Effect of Heat Treatment on
Mechanical Properties of Metal
Case Study
By
Saurabh kore (22MS021)
Apurv Nikam (22MS027)
Ayush lunavat(22MS24)
Sejal Mahajan (22MS025)
Branch: S.E. Mechanical Sandwich
Date of Submission:
Faculty Sign:
Heat Treatment
Heat treatment is the process of heating and cooling High-strength low alloyed (HSLA) steels are actively used in
metals, using specific predetermined methods to obtain bridge construction, oil and gas offshore platforms, the supports
desired properties. Both ferrous, as well as non-ferrous of wind generators, ships, high-pressure vessels, as well as in the
metals, undergo heat treatment before putting them to manufacture of railway transport [1–3]. The important task of
use. reducing metal consumption can be solved by increasing the
strength of rolled steel. There are several ways to increase the
strength of low carbon steels. The first is an increase in carbon
concentration, which has limitations associated with decreased
Heat treatment consists of heating the metal ductility and deterioration in weldability. The second way is
near or above its critical temperature, held for a additional doping with elements that offer solid solution
particular time at that finally cooling the metal in hardening (e.g., Mn and Si). This enables an increase in the
strength of metallic materials. However, to ensure ductility, the
some medium which may be air, water, brine, or
use of normalizing heat treatment is additionally required. An
molten salts. The heat treatment process includes
increase in the concentrations of Mn and Si, as in the first case,
annealing, case hardening, tempering,
also leads to a deterioration in weldability [4]. Microalloying with
normalizing and quenching, nitriding, cyaniding, carbide and nitride-forming elements (Nb, V, Ti) [5–7] is limited
etc. by the increased cost of rolled steels. The third strengthening
method is to apply heat treatment after rolling (e.g., the cost of manufacturing rolled steel [2]. The fourth is by
quenching in oil, high-temperature tempering, or obtaining a fine-grained structure of rolled steels using the
normalization). This, though, significantly increases method of the thermo-mechanical control process (TMCP) [3].
HLSA steel
High-strength low-alloy steel (HSLA) is a type of alloy steel that provides better mechanical properties
or greater resistance to corrosion than carbon steel. HSLA steels vary from other steels in that they
are not made to meet a specific chemical composition but rather specific mechanical properties. They
have a carbon content between 0.05 and 0.25% to retain formability and weldability. Other alloying
elements include up to 2.0% manganese and small quantities of copper, nickel, niobium, nitrogen,
vanadium, chromium, molybdenum, titanium, calcium, rare-earth elements, or zirconium.[1][2] Copper,
titanium, vanadium, and niobium are added for strengthening purposes. [2] These elements are
intended to alter the microstructure of carbon steels, which is usually a ferrite-pearlite aggregate, to
produce a very fine dispersion of alloy carbides in an almost pure ferrite matrix. This eliminates the
toughness-reducing effect of a pearlitic volume fraction yet maintains and increases the material's
strength by refining the grain size, which in the case of ferrite increases yield strength by 50% for
every halving of the mean grain diameter. Precipitation strengthening plays a minor role, too. Their
yield strengths can be anywhere between 250–590 megapascals (36,000– 86,000 psi). Because of
their higher strength and toughness HSLA steels usually require 25 to 30% more power to form, as
compared to carbon steels.[2]
Material & Method
C(%) Si s p mn nb v ti cr
0.16 0.60 0.025 0.03 1.7 0.05 0.12 0.05 0.30
mi No Cu Ai N CE***
0.80 0.20 0.55 0.02 0.025 0.65
Table1:The chemical compositions (in wt%) and CE of the investigated HSLA steels.
Condition Annealed Normalized Hardened Tempered
Temperature, °C 900 900 900 450
Holding time, min 90 90 40 90
Cooling medium Furnace Air Water Air
Table 2: Heat treatment conditions
Table 3: Mechanical Properties of heat treated and untreated steel
Results:
Conclusion:
The effect of the high-temperature heat treatment on the mechanical properties and microstructure
of the HSLA steels processed by various technologies have been investigated. It has been shown that
at a temperature T ≤ 650 °C, associated with the treatment of relieving welding stresses, the
mechanical properties of the investigated steels are stable within the error limits. At a temperature
T ≤ 750° C (for example, enough for thermal shaping) in the steel, obtained by TMCP, the yield
strength decreases from 15% to more than 25% at T ≤ 950 °C (for example, hot stamping). The
mechanical properties of the normalized steel are stable at all studied temperatures. It has been
established that the decrease in the mechanical properties of the TMCP steel is due to intensive
grains growth at T > Ac3 conditioned by several factors, e.g., high dislocation density, rolling
texture, dissolution, and uncontrolled growth of the hardening precipitation (carbonitrides). The
stability of the properties for normalized steel at T > Ac3 is caused by the high stability of austenite
due to the effect of preventing the intensive growth of the grains (Zener pinning).
