Stainless Steel - Grade 302HQ (UNS S30430)

Chemical Formula

Fe, <0.15% C, 17-19% Cr, 8-11% Ni, 3-4% Cu, <2% Mn, <1% Si, <0.045% P, <0.03%S

Topics Covered

Background

Key Properties

Composition

Mechanical Properties

Physical Properties

Grade Specification Comparison

Possible Alternative Grades

Corrosion Resistance

Heat Resistance

Heat Treatment

Welding

Machining

Cold Work Hardening

Applications

Background

302HQ is a specialised wire grade finding 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. This grade is the standard material for manufacture of self-tapping screws and light machine screws and is also used for some bolts, set screws, rivets and specialised fasteners. 302HQ has now totally replaced Grades 384 and 305. Alternative designations for Grade 302HQ include "XM-7", "304Cu" and "304HQ". The stable austenitic structure makes 302HQ non-magnetic, even after substantial cold work, and also results in excellent toughness, even down to cryogenic temperatures.

Key Properties

These properties are specified for wire in ASTM A493; wire is the only commonly available form for this grade.

Composition

Typical compositional ranges for grade 302HQ stainless steels are given in table 1.

Table 1. Composition ranges for 302HQ grade stainless steel

Grade C Mn Si P S Cr Mo Ni Cu
302HQ min. - - - - - 17.0 - 8.0 3.0
max. 0.03 2.00 1.00 0.045 0.030 19.0 - 10.0 4.0

Mechanical Properties

Typical mechanical properties for grade 302HQ stainless steels are given in table 2.

Table 2. Mechanical properties of 302HQ grade stainless steel

Grade Tensile Strength (MPa) max. Yield Strength 0.2% Proof (MPa) Elongation (% in 50 mm) Hardness
Rockwell B (HR B) Brinell (HB)
302HQ annealed 605 - - - -
302HQ lightly drawn 660 - - - -

Above values from ASTM A493. Higher strengths can be produced by heavy cold work - this may be required for certain applications.

Physical Properties

Typical physical properties for annealed grade 302HQ stainless steels are given in table 3.

Table 3. Physical properties of 302HQ grade stainless steel in the annealed condition

Grade 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

Grade Specification Comparison

Approximate grade comparisons for 302HQ stainless steels are given in table 4.

Table 4. Grade specifications for 302HQ grade stainless steel

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

These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted.

Possible Alternative Grades

Possible alternative grades to grade 302HQ stainless steels are given in table 5.

Table 5. Possible alternative grades to 302HQ grade stainless steel

Grade Why it might be chosen instead of 302HQ
304L A higher work hardening rate can be tolerated - or is needed.
316L Higher resistance to pitting and crevice corrosion is required in chloride environments; the higher work hardening rate of 316L is acceptable.
430 A lower cost is required, and the reduced corrosion resistance of 430 is acceptable.

Corrosion Resistance

Excellent. Equal to or exceeding that of Grade 304 in a wide variety of corrosive media. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. 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.

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.

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.

Applications

Typical applications include:

        All severe cold heading applications

        Self-tapping screws

        Roofing bolts

        Machine screws

        Bolts

        Set screws

        Blind rivets

Source: Atlas Steels Australia

For more information on this source please visit Atlas Steels Australia

Comments

  1. Stephan Davies Stephan Davies United States says:

    What is the permeability of S30430?

  2. Lichie Ang Lichie Ang Malaysia says:

    Does this material have temper?

    • Nick Gilbert Nick Gilbert United Kingdom says:

      Hi Lichie,

      Many thanks for your question. 302HQ is a specialised grade of stainless steel with similar or improved performance to 304. The inclusion of circa 3% copper helps to reduce the cold work hardening rate compared to 304.

      302HQ is typically not hardened by thermal treatments.

      Many thanks,
      Nick.

  3. Ed van Berkel Ed van Berkel Netherlands says:

    I have an request for wn 1.4567 but get offers for SUS302HQ AND 304 wich is the best material to meet 1.4567?

  4. Cris Young Cris Young United States says:

    How long should 302hq stainless steel last in a salt spray test?

  5. Douglas Holmberg Douglas Holmberg United States says:

    Would I achieve better tensile, torsional torque, and yield strength with 304L or 302HQ given the same wire diameter?

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com.

Ask A Question

Do you have a question you'd like to ask regarding this article?

Leave your feedback
Submit