Nippon Metal Industry (NTK)
D Series is an Austenitic Stainless Steel that NTK has succeeded to produce the stainless steel for 75years in large quantities for the first time in Japan.
D Series was made from the manufacturing experience results of 300 types of grades including the original steel kind.
D Series contain lower nickel that is a main element of SUS304, and collects the scrap by an original route in recycling in order to saving the resource.
Feature
- Decrease the amount of nickel content.
- It is difficult to stick with magnet.→Non-magnetism
- It is similar process ability with SUS304→Workability
- It is similar corrosion resistance with SUS304→Corrosion resistant
- It can be welded in the similar condition with SUS304→Weldability
Physical properties of D-series is almost same to that of SUS304, however, these have an advantage that the quantity of products can be obtained greater than SUS340 as its weight is lighter than SUS304's.
Mechanical properties of D-7S have higher tensile strength, proof stress and hardness than SUS304’s which show the most highest strength. When processing, it requires greater workload than the case of SUS304. Thickness can be reduced as it has high strength prosperities. The elongation of D-7S is 10% less than that of SUS304, a special attention is necessary in the case of processing like a bulging requiring high elongation.
D-10S have most close properties with SUS304 among D-series grade.
D-11 have slight higher tensile strength, proof stress and hardness than SUS304, positions the middle properties between D-7S and D-10S.
NTK D series Chemical Composition
D series has added chrome by 17% or more.
- D-7S (saving resource grade of D-7) is a stainless steel that saved the nickels which contains 2.5% nickel.
- To make it near the characteristic of SUS304, D-10S (saving resource grade of D-10) is assumed to contain nickels by 4.5%.
- The characteristic of D-11 is in the middle of D-7S and D-10S. D-11 applies to the EN1.4372 standard for a base.
Chemical Composition
| Type | Ni | Cr | Mn | Cu |
| D-7S | 2.5 | 17.5 | 6.0 | 2.5 |
| D-11 | 3.5 | 17.5 | 6.0 | 2.5 |
| D-10S | 4.5 | 17.5 | 4.0 | 2.5 |
| 304 | 8.0 | 18.0 | 1 | - |
NTK D-series Non-magnetism
D series steel does not wear magnetism easily as well as SUS316. SUS304 does not go out magnetism easily after its processing.
■ Magnetic Characteristic
NTK D series Workability
D series steel has good workability that is an equal and similar projection character and squeezing character with SUS304.
■ Cold Workability (Erichsen Test result)
| NTK D-7S | NTK D-10S | NTK D-11 | SUS304 | SUS436L |
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| NTK D-7S | NTK D-10S | NTK D-11 | SUS304 | SUS436L | |
| Erichsen value (mm) |
12.9 | 13.2 | 13.0 | 13.2 | 9.3 |
| Limit draw ratio (L.D.R.) |
（2.1） | 2.1 | 2.1 | 2.1 | 2.2 |
| Conical cup value (mm) |
37.9 | 37.6 | 37.8 | 38.0 | 39.5 |
NTK D series Corrosion Resistance
D series has corrosion resistance near the characteristic of SUS304.
■ Atmospheric Corrosion TestSagamihara City( About 30km from coast side) ：2 month
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| NTK D-7S | NTK D-11 | NTK D-10S | SU304 | SUS436L |
■ Salt Spray Test (5%NaCl Mist Spray)
| Before |  |
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| 500h |  |
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| 1000h |  |
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| NTK D-7S | NTK D-10S | NTK D-11 | SUS304 | SUS436L |
※The corrosion resistance is influenced by various factors, it is necessary to execute the examination of prior to the usage condition.
NTK D series Weldability
D series can be almost welded with SUS304 under the condition.
| Type | Microstructure of Weld zone | Macro photography | characteristics |
| D-7S |  |
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The grain coarsening can not be observed as well as SUS304. |
| D-11 |  |
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| D-10S |  |
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| SUS304 |  |
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| SUS436L |  |
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The grain coarsening can be observed. |
※The process ability in D series weld is equal to SUS304.
When use the fill metal that can be used the same as SUS304.
The welding with SUS304 is also easy.
NTK D-series Example of usage
- D-7S
Reefer Container、Barbecue Ware、Cabinet、Ornamental Tube、Building Hardware
- D-10S
Mug Cup、Grain Tank、Paint Churning Tank
- D-11
Table Ware、Electric Pot、Pot
