Din 934 hex nut, SAE1015, Q235, Q195

[Joesfast]

I have been tasked with buying hex nuts for a certain project overseas. The nuts would go directly from supplier in china to the project.
I have asked my local supplier for a certificate and I see they use SAE1015 they call it commercial 8 instead of class 8(which would be heat treated). Overseas our companies usual supplier uses Q195. Our other supplier claims that Q235 is closer to the spec of SAE1015. My concerns are
1) What would the difference be between Sae1015, Q195, Q235. What effect on performance of the nut?
2) Our first supplier claims that the Q235 would crack and recommends Q195, why would he say this? To get my business or is there a genuine concern?
I have included the material certificates of the M16 and M20 nuts that my local supplier has sent to me, please ignore the plating certificate included.

Thanks

 

[CoryPad]

1) The differences are chemical composition and mechanical properties. Each material potentially could produce different properties, possibly outside the limits identified in DIN 934.
2) There should be no concern for cracking in steel that has the composition identified as Q235.

You should not use DIN 934 labeling for these parts if they do not meet all requirements (such as the requirement for heat treatment).

Why are you using DIN 934, which was withdrawn? Why not ISO 4032?