Babitting

Here are good places to start.

http://en.wikipedia.org/wiki/Babbitt_(metal)

http://en.wikipedia.org/wiki/Plain_bearing

Also an internet search of "Babbitt bearing" or similar will give you plenty of information.

welder qualification is required for that

Depends on the application and local standards of the county.

Please provide much more information on your application if you need a better answer.

Some good info here http://www.thepetrostreet.com/forums/viewtopic.php?f=18&t=210