type casting char to string in static const member array

For c++, using visual studio command prompt (2010) as compiler, notepad++ as editor

I'm having such a specific issue I can't seem to find the answer I'm looking for in searches so here goes:

Regarding a program assignment with some constraints (I cant use different variable).
I have a class Card with a static constant member array called "faceName" in my untouchable header file.
I am initializing this member array in my implementation file with assignment operator and list of string literals.
Instead of the boring text "Spades" and "Hearts" etc for suit names, I want to use the char ascii codes 3,4,5, and 6 for the actual symbols.
I can't figure out how to typecast my char variables into something the string can read then load them into the string all in a single line (Since a constant can't be modified later, and I can't actually do the char creation in main, and must be done loosely floating in the implementation file.

Been years since I've programmed, sorry for my poor vocabulary usage if I stated anything incorrectly.

Card.h

class Card
{
    private:
        int face;
        int suit;

        static const int NUM_OF_SUITS = 4;
        static const int FACES_PER_SUIT = 13;

        static const string suitName[NUM_OF_SUITS];
        static const string faceName[FACES_PER_SUIT];

    public:
        string toString() const;
}

Card.cpp

const string Card::faceName[] = {"2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"}
const string Card::suitName[] = {(char)3, (char)4, (char)5, (char)6}

string Card::toString() const
{
    string nameOfCard;
    if (suit >= 0 && suit <= NUM_OF_SUITS && face >= 0 && face <= FACES_PER_SUIT)
    {
        nameOfCard = faceName[face] + " of " + suitName[suit];
    }
    else nameOfCard = "Error, card type doesn't exist.";
    return nameOfCard;
}

and my error: card.cpp(14) : error C2440: 'initializing' : cannot convert from 'char' to 'const std::string' No constructor could take the source type, or constructor overload resolution was ambiguous

And I can't simply create an sstream to do the conversion because where would I do that? In main - too late, I need to initialize the member arrays in the implementation file.

Thanks for any help!