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17-4PH stainless steel introduction

17-4pH alloys are precipitated, quenched, martensitic stainless steels, and this grade has high strength, hardness (up to 300 C/5000 C) and corrosion resistance. After heat treatment, the mechanical properties of the product are more perfect, and the compressive strength can reach up to 1100-1300 mpa (160-190 kSi). This grade is not intended for use above 300 0C (572 0F) or very low temperatures. It has good corrosion resistance to atmospheric and diluted acids or salts, as is the case with 304 and 430.

17-4PH stainless steel application field

Offshore platforms, helicopter decks, other platforms

The food industry

Pulp and paper industry

Aerospace (turbine blade)

Mechanical components

Nuclear waste barrels

17-4pH stainless steel standard

ASTM... A 693

ASME... SA 693

AMS... 5604

17-4PH stainless steel features - Corrosion resistance

The corrosion resistance of 17-4pH alloy is superior to that of any other standard hardened stainless steel plate. In most cases, it is no less resistant to corrosion than 304.

If there is a risk of STRESS corrosion cracks, the higher curing temperature must be above 550°C (1022°F) and preferably 590°C (1094°F).

The optimum tempering temperature in chloride medium is 550°C-1022°F.

The optimal tempering temperature in H2S medium is 590°C-1094°F.

The alloy is vulnerable to corrosion or crack corrosion in static seawater.

It has the same corrosion resistance as class 304L in petrochemical, food processing and paper industries.

• Chemical composition of 17-4PH stainless steel

• C	Cr	Ni	Cu	Nb/Cb	Mn
  0.04	16.5	4.5	3.3	0.3	0.7
  PREN (%Cr+3.3%Mo+16%N)≥17

• Mechanical properties of 17-4pH stainless steel

• heat treatment	YS 0.2%		UTS
  	N/mm		N/mm
  	Min.	Typ.	Min.	Typ.
  A	1070	1207	1170	1310
  B	790	931	965	1034
  heat treatment	YS 0.2%		UTS		El%
  	ksi		ksi
  	Min.	Typ.	Min.	Typ.	Min.	Typ.
  A	155	175	170	190	8	14
  B	115	135	140	150	10	17

17-4pH stainless steel heat treatment processing

Hot forming

Hot forming should be carried out in the temperature range of 950-1200°C (1742-2192°F). Complete heat treatment includes solid melt annealing, cooling (below 25°C), and curing (at established temperatures).

Cold forming

Cold forming can only be carried out on the soft sheet, and the conditions are more strict. After cold working, stress corrosion resistance can be enhanced by secondary curing at quenching water and hardening temperature.

The processing procedures are as follows: rolling, bending, hydrogen reforming, etc. (soft state).

cutting

Thermal cutting (plasma, saw, etc.) : This grade of cutting procedure should be appropriate to allow for thermal deterioration. After cutting, grind to remove the oxide layer.

Mechanical cutting: cutting, stamping, cold saw, etc.

welding

17-4pH alloy can be used for the following welding: SMAW, GTAW, PAW and GMAW. The SAW welding can be carried out only after preliminary tests (check for cracks and toughness of weld metal).

The possibility of hot cracking and thermal metamorphism of weld metal is reduced due to the curing of ferrite.

In general, no preheating is required and the intermediate temperature should be kept at 120°C (248°F). After a complete heat treatment (solid melt annealing + quenching hardening), the toughness will be enhanced.

Due to its own martensitic structure characteristics, the low oxygen content in the weld metal keeps good toughness and ductility. In order to avoid cold cracking, hydrogen intervention should be avoided as much as possible.

17-4pH alloys can be used with the same filler metal (E 630 (AWS A5.4)? ER 630 (AWS A5.9) for welding.

If the mechanical properties of 17-4pH do not need to be considered during welding, the austenitic filler metal can also be used without heat treatment.

17-4PH stainless steel machining

It is possible to machine17-4pH alloys that have been solution treated or quenched and hardened. The processing conditions vary with the hardness of the material. We usually use high - speed cutting tools or lubricated carbonized knives for machining. If the customer is very strict with tolerances, we should also take into account dimensional changes that may occur during heat treatment.