Titanium Cast Product Surface β Stabilizer Layer
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Solution Overview
Problem
Titanium cast products produced by electron-beam remelting or plasma arc remelting often exhibit coarse grains, leading to surface defects during hot rolling without a breakdown process, which increases production costs and reduces yield due to the need for extensive pickling to remove these defects.
Innovation Solution
Applying a material containing a β stabilizer element to the surface layer of the titanium cast product before hot rolling, creating a β stabilizer element-rich layer that suppresses grain growth and enhances surface properties, allowing for hot rolling without a breakdown process while maintaining excellent surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot rolling is performed without a breakdown process on a titanium cast product with coarse grains, then productivity is improved and cost is reduced, but surface defects occur due to deformation anisotropy in coarse grains
Solution Approach 1:
The patent changes the microstructural parameters of the titanium cast product by controlling solidification conditions (cooling rate, temperature gradient) to achieve a specific grain size range (5-50mm) and crystal orientation distribution. This parameter optimization allows the coarse-grained structure to produce acceptable surface quality even without breakdown processing, resolving the contradiction between productivity improvement and surface quality maintenance.
Solution Approach 2:
The patent applies local quality control by ensuring that the surface layer of the titanium cast product has optimized crystal orientation (c-axis angle of 35-90° to the surface normal) and controlled grain structure. This localized optimization of the surface region's microstructure enables the material to withstand hot rolling without breakdown while maintaining surface quality, addressing the contradiction between skipping breakdown processes and preventing surface defects.
2Productivity
If the breakdown process is omitted to improve cost and yield, then productivity increases, but extensive pickling is required to remove surface defects, worsening yield and increasing cost
Solution Approach 1:
By optimizing solidification parameters (cooling rate, temperature gradient, mold design) to control grain size and crystal orientation in the cast product, the patent enables direct hot rolling without breakdown processes. This eliminates surface defects at their source, reducing or eliminating the need for extensive pickling and associated material loss, thus simultaneously improving productivity and yield.
Solution Approach 2:
The patent performs preliminary action by controlling the solidification process to pre-establish an optimized microstructure with appropriate grain size and crystal orientation before hot rolling. This preliminary microstructural optimization prevents surface defect formation during subsequent processing, eliminating the need for corrective pickling operations and associated material loss.
3Ease of manufacture
If electron-beam remelting or plasma arc remelting is used to produce various shaped ingots, then ease of manufacture is improved, but coarse grains are formed leading to surface defects during hot rolling
Solution Approach 1:
The patent optimizes solidification parameters (cooling rate, temperature gradient, heating power distribution) during electron-beam or plasma arc remelting to control grain growth and crystal orientation. By carefully adjusting these parameters, the process produces ingots with controlled grain sizes (5-50mm) and favorable crystal orientation (c-axis angle of 35-90° to surface normal), enabling various shapes to be manufactured while maintaining surface quality after hot rolling without breakdown processes.
Solution Approach 2:
The patent applies local quality control by ensuring that the surface and near-surface regions of the cast product have optimized microstructural characteristics (grain size, crystal orientation) while allowing the interior to have different properties. This localized optimization of the surface layer enables various ingot shapes to be produced with good surface quality that can withstand hot rolling without breakdown processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces heating time, minimizes cutting treatments, decreases pickling requirements, and enhances yield by producing titanium materials with surface properties equivalent to conventionally processed materials, thereby lowering production costs and improving industrial efficiency.
Implementation Method 1
the surface layer at a surface corresponding to a surface to be rolled is subjected to melting and resolidification
Implementation Method 2
This slab surface layer is quenched and solidified to have fine and irregular crystal orientation distribution
Data Source
Figure 1
AI summary
Provided is a titanium cast product made of commercially pure titanium, the titanium cast product being produced by electron-beam remelting or plasma arc melting, comprising: a melted and resolidified layer in a range of 1 mm or more in depth at a surface serving as a surface to be rolled, the melted and resolidified layer being obtained by adding one or more kinds of β stabilizer elements to the surface and melting and resolidifying the surface. An average value of β stabilizer element(s) concentration in a range of within 1 mm in depth is higher than β stabilizer element(s) concentration in a base material by, in mass%, equal to or more than 0.08 mass% and equal to or less than 1.50 mass%. As the material containing the β stabilizer element, powder, a chip, wire, or foil is used. As means for melting a surface layer, electron-beam heating and plasma arc heating are used.