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Hardtec Stainless Steel

The highest performing all stainless steel self drilling screw


What is Hardtec Stainless Steel?


Hardtec is a registered brand name of an alloy known as KDS2000 made by Nippon Steel. It is a proprietary stainless grade that has been developed to combine the high corrosion resistance of Austenitic grades like 304 and 316 AND has the hardness of heat treated Martensitic grades like 410 stainless steel. Hardtec has a chemistry very similar to 410 stainless steel; but also has 1% of Molybdenum added to it.

Molybdenum is the element that gives grade 316 its corrosion resistance improvement over grade 304. Marutex and YUS 550 are other material brand names of stainless grades similar to Hardtec.

Hardtec stainless steel offers high levels of corrosion resistance, the decline of which was previously unavoidable with heat-treated grades like 410.

Hardtec Stainless Composition Comparison Table


What about Grade 304, 316, 410 or bi-metal self drilling screws?

There are other stainless steel self-drilling screw options on the market but they each have the following downsides:


304 and 316 grade self drilling screws

All 304 and 316 grade screws have good corrosion resistance but these grades are an Austenitic type of stainless steel and cannot be hardened by heat treatment, therefore they are relatively soft and can only self-drill through very thin aluminium at best.


410 grade self drilling screws

410 grade screws are a Martensitic grade of stainless steel and are hardened by heat treatment making them excellent for self drilling into steel. However 410 has a low PRE value and as such a low level of corrosion resistance. This makes 410 screws unsuitable for exterior coastal environments as they will rust and tea-stain easily.


Bi-metal self drilling screws

Most 304 and 316 self drilling screws that can drill well are actually Bi-metal. That is they have a 304 or 316 head and body and a carbon steel tip. The tip might have a protective coating such as Ruspert or similar. These screws drill well and are ok if it is acceptable for the tip to rust away, but they are not fully stainless steel and the carbon steel tips risk rusting and bleeding.


How well do Hardtec Stainless Steel screws perform?

Hardtec is stronger than both 304, 305 grade and 410 grade stainless.

Strength tests show that Hardtec screws have:

  • 18% more torsional strength than 410 self-drilling screws
  • 231% more torsional strength than 305 self-drilling screws
  • 18% more tensile strength than 410 self-drilling screws
  • 85% more tensile strength than 305 self-drilling screws
  • 26% more shear strength than 410 self-drilling screws
  • 80% more shear strength than 305 self-drilling screws

Hardtec Torsional Strength Chart


Hardtec is harder and better at self drilling through metal than 304/305 grade stainless and is similar to grade 410.

Hardness tests show that Hardtec has a surface hardness similar to that of grade 410 and 50% than that of 304, enabling it to self drill into metal. It's core hardness is 88% greater than 304 and even 18% greater than Carbon Steel (SWCH18A).

Hardtec Stainless Surface Hardness Comparison Chart


Hardtec is at least similar, but in practice slightly superior in corrosion resistance to grade 305 and 304.

Corrosion tests show that:

410 Screws have rust appearing after 48 hours of salt spray testing. Hardtec screws have no rust appearing after 1000 hours of salt spray testing, the same as grade 305 stainless.

Hardtec Stainless Salt Spray Test Comparison Table

Hardtec Salt Spray Tea-stain Test Comparison


Stainless Hardtec Self Drilling Screws Stainless Hardtec Csk Self Drilling Screw
Hardtec HWF Self Driller Hardtec CSK Self Driller

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