How to solve the processing deformation problem of Precision Round Steel Bar

Before processing, the steel is isothermally annealed (such as 860℃ austenitization + 650℃ isothermal transformation) to refine the pearlite grains to less than 10μm, and the residual stress can be reduced to less than 80MPa, reducing the deformation caused by the initial stress. High carbon steel (such as T10A) adopts spheroidizing annealing to make the carbides spherical and reduce the resistance to plastic deformation during cutting. After rough processing, stress relief annealing (550℃×3h) is arranged to release cutting stress. The semi-finishing/finishing allowance is controlled at 1.5-2mm and 0.3-0.5mm respectively to avoid one-time cutting stress concentration.

When cutting, carbide tools (such as YW1 brand) with a rake angle of 10°-15° and a main deflection angle of 75° are used to reduce radial cutting force by more than 30%; BTA drill + 20MPa high-pressure cooling is used for deep hole processing to reduce drill bit deflection. The slender shaft (length-to-diameter ratio>15) uses a center frame + a follower frame for joint support, with support points set every 150-200mm, and radial runout is controlled within 0.005mm; thin-walled parts use liquid plastic fixtures, evenly pressurized (pressure ≤5MPa), and the clamping deformation can be less than 0.002mm.

The machine tool guide rails are upgraded to hydrostatic bearings (oil film thickness 20-30μm), and the spindle preload increases the dynamic stiffness to more than 20kN/μm to suppress vibration (amplitude <5μm). Precision machining needs to be carried out in a constant temperature environment of 20±0.5℃. The lead screw is equipped with a grating scale closed-loop feedback (resolution 1nm), and the thermal deformation error is ≤0.001mm/m. After machining, the size can be further stabilized by low-temperature aging (120℃×24h) or shot peening (forming a 0.2-0.3mm compressive stress layer) to ensure that the deformation is controlled within the tolerance of 1/3 (such as φ50h6 shaft diameter deformation ≤0.003mm).