Samples of low basicity hematite pellets made from East-Anshen iron ore con-centrate and charged a 100m~3 experimental blast furnace have been taken fromfive equalized points along diameter of furnace shaft at 6.5m below the burdenline during processing. A petrographic observation on mineralogical reactionsof the samples has been made in comparison with the industrial fluxed sinters sam-pled in the same manner. It was shown that the indirect reducing reaction oc-curs under temperatures above that of the pellet firing in all samples. The reduc-ing gases of the furnace atmosphere penetrate through the pores and gaps of thepellet and react with its liquid and solid phase substances. The behaviour of thereducing reaction in the pellets appears to be better than that of sinters owingto their different micro-porous structures. Since the pellets flow downward alongindividual path with various courses of reaction, six typical models of concentriclayer structure of them would be proposed. The iron oxides matx is bonded es-sentially by molten silicates of CaO-Al_2O_3-SiO_2 system formed at high tempera-ture and by other systems, e.g. CaO-FeO-SiO_2, etc. as well. The magnetizingphenomena of CaO-Fe_2O_3 system has also been obviously observed.

A study was made of the macro- and microscopic structure and mineralogicalconstitution of sinter prepared by Baotou iron ore concentrate which differs fromothers by the presence of remarkable quantities of fluorine and rare earth com-pounds. The viscosity and surface tension of sinter slag phase have been measuredwith various additions of SiO_2 and CaF_2 in the sinter. It was observed that thefluorine, mainly as CaF_2, forms itself into cuspindine which is a major constituentinjurious to the properties of bonding phase and consequently the strength of thesinter. The fluorine-bearing mineral decreases obviously the viscosity and surfacetension of the slag in the sinter and makes in turn the sinter porous, with opentubular thin framework structure. Certain amount of SiO_2 may also lower thestrength of sinter slag bonding, yet it seems to be acted secondarily. In order toimprove the strength of Baotou sinter, decreasing its fluorine content to such anextent of less than 1.5% in the concentrate by benefciation may be preferable.Furthermore, both raising the slag basicity up to 2.0 and adding dolomite to sub-stitute partially the limestone in sinter burden materials may also be effective.An industrial process raising the sinter basicity up to 2.0 was found on trial inBaotou Iron and Steel Company to be successful.

The strengthening process of hematite pellets made from iron ore concentrateof Kunming Iron and Steel Company has been examined by SEM, X-ray diffrac-tion, etc. to ascertain the strengthening mechanism when they were fired undertemperatures between 1000 to 1350℃. The hematite crystallites began to growinto trigonal platelets and to cross-connect each other at temperature up to 1000℃.Until 1200℃, the cross-connexion was further strengthened into solid framework.Thus, it seems to be easily clarified why a rather firm strength of pellets isdisplayed earlier under lower firing temperatures. Perhaps, neither molten slagformed over the surface of hematite crystals with vein and impurities nor a fewof magnetite crystallized out of melt will play a dominante role in the strengtheningprocess of this hematite pellets.

Investigation of freckles observed in Fe-35Ni-15Cr-2. 4Al-2. 3Ti-2W-2Mowrought superalloy has been carried out. The freckles were actually dendrites whichmay appear as small spots or streaks depending on whether cross- or longitudinalsections of the bar are taken. Enrichment of Ti, Al, Si, Mo, Ni and minute C, B,S, etc. in interdendritic spaces in the freckles' region may result in the formationof γ', Ti(C,N) and M_3B_2 as well as in the growth of σ-phase which was observedonly in the freckle areas. In the case of the freckles' region, the temperature offusion would be low, being probably about 1190℃ which is nearly 40℃ belowthat of the matrix. If the hot working of the alloy is carried out at 1190℃ orthereabout, microcracks may be formed in such freckles' region. The freckles cannot be eliminated completebly even after soaking for a long time at elevated tem-peratures. The higher hardness associated with the freckles can be troublesome inmachining and in giving a rough machined surface. In vie of the fact that the', the brittle intermetallic σ-phase and the non-metallic inclusions are somewhatlocally concentrated, the mechanical properties of such an alloy might be expectedto be adversely affected. The freckle segregation is essentially associated with gravity segregation. It iscaused by upward movement of jets of liquid metals enriched with light elementsin the mushy zone during solidification. The tendency of forming freckles seemsto be related to the melting rate of the consumable electrode as well as to thedepth of the liquid metallic pool.

The effect of carbon and boron on the stress rupture properties at 600 and750℃ as well as on the tensile properties at room temperature and 650℃ of a35Ni15Cr type iron base alloy has been investigated. Both carbon and boronseemed to be markedly influential in the stress rupture life of the alloy whichreached its peak value with 0.03--0.05%C and about 0.006% B. However, thenotched-rupture sensitivity was hardly affected. The increment of boron content maycause lowering the eutectic temperature of boron-γ phase. The amount of borideeutectic increases with the increase of boron content and the solution treatmenttemperature. Minute boron-γ phase eutectic less affected the room temperaturetensile properties, but markedly shortened the rupture life.

The effect of decarburizing process on the magnetic properties of the grainoriented 3%Si-Fe has been studied. An empirical expression for the rate of decar-burization under given conditions was proposed. While the time of decarburizationwas given, the carbon content in 3%Si-Fe might be predicted, and vice versa.Another empirical expression for the rate of grain growth was also derived fromobservation of normal grain growth during decarburization. Based upon the aforementioned expressions, the functional dependence of thecarbon content before secondary recrystallization and time required for decarburi-zation on final magnetic properties of the grain oriented 3%Si-Fe has been dis-cussed. A two-demensional plot was then drawn on which the decarburizing pro-cess would be easily determined to acquire materials of superior quality.

The microstructure changes in the tempering process of a quenched 6Cr4Mo3Ni2WV Matrix steel have been studied by TEM. Special attention has been paidto the observation of the microstuctures near the peak of the hardness-temperingtemperature curve. It is shown that, the secondary hardening of the steel is main-ly brought about by the precipitation of V_4C_3 and M_2C. With the tempering tempera-ture below 450℃ or so, the cementite lathes precipitated at the twin boundariesand {112} planes are fairly stable. However, they are transformed into a meta-stable phase, and finally are replaced by V_4C_3 M_2C and a new fine cementitewhen the tempering temperature is raised to beyond 500℃ This process certainlyleads to an increase in strength (secondary hardening), and what is more, it leadsto a substantial improvement in impact toughness in the meantime. The best impacttoughness is obtained by the time the cementite lathes are completely trans-formed. When tempering in the range of 600-650℃, the V_4C_3, M_ and alsothe fine cementite coalesced to equiaxed particles-M_6C or Cr_7C_3 at the austeniticgrain and sub-grain boundaries, and the impact toughness of the steel drops ac-cordingly.

The fracture surfaces of certain fracture toughness specimens have been ex-amined by SEM. With materials fractured in quasi-cleavage mechanism, the meandistance, ξ, from the pre-crack tip to the site where the quasi-cleavage crackstarts is regarded to be a characteristic parameter. It seems that this related toG_(Ic) and can be used as an important parameter characterizing the stress field ofthe plastic zone.

The kinetics of hydrogen absorption in LaNi_5 has been investigated at initialpressures of 15--30 atm and temperatures in the range of 20--85℃. LaNi_5 was pre-pared in a ZrO_2 crucible in a graphite-tube furnace under vacuum. It is shownthat a linear relationship exists between the amount of hydrogen absorbed, W,and the time of reaction on a logarithmic scale and the rate of hydrogen absorp-tion depends on the initial pressure and the test temperature. The P-X-T curves of the LaNi_5 system have been determined. For each testtemperature there is a corresponding pressure plateau P_0 and it is therefore as-sumed that for every initial pressure P_0 there is a corresponding balance temperatureT_0, and T_0-T may be taken as the driving force of hydrogen absorption processin LaNi_5 at initial pressure P_0 and test temperature T. The absorption of hydro-gen takes place in three steps: (1) surface reaction, which seems to be rather com-plicated; (2) diffusion of hydrogen atoms and (3) phase transformation f LaNi_5 toa hydride phase. All these steps are thermal activation processes, and thereforethe e~(-U/RT) can be introduce in the hydrogen absorption process. The relatioshipbetween the absorption rate, the initial pressure, the test temperature and time isgiven as follow: dW/dt=A_0(T_0-T)e~(-U/RT)·1/tThe activation energy of the rate limiting step U is about 2 or 3.2 kcal/molaccording to whether the amount of hydrogen absorbed is less or more than 70%respectively. The parameter U of the rate-limiting step during hydrogen absorptionin LaNi_5 can be obtained as shown by our experiments.

The age-hardening processes of a Mg-5wt%Zn alloy have been studied bymeans of hardness measurement and X-ray diffraction analysis. On aging of thisalloy at 165℃, two hardness peaks with corresponding structural changes in thealloy were noticed. X-ray investigation of this alloy in quenched state revealedthat plate-like zinc clusters parallel to (0001) and {1010} planes of the magne-sium matrix were formed. At the initial stage of 165℃ aging, two-and three-dimensional metastable transition phase β'_1 particles and one-dimensional transitionphase β'_2 rods were precipitated out from the super-saturated solid solution. β'_1 existedonly for very short periods, while B'_2 still grew after aging for a total period of100h. when an equilibrium phase β began to precipitate out. During aging at190℃, only one hardness peak appeared, corresponding to the concurrent pre-cipitation of β'_2 and β phases. The structural parameters of β'_1 and β'_2 and theirorientational relationships with the matrix have en determined. The thermal stability of β'_2 was found to be rather high at 250℃, implyingthe probable applicability of the aged Mg-Zn alloys at higher temperatures.

Deoxidation and desulphurization equilibra between cerium, sulphur and oxygenin molten iron at 1600℃ have been determined and studied thermodynamically.The apparent solubility products of these reactions are:Ce_2O_(3(s))=2[Ce]+3[O] K_(Ce_2O_3)=[%Ce]~2[%O]~3=(1.0-3.2)×10~(-14)Ce_2O_2S_(s)=2[Ce]+2[O]+[S] K_(Ce_2O_2S)=[%Ce]~2[%O]~2[%S]=(1.6-3.5)×10~(-13)CeS_(s)=[Ce]+[S] K_(CeS)=[%Ce][%S]=(1.5-5.7)×10~(-4)The interaction coefficients are concerned:K_(Ce_2O_2S)=α_(Ce)~2 α_O~2 α_S=3.9×10~(-14)K_(CeS)=α_(Ce)α_S=1.9×10~(-5)The standard free energy change for reaction Ce_(1)=[%Ce] has been found to beΔG_(S,Ce)~0=-24000cal(100.4kJ) from which γ_(Ce)~0=0.39_7 is obtained. The self-interac-tion coefficient of Ce is calculated to be ε_(Ce)~(Ce)=1.9 and e_(Ce)~(Ce)=0.0032. Combining theseresults with those from literatures, the change of standard free energy for reaction2Ce_(1)+1/2S_2+O_2=Ce_2O_2S_(S) is ΔG_(Ce_2O_2S)~0=-241000 cal (1008.3kJ).

A Geometric invariant representution of thermodynamics in space Ω,Ω=∞~f states; f-degree of freedom,of reversible states is given in this paper. A reversible state is one attainable from∞~(f-1) directions (-dr)‖(-Δr) in Ω. A state function φ is distributed accordingto this law:■