Fillet Weld Size Based On Plate Thick 4

[Veer007]

Hey guys, so far I got this detail from AISC, Is there any calculation behind this when thinner part exceeds 3/4"? I couldn't get clear detail from J2.2b.

Thanks in advance!!

 

[gtaw]

Get yourself a copy of AWS D1.1. It will provide more details on structural welding, preheat, etc. Generally, prequalified welding procedures will meet the needs for most fabrication with the exception of the need to use a nonlisted base metal, i.e., base metals that are not prequalified.

The maximum size limitation of the fillet weld as a function of the base metal thickness is limited to lap joints. It does not apply to corner, tee, or other situations were a fillet weld is used. As noted, the restriction is to ensure the weld can be measured to verify the size.

D1.1 includes a table that addresses the maximum size limitation of single pass fillet welds and the thickness per layer for groove welds. It also includes limitations for the electrode diameter based on the position of the production weld. I didn't reference the table number because there have been changes in the clause numbering of the 2020 edition in comparison to the 2015 edition.

It will take more than a long weekend to work your way through D1.1 and absorb all the information.

Regarding the minimum size of groove welds and fillet welds, one would calculate the size of the weld based on the load being transferred through the weld and compare it to the minimum size requirement and use the larger of the two. As mentioned in a previous post, the minimum size is a function of heat input to mitigate the probability of developing an undesirable microstructure in the heat affected zone.

In addition to the minimum weld size used to control microstructure, preheat based on the material specification and thickness is specified. The two factors are intended to ensure good ductility by avoiding an undesirable microstructure in the HAZ. There are several methods that can be used to preheat steel and to maintain the minimum specified interpass temperature. Most contractors use gas torches such as propane-air or oxy-acetylene torches.

ASME offers a course titled PD359 Practical Welding Technology that covers many subjects related to welding. The course is offered on-line during the pandemic, but is also offered as a face-to-face seminar when the hotels and restaurants have opened up once again.

Best regards - Al

 

[Veer007]

Hi guys, loads of gratitude for the info. posted above.

Below is the detail from CISC showing the larger weld that you stated above, Is this a special case only to developing full wall strength?

Thanks in advance!!

 

[Veer007]

..

Thanks in advance!!

 

[dauwerda]

What do you mean by special case?

I am not familiar with CISC, but based on the image posted that table is providing tabulated information of fillet weld sizes required to develop the strength of the HSS. These fillet weld sizes would have been developed by running the required weld calculations.

In general, it is not good design practice (due to it being very uneconomical) to size welds in this fashion (developing the full strength of a member) unless it is actually required. As gtaw stated above, weld sizes should be determined by calculating the required size based on actual forces and comparing this size to the minimums presented in table J2.4. The larger of these two sizes should be the weld that is specified.

 

[CANPRO]

Veer007, the table you're showing from CISC is for matching the capacity of the HSS wall if you were to weld something like a baseplate to the end of the HSS. The HSS to base plate weld is creating a T-joint, the max fillet weld size is given for a lap joint. This has been stated in this thread already - you've been given some really good info here and it would be worth it for you to read through it again.

I just took a look at your thread history. I'll take a wild guess and say you're primarily designing connections for a fabricator, and you're new at it. You've also indicated that you work in both the US and Canada. I strongly suggest you read through the US codes provided above as well as CSA W59 (in addition to S16, but I assume you've browsed through the blue book a few times). Based on your recent history here you seem keen to learn - W59 makes for good evening reading and you'll pick up lots of great info that you can put to use immediately.

 

[Veer007]

Guys, I'm totally confused now. Please correct me if I'm wrong

A max fillet weld size should be 19mm.
t-1/16" is for lap joint only. also, we don't exceed 19mm if it is fillet weld right?
But if it is T-joint, there is no max weld size, we could use a fillet weld size more than 19mm? or We could use PJP or CJP whether required,
I could use a 25mm size fillet weld for a 19mm thick plate if it is T-Joint?
From the CISC table 3-46, this is a T-Joint, also we can use fillet weld size larger than HSS wall thickness and weld size can be exceeded 19mm? Right

By the by your guess is absolutely correct.


Thanks in advance!!

 

[CANPRO]

Veer007, I don't think you're totally confused, from your last post I think you understand.

As a summary, your fillet weld size can be limited in the following ways:

[ul]
[li]Joint Geometry - A 1/4" fillet weld can be brought right to the edge of plate, any fillet weld larger than 1/4" must stop at least 1/16" from the edge of the plate. Most common occurrence is probably in a lap joint - refer to dauwerda's graphic posted July 7. However, this could also come into play on a T-joint - say you had a cap plate on an HSS and the plate only overhangs the HSS wall by 3/8", your max fillet weld size is 5/16", since a 3/8" fillet would bring the weld flush with the edge of the cap plate[/li]
[li]Neccssity - The weld need not be stronger than required. Refer to the CISC table you posted. If you're exceeding those fillet weld sizes then you're exceeding the capacity of the member and the additional weld is wasteful.[/li]
[li]Economy - at a certain size fillet, it likely becomes more economical to use some sort of groove weld or revise the joint configuration/design. Not to say there can't be any circumstance where a 19mm fillet makes sense, but there is a good reason you rarely see a fillet weld that size[/li]
[/ul]

Your employer should have weld procedures for various joints and configurations - the procedures should show you the number of layers and passes for various weld sizes and configurations. I suggest taking a look through some of your shops approved procedures.

 

[WinelandV]

Veer007,

You could use a 25mm weld on a 19mm plate in a t-joint. At that point, however, it's unlikely that the weld strength will be the limit state that fails. Using AISC, Table J2.5 indicates that you need to check the shear capacity of the base metal for shear as part of the weld design. Thankfully, AISC provides an easy way to check that, by creating a relationship between the weld size and the part thickness. In the 15th edition of the Steel Construction Manual, Equation 9-2 is useful for determining the minimum thickness you need to develop the full strength of a fillet weld. For your 1" weld:

Steel Grade--------Min. Thickness to develop 1" weld
A500 Gr. B---------0.852"
A500 Gr. C---------0.797"

You can flip the equation around, though, and see what the maximum size of fillet weld is for a given part thickness (such as 19mm/0.75")

Steel Grade------Max weld size (16ths of an inch)
A500 Gr. B-------14
A500 Gr. C-------15

Long story short, you can spec the 1" weld on the 3/4" thick piece in a T-weld, but your capacity will be limited by the base material failure.

 

[Veer007]

Thanks for the info. guys, from my last post my understanding is correct where I put question mark?

Thanks in advance!!

 

[Veer007]

Except table 8-12, Does anywhere states 19mm is maximum fillet weld size? cos the table is for the number of passes to make the efficient weld.

Thanks in advance!!

 

[dauwerda]

A max fillet weld size should be 19mm.

As long as the size is not restricted by geometry (at edge of plate) as discussed above, there is no code provision that enforces a maximum weld size - you can make a fillet weld as large as you want.

t-1/16" is for lap joint only. also, we don't exceed 19mm if it is fillet weld right?

The t-1/16" is only applicable when the edge of a weld can melt the edge of the plate. There is no requirement to not exceed 19mm (other than economy). See image below showing different situations where the weld size is limited by an edge.

But if it is T-joint, there is no max weld size, we could use a fillet weld size more than 19mm?

Correct, the code does not limit the size of the fillet weld as long as there is not a geometry issue. However, a T-joint may still have a geometry that limits the weld size - see last picture in image above

or We could use PJP or CJP whether required,

Correct.

I could use a 25mm size fillet weld for a 19mm thick plate if it is T-Joint?

Correct, the code does not limit the size of the fillet weld as long as there is not a geometry issue.

From the CISC table 3-46, this is a T-Joint, also we can use fillet weld size larger than HSS wall thickness and weld size can be exceeded 19mm?

Correct.

Except table 8-12, Does anywhere states 19mm is maximum fillet weld size?

As long as the size is not restricted by geometry (at edge of plate) as discussed above, there is no code provision that enforces a maximum weld size - you can make a fillet weld as large as you want. As engineers it is our job to consider the economy of our design and look for the best solution - fillet welds at that size are generally not the most economical solution.


Now I am going to muddy the water a little bit. This is the only other time a maximum fillet weld size is enforced by the code:
If welding weathering steel with a carbon steel electrode (rather than alloy electrodes that replicate the weathering characteristics of the steel). AWS D1.1 limits the weld size to 1/4" (6 mm) for SMAW and 5/16" (8 mm) for FCAW, GMAW and SAW. This limitation does not apply if alloyed electrodes are used.

I should note when I reference the "code" above I am referring to AISC Steel Construction Manual and AWS D1.1

 

[Veer007]

Thanks for the excellent reply , this is what I want.. finally I'm seeing the light at the end of the tunnel.

Also, I know that I have to check shear capacity of base metal as above stated by "winelandv"

Thanks in advance!!

 

[johnie134]

be careful to comply with min max weld sizes.

 

[IFRs]

This might be considered a double post.
thread 507-472669

https://www.eng-tips.com/viewthread.cfm?qid=472669

 

[SALTRAM4567777]

If I have to weld two plates of 40mm thick using fillet weld of size of 36 mm . I cannot do it in single pass so I will be doing it in multiple passes as per Table at the begging of the post. Am I right?
Also is it still required to preheat the plates for proper fusion?

 

[kingnero]

Preheat has little or nothing to do with fusion.
Preheat with help a.o. against hardening, against internal stresses and deformation, for diffusing of hydrogen, but will have barely if any influence on penetration.
In general, 40 mm plates will require preheat. Be also carful for delamination (= lamellar tearing), especially in low quality steels.