High-Alloy Seamless Pipe Extrusion Temperature Control
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Solution Overview
Problem
Conventional hot extrusion techniques for producing high-alloy seamless tubes often result in cracking and seam flaws due to grain boundary melting caused by processing-incurred heat, especially in high deformation resistance alloys like high Cr-high Ni alloys.
Innovation Solution
A hot extrusion process that controls the heating temperature of the starting material based on its cross-sectional area, extrusion speed, and extrusion ratio, using specific formulas to prevent excessive temperature increases and minimize grain boundary melting cracking, with the heating temperature range determined by the contents of Mo and W.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional hot extrusion techniques are used for high Cr-high Ni alloys, then the seamless tubes can be produced, but grain boundary melting cracking occurs due to processing-incurred heat
Solution Approach 1:
The patent applies parameter changes by establishing specific heating temperature ranges based on alloy composition (Cr content and Mo+W content) and process parameters (extrusion ratio and extrusion speed). The heating temperature T is controlled within specific ranges: when Cr is 20-30% and Mo+W is 0.01-5.0%, T is 1100-1250°C; when Cr is 30-50% and Mo+W is 0.01-3.0%, T is 1050-1200°C. This precise parameter control prevents grain boundary melting while maintaining formability.
Solution Approach 2:
The patent applies preliminary action by pre-heating the billet to a controlled temperature range before extrusion. The heating temperature is predetermined based on the alloy composition and extrusion parameters, ensuring the material is at the optimal temperature for deformation without excessive heat accumulation that would cause grain boundary melting.
2Ease of manufacture
If the heating temperature is increased to improve formability, then the extrusion process can be completed, but grain boundary melting cracking is intensified
Solution Approach 1:
The patent applies parameter changes by establishing specific heating temperature ranges based on alloy composition (Cr content and Mo+W content) and process parameters (extrusion ratio and extrusion speed). The heating temperature T is controlled within specific ranges: when Cr is 20-30% and Mo+W is 0.01-5.0%, T is 1100-1250°C; when Cr is 30-50% and Mo+W is 0.01-3.0%, T is 1050-1200°C. This precise parameter control prevents grain boundary melting while maintaining formability.
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 process effectively prevents seam flaws on the inner surface of the tubes, ensuring high-quality seamless tubes with improved corrosion resistance and reduced defect rates.
Implementation Method 1
the degree of the temperature increase inside the tube wall is intensified by processing-incurred heat during extrusion
Implementation Method 2
a starting material to be extruded made of a high alloy containing Cr: 20 to 30% and Ni: more than 22% and 60% or less is heated to a temperature predetermined according to the contents of Mo and W and subjected to hot extrusion
Data Source
Figure 1~2
AI summary
A starting material to be extruded made of a high alloy comprising, in mass%, Cr: 20 to 30% and Ni: more than 22% and 60% or less is heated to a temperature predetermined according to the contents of Mo and W and is subjected to a hot-extrusion process, the heating temperature T (°C) satisfying a relationship of Formula (1), (2), or (3), which is expressed in terms of the average cross-sectional area A (mm2) of the starting material to be extruded, the extrusion ratio EL (-), and the extrusion speed V (mm/s). As a result, a high-alloy seamless tube can be produced without generating cracking and/or seam flaws. When0%≤Mo+0.5W<4%:T≤1343-0.001322×A-1.059×EL-0.129×V When4%≤Mo+0.5W<7%:T≤1316-0.001322×A-1.059×EL-0.129×V When7%≤Mo+0.5W:T≤1289-0.001322×A-1.059×EL-0.129×V