Mechanical properties and weldability of SUS321 stainless steel

Why do we need to understand the mechanical properties and weldability of SUS321 stainless steel?

In industrial scenarios where high temperature, corrosion and complex stress are intertwined, SUS321 stainless steel (1Cr18Ni10Ti) has become a key material for chemical pipelines, heat treatment equipment, and aerospace components due to its titanium stabilization design.
However, the performance advantages of SUS321 stainless steel are highly dependent on the precise control of mechanical properties and weldability - the former determines the reliability of the material under high temperature loads, and the latter directly affects processing and structural safety. From the perspective of engineering application, this article analyzes the technical connotation and practical significance of the two core performances, and provides a decision-making basis for industrial material selection, process design and quality control.

 

SUS321 stainless steel mechanical properties

SUS321 (corresponding to the national standard 06Cr18Ni11Ti) is an austenitic stainless steel. By adding titanium (Ti) to stabilize carbides, it has excellent high temperature strength and resistance to intergranular corrosion.
Tensile strength (σb): ≥520 MPa (solution treated state)
Yield strength (σ0.2): ≥205 MPa (solution treated state)
Elongation (δ5): ≥40% (good plasticity and toughness, easy to cold process)
Hardness: ≤187 HB (annealed state), suitable for scenes requiring subsequent processing such as welding and bending
High temperature performance: When used for a long time at 500-700℃, the creep resistance is better than 304 stainless steel, and the maximum temperature resistance can reach 850℃ (short-term peak temperature), which is suitable for structural parts in high temperature environments.

SUS321 stainless steel weldability

SUS321 stainless steel has good weldability. Titanium (Ti≥5×C%) can preferentially combine with carbon to form stable titanium carbide (TiC), avoiding the precipitation of chromium carbides (Cr23C6) at the grain boundaries, thereby significantly reducing the risk of intergranular corrosion in the heat affected zone (HAZ) of welding.
Applicable welding methods: TIG welding, MIG welding, and manual arc welding (SMAW) are all applicable. It is recommended to use a low heat input process to reduce grain coarsening and stress concentration.
Welding material selection: It is necessary to match filler materials containing titanium or niobium (Nb) (such as ER347 welding wire, E347 welding rod) to avoid the precipitation of carbides in the weld area, which leads to a decrease in corrosion resistance.
Pre-welding/post-welding treatment:
No preheating is required before welding, but if the workpiece is thick or the ambient temperature is low, it can be moderately preheated to 100-150℃ to reduce the risk of cold cracks.
Generally, heat treatment is not required after welding, but for applications with extremely high corrosion resistance requirements, solution treatment (1000-1100℃ rapid cooling) is recommended to restore material uniformity.
Note: Avoid ferrite contamination during welding (such as contact with carbon steel tools) to prevent intergranular corrosion and stress corrosion cracking; control the interlayer temperature ≤150℃ to reduce grain coarsening caused by heat input.