302HQ Stainless steel

What is stainless steel 302HQ？

Grade 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 designation 302HQ is not standardised – ASTM specifications list the grade as UNS S30430,

and alternative designations for the same grade include “XM-7”, “304Cu” and “304HQ”. The

standard specification for stainless steel fasteners, ISO 3506, includes 302HQ as an acceptable

composition for fastener grade “A2”; it is commonly produced in strength grades A2-70 and A2-80.

302HQ acer inoxidable 1.4567 Finished Products Form

• Coil – Strip
• Foil: Inquire with Ulbrich Stainless Steel Wire – Profile
• Round
• Flat
• Square

Applications for 302HQ acer inoxidable

• Food processing equipment
• Transport and storage equipment (e.g., beer brewing, milk processing, wine making)
• Kitchen benches, sinks, troughs, equipment, and appliances
• Architectural paneling, railings, and trim
• Chemical containers, including for transport
• Heat exchangers
• Woven or welded screens
• Threaded fasteners
• Springs

Equivalents of grade 302HQ

Nota	UNS No	Old British		Euronorm		Swedish SS	Japanese JIS
		BS	En	No	Name
302HQ	S30430	394S17	–	1.4567	X3CrNiCu18-9-4	–	SUS XM7

Composition ranges for 302HQ grade of stainless steel

Mechanical Properties 

Property	Value
Tensile Strength, min	515 MPa
Yield Strength (0.2% Proof), min	205 MPa
Elongation in 50 mm, min	40%
Hardness, max	201 HB

Physical Properties

Nota	Density (kg/m3)	Elastic Modulus (GPa)	Mean Coefficient of Thermal Expansion (µm/m/°C)			Thermal Conductivity (W/m.K)		Specific Heat 0-100 °C (J/kg.K)	Electrical Resistivity (nΩ.m)
			0-100 °C	0-315 °C	0-538 °C	at 100 °C	at 500 °C
302HQ	8027	193	17.2	17.8	18.8	16.3	21.5	500	720

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.

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.

Cold Work Hardening

302HQ has the lowest work hardening rate of any of the common austenitic stainless steels. This results in a tensile strength increase of approximately 8MPa/%Ra (8MPa increase in tensile strength for each 1% reduction of area of cold work – this data from wire drawing). Even after substantial cold work this grade remains essentially non-responsive to a magnet.

Welding

Stainless steel AISI 304CU (1.4567, X3CrNiCu18-9) has good weldability and can be used with many common welding processes such as TIG welding and MIG welding. It can also be used for arc welding, but this should be carried out with appropriate welding parameters to avoid overheating and distortion. To reduce tension and maintain the mechanical properties, the material should be allowed to cool in the air after welding. No heat treatment is required.

Machinability

AISI 304CU (1.4567) stainless steel is generally machinable, but this material hardens during machining. Therefore, care must be taken to select a sufficient cutting depth. In addition, suitable tools and coolants should be used to prevent overheating and extend tool life.