I came across this document from BOC a while ago which explained the different gasses and their effects in welding. I thought that it was very informative and a excellent read and may be of interest to those who are not sure on what gas to get. It shows welds using different gas mixes which are made using a robotic welder so there is no human intervention to correct or modify the results. It is made my BOC but you could always use the gas ratios to see if your local gas supplier could match them to give you what you require.
https://boc.com.au/boc_sp/downloads/gas_brochures/BOC_216295_GeneralGasesBrochure_AUS_v12.pdf
https://boc.com.au/boc_sp/downloads/gas_brochures/BOC_216295_GeneralGasesBrochure_AUS_v12.pdf