I assume you are familiar with stainless steel as it is widely used in many electrical appliances in our daily lives.
For example, the commonly used electric kettle.
Observant individuals may have noticed that there are groups of numbers on the inner wall of the electric kettle, some of which are 304 and others are 316.
So what do these numbers indicate and what sets them apart?
Today I will clarify this mystery.
See too:
- Stainless steel 304, 304L, 316, 316L: the definitive difference
304 and 316 are codes for different types of stainless steel. Although both are considered stainless steel, they have distinct differences.
Let's examine the chemical composition, physical properties, mechanical properties, national brands, characteristics and applications of these two types of stainless steel.
Comparison of chemical compositions of 304 and 316 stainless steel
| Chemical composition: | 304 | 316 |
| C (carbon) | ≤0.08 | ≤0.08 |
| Si (silicon) | ≤1.00 | ≤1.00 |
| Mn (manganese) | ≤2.00 | ≤2.00 |
| P (phosphorus) | ≤0.045 | ≤0.045 |
| S (sulfur) | ≤0.030 | ≤0.030 |
| N (nickel) | 8:00 ~ 11:00 | 10am~2pm |
| Cr (chromium) | 6:00pm~8:00pm | 4pm~6pm |
| Mo (aluminum) | 2:00~3:00 |
Comparison of physical properties of 304 and 316 stainless steel
| Physical performance parameters | 304 | 316 | |
| Density / (kg/ dm3 ) 20 ℃ | 7.93 | 8:00 am | |
| Cooking point / ℃ | 1398-1454 | 1370-1397 | |
| Specific heat capacity / (kJ / (kg K)) 0 ℃ ~ 100 ℃ | 0.50 | 0.50 | |
| Thermal conductivity / (w / (m·k)) | 100°C | 16.3 | 16.3 |
| 500℃ | 21.5 | 21.5 | |
| Linear expansion coefficient / (10 – 6 /k) | 0℃~100℃ | 17.2 | 16.0 |
| 0℃-500℃ | 18.4 | 18.5 | |
| Resistivity / (Ω mm 2 / M) 20 ℃ | 0.73 | 0.74 | |
| Longitudinal elastic model / (KN / mm 2 ) 20 ℃ | 193 | 193 | |
| Magnetic | anything | anything | |
Comparison of 304 and 316 stainless steel grades in different countries
| Comparison of stainless steel grades from various countries: | 304 | 316 | |
| ChinaGB/T20878-2007 | Uniform numeric code | S30408 | S31608 |
| New brand | 06Cr9Ni10 | 06Cr17Ni12Mo2 | |
| Old brand | 0Cr18Ni9 | 0Cr17Ni12Mo2 | |
| America ASTM A959-04 |
S30400 304 |
S31600 316 |
|
| Japan JIS G4303-1998 JIS G4311-1991 |
SUS304 | SUS316 | |
| International IS0/TS 15510:2003 ISO4955:2005 |
X5CrNi18-10 1.4301 |
X5CrNiMo17-12-2 1.4401 |
|
| European EN 10088:1-1995 EN10095-1999 |
X5CrNi18-10 1.4301 |
X5CrNiMo17-12-2 1.4401 |
|
Observation:
The chemical composition, physical performance and comparison of stainless steel grades in different countries are based on the national standard for stainless steel and heat-resistant steel grades and chemical compositions (GB/T 20878-2007).
Comparison of mechanical properties of 304 and 316 after solid solution treatment
| Mechanical properties after solution treatment | 304 | 316 | |
| Specified plastic extension force R p0.2 /MPa | ≥205 | ≥205 | |
| Tensile strength R eu / MPa | ≥515 | ≥515 | |
| Elongation after fracture A/% | ≥40 | ≥40 | |
| Hardness value | HBW | ≤201 | ≤217 |
| HRB | ≤92 | ≤95 | |
| High voltage | ≤210 | ≤220 | |
Comparison of the mechanical properties of states 304 and 316H 1/4
| Mechanical properties in the H 1/2 state | 304 | 316 | |
| Specified plastic extension force R p0.2 /MPa | ≥515 | ≥515 | |
| Tensile strength R eu / MPa | ≥860 | ≥860 | |
| Elongation after fracture A/% | Thickness <0.4mm | ≥10 | ≥10 |
| Thickness: 0.4mm ~ <0.8mm | ≥10 | ≥10 | |
| Thickness ≥ 0.8mm | ≥12 | ≥10 | |
Comparison of the mechanical properties of states 304 and 316H 1/2
| Mechanical properties in the H 1/2 state | 304 | 316 | |
| Specified plastic extension force R p0.2 /MPa | ≥760 | ≥760 | |
| Tensile strength R eu / MPa | ≥1035 | ≥1035 | |
| Elongation after fracture A/% | Thickness <0.4mm | ≥6 | ≥6 |
| Thickness: 0.4mm ~ <0.8mm | ≥7 | ≥7 | |
| Thickness ≥ 0.8mm | ≥7 | ≥7 | |
Characteristics and uses
304 stainless steel is a widely used, heat-resistant type of stainless steel that can be found in food equipment, general chemical equipment, and the atomic energy industry, among others.
On the other hand, 316 stainless steel has better corrosion resistance compared to 06Cr19Ni0 in seawater and other environments. It is mainly used for applications that require corrosion resistance.
Heat Treatment Schedule
Both 304 and 316 stainless steel undergo the same heat treatment process.
The heat treatment temperature is ≥ 1040 ℃ and is cooled with water or other rapid cooling method.
Note: The information in the mechanical property tables for solid solution treatment, H1/4 and H1/2, as well as the characteristics, applications and heat treatment system, are all from the national standard for cold-rolled stainless steel sheets and strip (GB/T 3280-2015).
Difference between 304 and 316
The main difference between 304 and 316 stainless steel is in their market applications.
304 stainless steel is generally more affordable than 316 stainless steel and is widely used in various applications, such as kitchen utensils and cutlery, building decoration, food industry, agriculture, ship parts, sanitary ware and automobile parts, among others.
Although a small portion of 316 stainless steel is used in daily life, it is mainly used in equipment exposed to seawater and production equipment that requires strong corrosion resistance.
This is due to the addition of 2-3% molybdenum, which strengthens the structure of 316 stainless steel, making it more resistant to wear and oxidation, and significantly improves its corrosion resistance.
The difference between 304 and 316 stainless steel materials
Forms:
304 stainless steel is mainly used in containers, tableware, furniture, railings and medical equipment that require corrosion resistance. On the other hand, 316 stainless steel is mainly used in the food industry, watch accessories, pharmaceutical industry and surgical equipment.
Chloride corrosion resistance:
304 stainless steel is non-magnetic and its metallographic structure remains unchanged even after heat treatment.
However, the addition of the element molybdenum gives 316 stainless steel a unique corrosion-resistant structure, resulting in greater resistance to chloride corrosion. This type of stainless steel is also commonly referred to as “marine steel”.
Extension:
316 stainless steel is a type of austenitic stainless steel that is characterized by its better corrosion resistance and resistance to high temperatures, thanks to the addition of Mo. It has a high temperature resistance of up to 1200-1300 degrees and is suitable for use in harsh conditions.
On the other hand, 304 stainless steel is a common type of stainless steel with a density of 7.93 g/cm3. It is also known as 18/8 stainless steel in the industry and is capable of withstanding high temperatures of up to 800℃. It has good processing performance and high toughness and is widely used in various industries, including furniture decoration, food and medical industries.
Stainless steel is a term used to describe stainless and acid-resistant steel. Steel that is resistant to air, steam, water and other weak corrosive media or rust is called stainless steel, while steel that is resistant to corrosive chemical media (such as acid, alkali, salt, etc.) is called acid- resistant steel.
Stainless steel has excellent inherent resistance to corrosion and can maintain its physical and mechanical properties even at high temperatures. It is also widely used in the field of 3D printing.
