May. 21, 2026
Refining is a crucial process in modern steelmaking. It refers to transferring molten steel from the converter or electric arc furnace after primary refining to another reaction vessel for further purification and composition adjustment, also known as “secondary refining”.
Modern steelmaking processes are generally divided into two stages: primary refining and secondary refining. Primary refining mainly involves melting the charge materials, dephosphorization, decarburization, and preliminary alloying under an oxidizing atmosphere. Secondary refining, however, is carried out under vacuum, inert gas, or controlled atmosphere conditions to perform deep decarburization, degassing, deoxidation, inclusion removal, and inclusion modification treatment, while also precisely controlling the chemical composition and temperature of molten steel. The purpose is to improve steel cleanliness, optimize product structure, develop high value-added steel grades, reduce energy consumption and production costs, and improve economic efficiency.
RH vacuum refining technology originated in the 1950s. In 1957, the Allegheny Ludlum Corporation applied for a patent on molten steel vacuum degassing technology, marking the beginning of vacuum degassing development. In 1958, Rheinstahl Company of Germany cooperated with Heraeus Vacuum Pump Works to successfully carry out industrial production trials and achieved excellent refining results. In 1959, the German Metallurgical Association officially named the process “RH”.
Japan subsequently became one of the fastest-growing countries in RH technology development. In 1972, Nippon Steel developed the RH-OB process, which enabled temperature compensation through oxygen blowing and significantly improved decarburization efficiency. During the 1980s and 1990s, Kawasaki Steel further developed RH-KTB and KPB (MFB) injection technologies, realizing secondary combustion, oxygen blowing decarburization, and desulfurizing agent injection through top lance systems. These advanced technologies enabled the production of ultra-low carbon steel with carbon content below 20 ppm.
The development of RH technology in China began after the 1990s. At present, most medium and large-scale steel plants in China are equipped with RH vacuum refining furnaces, and RH technology has become one of the key core processes for producing high-quality clean steel.
At the beginning of RH vacuum refining, the ladle containing molten steel is transported by overhead crane onto the RH ladle car. The ladle car then moves beneath the vacuum vessel, where the hydraulic lifting system raises the ladle to the designated treatment position. Operators first carry out temperature measurement, sampling, and oxygen content analysis. The ladle is then lifted further so that the snorkels at the bottom of the vacuum vessel are immersed into the molten steel, while argon gas injection begins through the up-leg snorkel and the vacuum pump system starts operation.
As argon gas is continuously injected into the up-leg snorkel, the density of molten steel inside the up-leg decreases, creating a static pressure difference between the up-leg and down-leg snorkels. This pressure difference drives the molten steel to circulate continuously through the up-leg, vacuum vessel, and down-leg. During this circulation process, metallurgical reactions such as hydrogen removal, decarburization, and inclusion removal are carried out under high vacuum conditions.
During the vacuum degassing stage, molten steel continuously circulates under specified low-pressure conditions, reducing hydrogen content to the target level and thereby improving steel quality and resistance to defects.
For low-carbon or ultra-low-carbon steel production, vacuum decarburization treatment is required. In this process, carbon in the molten steel reacts with oxygen to form carbon monoxide gas, which is removed by the vacuum system. When oxygen content in the steel is insufficient, oxygen can be supplied through the top lance to maintain the decarburization reaction. After decarburization is completed, aluminum is added for deoxidation treatment.
Subsequently, alloying materials are added into the vacuum vessel through the vacuum hopper system for precise composition adjustment. After refining is completed, temperature measurement, oxygen analysis, and chemical composition inspection are performed again. Once the molten steel meets process requirements, the vacuum pump system is shut down sequentially, the vacuum vessel is returned to atmospheric pressure, and the ladle car is lowered back onto the rail position. The up-leg gas injection automatically switches from argon to nitrogen. The ladle is then transferred to the insulation and wire-feeding station before finally being transported by crane to the continuous casting turret for casting.
The RH vacuum refining furnace mainly consists of the vacuum vessel, ladle lifting system, vacuum pump system, condenser, alloy feeding system, and top lance system.
The vacuum vessel is the core area where vacuum metallurgical reactions take place. Its inner wall is lined with refractory materials, and two snorkels are installed at the bottom: the up-leg snorkel and the down-leg snorkel. Through argon blowing, circulation flow is generated to realize continuous vacuum treatment of molten steel.
The ladle lifting system mainly consists of the ladle car, lifting mechanism, and hydraulic system. Its function is to lift the ladle as a whole so that the snorkels can be immersed into the molten steel while ensuring stable and reliable refining operation.
The vacuum system generally adopts multi-stage steam ejector vacuum pumps. High-speed steam creates a negative pressure zone that continuously extracts gases generated inside the vacuum vessel, thereby establishing a high-vacuum environment. The condenser in the system is responsible for condensing condensable steam in the mixed gas flow, reducing the load on downstream ejectors and improving vacuum efficiency.
The alloy feeding system adds alloy materials and deoxidizers into the vacuum vessel through vacuum hoppers to achieve precise control of molten steel composition. The vacuum vessel transfer car is used for vacuum vessel replacement and maintenance operations.
The top lance and preheating burner are important auxiliary devices in vacuum refining. The preheating burner is mainly used for vacuum vessel preheating and refractory baking. The top lance performs functions such as melting cold steel additions, oxygen blowing decarburization, aluminum heating compensation, and vacuum vessel baking, making it an essential tool for ultra-low-carbon steel production.
Compared with traditional steelmaking processes, RH vacuum refining offers significant advantages. It can effectively remove hydrogen, nitrogen, oxygen, and non-metallic inclusions from molten steel, greatly improving steel cleanliness. At the same time, RH technology possesses excellent decarburization capability, enabling stable production of ultra-low-carbon steel, automotive sheet steel, high-strength steel, silicon steel, stainless steel, and other high-end steel grades.
In addition, RH refining features fast circulation speed, high refining efficiency, precise composition control, and excellent compatibility with continuous casting operations. Therefore, it has become an indispensable process in modern clean steel production.
With the continuously increasing demand for high-quality steel products, RH vacuum refining technology is continuously developing toward higher vacuum levels, greater automation, lower energy consumption, and higher refining efficiency. In the future, RH vacuum refining technology will play an even more important role in advanced steel manufacturing.
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Customized metallurgical machinery and equipment range: Electric Arc Furnace, Submerged Arc Furnace, LF Refining Furnace, Vacuum Furnace, Induction Furnace, Dust Remove System, Water Treatment Equipment, etc. Providing the most advanced equipment integration services, metallurgical equipment can be customized according to different needs of customers, and production capacity can be adjusted according to customer requirements.
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The 5 ton electric arc furnace for steel-making is a special purpose equipment that makes ordinary steel, quality carbon steel, alloy steel and non-corrosive steel with electric arc as heat source and scrap steel (iron) as raw material.
15-ton electric arc furnace is used for the short-process steelmaking process, using 100% scrap steel or scrap steel + molten iron (pig iron), or scrap steel + sponge iron (DRI) as raw materials for steelmaking.
The 30-ton AC electric arc furnace is used to melt scrap steel to produce steel. Electrical energy is used to melt scrap steel. An arc forms between the charged material and the electrode.
30 Ton electric arc furnace is used for steelmaking short process smelting, using 100% scrap steel or scrap steel + molten iron (pig iron), or scrap steel + sponge iron (DRI) as raw materials for steelmaking.
The 50-ton ultra-high power electric arc furnace (50TUPH EAF) adopts ultra-high power, high impedance technology, bottom tapping technology (ETB), furnace wall oxygen oil burner and furnace door carbon-oxygen gun technology.
DC electric arc furnace is an electric arc furnace supplying electric energy with DC power supply. There is only one electrode on the top of the DC arc furnace, which is the negative electrode, and the bottom electrode is the positive electrode.
Electric arc furnaces are used to melt scrap steel for steel production. Electrical energy is used to melt scrap steel. An arc forms between the charged material and the electrode. The heat generated by the arc melts the scrap.
Electric arc furnace steel making is a steelmaking method that uses the thermal effect of electric arc to heat the charge for melting.
Ultra-high power electric arc furnace mainly changes the arc characteristics of high voltage and long arc to the arc characteristics of high current, low voltage and short arc
1 ton electric arc furnace is used for melting steel and titanium scrap metal. The principle of electric arc furnace is based on the generation of direct current, which converts electrical energy into heat energy through electrodes to melt the metal.
The closed pig iron furnace (submerged arc furnace iron making) is a non-blast furnace iron making method. Under the premise of guaranteeing the power supply, it is easy to solve the problem by using the reducing agent required by the submerged arc furnace iron making.
The main mechanical device design of Sanui ferroalloy refining furnace combines China's national conditions and draws on international advanced technologies such as Demark and Pyremate.
The Ferronickel submerged arc furnace is a special submerged arc furnace used for smelting nickel-iron alloy. Its main function is to add nickel ore, carbonaceous reducing agent (such as coke) and limestone and other raw materials into the furnace in a certain proportion
The main mechanical device design of Sanui ferrosilicon furnace combines China's national conditions and draws on international advanced technologies such as Demark and Pyremate.
The main mechanical device design of Sanui high carbon ferrochrome furnace combines China's national conditions and draws on international advanced technologies such as Demark and Pyremate.
Industrial silicon submerged arc furnace is an important equipment in silicon ore processing, playing a key role in the silicon industry.
The manganese silicon alloy furnace is mainly used to smelt silicon-manganese alloy, which is an alloy containing silicon and manganese.
The design of the submerged arc furnace main mechanical device by Sanui is based on China's national conditions and draws on international advanced technologies such as Demark and Perlmutter.
Submerged electric arc furnace is mainly used for reducing and smelting raw materials such as ore, carbonaceous reducing agent and solvent. It mainly produces ferroalloys such as ferrosilicon, ferromanganese, ferrochrome, ferrotungsten, silicon-manganese alloy, etc.
Titanium slag production adopts titanium slag electric furnace (circular furnace and rectangular furnace according to its shape) smelting process.
The LF 20 T ladle refining furnace has the functions of arc heating under normal pressure, argon blowing and stirring at the bottom of the ladle, and reducing slag making in the ladle.
LF ladle refining furnace is a bottom-blown argon ladle furnace with three-phase submerged arc heating under normal pressure. It is a device for refining molten steel in a ladle.
VD vacuum refining furnace is a commonly used refining process equipment, mainly used for deoxidation, impurity removal and other operations of molten steel, so as to obtain high purity, low impurity content of high quality steel.
VOD vacuum refining furnace has multiple functions such as vacuum degassing, oxygen blowing decarburization, vacuum charging, argon blowing stirring, non-vacuum temperature measurement sampling, wire feeding, etc.
The cast steel melting induction furnace has outstanding advantages in heat penetration or melting soft magnetic alloys, high resistance alloys, platinum group alloys, heat-resistant, corrosion-resistant, wear-resistant alloys and pure metals.
Metal silicon smelting furnace is a metal silicon medium frequency melting furnace, which consists of furnace body, water and electricity introduction system, furnace tilting device, etc. It has fast melting temperature rise, easy to control furnace temperature and high production efficiency.
Medium frequency induction furnace mainly used for melting steel, alloy steel, special steel, stainless steel, and can also be used for melting and casting non-ferrous metals such as copper, aluminum, lead, zinc, etc. The customized range of induction furnaces sold by Sanrui ranges from 0.1 tons to 10 tons.
Medium frequency induction furnaces are mainly used for melting steel, alloy steel, special steel, stainless steel, and can also be used for melting and casting non-ferrous metals such as copper, aluminum, lead, and zinc.
Medium frequency aluminum melting furnace is used for melting and heating aluminum, scrap aluminum, aluminum ingots, and aluminum alloys; The melting capacity ranges from 100KG to 3000KG.
An induction furnace is an electric furnace that uses the induction electrothermal effect of the material to heat or melt the material. The main components of an induction furnace are sensors, furnace body, power supply, capacitors and control system.
The 3-ton medium frequency coreless induction furnace adopts a 6-phase 12-pulse double rectifier control system. A 2000KVA special rectifier transformer is used for the 2000KW medium frequency power supply.
The conductive arm of an electric arc furnace (EAF) is primarily composed of the front electrode conductive arm holder, a water-cooled clamping ring, the arm body, and the rear conductive copper plate.
The scrap charging basket of the electric arc furnace is mainly used for loading and conveying raw materials such as scrap steel into the electric arc furnace for smelting.
There are many insulation links between the EAF electrode holder and the conductive cross arm body, which greatly simplifies the cconductive cross arm structure and is a new type of electrode arm on the ultra-high power arc furnace.
Generally, the furnace cover of the electric arc furnace adopts the tubular water-cooled closed tube furnace cover structure.
The electrode lifting mechanism of electric arc furnace is composed of conductive cross arm and electrode column device.
Forged copper tile is one of the main accessories in submerged arc furnace (silicon metal furnace, calcium carbide furnace and iron alloy furnace). It generates heat energy due to passing through large current at high temperature, and is easy to be damaged due to poor working environment.
The furnace cover lifting and rotating device consists of a furnace cover lifting mechanism, a rotating mechanism and a rotating frame.
Submerged arc furnace pressure ring is used to monitor the change of air pressure in the furnace in real time, and adjust the air pressure automatically or manually according to the preset parameters to ensure the stability of air pressure in the furnace
Submerged arc furnace water-cooled Roof is an important part of submerged arc furnace (also known as electric arc furnace, calcium carbide furnace or mining furnace), which is mainly used to close the top of furnace body and bear the high temperature and pressure in the furnace.
Short network bus systems), also known as high current line, refers to the general term of the carrier fluid from the secondary outlet terminal of the transformer to the electrode (including the electrode).
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