Influence of Conformal Cooling Channel Parameters on Hot Stamping Tool and Press-Hardening Process

Abstract

Press hardening is a technology increasingly used in the automotive industries to produce high-strength structural parts in boron steel. The part strengthening is due to a martensitic microstructure, which is obtained during the quenching phase of the process by imposing cooling rates typically higher than 27 K/s. To improve cooling efficiency, conformal cooling channels (CCC) are increasingly adopting thanks to opportunities offered by additive manufacturing (AM) technologies in combination with the development of powders with high thermal conductivity.In this work a methodology for the design of CCC inside hot stamping tools is presented and the press hardening of an automotive B-Pillar in 22MnB5 has been used as case study. The proposed methodology provides for an optimization of the distance between the cooling channels (p) and distance between the tool surface and the cooling channel center (d).

Effects of the Intermediate Precooling Parameters on the Mechanical Properties of a Tailored Press‐Hardened Component in Advanced High‐Strength Steel

“…The value of these process parameters was set based on previous studies. [23,24,38] The HTC at the blank-tools interface was set at 3500 W (m 2 K) À1 . This value was multiplied by a scale factor according to the contact pressure and the gap between the blank and the tools, as described by Palmieri et al [38] For the lubrication conditions, the Coulomb model was adopted, and the friction coefficient was set equal to 0.4.…”

“…These effects are even more pronounced with a higher cooling rate. means of a laser source or induction heating; [21] 2) tailored blank heating (TBH) technology; and [22] 3) tailored tool tempering (TTT) technology [23,24] The technologies mentioned so far are conventional technologies in which a clear delineation between the hard and soft areas exists. To overcome this problem, a new generation of tailored tempering technology, known as intermediate precooling (IPC), able to distribute soft zones more freely over part geometry (soft flanges around the part or soft spots in the middle of a part), was developed.…”

“…Tailored process technologies, on the other hand, allow to obtain components with customized mechanical properties by modifying microstructural properties of the part through heat treatments after the process or through the variation of thermal cycles (modification of the process). Some examples of tailored process technologies are detailed below: 1) partial annealing by means of a laser source or induction heating; [ 21 ] 2) tailored blank heating (TBH) technology; and [ 22 ] 3) tailored tool tempering (TTT) technology [ 23,24 ]…”

Additive manufacturing of carbon-martensitic hardening ledeburitic cold work tool steels using Fused Filament Fabrication and subsequent Supersolidus Liquid-Phase Sintering

“…In the case of DRT, the component is directly processed and can subsequently be used as a tool for material forming or cutting, for example. In particular, in the manufacture of tools that require optimal temperature control (e.g., press-hardening tools [4,5]) or the addition of local lubricants (machining and forming tools [6][7][8]), AM makes it possible to introduce inner cavities, which is hardly achievable by subtractive or formative processes. The current state of knowledge on AM of tools is provided by the work of Hölker-Jäger [9] and Levy et al [10].…”