The 34-year-old outside back has signed a one-year deal with the club after leaving Featherstone Rovers at the end of last season and is expected to be a key player at the Olympic Legacy Park (OLP) in 2022.
"I was speaking to a couple of clubs but Mark really sold it to me better than any other clubs,” said former Salford and Hull KR regular Welham.
"I’m just looking forward to getting down and seeing what it’s like.
"The OLP pitch can get a little bit sore for us old boys but it’s always a fast track. It will suit me.”
The pair were already familiar with each other through Welham’s father-in-law, former Sheffield Eagles coach Gary Wilkinson.
Welham said: "He’s been in the game and around the game a long time. My father-in-law who I work for used to coach Sheffield with Mark.
"I’ve heard stories from him about his reputation. When he speaks everyone listens, he’s got that authority about him.”
Welham is also familiar with several of the other five Hull-based players in the Sheffield team – and has been tasked with sharing his experience and wisdom in the dressing room.
He said: “I have known Anthony Thackeray for a long time. Josh (Guzdek), I was with him at Hull KR.
"When I spoke to Mark about signing he said to me if I did sign he would like me to be that leader player and take some of the young lads under my wing.”
Connor Bower and Ryan Johnson are among those who are set to benefit from his tutelage next season.
Another ex-Super League star jetting in for the 2022 season is Jamaica international Ben Jones-Bishop, formerly of Leeds Rhinos, Salford Red Devils and Wakefield Trinity.
The 33-year-old won two Super League Grand Final’s during a six-year spell with the Rhinos between 2008 and 2014.
Sheffield’s director of rugby Aston said of his capture: “Ben is a fantastic player, it goes without saying.
“His CV speaks for itself, he is a champion in everything he does and is a brilliant acquisition.”
Sheffield Eagles will begin the 2022 season away to Barrow Raiders on 30 January.