304 is a low carbon modification of 302 SST (which is the general purpose austenitic or 18-8 SST) for restriction of carbide precipitation during welding. 304L is a lower carbon modification of 304 for further restriction of carbide precipitation during welding. Max carbon in 304 is 0.08 versus 0.15 in 302 and 0.03 in 304L.

316 is more corrosion resistant than 302 and 304, with higher creep strength, primarily due to the higher Nickel content. 316L is again primarily used for welded construction. 316 has the same carbon content as 304 and 316L as 304L.

302 304 304L 316 316L

Cr 17/19 18/20 18/20 16/18 16/18

Ni 8/10 8/12 8/12 10/14 10/14

C max 0.15 0.08 0.03 0.08 0.03

Mn max 2.0 2.0 2.0 2.0 2.0

Si max 1.0 1.0 1.0 1.0 1.0

P max .045 .045 .045 .045 .045

S max .03 .03 .03 .03 .03

Other - - - Mo 2.0/3.0

316L can be used in place of 316 in all applications but the reverse is not true. 316L should be used for welded structures requiring high corrosion resistance. 316L is more expensive than 316 in most regions of the world.

Sir,

Can you please define more briefly creep strength of a material and also the effect of carbide Preciptation during welding.

Regards,

Day Antony

Creep is the flow or plastic deformation of metals held for long periods of time at stresses below the normal yield strength. This effect is particularly important if the stress occurs in the vicinity of the recrystallization (the formation of crystals by the atoms assuming definite positions in a crystal lattice. This is what happens when a liquid metal solidifies.) temperature of the metal.

Carbide precipitation (or more properly chromium-carbide precipitation) is a chemical reaction that sometimes occurs in chrome-nickel SST in which the chromium, near the boundaries of the grains, flows to the boundaries and unites with carbon, thus forming chrome carbides and depleting the chromium supply in the metal near the grain boundaries. This makes the steel susceptible to intergranular corrosion when brought into contact with various acids or alkalis. Failures due to intergranular corrosion are brittle.

Hi, A question slightly off the chemical compostion side of things but related to SS304 heat resistance:

The data sheets for SS304 note a maximum operating temperature of 1600°F to 1700°F. But what happens after these temperatures? For example, I am looking at using SS304 for a protective plate to cover the edge of wall insulation in an industrial furnace. The plate only serves to protect the edge while the furnace is cool and loading equipment might damage the insulation. While the furnace is in operation, the plate is under not under any load therefore creep resistance is unimportant. Effectively, what I need is simply a plate that won't warp/deform under repetitive heat ups to 2300°F (6 hours per heat up, once per day). We usually use SS310 and other high temperature alloys RA253, RA330 etc, but because of their high costs we would like to see of SS304 might be sufficient in this application. What I would like to know is what is likely to actually happen to the SS304 plate when exposed to higher than recommended serviceability temperatures (up to 2300°F)?

Regards!

Dear sir/Mam.

Can you please send me the details regarding tool materials used for Machining SS316L.

Thank you.

AISI 304 SS (carbon content ~0.08%)is the workhorse in Industrial Use and can be used with a good performance in less demanding environment in non-welded form. But with pipelines,heat -exchangers, reactors, reboilers etc. to avoid intergranular corrosion AISI 304L (carbon Content ~ 0.03%)is preferred but the environment has high halide content like Chloride Mo addition is needed and the resultant material is AISI 316 (18Cr-8Ni-2Mo) and welded virsion is AISI 316 L (~0.03% C) to avoid high temperature effect of welding like Intergranular Corrosion (IG)and IG stress corrosion cracking. Let me know, wheteher your query is satified?

Sir,

an you please explain me in brief the terminology Intergranular Corrosion and Intergranular stress corrosion cracking.

Thank you for responding to my comments

Regards

Day Antony.

You are rigth. We have been repairing these SS Turbine Runners for the last 25 years and in the very beginning we found that the cavitation erosion was heavier on the heat affected zone (at that time, the welding repairing procedure from the manufacturer ask for 309-16 welding rods without preheating and peening). We suspected of the sensitization problem and consulted the manufacturer and together we found that the 309-L16 welding electrode works, an perform over the year, better than the 309-16. We would like to point that the important thing here is to find a solution to a problem through different thinking or approaches. Hope this simple case enlights our general konwledge on this and other related fields. regards. Luis

Thank You.

we normally recommend use of E / ER 309 filler metals for (SMAW and GTAW processes respectively ) for welding of 13 Cr / 13Cr-4Ni as well as 17Cr /17Cr-4Ni as this will help to avoid pre heating. and post stres relieving operations. Alternatively E310 will also helps to weld all above 4 types.

For any SS welding most important factors considered are.

1. Use of lower heat input ( to make sure that the weld metal and HAZ should not turn Blueish but always maintain white (or) pale yellow colour to retain Chromium in the weld) to avoid Chromium carbide circles.

2. Right combinations of filler metals .

3. no peening is required and use low carbon version or with stabilizers like E309-Cb, E 347, E321 etc., to avoid or reduce corrosion.

Sridhar.

Hola Sridhar.

Thanks for your comments. Do you have this information on .pdf so We can have a copy for using on our next cavitation repair?

Thanks againg. llizarraga@pancanal.com Regards.

Luis

SRIDHAR;

I am preparing a thesis about sand erosion of hydroturbine blades. So i need some information about welding 17Cr4Ni PH Steel.

Can you please give me more information about weldability of 17Cr4Ni?

Sridher,

I will appreciate if you can kindly inform me selection of SS 316 or SS 316L for the impulse tubing where joints are made with compression tube fittings and not by welding. So can we go ahead with SS 316 instead of SS 316L and save money? This is requirement for offshore project with climatic condition too Sevier duty humidity, high temperature etc. Your reply with a supporting references/copy will help me to get the approval.

Please also send your reply to bhautik.vaidya@gmail.com

Your earliest reply will be appreciated.

Thanks and regards,

Bhautik V. vaidya

Dear Vaidya and others in the forum,

Is there any recommendations to question raised by Vaidya (see below). We are also in similar dilemma and hence are keen to know the industry experts opinion on the same.

"I will appreciate if you can kindly inform me selection of SS 316 or SS 316L for the impulse tubing where joints are made with compression tube fittings and not by welding. So can we go ahead with SS 316 instead of SS 316L and save money? This is requirement for offshore project with climatic condition too Sevier duty humidity, high temperature etc. Your reply with a supporting references/copy will help me to get the approval.

Please also send your reply to jtmanju@gmail.com

Thanks

Manjunath

Hello to every one in the forum,

We are developing hoses to be used in the hydraulic system of aircrafts. The end fitting is made of SS304 material. I wanted to know the composition of this material. And I happened to stumble upon this site. I, ofcourse, got some valuable inputs from you all. Thank you for the same. Working minds shall certainly be sharing ones. Only then this world will go on. Thanks a lot!!. Contact me at devdoss@yahoo.com for any help. I am in to Indigenisation and vendor development.

there is some error in the temperature range of sensitization. It is mentioned at 615C to 815C or 800F to 1500F. It should be 425C to 870C (800F to 1600F).

Now I have to heat treat SS304 dished end after cold forming at 600C for 2hrs or at 520C for 10hrs. and then furnace cool.

What will be sensitization effect at these temperatures. Which heat treatment is better among two.

Thanks

V.K.Pahwa

WHAT IS THE DIFFERENCE BETWEEN SS316 AND SS316L

In 316L fabricated Axial Flow pumps that are used in seas water and 10% sulfuric acid solutions the weld and its "affected area" need to be protected with a coating. The addition of Belzona abrasion resistant pump coatings has a dramatic effect. Without the coating the weld will disappear and with the coating there is no damage detected. If you are talking about weldments then 316L is the best choice for fabrication. Remember that this class of material will work harden and design the device to minimize bending or forming.

Hola. Stainless Steels particularly the 300 series (s30000) are subject to a heat-treating effect called SENSITIZATION. These steels, when heated in the 427 to 760 C (800 to 1400 F) range, form chromiun carbide. During short exposures at these temperatures, the chromiun carbide forms only at the grain boundry. (This is analogous to the CuAl2 precipitates referred to in aluminun alloy aging treatments.) Thus, the chromiun near the grain boundaries is tied up as carbide and no longer can act as a deterrent to corrosion. The grain boundaries are susceptible to intergranular attack and are anodic to the surrounding grains. In this state, the most highly resistant of the 300 series stainless steels can fail rapidly by corrosion attack in certain media. Sensitized stainless steels can deteriorate completely in the space of hours in strongly acidic solutions.

Through the application of heat, welding may:

1. Induce phase transformations,

2. Cause secondary precipitation,

3. Produce high stresses in and adjacent to welds which can greatly reduce corrosion resistance in these zones.

In the heat-affected zone adjacent to welds, sensitization can occur in austenitic stainless steels which can lead to rapid deterioration and destruction.

During welding, a large variation of thermal expansion occurs between the solidifying molten metal pool and the base metal. Upon solidification, this often can result in high residual tensile stresses. Under certain cicunstances, the highly stressed areas can be susceptible to stress corrosion cracking in a corrosive environment. It is important to stress relieve welds exposed to environments that could cause stress corrosion cracking. Design changes can often eliminate a weld zone which might induce stresses that could lead to stress corrosion failure.

For optimun corrosion resistance, it is important to maintain homogeniety between the weld and base metal. Weld filler-metals should be used which are chemically and electrochemically ( neither strongly anodic nor cathodic to the base metal) similar to the base metals. In addition, any phase transformations which could occur in welding, specially in the heat-affected zone (HAZ), must be considered in estimating the corrosion stability of welded structures.

It is possible to reduce or prevent corrosion by application of the following metallurgical principles

1. Use of high-purity material,

2. Use of alloying additions,

3. Effective heat treatment,

4. Surface coatings, and

5. Knowledge of the metallurgical history of the material, etc

In our case we repair our cavitated stainless steel runner (13Cr. 4Ni cast stainless steel such as CA6NM) with 309L16 welding electrode. The idea is to use an electrode with the lowest carbon content, in order to avoid the chromiun carbide; also we have to preheat to 200 F the area next to the weld and finally some pinning for stress relief. We have used belzona as a coating erosion protection but the cavitation on the runner always remove the coating on the cavitated areas. At the end the best solution is choosing the best electrode and the welding procedure that best works for your application. Regards. Luis. llizarraga@pancanal.com

about alliy：Cr34-Mo40，C%~0.02%

plan to weld with 309L.

QUSTEN: how heated at finished weld?

Hola Zhanqqd. Would you please give us more details on your application? How is the enviroment? Stresses and working conditions? At the end these details will tell you what could be your best welding procedure. Regards. Luis

Can anyone please tell me how to estimate the braking strength of SS304L with respect to temperature?

Suppose I want to calculate Breaking Strength of SS304L at 22C & 160C, how can I do that?

Hi,

Just wondering, after all those discussion from above, How much actually is the difference in pricing for SS304 and SS316?

Thanks,

yvi (sorry i'm not logged-in)

Hello,

This may appear a stupid question but what kind would you recommend for making a stairs rampe? thanks

hi,

i give you info.main difference in betn.ss304 n 316.

it is that ss 316 have molebdenum 1-1.5 % gives good machinability.thats all.

best regards.

durgesh

mobile.09376318005