however values of Shear Strength and Tensile Strength are arrived experimentally, and depend on a lot of factors as I have mentioned above. I do not know of any relation between them.
If you are looking for applications in structural design, and maximum allowable stresses, I would suggest you to read about principal stresses, Mohr's circle (an easy way to understand), and factors of safety. The following is a short guide for your reference:
Factor of safety will be different for different types of applications, but shall give you an understanding of the requirements for your application and the standards against which it will be tested, and from there you can get the strength requirements.
Well, it depends on various factors and loading conditions. However, using poison ratios and Mohr circle should possibly lead you to comment on any relationship between the shear and tensile strength of ferrous alloys. In my opinion, it would be quite difficult to predict any solid relationship between shear and tensile strength of the HSS.