What Is Work Hardening?

Work hardening (also called strain hardening or cold working) is the strengthening of metal wire through plastic deformation during the wire drawing and weaving processes. When metal is deformed at temperatures below its recrystallization point, dislocations -- defects in the crystal lattice -- multiply and interact, making further deformation progressively more difficult. This increases the wire's tensile strength, yield strength, and hardness above the values of the annealed base alloy. In vibratory screening, work hardening is a beneficial consequence of screen cloth manufacturing that improves wire durability and fatigue life under continuous vibration.

The wire drawing process that converts rod stock into the fine wire used for screen cloth involves pulling the metal through a series of progressively smaller dies. Each die pass reduces the wire diameter and increases the percent cold work. A 304 SS wire drawn from 5.5 mm rod to 0.10 mm finished diameter undergoes approximately 99.97% area reduction, transforming the soft, annealed alloy into hard, spring-temper wire with dramatically higher tensile strength. This same work hardening continues during the weaving process as wires are bent around each other at each intersection point.

Work Hardening Effect on Common Screen Wire Alloys

Why This Matters in Vibratory Screening

Work hardening is an inherent benefit of the screen cloth manufacturing process that directly improves screen performance under the continuous cyclic stress of vibratory operation.

• Improved fatigue resistance -- Cold-worked wire has higher yield strength, meaning it resists permanent deformation under cyclic loading. Screen cloth woven from properly work-hardened wire maintains its aperture dimensions longer under vibration than screens made from softer, less-worked wire.
• Reduced wire breakage -- Higher tensile strength from work hardening means the wire can absorb more stress before fracturing. This is particularly important at weave intersection points where bending stress concentrates, and at frame bond locations where vibration forces are transmitted into the cloth.
• Magnetic considerations -- Work hardening of austenitic stainless steels (especially 304 SS) can induce a martensitic transformation that makes the wire slightly magnetic. This increased magnetic permeability can improve detectability by metal detectors (beneficial for food safety) but may also cause false rejects in sensitive detection systems.
• Temperature sensitivity -- Work hardening effects are eliminated if the wire is heated above its recrystallization temperature (approximately 1,040 C for 304 SS). This means high-temperature screening with Inconel or other superalloys may reduce or eliminate work-hardening benefits during service.

Related Glossary Terms

• Fatigue Life -- Vibration cycles before wire failure, improved by work hardening
• Magnetic Permeability -- Material magnetic response, affected by work hardening in 304 SS
• 304 Stainless Steel -- The most common screen alloy, highly responsive to work hardening
• Corrosion Resistance -- Can be slightly reduced by heavy cold work in some alloys
• Screen Cloth -- The end product of the wire drawing and weaving process

Work Hardening FAQs

How does work hardening affect vibratory screen cloth?

Work hardening increases the tensile strength and hardness of screen cloth wire beyond the values of the base alloy. During wire drawing, the metal is pulled through progressively smaller dies, plastically deforming the crystal structure and increasing dislocation density. This cold working can increase 304 stainless steel wire tensile strength from 515 MPa (annealed) to over 1,000 MPa (heavily cold worked). The result is screen cloth wire that better resists breakage, stretching, and fatigue failure under continuous vibratory stress.

Does work hardening affect the magnetic properties of stainless steel screen?

Yes. Work hardening can transform a portion of the austenite phase in 304 stainless steel to strain-induced martensite, which is magnetic. Heavily cold-worked 304 SS wire may become slightly magnetic, which can affect downstream metal detection sensitivity. 316 SS is more stable and less susceptible to this transformation. If magnetic permeability is critical for your metal detection system, specify 316 SS or request low-permeability wire.