You mean, "tungsten carbide"?
Use a silver brazing alloy. Best to use either something like AWS BAg-3, or BAg-22. which are specifically designed for tungsten carbide. I'd reccomend BAg-22 because it's cadmium-free, though it's wetting ability is somewhat less. Also it's easier to find. Both of these have a high silver content and so they're a tad expensive.
Use a brazing flux that contains potassium fluoroborate. This is often referred to as "black flux." Generic white brazing flux can be used also but it doesn't perform as well.
Clean both the tungsten carbide and the steel with oven cleaner before brazing. Note: this is caustic stuff, so be sure to wear eye protection and rubber gloves, and follow the safety instructions. you may also try sanding the parts with aluminum oxide sandpaper.
It helps to quench the parts after brazing, which loosens the flux. Parts should be thoroughly cleaned with hot water to remove flux. Otherwise you can end up with corrosion problems.