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| Properties |
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Chemical Properties |
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The chemistry offered is derived from the parent AISI 200 series, with suitable technical modifications to achieve the final properties in a cost effective manner as compared to the existing 304 Grade SS.
Literature survey reveals that AISI 200 series were developed in 1950's in the United States, that development was strictly by the nickel shortage which was prevalent at that time.
The composition of these Steels varied widely with carbon ranging from 0.08 to as high as 0.25% ,nickel from 0.3 to around 7% ,Nitrogen from 0.10 to 0.4% with a chromium level of 14 to 18%.The technical theme behind development of these grades was mainly to substitute the costly nickel with manganese and nitrogen to achieve the austenitic structure by controlling the ratio of austenite forming elements and ferrite forming elements ( Ferrite Factor )
The drawbacks with these steels were higher carbon ( > 0.1%) and higher nitrogen resulting into poor cold formability characteristics. With these back ground a new chemistry was designed in which the carbon is controlled to a maximum level of 0.09% and nitrogen upto 1700ppm to aid in formability addition of Copper is made so that the work hardening rate is controlled.
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Thus the optimized chemistry offered by us is |
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Grade |
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SI4 |
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S |
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0.015 |
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C |
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0.07-0.09 |
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Ni |
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0.75-0.95 |
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Mn |
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9.2 - 9.4 |
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Cr |
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14.8-15.2 |
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Si |
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0.4 -0.6 |
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Cu |
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1.7-1.9 |
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P |
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0.075 |
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N2 |
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1550-1750 |
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Physical Properties |
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| Physical properties of annealed AISI 200 Series |
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| Density |
gr/cu.cm |
7.74 |
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| lb/cu.in |
0.28 |
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| Thermal Conductivity |
20-100°C Cal/cm/sec/°C/cm |
0.039 |
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| 68-212°C Btu/ft2/hr/°F/ft |
9.4 |
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| Specific Heat |
0-100°C Cal/gm/°C |
0.122 |
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| 32-212°F Btu/lb/°F |
0.12 |
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| Coefficient of Thermal Expansion |
20-100°C cm/cm/°C |
16.6*10^-6 |
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| 68-212°F in/in/°F |
9.2*10^-6 |
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20-316°C cm/cm/°C |
18.0*10^-6 |
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| 68-600°F in/in/°F |
10.0*10^-6 |
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20-538°C cm/cm/°C |
19.6*10^-6 |
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| 68-1000°F in/in/°F |
10.0*10^-6 |
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20-871°C cm/cm/°C |
203*10^-6 |
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| 68-1600°F in/in/°F |
11.3*10^-6 |
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Mechanical Properties |
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200 Series |
300 Series |
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| 0.2% proof stress (kg/mm2) |
35.5 |
26.7 |
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| Tensile Strength (kg/mm2) |
77.2 |
59 |
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| Elongation |
50.0 |
55.6 |
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| GSN |
8-9 |
7.8 |
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| Hv |
208 |
157 |
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| Erchsen value |
12.5 |
12.9 |
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| Limited Drawing Limit |
2.0 |
2.3 to 2.5 |
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Corrosion Properties |
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| Considering that the components manufactured out of these sheets are used in normal atmospheric conditions chromium level 14.5% to 15.5% is quiet to resist pitting corrosion. |
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| Experiments carried out showed the following result |
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• Kitchen utensils and cutleries retained their surface finish and luster similar to 304 Grade
•Laboratories scaled experiments carried out under different media revealed the following data: |
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| Corrosion Rates of the Stainless Steels Fully Immersed in |
| 3% Sodium Chloride |
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| Stainless Steel |
Temperature |
Duration |
Corrosion Rate |
Visual Observation |
| °K |
°C |
(Hour) |
x 10^-2mmpy |
| J |
303±2 |
30±2 |
720 |
2.58 |
Localised Attack |
| S |
303±2 |
30±2 |
720 |
3.29 |
Localised Attack |
| J |
371±2 |
98±2 |
100 |
0.25 |
Material Remained Same |
| S |
371±2 |
98±2 |
100 |
0.43 |
Localised Attack |
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| Corrosion Rates of the Stainless Steels Fully Immersed in Organic Acid Mixture(0.5% Citric Acid+0.5% Tartaric Acid) |
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| Stainless Steel |
Temperature |
Duration |
Corrosion Rate |
Visual Observation |
| °K |
°C |
(Hour) |
x 10^-2mmpy |
| J |
303±2 |
30±2 |
720 |
0.44 |
Fungal growth |
| S |
303±2 |
30±2 |
720 |
0.38 |
Fungal growth |
| J |
371±2 |
98±2 |
100 |
0.34 |
Material Remained Same |
| S |
371±2 |
98±2 |
100 |
0.17 |
Material Remained Same |
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| Dissolution Behaviour of the three stainless steels in 3% NaCl on total Immersion |
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| SS |
Temp°C |
Duration(hours) |
Elements estimated by AAS (ppm) |
| Fe |
Cr |
Cu |
Mn |
Ni |
Ti |
| J |
30±2 |
720 |
0.177 |
0.011 |
0.003 |
0.508 |
- |
- |
| S |
30±2 |
720 |
0.157 |
0.048 |
0.024 |
0.048 |
- |
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| J |
98±2 |
100 |
0.057 |
0.007 |
0.015 |
0.829 |
- |
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| S |
98±2 |
100 |
0.010 |
0.012 |
0.028 |
0.035 |
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| The above data suggest that the corrosion resistant as good as 304 Grade SS under normal atmospheric conditions |
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Formability |
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The blanks cut from the annealed sheets respond favorably to the commonly fabrication operations such as deep drawing ,spinning, welding ,bidding ,rib formation, embossing, electro deposition of metals like Copper and necking of cylindrical parts.
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The quantified data on formability is given below: Limited Drawing
Ration - 2
Percentage Stretch in Spinning - 30%
Erichsen Value - 12.5
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