Best Formability for Chosen Processing Path Requires Generation A Consistent Good FROM THE CUPETING Operation.
Blanks. Tool, Blank, and Process Development Must of the LOWER-DUCTILITY SHEARED EDGES in Production Blanks.
Testing Article has additional informing point to the effect of burr orientation and painch shape.
Improved Edge Ductility. Laser, EDM or Water Jet Cutting Approaches Minimize Working At the Edges and the Association N-Value Reduction, Also Leading TO Improved GeedgEd GEDGEDDGEDDGED EDGEDDGEDDGED EDGEDDGEDDGEDDGED EDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDDGEDEDEDEDEDERATDDGED
Tool and Press Life.
Rake Angles on Mechanical Shearing Operations.
A Typical Mechanicals Sheared Steel Edge Has 4 Main Zones -Rollover, Burnish, Fracture, and Burr, As Shown in Figure 1.
LED to Sharpence or Replacing The Trim Steels, OR Less Likely, Adjusting The Clearances to Minimize the Burr.
Greater burr height is associated with additional cold working and creates stress risers that can lead to edge splitting. These splits, however, are global formability related failures where the steel thins significantly at and around the split, independent of the local formability edge fractures associated with AHSS.? A real-world example is shown in Figure 2, which presents a conventional BH210 steel grade liftgate with an excessive burr in the blank that led to global formability edge splitting in the draw die.? The left image in Figure 2 highlights the burr on the underside of the top blank, with the remainder of the lift below it.? The areas next to the split in the right image of Figure 2?shows the characteristic thinning associated with global formability failures.
Due to their progressively higher yield and tensile strengths, AHSS grades experience less rollover and smaller burrs. They tend to fracture with little rollover or burr. As such, detailed examination of the actual edge condition under various cutting conditions becomes more significant with AHSS as opposed characterizing edge quality by burr height alone. Examination of sheared edges produced under various trimming conditions, including microhardness testing to evaluate work hardening after cold working the sheared edge, provides insight on methods to improve cut edge formability.? The ideal condition to combat local formability edge fractures for AHSS was to have a clearly defined burnish zone with a uniform transition to the fracture zone. The fracture zone should also be smooth with no voids, secondary shear or edge damage (Figure 3).
To the frame zone is also undeSirable. These non-identifications create propagation sites for edge frameres.
There are Multiple Capes for a POOR Sheared Edge Condition, Including But Not Limited to:
The Die CleaRARANCE BeING TOO LARGE OR TOO SMALL,
a cutting angle that is too small,
WORN, Chipped, or DAMAGED Tooling,
Improperly Group or Sharpened Tooling,
Improper Die Material,
Improperly head-treated die material,
Improper (or Non-EXISTENT) Coating on the Tooling,
MISALIGNED DIE Sections,
WORN Wear Plates, AND
Out of Level Presses or Slitting Equipment.
AS Well as a Thick Burnish Zone with a Non-Uniform Transition from the Burnish Zone to the Fractor Zone.
WERE 1.0 MM Samples of DP 350Y600T (A80 = 20%), DP 500Y800T (A80 = 8%), and MS 1150Y1400T (A80 = 3%). Tests of Mild Steel used a 6%Cleaarence and W.NR. 1.2363 / AISI% for the MS 1150Y1400T Grade and 14% for DP 500Y800T.
Ahss are also shownn, indicating that user scament high Quality Tool Steels Results in the same level,
Combinations Evaluated Were SUFFICiently Similar that they are shown as a single curve.
TOOL to Achieve Targeted Performance.
tensile stream of the sheet metal increases.
On the punch edge, who increases the risk of chipping.
Right Image Shows An Optimal Edge Likely to Result in Good Edge Ductility.
The Recomgended Cleaarence is a function of the sheet grade, thinkness, and tensile stream.
of ISO 16630, Which Specifies the Use of 12% Cleaarence.
Smoother Sheared Sheared Surface and Negligible Burr. Two Grades Wee Evaluated: A Dual Phase Steel with 780MPA Minimum Tensile Streangth and A 3rd Generation Steel With
Produced Greater Hlener Expansion Ratios than Those Formed with 20% Cleaarence, But the Magnitude of the Improvement Was Not Consisteent Between The Diffrent SUPPLIERS.K-56
To altering the punch forward and impacting angle.
Punch and the Sheet Surface, Which Makes Crack Initiation More Difficult Without Higher Forces.
RISK of Plastic Deformation of the Punch Tip.t-20
on the results. (Figure 19)
% Depending on the Conditions, Which Represses A Tremedous Drop in Snap-Through or Reverse Tonnage. Figure 22 Visually Describes The Upper and LOWER BLADE RAAKE ANGLES and Thlees and ThleS AND THISD THE
DEGREE RAKE ANGLE on Both the Upper and LOWER BLADES, as defined in Figure 22.
Conclusions from this study include:
Mechaanically Shearing the Edge Cold Works the Steel and Reduces the Working Exponent (N-Value), Leading to LESS EDGE Stretchability.
Samples Prepared with Processses that avoided Cold Working the Edges, like laser or water jet outPerformed Mechanical Sheared Edges.
Optimizing the Trim Shear Conditions or Polishing A Flat Trimmed Edge Achieved With Laser Trimming and Water Jet Cutting.
Shearing Parameters Such as Cleaarence, Shear Angle and Rake Angle Also Play a Large Part In Improving Edge Stretch.
The Creation of Locally Softened Zones to Improve Cut Edge Ductility in SOME Applications of Press Hardening Steels.
And intropucess the risk of rust forming at the newly cut edge.
Improved the Hole Expansion Ratio to 40%.
Figure 28 Highlights the Benefits of Two-Stage Pre-PierCing for Specific Grades, showing a 2x to 4X Improvement in Hole Expansion Ratio for the Grades Presented.
LOWER PUNCH/DIERARANCES Lead to accelerated too wear. Higher Punch/Die CleaRANCES Generate More Rollover/Burr.
ISO 16630, The Global Specification for Hole Expansion Testing, Specifies the Use of 12% PUNCH-TO-DIERARANCE.
Recommended Cleaarence as a Percentage of Sheet Thickness Increases with Thickness, Even at the Same Streangth level.
Edge Preparation Methods Like Milling, Laser Trimming, and Water-Jet Cutting Minimize Cold Working at the Edges, Resulting in the Greatest Edge Ductility,
Shear or Bevel on Punches and Trim Steel Reduces Punch Forces, Minimizes Snap-Through Reverse Tonnage, and IMPROVES EDGE DUCTILITY.
Mild STEEL PUNCHED with Conventional Tools and Ahss Grades PUNCHED with Surface Treated Engineered PM Tool Stels Experble Wear.
Maintenance of Key Process Variables, SUCH As Cleaarence and Tool Condition, is Critical to Achieving Long-Term Edge Stretchability.
The Optimal Edge APPEARANCE BLANKINGINGINGINGINKIWS A Uniform Burnish Zone with A University Transition to a Smoolh Fraction Zone.
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EDGE DUCTILITY MEASUREMENTS
Cut Edge Quality
Cutting clearnces: Burr Height and Tool Wear
Cutting Cleaarences: General Recommendations
Punch Face Design
Effect of EDGE Preparation Method on Ductility
Key Points