Be careful, While ordering ASTM instead of API 5l. If you order 4" dia ASTM pipe, you would end up getting 114.3mm OD(4" NPS) pipe, where as in API 5l (After year 2000) the Diameter is OD that is 102mm OD. Hence while substiuting material spec specify the OD CLEARLY.
The tensile requirements for API 5L Grade B has a minimum yield strength = 241Mpa. and Minimum Ultimate Tensile Strength = 413Mpa. You may need to find out the pressure rating, (Standard Weight or Extra strong) and the size required.Then I may be able to better assist.
API 5L are most commonly specified for pipelines of large size (as 12" and higher) and long (more than 300 ft) pipes for services offsite process plants. ASTM A106 is more used for process plants service. If it is your case of transportation of oil, water or gas at not high temperatures nor below 20F you can specify ASTM A53 GrB