316L WAAM and pressure machining influence

Wire arc additive manufacture (WAAM) technology has a good development prospect, and can be used to manufacture large metal components with complex shapes in combination with traditional machining equipment. This paper adjusts the parameters from the perspective of heat input and arc control. It is found that the stacking quality of 316L stainless steel is the best when the arc voltage is 40V and the arc current is 360A. It is proposed to obtain the flat layers by pressure machining after every layer is stacked, which can create favorable conditions for manufacturing large-size components. And through the hot rolling experiment, it is proved that pressure machining can improve the density and uniformity of the microstructure, and thus enhance the comprehensive mechanical properties of components built by WAAM.

Influence of Coiling Temperature on Microstructure, Precipitation Behaviors and Mechanical Properties of a Low Carbon Ti Micro-Alloyed Steel

The microstructural evolution, nanosized precipitation behaviors and mechanical properties of a Ti-bearing micro-alloyed steel at different coiling temperatures were studied using optical microstructure (OM), scanning electron micrograph (SEM), transmission electron microscopy (TEM), Vickers hardness and tensile tests. When the coiling temperature was 500 °C, the specimen showed mainly bainitic structure, whereas polygonal ferrite was visible as the coiling temperature increased to 650 °C and 700 °C. The Vickers hardness of tested steel reached the maximum, which can be attributed to the largest number of nanosized precipitates in ferrite at the coiling temperature of 650 °C. A coiling temperature of 650 °C was optimal for the formation of TiC because of the high diffusion rate of alloying elements and kinetics of precipitation. In the laboratory rolling experiment, when the coiling temperature was 630 °C, the steel with yield strength of 682 ± 2.1 MPa and tensile strength of 742 ± 4.9 MPa was produced. The fine-grain strengthening and precipitation strengthening were 262 MPa and 268 MPa, respectively.

Effects of Mg and Mn Contents on Hot-Rolling Temperature and Resultant Tensile Properties of Al-Mg-Mn Alloys

The effects of Mg and Mn contents on hot-rolling temperature and resultant tensile properties of Al-Mg-Mn alloys were investigated. The Al-3.5Mg-0.3 alloy as a reference and Al-7.5Mg-0.3Mn, Al-3.5Mg-1.0Mn alloys were prepared by casting for hot-rolling experiment. The rolling temperatures of both Al-7.5Mg-0.3Mn and Al-3.5Mg-1.0Mn alloys had to be decreased due to surface cracking during hot-rolling, which is caused by increased fractions of Mg-containing phases like Mg2Al3. The tensile strength of the hot-rolled Al-7.5Mg-0.3Mn alloy was highly increased by the combined effects of enhanced solid-solution and work-hardening at lower rolling temperature. And the resultant tensile strengths of the hot-rolled Al-3.5Mg-1.0Mn alloy were also increased due to dispersoid hardening by increased Mn content and work hardening during hot-rolling.

Study on the Lubricating Performance of Nano-TiO2 in Water-Based Cold Rolling Fluid

A type of water-based cold rolling fluid has been developed by adding TiO2 nanoparticles. The tribological behavior of nanoTiO2 water-based rolling fluid was investigated by using four-ball machine. The worn surfaces of the steel balls were analyzed by using OLYMPUS laser confocal microscopy. Results indicate that nanoTiO2 nanoparticles significantly improved the anti-wear properties in the way of micro-ball bearing and perfecting the tribological behavior of water-based rolling fluid. The cold rolling experiment shows that the nanoTiO2 water-based rolling fluid had a good rolling lubricant performance under the condition of concentration of 0.7wt.% for the upper limit. The nanoTiO2 water-based rolling fluid can not only decrease the minimum rolling gauge and the surface roughness of the work piece, but also prevent direct contact between roller and work piece which could lead to the rolled surface scratches and adhesion defects.

On the Utilization of Shear Modified GTN Damage Model in Cold Rolling

Edge cracking is a commonly observed phenomenon in cold rolling process, but researchers appear to be far from fully understanding its failure mechanism due to the complex stress conditions of steel strip under the rolling condition. In this research, the shear modified GTN damage model coupled with Nahshon-Hutchinson shear damage mechanism was applied to investigate the damage and fracture behavior of steel strip in cold rolling. The results show that the shear modified GTN damage model is competent to predict the damage and fracture behavior of steel strip in cold rolling. By comparison to the cold rolling experiment, it presents that the prediction of edge crack occurrence of the shear modified GTN damage model is more accurate than that of the original GTN damage model.

Effect of Mo on Transformation, Microstructure and Property of Hot-Rolled DP600 Steel

In according with the transformation rules of C-Si-Mn-Cr and C-Si-Mn-Cr-Mo tested steels, rolling experiment was carried out in lab. to analyze the effect of Mo on transformation, microstructure and property of high strength hot rolled dual phase steels. The results showed that the addition of element Mo decreased start temperature of ferrite transformation and restrains pearlite transformation. There was a metastable austenite zone between ferrite and bainite transformation zone of No.2 steel with 0.35% of Mo. After controlled rolling and step cooling process, dual phase microstructures in which fine martensite islands dispersed in soft ferrite matrix were obtained by two kinds of tested steel. With the addition of Mo, yield strength and tensile strength increased by 80MPa and 60MPa respectively, meanwhile, elongation increased slightly.

Experimental and Numerical Simulation of Multipass Hot-Rolling on 7150 Aluminum Alloy

The content discussed in this paper about 7150 aluminum alloy is based on the thermal simulation technology, which is an experiment using the way of temperature compression to do high temperature shaping and passes softening. And using the popular business-oriented finite element software simulates the related data of the multipass hot-rolling on 7150 aluminum alloy. By the obtained parameters, it carries out the hot-rolling experiment and processing of RRA technology. Based on this, it analyzes the experimental and data simulation of multipass hot-rolling on 7150 aluminum alloy.

FEM Analysis of the Deformation Behavior at Thickness Direction in Laboratory Plate Hot Rolling

As significant theory evidence in thick plate or heavy gauge plate hot rolling, the deformation behavior at the thickness direction was investigated. In the present work, multi and single pass rolling processes were studied by 2D explicit dynamic finite element method (FEM) simulation and verified by laboratory hot rolling experiment. The value of stress and strain could be obtained in any passes and time in the hot rolling process accurately. The verified FEM model could be used as an important reference factor for other hot rolling processes. Strain and stress distribution data was obtained from four portions at the thickness direction. A cooper rod was knocked into the hot rolling specimen, as a reference substance to observe the deformation after the hot rolling experiment. In the multi-pass simulation with nearly 10% per-pass reduction, the core metal yield when the total reduction was 40%. The same performance could be achieved when the first pass reduction larger than 20%. However, extremely first pass reduction would cause an instability deformation result in a confusion of microstructure. Finally, the relation between the reduction and the number of rolling passes was discussed.