forging of 17-4 PH steel 2

[mk2003]

i am working in a valve manufacturing company. we plan to change the material used for gate and plug valves.

Before my joining my collegues forged the 17-4 PH steel but it was cracked. they tired again and left that plan.
note: they are all basically from mechanical background.
since i am the metallurgist in the company, i am facing lot of problems.

please give the exact forging temperature and soaking time before forging and all details

MK

 

[TVP]

The following data is from Carpenter, one of the largest producers of 17-4 PH stainless steel:

Heat uniformly to 2150/2200°F (1177/1204°C) and hold one hour at temperature before forging. Do not forge below 1850°F (1010°C). To obtain optimum grain size and mechanical properties, forgings should be cooled in air to below 90°F (32°C) before further processing. Forgings must be solution treated prior to hardening.

You can obtain more information from their website:

http://www.cartech.com

 

[Maui]

17-4PH is a precipitation hardening stainless steel that is usually supplied in the solution annealed condition, i.e. annealed at 1900 F and cooled to room temperature. This treatment produces a low-carbon martensite upon cooling to room temperature which results in a hardness of 30 to 35 HRC. Machining can be more easily performed on material supplied in this condition. Subsequent hardening is accomplished by holding at temperature between 925 F and 1150 F for one hour per inch of thickness (4 hours minimum) and cooling to room temperature.

Material for forging is typically supplied in the overaged condition. This is accomplished by holding solution annealed material at 1150 F. Material in this condition may be readily cold sawed (abrasive wheel cutting is not recommended due to the possibility of cracking). For cross sections less than 16 square inches the recommended forging temperature is 2150 F. For larger cross sections a lower forging temperature should be used. Charging thick sections into too hot of a furnace may result in internal cracking due to the relatively high internal stresses developed. If it is necessary to re-heat during forging, the steel should be charged into a furnace at 2150 F. Heating time should be 30 minutes per inch of thickness, with a minimum soak time of 15 minutes for thin sections. A uniform temperature distribution in the forging results in uniformity of mechanical properties, and so reduces the probability of cracking during forging. Make sure thsat the parts are heated uniformly.

Cooling after forging should also be controlled to some extent. Sections greater than 3 inches and small intricate sections should be returned to the heating furnace and equalized at the forging temperature prior to cooling. Temperature equalization reduces the chances of cracking during cooling. Sections under 6 inches in thickness may be air cooled, while thicker sections should be covered with a light gage steel sheet during cooling. I hope that this helps.


Maui

 

[mk2003]

From MK2003

Thankyou TVP,
we brought the material from the carpenter only. the same procedure we had given to our vendor last week, possibly this weekend or next week we will forge with this procedure.

Maui, thousands of thanks to you for your valuable information.
Thanks to eng-tips

M Karthikeyan

 

[BobUXL]

You will also need to make sure you have forge quality 17-4. Many mills will have a couple of flavors of 17-4. One flavor will suit the machining inductry and the other forgers. The forge quality type of material has reduced levels of sulfur that will reduce cracking tendencies.