No abstract

Seat and plug are components of control valve that are always in friction contact. The plug usually wears out. One of the efforts in battling this wear is hardfacing, a process of cladding the base metal to increase its surface hardness using SMAW. This research is aimed to investigate the effect of welding current on weld surface hardness. The experiments used stainless steel (ASTM A316) for the plug materials and Stellite 6, which was an electrode with 3.2 mm in diameter, for the filler metal. Flat welding position was used. The current was varied from 120 A to 140 A and then to 160 A. Results of the hardness tests done on the weld surface show that when the welding current was increased from 120 A to 140 A, it increased the surface hardness from 465 HV to 514.7 HV. Subsequent current increase from 140 A to 160 A decreased the surface hardness from 514.7 HV to 423 HV.Sebuah control valve memiliki seat dan plug yang selalu bergesekan, sehingga plug sering mengalami keausan. Salah satu upaya untuk mengurangi keausan dengan cara hardfacing, yaitu penambahan material (cladding) pada logam induk dengan maksud meningkatkan kekerasan permukaan. Penambahan material dapat dilakukan dengan pengelasan SMAW, dimana salah satu parameter yang berpengaruh terhadap kekerasan lapisan lasan adalah besarnya arus listrik pengelasan. Tujuan penelitian adalah untuk mengetahui pengaruh arus listrik pengelasan terhadap kekerasan lapisan lasan. Metode penelitian dimulai dengan menyiapkan baja tahan karat (ASTM A316) digunakan sebagai material plug dan material stillite 6 sebagai material penambah yang berupa berupa elektroda berdiameter 3.2 mm. Pengelasan dengan posisi datar dengan variasi arus pengelasan adalah 120 A, 140 A dan 160 A. Hasil pengujian kekerasan menunjukkan bahwa peningkatan arus lasan dari 120 A ke 140 A meningkatkan kekerasan permukaan lasan  dari 465 HV menjadi 514.7 HV. Peningkatan arus lasan berikutnya dari 140 A ke 160 A menyebabkan terjadinya penurunan kekerasan permukaan lasan dari 514.7 HV menjadi 423 HV.

Aluminum and steel are used to be a construction for a building outdoor panel. Aluminum and steel are connected by bolt and nut. An atmosphere due to a corrosion of the aluminum. The corrosion possibly to cause the hole diameter of bolt and nut to become larger. Thus the bolt and nut can not enough strong to hold the panel. The panel may collapse. The aim of the research is first to answer a question where does the corrosion starts. The second is to know the effect of ratio surface area of steel with aluminum on the corrosion rate of aluminum. The research is started to cut a steel and aluminum flat into variation surface areas. Next, the steel and aluminum are bolted as samples for corrosion test. The samples are divided into two groups. The group A was immersed in NaCl (10%) and the groups B was immersed in HCl 10%. The corrosion rate is calculated with loss weight method. The conclusions are as follow. The corrosion does not start from the bolt hole but from the edge of aluminum. Increasing the ratio of surface area (steel/aluminum) increases the corrosion rate of aluminum.

Steel that has been aluminized said as hot dipping aluminizing has better protection against corrosion and can protect against temperatures as high as 800°C. In hot dipping aluminizing, Steel is immersed into a molten aluminium for certain dipping time. The research aims to know the effect of preheating and dipping time on the toughness of low carbon steel. The method research was started by cutting the low carbon steel plate, according to ASTM E23 (Charpy test sample) into 16 pieces samples. Then the samples were grouped into four groups. Group-1 was initial samples. The Group-2 was directly immersed into molten aluminum 700 0C, for dipping time 5 minutes. The Group-3 was preheated at 700 oC for 30 minutes and then to be aluminized (700 oC) for dipping time 5 minutes. The Group-4 was preheated at 700 oC for 30 minutes and then to be aluminized (700 oC) for dipping time 10 minutes. Finally, all groups were tested by the Charpy test at room temperature. The results show that the aluminizing increases the toughness of low carbon steel from 228.125 KJ/m2 to 312.5 KJ/m2. The preheating process before aluminizing increases sharply the toughness of low carbon steel from 228.125 KJ/m2 to 512.5 KJ/m2. The increasing dipping time from 5-minute to 10-minute increase gradually the toughness from 512.5 KJ/m2 to 556.25 KJ/m2.

Wire rope is made from several steel  wires a combined form a strand, a couple of strands twisted around the core to form a steel rope. One example of its usage is on the bridge to provide support for a heavy load. The steel wire is composed of several parts that is, steel wire, core and wire strand. Increasing the hardness of steel wire have the impact, the hardness of the steel wire. In an effort to improve the hardness of steel wire, there are opportunities to increase the hardness of steel wire with aluminizing method. The aim of this research is to find out the hardness of Wire in aluminizing process with alloys Al - Cu - Sn. Moreover to the research also aims to focus on the addition of Sn element in Al - Cu liquid. The methodology research was preceded by spliting wires from the wire rope. After that cut the wire into the sample wire. Then soak the wire into Al - Cu – Sn liquid at a temperature of 700ºC for ± 3 minutes. Elements of Sn which contained in the composition of Al - Cu - Sn vary from 0 % , 10 % and 20 % , while for CU’s component is 10 % and the rest of is Al, and the latter only elements of Al - Sn, without adding Cu element. Wire samples were then take away and cooled at room temperature, then test the wire by using micro hardness test, the test data was analyzed with Anova and finally made a conclusion. The results of this of this research showed that for the violence that occurs in the intermetallic layer shows the increase in value of hardness obtained on steel wire.