UGI® 4462 Cold Drawn Bar

Drawing – Profiling:

Owing to the high limit of elasticity of UGI® 4462, its cold working will require strengths greater than those needed to form an austenitic grade of the 1.4404 (316L) type. See the hardening curve of UGI® 4462 in the right side of the material page.

Cold heading: UGI® 4462 is not a grade optimised for cold heading. Its high mechanical properties will induce significant forming forces and rapid wear of the forming dies. However, the surface aspect of the parts formed in UGI® 4462 is much better than that observed on austenitic grades (no orange peel phenomenon). Thus UGI® 4462 can be used in ordinary cold heading or bending when orange peel phenomena are observed with austenitic grades. In the cold impact test, the UGI® 4462 allows for a 40% expansion deformation before cracking.

UGI® 4462 can be used in applications where corrosion resistance properties are essential:

Because of its low sulphur content (to preserve its very good corrosion resistance) and strong mechanical properties, UGI® 4462 is a difficult-to-machine grade. The absence of sulphides in large quantities prevents good chip breaking in machining operations. The high mechanical properties generate, in turning, high cutting forces which lead to rapid tool wear. That is why the choice of cutting tools (carbide grade and chip breaker) is essential to machine UGI® 4462 correctly. Moreover, the choice of cutting conditions is more difficult than with grades having lower mechanical properties. It will be necessary to lower cutting speeds compared to austenitic grades, while avoiding taking them too low because one has to be able to maintain temperatures high enough at the tool tip to limit the cutting forces. As for cutting feed rates, they must be maintained at a level that allows the chips to be broken successfully.

The graphs below give an idea of the decreases in cutting conditions that may be carried out on UGI® 4462 compared to those of a 1.4404 for turning with a coated carbide tool and for drilling with a high-speed steel tool.

Our technical support department will be pleased to answer any questions on the subject

The solution annealing heat treatment using must be performed at a temperature between 1020°C and 1100°C followed by rapid cooling in air or water. This treatment restores the ductility of the grade UGI® 4462 after hot or cold working.

Forging

UGI® 4462 has satisfactory hot workability between 1220 and 950°C, although lower than that of ordinary austenitic steels (1.4301, 1.4404). Hot ductility is related to the ferrite content of the grade, which increases with temperature; it will therefore be better for high forging temperatures.

At forging temperatures, the mechanical strength of UGI® 4462 is lower than that of an austenitic, which gives rise to lower loads on tools, and sometimes it is necessary to take precautions to limit the creep deformation of the parts. Hot processing must be followed by a solution annealing heat treatment with rapid cooling, in order to restore the ferrite-austenite equilibrium, the mechanical properties and corrosion resistance of the grade.

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General points

UGI® 4462 can be welded by friction, resistance, arc, with or without a filler wire (MIG, TIG, coated electrode, plasma, in a stream, ...) by laser beam, electron beam, etc. However, unlike austenitic stainless steels, UGI® 4462 must be welded in accordance with a field of linear welding energy to ensure good toughness of the welded areas. If the linear welding energy is too high, there is a risk - due to too-slow cooling after welding - of an embrittling sigma phase forming in a Heat Affected Zone (HAZ). If the linear welding energy is too low, there is a risk - due to too-rapid cooling after welding - of having too ferritic and, therefore, fragile HAZs.

The field of linear welding energy to be respected depends mainly on the geometry of the pieces to be welded, and in particular on their thickness. The thicker the work pieces are, the faster the cooling of the weld, which shifts the field of linear welding energy towards the high energies. The linear energy field to be respected also depends on the welding process used (MIG, TIG, …). In the case of multipass welding, it is important to allow the weld to cool to below 150°C between each pass. Preheating of parts before welding is not desirable and no heat treatment should be performed after welding, except, if necessary, for a solution annealing described in the paragraph on "Heat Treatment".

MIG welding

The filler wire that is best suited for MIG welding of UGI® 4462 is ER2209 - 22.9.3NL - UGIWELD TM 45N. Its more austenitic balance than that of UGI® 4462 limits the proportion of ferrite in the weld zone (WZ) and thereby the risk of fragility in WZ. We prefer a slightly oxidizing shielding gas (Ar + 1-3% O₂ or CO₂) to limit the oxygen level in WZ and thereby to ensure good toughnessin WZ. Under no circumstances should one add hydrogen to the shielding gas to avoid the risk of cold cracking in WZ. If necessary, one may add a few % of N₂ to the shielding gas to offset any loss of nitrogen in WZ during the welding operation.

TIG welding

It is imperative that the shielding gas to be used be absolutely neutral (Ar, partially substituted or not by He) to protect the tungsten electrode. As in MIG welding, hydrogen is prohibited in the shielding gas. Due to the absence of oxygen in the gas supply, this process ensures more easily good toughness in WZ.