Chemical Formula
Fe, <0.15% C, 12.0-14.0% Cr, <1.25% Mn, <1.0% Si, <0.06% P, >0.15% S
Topics Covered
Introduction
Key Properties
Composition
Mechanical Properties
Physical Properties
Grade Specification Comparison
Possible Alternative Grades
Corrosion Resistance
Heat Resistance
Heat Treatment
Welding
Machining
Applications
Introduction
Grade 416 steel is a free-machining stainless steel with a machinability of 85%, highest of all stainless steels. With most of the free-machining stainless steels, the machinability can be improved by adding sulphur, which leads to the formation of manganese sulphide inclusions. Addition of sulphur also reduces the formability, weldability and corrosion resistance of 416 steels to below that of grade 410. Because of their high machinability and low cost, grade 416 steels are available in highly tempered, hardened or unhardened forms.
Martensitic steels with high hardness are manufactured using methods that require final hardening and tempering treatments. The corrosion resistance of these steels is lower than that of austenitic steels. Decrease in the ductility of martensitic steels at sub-zero temperatures, and strength at high temperatures due to over-tempering, are the two key factors that affect their operating temperatures.
Key Properties
The following sections will discuss the properties of grade 416 steel bar products of ASTM A582. The specified properties may not be similar to other forms such as forgings and wires.
Composition
The chemical composition ranges of grade 416 stainless steels are given in the following table:
Table 1 - Composition ranges for grade 416 stainless steels
|
Grade
|
C
|
Mn
|
Si
|
P
|
S
|
Cr
|
Mo
|
|
416
|
min.
max.
|
-
0.15
|
-
1.25
|
-
1
|
-
0.06
|
0.15
-
|
12
14
|
-
0.6
|
Mechanical Properties
The table below provides the mechanical properties of grade 416 stainless steels:
Table 2 - Mechanical properties of grade 416 stainless steels
|
Tempering Temperature (°C)
|
Tensile Strength (MPa)
|
Yield Strength
0.2% Proof (MPa)
|
Elongation
(% in 50mm)
|
Hardness Brinell
(HB)
|
Impact Charpy V (J)
|
|
Annealed *
|
517
|
275
|
30
|
262
|
-
|
|
Condition T **
|
758
|
586
|
18
|
248-302
|
-
|
|
204
|
1340
|
1050
|
11
|
388
|
20
|
|
316
|
1350
|
1060
|
12
|
388
|
22
|
|
427
|
1405
|
1110
|
11
|
401
|
#
|
|
538
|
1000
|
795
|
13
|
321
|
#
|
|
593
|
840
|
705
|
19
|
248
|
27
|
|
650
|
796
|
670
|
17.5
|
253
|
38
|
* Annealed properties are typical for Condition A of ASTM A582.
** Hardened and tempered Condition T of ASTM A582 - Brinell hardness is specified range, other properties are typical only.
# Tempering of this steel at temperatures of 400 to 580°C should be avoided due to low impact resistance.
Physical Properties
The key physical properties of annealed grade 416 stainless steels are tabulated below:
Table 3 - Physical properties of annealed grade 416 stainless steel
|
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
|
|
416
|
7800
|
200
|
9.9
|
11
|
11.5
|
24.9
|
28.7
|
460
|
570
|
Grade Specification Comparison
The following table outlines the grade comparisons for 416 stainless steels:
Table 4 - Grade specifications for grade 416 stainless steels
|
Grade
|
UNS No
|
Old British
|
Euronorm
|
Swedish SS
|
Japanese JIS
|
|
BS
|
En
|
No
|
Name
|
|
416
|
S41600
|
416S21
|
56AM
|
1.4005
|
X12CrS13
|
2380
|
SUS 416
|
Possible Alternative Grades
Appropriate alternatives to grade 416 stainless steels are given in the table below:
Table 5 - Possible alternatives to 416 grade stainless steels
|
Grade
|
Why it might be chosen instead of 416
|
|
410
|
The high machinability of 416 can be sacrificed to gain better corrosion resistance and formability.
|
|
303
|
A slight drop in machinability to gain better availability. Grade 303 is non-hardenable.
|
|
182
|
A free-machining Ferritic grade with better "soft magnetic" performance for solenoid shafts. Grade 182 is non-hardenable.
|
Corrosion Resistance
Grade 416 steels are highly resistant to acids, alkalis, fresh water and dry air. However, they are less corrosion resistant than non-free-machining steels, austenitic grades and grade 430 Ferritic alloys with 17% chromium. These steels are hardened to obtain maximum corrosion resistance and smooth surface. 416 free-machining grades with high sulphur content are inappropriate for chloride and marine environments.
Heat Resistance
Scaling resistance of grade 416 steels under intermittent conditions can be extended up to 760°C, and up to 675°C under continuous operations. Considering the sustainability of mechanical properties, 416 steels should not be employed at temperatures greater than the standard tempering temperatures.
Heat Treatment
Full Annealing - Grade 416 steel can be annealed at temperatures of 815 to 900°C for ½ h. This process is followed by cooling at 30°C for an hour and air-cooling.
Sub-Critical Annealing - Grade 416 steel is heated to 650 to 760°C and air-cooled.
Hardening – This process involves heating grade 416 steels to 925 to 1010°C, oil quenching and tempering to improve mechanical properties. Tempering should not be carried out at temperatures ranging from 400 to 580°C, owing to poor ductility of grade 416.
Welding
Grade 416 steel exhibits poor weldability. Welding can be carried by pre-heating 416 steels to 200 to 300°C, followed by re-hardening, annealing or stress relieving at 650 to 675°C.
Grade 410 low hydrogen electrodes can be used for welding purposes. Grade 309 filler rods can also be used for materials that require moderate hardening.
Machining
Grade 416 steels offer the highest machinability of any stainless steel in their sub-critical annealed condition.
Applications
Some of the major applications of grade 416 stainless steels are listed below:
-
Valves, pump shafts and motor shafts
-
Parts of washing machines
-
Gears, bolts, nuts and studs
-
Automatic screw-machined components