The Control And The Role Of Boron In Carbon Silicon Manganese Steel
From the surveys by metal powder supplier, the main difference of the different types
of high manganese is the content of carbon, the range is 0.75% -1.45%. By the large impact, low carbon content. Manganese content is between 11.0% and 14.0%, and generally should not be less than 13%. The high manganese steel is no international standard, manganese content should be greater than 18%. The level of the silicon content, to the impact of toughness is greater, it should be taken as the lower limit, not more than 0.5% is appropriate. Hypophosphatemia low sulfur is a basic requirement, due to the high content of manganese played desulfurization, lowering phosphorus is the most important thing, and try to make the phosphorus less than 0.07%. Chromium is to improve the abrasion resistance, usually in about 2.0%.
The main charge is a high-quality carbon steel (or ingot), high-carbon ferromanganese, medium carbon ferromanganese, high-carbon ferrochrome and high manganese steel scrap. Not only high-manganese steel, any metal castings must not be excessive use of scrap, scrap should not exceed 25%. Then how to deal with the excess back charge? Back charge as long as the waste to a minimum, not to excess. Both intermediate frequency furnace, electric arc furnace melting, always first melting carbon steel, various types of ferromanganese and other precious alloy material, several little at a time into the furnace, precious elements added at the last, in order to reduce the burning . Material block should be as small as possible, the 50-80mm is appropriate. Melting clear, the furnace temperature is 1580-1600 , deoxidation, dehydrogenation, denitrification, available aluminum wire, Si-Ca alloy or SiC material can also be used. Deoxidizer certain pressure deep into the furnace. The molten metal level the cover agent Gaiyan partition outside air. But also calm for some time, so that the oxide inclusions have enough time to go up. However, many companies, only sprinkle the aluminum wire and even aluminum shavings on the molten metal level, do not coverage, it is wasted! During this period, use the carbon ferromanganese to adjust the content of manganese and carbon in time.
Add a small amount of boron powder in the steel can significantly increase the hardenability of steel resistance, and therefore, improve the ability of the hardenability of the boron in the quenched and tempered steel is what other alloying elements could not comparable. Use add aluminum and given nitrogen method, to control the acid-soluble boron content of the steel. Carbon silico-manganese steel quenched and tempered before rolling state. In the regulated quality processed steel, the distribution of boron and impact properties of the different heat treatment or thermal processing. The results show that the different thermal processing course, reversed the impact properties of boron carbide steel after tempering treatment at Grain Boundaries poly precipitation and steel have varying degrees of impact. To improve the degree of uniformity of the boron in the steel, on the one hand to the extent permitted by the process to select a higher thermal processing temperature, on the other hand, oil-cooled fast cold quenching can be avoided along the grain of the boron carbide segregation precipitated .
In carbon silicon manganese steel containing boron swapped tempering treatment, when the nitrogen content in steel is 0.005 wt%, aluminum added in an amount of 800g / t, the acid-soluble boron content of the steel can be controlled close to the total boron content. Boron steel thermal processing or heat treatment temperature is higher than 900 C, most of the boron carbide steel dissolution, the subsequent cooling rate has a great influence on the deposition of boron carbide, the cooling is slower, the more the number of precipitated along the grain, resulting in the precipitation of grain boundary grew up in blocks (such as stacking cooling after hot rolling). Before the heat treatment of quenching and tempering treatment, the thermal processing temperature and the cooling rate can affect the distribution of boron in the steel after quenching and tempering treatment, and impact properties. After 1180 thermal processing, quenched and tempering temperature range of 450 ~ 550 , tempering temperature on the impact properties of boron distribution is not obvious.
Source:http://www.mhcmp.com
by: anelwew
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