Shubhanshu with your 70 marks in JEE Advanced 2018 exam under the SC category according to last year marks vs rank distribution you can get a rank around 2500 in the SC category. Although at this time according to coaching's expert paper was a little difficult and there have been no errors like last time when 18 marks were given to each student so it is expected that cut-off will go down and your rank can be a little better but still with the 2000-2500 range of SC category rank your chance of getting admission in any of the IIT will be very difficult. 

To get a better and clear understanding you can go through the link given below which shows the cut-off rank of each category in each branch of each IIT:

• https://engineering.careers360.com/articles/jee-advanced-cutoff-for-iits

Honestly with this marks the range rank i.e. expected to get you will not get any branch in any of the IIT. Thera is only slim chance that your rank improves drastically this year in comparison to last year and reach around 1500 in your SC category then you might get MEchanical or civil in newest IITs like IIT Bhilai, IIT Dharwad, IIT Jammu.

Feel free to ask if you have any more queries. All the best!!