Study On The Effect Of Sulphurization On Organization And Properties Of Mould Steels

Mould steel with a good impact resistance,anti-cracking,wear and heat distortion and other characteristics widely used in hot extrusion die,forging die,die-casting mold and other hot parts;W360 hot work die steel with high hardness,high toughness,excellent resistance to tempering softening performance and good thermal conductivity and other characteristics widely used in warm forging,hot forging mold die,punch mold material and friction stir welding head material.However,the study found that W360 steel for the aluminum extrusion die when the wear is serious,for the stirring head welding aluminum alloy when the service life is also short,the analysis shows that the friction and wear in the hot environment during extrusion or welding are the common causes of low performance.In view of this,we use the low temperature liquid sulphurizing process to deal with w360 steel.By forming a porous and easy to slippage iron sulfide layer on the surface of the material,enhancing the anti-abrasion and adhesion,reducing the friction heat,improving mold or stirring head wear resistance and service life.Using sulfur content to adjust the sulfurizing agent to explore how to improve the formula;Using metallographic microscope,field emission scanning electron microscope(FESEM),X-ray diffraction(XRD)and other micro analytical instruments to analysis the matrix structure,the morphological structure phase composition element composition of the sulfide layer,the morphology structure element distribution of the wear trace and so on;The surface hardness of the material before and after sulphurization was measured by hardness tester;The tribological properties of the sulfide layer were evaluated using the MRH-3A high-speed ring block wear tester.The results show that the W360 steel using low temperature liquid sulphurizing process,the sulfide layer formed a "micro-particles + gap" structure,the shape like "dimple" fracture,between the particles and particles within the loose porous,the pores can store lubricating oil,The surface is easy to form oil film,is easy to form a "fluid + solid" synergistic lubrication effect;The hardness of the material before and after sulphurization did not change,so after the sulphurizing treatment of hardness on the friction and wear properties of the material does not produce a role;The low temperature liquid sulphurizing process can obviously improve the surface abrasion resistance of H13 steel,especially the friction coefficient of the initial stage of the material is significantly lower;The study also found that the sulfurizing agent component have a significant effect on the anti-scratch and anti-sticking properties of the sulfide layer,and the anti-abrasion and adhesion properties are best when the sulfur content is 1.5%(mass fraction).Based on the self-lubricating effect of iron sulfide,around the W360 steel hot conditions on the steel surface friction and wear performance requirements,in this paper,we use low temperature liquid sulphurizing process in the W360 steel surface formation of FeS film,the results of the study have some guiding effect on improving the abrasion resistance and wear resistance of the mould steel and the products,which can provide some technical reference value for the aluminum processing enterprises to reduce the cost and improve the efficiency.