The generation, harm, reduction, and treatment of oxidation during forging heating process

During the heating process, forging materials may produce defects such as oxidation, decarburization, overheating, overburning, cracking, etc. Among them, oxidation is difficult to avoid.

Oxidized skin · generation

During the combustion process, oxidizing gases (such as O2, CO2, H2O, SO2, etc.) combine with iron elements to form an oxide layer composed of Fe2O3, Fe3O4, FeO, etc. from the inside out, which is called oxide skin. The amount of oxide scale depends on the type of steel, furnace type, and heating atmosphere.

Oxidized Skin · Hazards

▶ Material loss and waste;

▶ Affects the surface quality of forgings;

▶ Intensify the wear of tools/molds and reduce their lifespan;

▶ Corrosion of the bottom of the heating furnace reduces its lifespan.

Oxidized Skin · Causes of Formation

▶ Furnace gas. There are generally three types of gases in flame heating furnaces, namely oxidizing gases (such as O2, CO2, H2O, SO2, etc.), reducing gases (CO, H2, etc.), and neutral gases (N2). When there is too much gas in the furnace, the flame burns fully, and the nature of the furnace gas shows oxidation, which is easy to form thick oxide skin; When the gas supply in the furnace is insufficient, the flame combustion is not sufficient, and the nature of the furnace gas appears to be reducing. The formed oxide skin is very thin, but it is not easy to remove;

▶ Heating temperature. The higher the temperature of the billet, the more intense the oxidation and the thicker the oxide skin. When the temperature is below 600 degrees Celsius, the oxidation rate is slower, and when the temperature is above 900 degrees Celsius, severe oxidation begins;

▶ Heating time. The longer the heating time of the billet, the more intense the oxidation, and the thicker the oxide skin;

▶ Material. The higher the carbon content in the steel material, the less oxide skin forms. This is because the reducing gas CO is formed during the steel oxidation process, weakening the effect of the oxidizing gas; The alloy elements in steel (such as Cr, Ni, Al, Mo, etc.) can form a dense oxide film during the heating process, preventing further oxidation and reducing oxidation.

Scale prevention and reduction

▶ Before heating the raw materials, ensure that they are not decarburized or oxidized;

▶ On the premise of ensuring the quality of the billet, try to shorten the heating time as much as possible, especially during the high-temperature stage;

▶ On the premise of ensuring complete combustion, try to reduce gas or water in the furnace as much as possible;

▶ Prevent external air from entering the furnace. For example, the sealing of the furnace should be strict to ensure relatively low positive pressure inside the furnace;

▶ The raw materials are loaded less, loaded frequently, and discharged in a timely manner;

▶ Using antioxidant media/coatings;

▶ Adopting electric heating, low oxidation/no oxidation heating, especially precision die forging, high alloy and non-ferrous metal forging.

Scale removal before forging

▶ Soak in cold water. After the blank is produced, it can be immersed in cold water for 2-3 seconds to cause the oxide skin to contract, crack, or become brittle, and fall off when cooled;

▶ High pressure water cleaning. The oxide skin contracts, cracks or becomes brittle when cooled, and is washed away by high-pressure water. It is suitable for hot blanks with larger cross-sectional dimensions (50-150mm);

▶ Use tools such as wire brushes, scrapers, scrapers, etc

Technical Measures for Forging Special Alloys

What are the working principles of Screw press?

Technical Measures for Forging Special Alloys

What are the working principles of Screw press?

In July 2019, Minghui Company signed contracts with Korean clients for J58A-4000T and J58A-630T

2020-12-04

Successful installation and commissioning of J58A-4000T electric Screw press exported to South Korea

2020-12-04

Qingdao Minghui Metal Forming Machinery Co.,Ltd specializes in the production of J58A series electric CNC Screw press and FP/MP series hot die forging presses. The company has a strong technical force. Since its inception, the company has been adhering to the business philosophy of "responsibility, integrity and pragmatism", and has been forging ahead in business activities.

Qingdao Minghui Metal Forming Machinery Co.,Ltd

Address: Taiwan Industrial Park, Jiaozhou City, Qingdao, Shandong
E-mail: sales@qdmhjx.com

Contacts: Mr Wang
Phone: +86 18663977787

Fax: 86-0532-83281398

Address: Taiwan Industrial Park, Jiaozhou City, Qingdao, Shandong
E-mail: sales@qdmhjx.com

Contacts: Mr Wang
Phone: +86 18663977787

Fax: 86-0532-83281398