Here we (WixSteel Industrial) will tell the detailed difference about 45CrNiMo1V, 45CrNiMo and 45 CrNiMoVa
45CrNiMo1V was created (in 1995) by China steel factory follow the USA steel grade D6AC(ASTM A29/A29M-4), China adjust some element a little to get similar performance.
In 1995, China steel factory is not such good on process control, so engineer add more Mo into it, reduce the Ni percentage, to get the similar performance with D6AC. Here you can sheck the chemical composition of this 3 materials below:
Because Mo is expensive, in 1999, steel factory update the process, they can control the final performance of 45CrNiMo1V with less Mo, so, when China start to write GB/T 3077-1999 , china engineer reduce the Mo percentage, also change the alloy name from 45CrNiMo1V into 45CrNiMoV.
The newest version of this standard is GB/T 3077-2015 , in 2015 the name is still 45CrNiMoV.
45CrNiMoVa was created in 1988, from GB/T 3077-1988, when China first start to produce their own "D6AC" alloy steel, they name this material call 45CrNiMoVa, the oldest version.