about of malleable iron pipe fittings casting chemical composition
Effect of chemical composition on the malleable including obtaining vermicular graphite and on the substrate, both of which successively affect the mechanical properties and other properties of compacted graphite forged iron , the chemical composition of those effects should choose according malleable.
(1) carbon, silicon and carbon equivalent compacted graphite iron production within the general vicinity of the eutectic composition, so as to assist improve the performance and reduce the chilling tendency casting, commonly used carbon equivalent of taking 4.3% -4.6%.
Effect of Carbon on malleable lastingness almost like gray iron and ductile iron, with increasing carbon content, malleable lastingness will increase thanks to graphite, pearlite decrease and decline, but this effect is smaller than gray forged iron was many. so as to scale back the chilling tendency, carbon content and usually 3.6% -3.8%, thin pieces take the upper limit, thick bulky take the lower limit.
Silicon inhibits the chilling tendency malleable, silicon also strongly promote the formation of ferrite elements, the strength of the decline; but only by reducing the silicon content is difficult to stop the formation of ferrite surrounding graphite. Therefore, to stop produce white, compacted graphite iron end silicon content is usually controlled between 2.4% -2.8%. Taking under consideration the creep process to bring great deal of silicon, therefore the mass fraction of iron melt silicon is usually controlled at between 1.5% -1.8%.
(2) Manganese play a stabilizing role within the pearlite malleable, but because the more branches vermicular graphite, manganese role greatly reduced. For hybrid Magang can adjust the manganese content to get the corresponding mechanical properties, manganese content is usually controlled between 0.4% -0.7%. For the ferrite compacted graphite iron manganese content should be strictly controlled so as to extend the matrix ferrite content, manganese highest quality control scores below 0.4%.
(3) Linlin no creep of impact, but is made within the substrate phosphorus eutectic greatly reduce mechanical strength and impact toughness, produced within the casting shrinkage and cold cracking. Thus, additionally to wear Magang, the phosphorus content is usually controlled at 0.08% or less.
(4) sulfur and sulfur vermicularizing alloy affinity, consume more vermicularizing, both increased material consumption and production costs, while an outsized number of iron sulfide will affect the flow of the liquid, acceleration of creeping recession. Therefore, malleable sulfur content should be strictly controlled, the overall control of the mass fraction 0.07% or less.
(5) the addition of rare-earth element elements rare-earth element elements in liquid iron from the primary purification to get rid of iron liquid sulfur, oxygen, hydrogen, nitrogen. Purified liquid iron, rare earths play the remaining graphite metamorphism, creep is that the main agent of Magang. to form degenerates into worm-like graphite, rare-earth element iron liquid residues should be controlled 0.045% -0.075% (by mass). Below the critical mass, the resulting flake graphite; exceeds the upper limit, the resulting spherical graphite, reduce creep rate.
(6) Magnesium with rare earths, is another important component vermicularizing deterioration of Magang. Research and practice show that, to urge an honest vermicular graphite, magnesium content generally should be controlled 0.015% -0.03%. Below the lower limit or above the upper limit can't obtain adequate creep rate of Magang.
(7) the most alloying elements alloying elements wont to adjust the malleable ferrite content of the matrix, so as to realize improved creep agent added to expand the scope and purpose of the mechanical properties.
Malleable commonly used alloying elements mainly Cu, Mn, Sb, Sn, Ni, Cr, Mo, V, Ti, B then on. Addition of alloying elements are often added one element to be added a spread of complex elements, achieve the aim of improving performance.