Abstract
This article is focused on an analysis of factors negatively affecting the tube production process of tubes made from austenitic stainless steel with a very small diameter of ϕ 0.34 mm. The analysis was concentrated on factors that affect the drawing process stability of the seam tubes where the desired final dimensions—a diameter of ϕ 0.34 mm and a wall thickness of 0.057 mm—are limiting factors. Seam tubes made from steel 1.4306 and 1.4301, from producers KT and EW with a longitudinal weld line made by tungsten inert gas (TIG) welding, were used as blanks for constituent drawing operations. It is desirable to provide sufficient inert gas flow and cooling during the formation of a weld joint in a protective atmosphere chamber. A significant temperature gradient prevents the formation of undesirable Cr23C6 carbides in the heat-affected zone (HAZ) which negatively affects the plasticity and formability of the steel and is the cause of technological fractures.
Highlights
Seam tubes made from austenitic stainless steel are used as the workpiece in the production of medical needles
Geometry of functional tools parts: geometry of the drawing die and a mandrel for wall thickness reduction with a floating mandrel and geometry of the drawing die during tube drawing without a mandrel [1,2,3]; Stress conditions in the compress and size fixing area of the functional tool parts [4,5,6]; Effect of tool parameters on the drawing process [1,7]; Similarity of the geometric tubes and thick-walled criterion [8,9,10]; Effect of a weld and the heat-affected zone on tube eccentricity and the drawing process [6,9]; Metals 2020, 10, 709; doi:10.3390/met10060709
Seam tubes, such as those considered for the production of injection needles, are made of austenitic steels complying with the EN 1.4306, respectively, EN 1.4301 and EN 10088-2 standards
Summary
Seam tubes made from austenitic stainless steel are used as the workpiece in the production of medical needles. They are produced by a combination of forming and welding technologies. The process includes the following stages: (1) Continual bending of blanks in a sheet metal roll form, with the dimensions 10 mm × 1 mm; (2) Tungsten inert gas (TIG) welding; (3) Drawing over a floating mandrel in the diameter, and thickness reduction of the wall; (4) Tube drawing without a mandrel in the diameter reduction. The factors affecting the formation of technological fractures are: Geometry of functional tools parts: geometry of the drawing die and a mandrel for wall thickness reduction with a floating mandrel (the first two operations) and geometry of the drawing die during tube drawing without a mandrel (subsequent operations) [1,2,3]; Stress conditions in the compress and size fixing area of the functional tool parts [4,5,6]; Effect of tool parameters on the drawing process [1,7]; Similarity of the geometric tubes and thick-walled criterion [8,9,10]; Effect of a weld and the heat-affected zone on tube eccentricity and the drawing process [6,9]; Metals 2020, 10, 709; doi:10.3390/met10060709 www.mdpi.com/journal/metals
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