304(Cr-Ni)

Post Views: 10

1. Introduce

– Composed of approximately 18% Cr and 8% Ni, hence the name 18-8 stainless steel

– Due to its small carbon content, it retains its strength even after heat treatment

– Good oxidation resistance to temperatures up to 925°C, but not recommended for long-term use in the 425~860°C temperature range

– UNS S30400

* 18-8 Stainless Steel

– “18-8” : Part of the chemical composition (18 : Cr content, 8 : Ni content)

– Definition : 300 series grade stainless steel containing about 18% chromium and 8% nickel

– Types : 301, 302, 304 stainless steel

* Types of 304 stainless steel : related to carbon content

– 304L : A low carbon version of 304 stainless steel, containing up to 0.3% carbon
→ Due to its low carbon content, it is less likely to cause carbide precipitation when used at temperatures above 425°C and is used to improve weldability

– 304H : High carbon version of 304 stainless steel, containing approximately 0.04-0.1% carbon
→ Good corrosion resistance and resistance to temperature extremes

* Stainless Steel Comparison

Type	Composition	Properties
304	18%Cr, 8%Ni	– Excellent corrosion resistance and machinability, suitable for use in everyday environments (kitchen utensils, building materials, automotive parts, etc.), – Excellent high temperature properties, but corrosion occurs when used for a long time in the temperature range of 425~860℃
316	17%Cr, 10%Ni, and 2Mo (Similar composition to 304, but contains an additional 2-3% Mo)	Better corrosion resistance than 304, suitable for use in marine and chlorinated environments, Excellent performance at temperatures above 843°C and below 454°C
200 Series	Reduced Ni content, increased Mn and N content	Reduced Ni content and increased Mn and N content for lower manufacturing costs, but reduced corrosion resistance compared to 304 and 316

* UNS

Abbreviation for the Unified Numbering System for Metals and Alloys
Unified unique numbering system for metals and alloys
A representative number compatible with metals and alloys defined in several material-related codes, including ASTM, AISI, ASME, AWS, etc.

* S : Heat and corrosion resistant (stainless) steel

2. Property

– Corrosion resistance, heat resistance, weldability, resistance to acid and base environment, good machinability

Element	Impact
Cr, Ni	Provides corrosion resistance

[304 Chemical Composition (%)]

C	Mn	P	S
Max. 0.08	Max. 2.00	Max. 0.045	Max. 0.030

Si	Cr	Ni	N
Max. 0.75	18.0~20.0	8.0~10.5	Max. 0.10

[304 Mechanical Properties]

Tensile Strength (Mpa)	Yield Strength (Mpa)	Elongation (%)
Min. 515	Min. 205	Min. 40

[304 Physical Properties]

Density (g/㎤)	Melting Range (℃)	Specific Heat (0-100℃), J/kg*℃
8.0	1400~1450	500

3. Standard & Specification

– Specification : UNS S30400

AMS	5501, 5513, 5560, 5565, 5566, 5567, 5639, 5697
ASME	SA182, SA194, SA213, SA240, SA249, SA312

Product Form	ASTM
Bar, Rod	A276, 276M
Plate, Sheet, Strip	A240, A240M

4. Available Form

– Bar, Rod

– Plate, Sheet, Strip

– Coil, Wire

– Tube, Pipe

– Fittings

5. Application & Product

– Medical, Construction, Chemical, Automotive, Food

Application	Product
Medical	Surgical instruments, implants
Construction	Exterior wall cladding, handrails, door handles
Chemical	Storage tanks, pipelines
Automotive	Exhaust systems
Food	Kitchen utensils, cookware, food processing equipment