Our firm had a similar problem with one of our steel suppliers. We tried using IFC but that was too much. Try this: have them save as a .dwg, then in your archicad model do File>Libraries & Objects>Open Object, then select the .dwg file (be sure to change the 'File Type' to dwg) and that will make it a gdl object that you can then place in your model.
It has worked like a charm for us. Although I'm not sure what software our steel supplier uses.
Good Luck
Casey Grimley
Casey Grimley
AC24
iMac Pro (2017) - macOS 10.14.6- 3.2GHz Intel Xeon W - 32GB RAM - Radeon Pro Vega 56 8GB