Bintang Adjiantoro

Tensile properties of the modified 13Cr martensitic stainless steels

This paper reports the influence of Mo and Ni on the tensile properties of the modified 13Cr martensitic stainless steels in tempered condition. Four steels with different content of Mo and Ni were prepared by induction melting followed by hot forging, quenching and tempering. The experimental results showed that the addition of about 1% and 3% Mo has a beneficial effect to increase both the tensile strength and the elongation of the steels. On the contrary, the addition of about 3% Ni into the martensitic stainless steel results in decreasing of both the tensile strength and the elongation. Among the alloys investigated the 13Cr3Mo type steel exhibited largest tensile strength of 1348 MPa and largest elongation of 12%. The observation on the tensile fractured surfaces by using scanning electron microscope supported these findings.

The effect of tempering treatment on mechanical properties and microstructure for armored lateritic steel

High demand of armor material impacts on the use of lateritic steel as alternative armored material, therefore an increase of its mechanical properties is necessary. Quenching and tempering process can be used to increase the mechanical properties of the lateritic steel. The variables that used in this research are variation in media quench (water, oil, and air) and variation in tempering temperatures (0, 100, and 200 °C). The results show that specimen with water quenchant tempered at 100 °C have the highest average on hardness (59.1 HRC) and tensile strength. Specimen with oil quenchant tempered at 100 °C has the highest impact toughness (52 J). Secondary hardening and tempered martensite embrittlement phenomenon is found in some specimens where its hardness increased and its impact toughness decreased after the tempering process. Microstructures which formed in this process are martensite and retained austenite phase with fracture types are brittle.

Characteristic of Mechanical and Morphological Properties of Heat Rolled Laterite Steel with Variety of Size Reduction

Indonesia has the most laterite ore reserves in the world. The element originated from the laterite ore is one of the materials in the steel industry. Despite its plentiful of reserves, laterite steel ore has not been used to its maximum potential. This research aims to overview reduction effect on mechanical properties of laterite steel as a result of heated rolling process with various reduction. The reduction variety used in this research were 30%, 40%, 50%, and 60%. Also, the temperature was 980oC. As a result of this research, the increment of reduction followed by the increment of hardness and firmness level of laterite steel. It is proofed by hardness and tensile test. Firmness of the material increased as the reduction increases. The most optimized mechanical properties obtained by 50% reduction, the hardness number was 280.03 HB, tensile strength 620 MPa, elongation 32%, yield 493.33 MPa. Micro structures which formed in this process are ferrite and pearlite phase with very fine pellet size and even pearlite distribution. Fracture types are brittle and ductile fracture with very fine pellet size.

Developing of Mechanical Properties for Reinforcing Bar Steel through Heat Treating with Various Cooling Media

In this study, mechanical properties development of reinforcing bar steel (rebar) has examined through heat treatment process. This rebar was made from low carbon lateritic steel with the small amount of alloying elements Cr,Mn and Ni. There were 4 rebar steel samples that consisted of rebar steel was applied hot rolled at 1200 °C at the beginning process in factory (sample A) and three others were conducted by quenching (sample B, C and D). The various of cooling media such as water (sample B), oil (sample C) and air (sample D) have applied to obtain different microstructure behavior and also mechanical properties. Initial heating was conducted to B,C and D rebar specimens at the austenitizing temperature (950 °C) for 1 h and followed by quenching. The experimental results showed that water quench exhibited of higher hardness level (50,26 HRC) for rebar steel but decreasing in toughness (34 Joule) and elongation (4%) than as cast because of martensite phase formed. Sample C showed that martensite and the small amount of retained austenite with hardness and tensile strength below the sample B, but elongation and energy absorbed were above. The lowest of hardness and tensile strength were obtained from sample D. It was appropriate with microstructuree formed as follows ferrite-pearlite phase and widmanstatten-bainite cluster. Nevertheless, sample D is suitable treatment for tensile strength and elongation requirements rebar standard, there are 558 Mpa and 26% respectively (min. 440 MPa and 20%).