The Effect of Sintering Time on Tensile Strength of Nb-v Microalloyed Powder Metallurgy Steels

Abstract

Microalloyed steels can be defined as low alloyed high strength steels which increase the strength of steel by mechanisms such as precipitation hardening, aggregation hardening, particle size reduction, dispersion hardening by adding microalloy elements such as aluminium, niobium, vanadium and titanium in the range of 0.05% and 0.20%. Powder metallurgy is one of the manufacturing methods in which small parts which are difficult to manufacture can be produced in series with some parts which are close to the final shape with minimum material loss and which cannot be produced by other production methods. In this work, effect of different sintering time (1h., 2h. and 3h.) on the tensile strength of powder metallurgy (PM) plain carbon steel and microalloyed steels with different amount of niobium and vanadium content (0-0.1-0.2 wt%) were investigated. As a result, it was determined that the added alloying elements increased the mechanical properties. 0.2 wt % Nb-V added and sintered 2 h. PM steel showed the highest values in yield strength (YS), ultimate tensile strength (UTS).

The Effect of Nickel on the Microstructure, Mechanical Properties and Corrosion Properties of Niobium–Vanadium Microalloyed Powder Metallurgy Steels

“…The densities slightly increased after the sintering process. The findings of similar studies support that the density increases with the sintering process [5,14,[22][23][24]. The contact points expand, and the formation of the neck occurs, and the pores are reduced between the powder particles during sintering.…”

“…When the average grain sizes of alloy 1 and alloy 2 are calculated, while the average grain size of alloy 1 was 36.8 µm, it could be seen that the average grain size of alloy 2 decreased to 30.5 µm due to forming precipitates such as VC(N) and NbC (N) during sintering. The precipitates prevented the austenite grains growth [7,[21][22][23][24]. This may be the result of the creation of small precipitates such as niobium carbonitride (NbCN) and vanadium carbonitride (VCN) during the sintering at 1400 °C or during the post-sintering cooling process.…”

“…calculated, while the average grain size of alloy 1 was 36.8 μm, it could be seen that the average grain size of alloy 2 decreased to 30.5 μm due to forming precipitates such as VC(N) and NbC (N) during sintering. The precipitates prevented the austenite grains growth [7,[21][22][23][24]. In the microstructures of alloys containing 5% and 10% Ni, bainitic structures in which cementite lamellars are shorter than those of pearlite and the austenite grains were observed in the microstructure (see Figure 2).…”

“…When the average grain sizes of alloy 1 and alloy 2 are calculated, while the average grain size of alloy 1 was 36.8 µm, it could be seen that the average grain size of alloy 2 decreased to 30.5 µm due to forming precipitates such as VC(N) and NbC (N) during sintering. The precipitates prevented the austenite grains growth [ 7 , 21 , 22 , 23 , 24 ].…”

Investigation of Thermomechanical Processing of Nb Microalloyed Steel Produced by Powder Metallurgy

“…These include alloying, sintering temperature and time, pressing technique such as cold, warm and hot pressing, and deformation rate. Alloying generally increases porosity [18,33], however sintering time and temperature reduce porosity [33,34]. Table 3 shows the relative density (%) of the unalloyed and Nb microalloyed steels.…”