There are many different types of cracking and and specific reasons of why it happens and the negative impact. I recently read an article listing types of cracking and hot cracking, centerline cracking, underbead cracking, crater cracking, The one that caught me off guard was liquation cracking. Can anyone help me with this one. What causes it ,where does it occur. how can you prevent it.
By -
Date 09-21-2005 17:16
Liquation cracking in the weld or HAZ is associated with multipass welding, mainly sub-arc welding, although other welding processes can also experience this type of cracking. Repeated welding passes may cause re-melting of secondary phases. In combination with high restraint, this may lead to cracking. This cracking morphology is generally intergranular. Liquation cracking can usually be prevented by careful monitoring the heat input and interpass temperatures.
Chuck
Here is an article published in the welding journal that confirmed our experience in the Turban engine repair field.... The focus is on Liquation cracking in the heat affected zone in 718 inconel.
http://files.aws.org/wj/supplement/06-2003-QIAN-s.pdf
Here is a link to an nice article that includes a description of liquation cracking in Aluminum alloys and has a nice picutre as well. From "The Welding Institute. (TWI)
http://www.twi.co.uk/j32k/protected/band_3/jk21.html
To add to what has already been said, liquation cracking is caused by the separation of low melting point grain boundary constituents of an alloy from the remaining constituents, which lead to small micro cracks. These micro cracks are usually more apparent in alloys having a wide melting range. Here's another related link: "Solidification and Liquation Cracking Issues in Welding"
http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/JOM-0306-37/$FILE/JOM-0306-37F.pdf?OpenElement
If anyone is interested, this link can't be accessed by clicking it, it must be copied and pasted into the browser.
