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SUS416 Stainless Steel

SUS416 Stainless Steel

416 Martensitic Stainless Steel Bar

416 is a free machining basic straight chromium high hardenability martensitic stainless steel with excellent machinability, reasonable strength and corrosion resistance. Generally supplied either hardened and tempered in the tensile range 550 - 700 Mpa (condition P) Brinell range 152 - 207, or in the annealed condition with a maximum Brinell hardness of 207. 

Characterised by excellent machinability, non-galling and non-seizing properties due to its higher sulphur content which has the effect of lowering its corrosion resistance. It is however resistant to mild corrosive atmospheres, fresh water, steam, organic materials, many mild acids and petroleum products, coupled with reasonable strength in the hardened and tempered condition.

416 due to its excellent hardenability is capable of being through hardened up to Rc40 depending upon carbon content and section size. Small sections can be air cooled and larger sections oil quenched for maximum through hardness.

Pre hardened and tempered 416 will also respond readily to nitriding achieving a typical surface hardness of over Rc65. The nitriding process however reduces the corrosion resistance and is therefore not generally recommended except for critical applications where the benefit outweighs all other considerations.

Material magnetic in all conditions.

Chemical Composition Min. % Max. %
*Nickel & Molybdenum addition optional. Carbon 0.09 0.15
Silicon 0 1.00
Manganese     0 1.50
*Nickel 0 1.00
Chromium   11.50  14.00
*Molybdenum 0 0.60
Phosphorous 0 0.06
Sulphur 0.15 0.35

 

Mechanical Property Requirements For Material in the Annealed and Heat Treated - Condition P To AS2837 - 1986 416 and BS970 Part3 1991 416S21

Condition Tensile Strength Mpa 0.2% Yield Strength Mpa
Min
Elongation on 5.65 %
Min
Impact Izod J Min Hardness HB
Min Max Min Max
Annealed             207
P 550 700 340 15 34 152 207

Material stocked generally in annealed condition 76.2 mm dia and larger. 

Material stocked generally in condition P up to and including 63.5 mm dia.

NB. Check the mill certificate if critical for end use.

 

Typical Mechanical Properties At Room Temperature - Annealed and Hardened and Tempered to Condition P

Condition Tensile Strength
Mpa
0.2% Yield Strength
Mpa
Elongation in 50mm
%
Impact Izod
J
Hardness
HB
Annealed 530 290 27 75 160
*P 650 490 24 95 190

*Typical Hardening Temperatures    950 oC - 1020 oC

*Typical Tempering Temperatures    650 oC - 750 oC

 

> Elevated Temperature Properties

While 416 displays a reasonable resistance to scaling in continuous service up to 650 oC, it does however experience a substantial drop in tensile strength, creep and stress rupture strength at relatively low working temperatures. It is also susceptible to hot cracking due to its high sulphur content. 

NB. High temperature use is therefore not generally recommended.


Low Temperature Properties

416 is not recommended for use at sub-zero temperatures due to a substantial drop in impact properties consistent with most steels other than the austenitic steel types.


Cold Bending

416 has limited cold bending properties and it is generally not recommended.


Hot Bending

In the hardened and tempered condition, it is not recommended due to its affect on the mechanical properties within the heat affected zone. Even in the annealed condition it should also be avoided if possible due to its susceptibility to hot cracking.


Corrosion Resistance 

416 due to its higher sulphur content has lower resistance to all corrosion types than grade 410, and indeed all of the 400 series martensitic stainless steels. 

Its selection therefore is generally based upon its excellent machinability coupled with its lower corrosion resistance capabilities.

NB. It has optimum corrosion resistance in the hardened and tempered condition and is not therefore recommended for use in the annealed condition.

It is most important that oxygen is always allowed to circulate freely on all stainless steel surfaces to ensure that a chrome oxide film is always present to protect it. If this is not the case, rusting will occur as with other types of non stainless steels.

For optimum corrosion resistance surfaces must be free of scale and foreign particles.

Finished parts should be passivated.

 

Forging

Heat uniformly to 1150 oC - 1200 oC, hold until temperature is uniform throughout the section. 

Do not soak but commence forging immediately.

Do not overheat as this can cause a loss of toughness and ductility.

Do not forge below 900 oC

Finished forgings should be cooled slowly in air, ashes or dry lime etc. to room temperature and annealed immediately.

NB. Severe upset forging of this grade is not recommended.

 

Heat Treatment

Sub-Critical Annealing

Heat uniformerly to 650 oC - 750 oC as required, hold until temperature is uniform throughout the section. 

*Soak as required, cool in air.

Annealing

Heat to 820 oC - 900 oC, hold until temperature is uniform throughout the section. *Soak as required. Cool in furnace.

Hardening

Heat to 950 oC - 1020 oC, hold until temperature is uniform throughout the section. *Soak as required. 

Quench in oil or air cool. Temper immediately while still hand warm.

Nitriding

Prior to nitriding, the chrome oxide film which protects the surface must be broken down by pickling or fine sand blasting. 

Nitriding is carried out at 500 oC - 550 oC followed by slow cooling (no quench) reducing the problem of distortion. Parts can therefore be machined to near final size, leaving a grinding tolerance only. Always ensure that the tempering temperature employed during the initial heat treatment was higher than the nitriding temperature otherwise the core strength will be affected.

Tempering (Condition P)

Heat to 650 oC - 750 oC as required, hold until temperature is uniform throughout the section. *Soak as required. Cool in air. 

416 can of course be tempered at much lower temperatures, producing much higher tensile strengths, but with subsequent lower impact properties.

NB. Tempering however within the range 400 oC - 580 oC should be avoided due to the brittleness, resulting in a considerable reduction in impact properties and loss of corrosion resistance.

*Heating temperatures, rate of heating, cooling and soaking times will vary due to factors such as work piece size/shape, also furnace type employed, quenching medium and work piece transfer facilities etc.

Please consult your heat treater for best results.

 

Machining

416 was developed as a free machining grade and has by far the best machinability of all the 400 series martensitic stainless steels. It also has much better machinability than grade 303 free machining austenitic stainless steel and all operations such as turning, drilling, broaching, tapping, milling, reaming and threading etc. can be readily carried out as per machine manufacturers recommendations for suitable tool type, feeds and speeds.

 

Welding

416 is not generally recommended for welding in either the annealed or hardened and tempered condition, due to its high sulphur content resulting in hot cracking or its hardening capability resulting in cold cracking. 

If it is really necessary to weld in either condition the following procedure may be taken as a guide only.

Welding Procedure

Welding electrodes or rods should be low hydrogen types 410 or *similar when strength is required or post-weld hardening and tempering, otherwise an austenitic stainless electrode or rod such as 308 or *similar may be used to give a more ductile weld, when strength is not so critical and post-weld annealing is not possible or intended. 

Pre-heat at 200 oC - 300 oC and keep heat input to a minimum to reduce dilution of sulphur and filler metal. On completion of welding cool slowly as possible until hand warm and as required:

Post-weld sub-critical anneal at 650 oC - 750 oC or full anneal and harden and temper as required.

*Please consult your welding consumables supplier.