Mae'r fricsen cromlech bondio uniongyrchol yn cael ei wneud o magnesia sintered purdeb uchel a chanolbwyntio chrome gyda SiO2< 2%="" as="" raw="" materials="" through="" high-temperature="" sintering.="" the="" direct="" bonding="" degree="" of="" the="" product="" increases="" with="" the="" reduction="" of="" sio2="" content="" and="" the="" increase="" of="" sintering="" temperature.="" the="" formation="" of="" direct="" bonding="" is="" a="" process="" of="" dissolution="" precipitation.="" increasing="" the="" content="" of="" fine="" powder="" of="" chromium="" concentrate="" is="" conducive="" to="" the="" formation="" of="" direct="" bonding.="" in="" the="" presence="" of="" silicate,="" the="" bonding="" between="" periclase="" and="" periclase="" will="" be="" strengthened="" by="" cr2o3,="" but="" reduced="" by="" al2o3="" and="" fe2o3.="" the="" higher="" the="" content="" of="" cr2o3,="" the="" more="" intragranular="" and="" intergranular="" spinels,="" the="" higher="" the="" strength="" of="" the="" product="" and="" the="" stronger="" the="" slag="">
Yn gyffredinol, rhennir y brics cromlin magnesia wedi'u bondio'n uniongyrchol i wahanol raddau o Cr2O3% ≥ 12% a Cr2O3 ≥ 20%, gyda porosedd isel, cryfder uchel, ymwrthedd gwisgoedd cryf, ymwrthedd cyrydu da a gwrthiant sbamio da. Mae'r cynhyrchion yn cael eu defnyddio'n helaeth mewn ffwrneisi arc trydan, ffwrneisi mwyndoddi copr, a ffwrneisi ailddiffinio allanol
