Corrosion Resistance Stainless Steel Wire Grade 302HQ 304HC 0.05mm ~ 10mm ASTM A493

302HQ 304HC 0.05mm ~ 10mm stainless steel wire high tensile strength

Description:
302HQ is a specialised wire grade with very wide usage for manufacture of stainless steel fasteners. The inclusion of 3% copper in the composition reduces the cold work hardening rate substantially compared to Grade 304. 302HQ is standard for manufacture of self-tapping screws and light machine screws; it is also used for some bolts, set screws, rivets and specialised fasteners. It has now totally replaced Grades 384 and 305 for cold heading applications, copper being a lower cost alternative to their high nickel contents.
The stable austenitic structure makes 302HQ non-magnetic, even after substantial cold work, and also results in excellent toughness, even down to cryogenic temperatures.

Chemical composition:

Physical Properties (typical values in the annealed condition)

Grade Specification Comparison

Corrosion Resistance
Equal to or exceeding that of Grade 304. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 50°C. 302HQ is considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures, reducing to about 150mg/L at 60°C. Consult hao Technical Assistance for specific environmental recommendations.

Heat Resistance
Good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of Grade 302HQ in 425- 860°C range is usually safe (free of carbide precipitation) as the grade has a very low carbon content.
 

Heat Treatment
Solution Treatment (Annealing) Heat to 1010-1120°C and cool rapidly. This grade cannot be hardened by thermal treatment.
 

Welding
Use Grade 308L rods or electrodes. Excellent weldability by all standard fusion methods, both with and without filler metals. Because of its applications this grade is not often welded. Exceptions are resistance butt welding to join wires together during wire manufacture, and when the grade is used to make stud welding fasteners. 302HQ is not specifically listed in AS 1554.6.
 

Machining
302HQ is rarely machined, because of its form and likely products. The grade always has very low sulphur content as this aids formability, but unfortunately this also reduces machinability. Machining is certainly possible.
An Improved Machinability version of Grade 302HQ is produced, having a very high machinability. This version has a slightly higher sulphur content and is also calcium treated. This Improved Machinability grade (referred to as Ugima 4567) is available only to special order, but should be considered as an option where an “18/8” type grade needs to be both heavily cold formed and extensively machined.

Specified Properties

These properties are specified for grade S30430 wire in ASTM A493; wire is the only commonly available form for this grade. Properties of finished fasteners are covered by other specifications, such as ISO 3506-1 and 3506-3.