula: Force = Shear Stress x Shear Area.
- Substituting the given values, we have: Force = 450 MPa x Shear Area.

5. Conversion of Units:
- The given shear strength is in MPa (MegaPascals), but the required answer is in kN (kilonewtons).
- To convert from MPa to kN, we need to multiply the force in MPa by the shear area in square meters.
- 1 MPa = 1 N/mm², and 1 kN = 1000 N.

6. Calculation of Blanking Force Required:
- We calculate the shear area using the given diameter of 75 mm and the thickness of 2 m.
- Shear Area = 2 m x π(75 mm)
- Convert the shear area to square meters.
- Multiply the shear strength of 450 MPa by the shear area in square meters to get the force in Newtons.
- Convert the force from Newtons to kilonewtons by dividing by 1000.
- The resulting value will give us the blanking force required.

The correct answer is between 205 kN and 220 kN.