Search results

The differences of surface topography and chip morphology of Inconel 718 machined by single diamond grain and single CBN grain were evaluated.
The space between the sawteeth narrows and the number of sawtooth increases while the grinding speed ranges from 20m/s to 150m/s.
Normally, the grinding forces of single-grain are small.
(2) The morphologies of the grooves machined by single diamond grain and single CBN grain show no big difference, are all relatively smooth.
With the increase of grinding speed, the space between inter-sawteeth of the chip narrows, the number of sawtooth increases

Effect of grain refinement on cold formability behavior on medium C-Boron steel Ilaria Salvatori1, a, Claudio Guarnaschelli1, b and Tommaso Coppola1, c 1Centro Sviluppo Materiali SpA, Via di Castel Romano 100, 00128, Roma, Italy ai.salvatori@c-s-m.it , bc.guarnaschelli@c-s-m.it, ct.coppola@c-s-m.it Keywords: Ultrafine Grain Steel (UFG), ferrite grain refinement, cold formability, plastic damage.
Calibration of the model was carried out by analyzing the ultrafine grained steel, produced in pilot mill whose grain size was about 2-3 mm and the conventional steel industrially produced (grain size about 12 mm).
The screw head is formed through a number of steps including a) Step 1: extrusion in die; b) Step 2: first heading; c) Step 3: second heading; d) Step 4: flange and key hole forming.
The conventionally rolled material grain size was around 12 mm.
Actually, it has been found that for a significant number of pieces the real cause of rejection was not due to forging bursts, but to surface defects which were pre-existing on the wire rod.

This paper analyzed the microstructure evolution and grain-refining mechanism in producing ultra-fine grained steel sheet by heavy rolling of lath martensite.
The initial austenite grain size was about 200μm.
During phase transformation, an austenite grain will divide into four martensite packets with the same habit plane; a martensite packet is composed of three martensite blocks with different K-S orientation; each martensite block contains two variants with specific K-S relationship; each variants formed by a number of laths.
The average size of new equiaxed grains was 22.4nm.
Fig. 4 Effect of annealing temperature on hardness and grain size Curve 1-hardness; Curve 2¬-grain size Conclusions Heavy cold-rolling of lath martensite is a simple method to produce ultra-fine grained steels without severe plastic deformation.

Grain-Workpiece Interaction Study of Grinding Process through Single Grain Cutting Simulation Lan Yan1, Zhixiong Zhou1, Feng Jiang 2 , X.K.
From this point of view, a number of grinding experiments with a single abrasive grain were performed [1-3].
Single Grain Cutting Model The shape of abrasive grain is irregular because the grains are made from breaking of crystal, and they are very difficult to classify geometrically.
The single grain cutting parameters are shown in Table 1. 46 # alumina grain is selected, as the 46# grinding wheel is widely used in the coarse grinding.
Grinding process A r Cutting speed V Workpiece Single grain cutting TO 2θ Grain Depth of cut Single grain Fig.1 Optical image of a wheel surface Fig.2 Single grain cutting Table 1 Cutting parameters of single grain cutting simulation Grain material Al2O3 (10~15% ZrO2) Grain shape[9] 46# grain; 2θ = 110°; r=0.028mm Workpiece material D2 steel Cutting speed (m/min) 1200, 1800, 4200, 5400 Depth of cut (mm) 0.006, 0.008, 0.01, 0.012, 0.032, 0.08, 0.12 Grinding condition Dry Results and Discussion Cutting Force.

Al3Ti except for Ti powder sample (200 mesh) Almost can not be found, Most of the Al3Ti is the block in the others sample （2）From the view of TiC distribution, TiC are small and scattered, but with the reduce of the TiC powder particle size, TiC size slightly decreased and the number also increased
Besides, with the reduce of the grain size of C powder, the distribution of Al3Ti in the master alloys is more dispersed and the numbers are increasing.
When the grain size of C powder is reduced, the grain size of TiC is also reduced.
When the grain size of C powder is 1200 mesh, the grain is homogeneous equiaxed crystal.
Conclusions （1）Refinement is the result of the interaction of refinement phase Al3Ti and TiC in the master alloy （2）When the grain size of Ti is much smaller，the TiC and Al3Ti particles in the master alloys that is formed by Contact Reaction Method is fine and scatter , and when the more large its number is, the more complete the reaction of the Ti powder is.

The grain selection behavior in grain selector directly determines the casting's final microstructure and properties.
The grain selection process in the grain selector and final microstructure of casting were simulated.
Based on simulated results, a newly designed grain selector with optimized geometry was proposed to avoid stray grains.
Usually it's difficult to calculate the heat radiation in directional solidification, because of the huge number of memories required to store the view factors for each surface cell against others.
Fig. 8 shows the grain evolution with optimized geometry grain selector during solidification.

In the oxidation at temperatures of more than the solid solution temperature, the grain size before the oxidation changed to coarse grain size.
It was confirmed that the steel with ASTM grain size finer than number 8 forms a uniform and protective Cr rich oxide layer at the metal–oxide interface, but the steel with coarser grains forms the Cr2O3 oxide scale only locally, in the steam oxidation of 18Cr-10Ni austenitic steels used in the superheater tubes of actual boiler for 15,000 hours [3].
However, when the fine grains changed to coarse grains in the temperature range of 1,000º to 1,100ºC, the steel with fine grain size showed abnormal oxidation because the oxide scale fractured due to the shift of grain boundaries [7].
Fig. 7 Effect of grain size on the flux ratio of Cr from grain boundary diffusion and internal diffusion during oxidation.
At every temperature, when grain size was less than 10 μm, the ratio of Cr from grain boundary diffusion is extremely large.

Silicon grains have multiplied.
Number of particles per unit area.
The intermetallics initially grow, but their number diminishes.
In the first stage, a rapid decrease of the number of β-AlFeSi-particles is observed, coupled with a significant increase of their size.
Their number decreases only slowly, as is expected for a process of gradual dissolution.

Based on stereology, the reciprocal of grain size is proportional to grain boundary area.
Even if the s phase is precipitated at the fcc grain boundaries, some precipitates are left inside the fcc grains after the grain boundary motion.
In general, diffusion rate along grain boundary is higher than that in grain interior.
(3) The average grain size is known to be inversely proportional to the total grain boundary area.
Acknowledgement This work was supported by Grant-in-Aid for Scientific Research (B) (JSPS KAKENHI Grant Number 20H02464) in Japan.

Many grain and oil depots have been established.
For instance, total investment of Da Lian Nrth Liang grain depots are 82 million RMB; 15.5 million was invested for Shanghai Wai Gao Qiao grain depots, and also 10 million RMB for exlarge construction work of Xin Sha grain depot in Guang Dong Province. ②Big floor area is needed.
One group is composed by grain depots, oil depot, delicate railway and dock, deep processing for the grain and oil factory, test office.
The arrangement of sand drains are quincunx with diameter of 0.4 m ,distance between drains of 2.5m ,length of 18m and the total number of sand drains is 283.
A large number of practical projects show that the ground bearing capacity of the region can improve 15 to 30 kPa by vacuum preloading method.