Titanium Slab Edge Remelting for Defect-Resistant Hot Rolling
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Solution Overview
Problem
Conventional methods for producing hot-rolled titanium plates often result in surface defects at the edge portions due to pores in the ingot not being addressed during the breakdown process, leading to reduced yield and increased scarfing or cutting of defective areas.
Innovation Solution
A method involving electron beam re-melting or plasma arc melting processes to form a titanium slab, followed by a melting and re-solidification process on the side surfaces to create a fine-grained microstructure layer, and a finishing process to ensure slab flatness, which inhibits pore opening during hot rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional melting methods (VAR, EBR, PAM) are used to produce titanium ingots, then the ingots can be produced efficiently, but surface defects at edge portions occur due to pores not being addressed during breakdown process
Solution Approach 1:
The invention applies preliminary action by performing electron beam melting to create an ingot with a specific internal structure before the breakdown process. The melting conditions are carefully controlled to ensure that pores are positioned away from the surface that will later be rolled, preventing surface defects without requiring extensive breakdown processing.
2Reliability
If breakdown process is performed to address surface defects, then surface quality improves, but production time and complexity increase
Solution Approach 1:
The invention extracts the harmful pores from the surface region by controlling their formation during electron beam melting to be located away from the rolling surface. This eliminates the need for complex breakdown processes to remove surface defects, as the pores are already positioned in non-critical locations.
3Productivity
If breakdown process is omitted to simplify production, then productivity increases, but surface defects at edge portions occur
Solution Approach 1:
The invention changes the parameters of the melting process by using electron beam melting with specific energy density and cooling rate controls. This creates an ingot structure where pores are naturally formed away from the surface, allowing omission of the breakdown process while maintaining high surface quality.
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
The method effectively suppresses surface defects at edge portions, reducing the need for excessive scarfing or cutting, thereby increasing yield and improving surface properties of the hot-rolled titanium plates.
Implementation Method 1
an electron beam re-melting process (EBR)
Implementation Method 2
a plasma arc melting process (PAM)
Implementation Method 3
melting at least one part on the surface to be rolled side of the side surface of the titanium slab by radiating a beam or plasma toward the side surface
Implementation Method 4
radiating a beam or plasma toward the side surface
Implementation Method 5
thereafter causing re-solidification to form, in the side surface, a microstructure layer
Data Source
AI summary
A method for producing a hot-rolled titanium plate includes, [1] melting at least one part of the side surface of the titanium slab by radiating a beam or plasma toward the side surface, not toward the surface to be rolled, and thereafter causing re-solidification to form, in the side surface, a layer having grain diameter of 1.5 mm or less and a depth of 3.0 mm or more from the side surface; [2] performing a finishing process on the surface to be rolled of the titanium slab in which the layer is formed, to thereby bring a slab flatness index X to 3.0 or less; and [3] subjecting the titanium slab after the finishing process to hot rolling under a condition in which a length of an arc of contact of a roll L in a first pass of rough rolling is 230 mm or more.