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Quenched and tempered steels are needed for highly-stressed structures in military and non-military equipment. This paper was written for studying the structure and properties (hardness and impact energy absorbed) of medium-carbon and carbon-manganese steels before and after Quench+Temper and Double Quenched+Tempered. Because water is cheap and easy to control, it was used as a quenching medium. This study compares the hardness and impact energy absorbed of quenched plus tempered and double quenched plus tempered steels. The results showed that double quenched plus tempered steel hardness was higher than in quenched plus tempered steels. Besides, the grain structure is refiner than that of quenched plus tempered steel. The taking of the austenite temperature and holding time is essential because of the hardness at the end of the quenching process. The study aims to obtain hardness and impact energy from quenching+tempering and double quenching+tempering of medium-carbon and carbon-manganese steel for armor steel. In the first step, five specimens were heated at 900 o C (held for 30 minutes), cooled in freshwater and produced Q900 Steel. Then, these specimens were heated at 750 o C, 800 o C, 850 o C, and 900 o C, held for 30 minutes and provided Q900+750 Steel, Q900+800, Q900+850 Steel, and Q900+900 Steel. These specimens were tempered at 150 o C (held for 30 minutes) and produced Q900+750&T Steel, Q900+800&T Steel, Q900+850&T Steel, Q900+900&T Steel. Martensite reached the cooling period 357 o C to 182 o C, tempered at 150 o C (held for 30 minutes). Hardness for double-quenching and tempering is higher than for conventional. The maximum impact energy of double-quenching and tempering heat treatment of Q900+850&T steel is suitable for armor steel used

Taxes are the main source of government revenue, both central and local governments. Various ways have been done to increase revenue from this tax, including local governments through various regional tax reforms. The purpose of tax reform is to increase regional revenues from the taxation sector which will be used for the prosperity of the people through economic growth and regional development. This study aims to investigate the effect of tax revenue on economic growth in DKI Jakarta Province. The research method used is a quantitative method with data from the DKI Jakarta Province in the 1987-2019 period. Regression analysis will be used and processed with SPSS software. The result obtained from this research is that local tax revenues have a positive and significant effect on economic growth in the DKI Jakarta Province during the period 1987-2019. Regional autonomy policies also affect the economic growth of DKI Jakarta. The implication of this finding is that the sustainability of local tax revenues is needed to increase economic growth in DKI Jakarta. Local tax revenues should also be used to fund productive projects or activities so as to accelerate economic growth.

Armor steel is a high strength and hardness steel that used to protect against damage by an object, individual or vehicle from direct pressure of projectile. In Indonesia, this steel is made of hot rolled plate steel and heat treated by quench and temper, the result is Quenched & Tempered Steels used for military components (such as main batle tank and the like) and commercials (such as making heavy equipment and others) manufactures. The problems of this study can be formulated by "What are the optimum hardness number and toughness that can be achieved by HRP Steel made in Indonesia?". This study aims to find of optimum parameter of quenching and tempering heat treatment to hardness and toughness of HRP Steel made in Indonesia. The method of this study to combining quench and temper heat treatment by optimizing austenitization temperature; holding time of austenization; tempering temperature; holding time of tempering. Optimization are done by using Minitab 16 Software. The result of study are austenitization temperature 900 o C; holding time of austenization 45 minutes; tempering temperature 125 o C; holding time of tempering 45 minutes; hardness prediction 569,96 HVN (and hardness influenced by tempering). For austenitization temperature 900 o C; holding time of austenization 45 minutes; tempering temperature 175 o C; holding time of tempering 45 minutes; prediction of toughness 30.50 J (and toughness influenced by tempering).