Application of permanganese steel

Permanganese steel is an anti-wear steel specifically designed for heavy industry in quarrying, mining, mining, coal, foundry and steel. Permanganese steel can be divided into two categories according to its use:

Wear-resistant steel：

This type of steel contains 10% to 15% manganese, high carbon content, generally 0.90% to 1.50%, most of which is more than 1.0%. Its chemical composition is (%):

C0.90~1.50Mn10.0~15.0

Si0.30 to 1.0 S≤0.05 P≤0.10 this kind of permanganese steel is used the most, often used to make excavator teeth, conical crusher rolling wall and broken wall, jaw crusher fork, ball grinder lining, railway rut, plate hammer, hammer head and so on.

The cast tissue of the above-mentioned components of permanganese steel is usually composed of australs, carbides and pearlescers, and sometimes contains small amounts of phosphorus cocrystalline. When the number of carbides is high, it is often meshed on the crystal boundary. Therefore, the casting tissue of permanganese steel is very brittle, can not be used, need to be solid soluble treatment. The usual heat treatment method is solid soluble treatment, the steel is heated to 1050 to 1100 degrees C, insulation eliminates the cast tissue, obtains a single-phase austral tissue, and then water quenches, so that the tissue remains at room temperature. The strength, plasticity and toughness of steel after heat treatment are greatly improved, so this kind of heat treatment method is often called water tough treatment. The post-heat treatment performance is: b615 to 1275MPa s340 to 470MPa ζ15% to 85% ψ15% to 45% aKl96 to 294J/cm2 HBl80 to 225

Low impact load, can reach HB300 to 400, high impact load, can reach HB500 to 800. Depending on the impact load, the surface hardening layer can reach a depth of 10 to 20mm. The hardened layer of high hardness is resistant to impact abrasive wear. Permanganese steel in the strong impact abrasive wear conditions, has excellent anti-wear performance, so it is often used in mining, building materials, fire and electricity and other machinery and equipment, the production of wear-resistant parts. Under low impact conditions, permanganese steel can not play the characteristics of the material because the hardening effect of processing is not obvious.

The brand size and application range of high manganese steel commonly used in China are: ZGMn13-1 (C 1.10% to 1.50%) for low impact parts, ZGMn13-2 (C1.00% to 1.4%) 0%) for ordinary parts, ZGMn13-3 (C0.90% to 1.30%) for complex parts, ZGMn13-4 (C0.90% to 1.20%) for high impact pieces. The manganese content of the above 4 brand steels is 11.0% to 14.0%.

In the process of cold deformation of impact load, the steel is strengthened by the interaction between misplaced intersection, mislocation and misalisement and misalisement and solute atoms due to a large increase in misplaced density. This is an important reason for process hardening. Another important reason is that the layer error of permanganese Austry is low, and the stacking layer error is easy when deformation occurs, thus creating the conditions for the formation of the ε mastina and the generation of deformation twin crystals. High density misalmicks, misplaced plugs and tangles can often be seen in the deformed hardening layer of conventional components of permanganese steel. ε the appearance of marsomes and metamorphic twin crystals makes it difficult for steel to deform, especially the latter. All these factors make the hardening layer of permanganese steel to be strengthened to a high degree, and the hardness is greatly improved.

Permanganese steel is very easy to process hardening, so it is difficult to process, the vast majority of castings, very little use of forging methods. The casting performance of permanganese steel is good. The melting point of steel is low (about 1400 degrees C), the temperature interval of the liquid and solid phase lines of steel is small, (about 50 degrees C), and the thermal conductivity of steel is low, so the water is well-flowing and easy to pour into molding. The coefficient of line expansion of permanganese steel is 1.5 times that of pure iron and 2 times that of carbon steel, so the volume shrinkage and line shrinkage are larger when casting, and stress and cracks are easy.

In order to improve the performance of permanganese steel, many studies have been carried out on alloying, microalloying, carbon-manganese content adjustment and precipitation enhancement treatment, and have been applied in production practice. The appearance of stable austry manganese steel can greatly reduce the carbon and manganese content of steel and improve the deformation strengthening speed of steel, which can be applied to the working conditions of high and medium impact loads, which is a new development of permanganese steel.

No magnetic steel：

This kind of steel contains manganese is greater than 17%, the carbon content is generally less than 1.0%, often used in the motor industry to make rings and so on. The density of this type of steel is 7.87 to 7.98g/cm3. Because of the high carbon and manganese content, the thermal conductivity of steel is poor. The thermal conductivity is 12.979W/(m.C), about 1/3 of carbon steel. Since steel is a austial tissue, non-magnetic, its magnetic conductivity μ 1.003 to 1.03 (H/m).

Chemical composition:

Permanganese steel is divided into 5 brands according to national standards, the main difference is the carbon content, the range is 0.75%-1.45%. The impact is large and the carbon content is low. Manganese content is between 11.0% and 14.0%, generally should not be less than 13%. Ultra-permanganese steel has no national standard, but the content of manganese should be greater than 18%. The silicon content has a great impact on the impact toughness, so the lower limit should be removed to not be greater than 0.5%. Low phosphorus low sulfur is the most basic requirement, because the high manganese content naturally plays the role of desulfurization, so phosphorus reduction is the most important, try to make phosphorus less than 0.07%. Chromium is improved for wear resistance, generally around 2.0%.

Burden：

The furnace material is determined by the chemical composition. The main furnace materials are high-quality carbon steel (or ingots), high carbon manganese iron, medium carbon manganese iron, high carbon chromium iron and high manganese steel back furnace material. A special reminder here is that people think that as long as the chemical composition is appropriate, you can use more furnace material. This understanding is harmful. This is why some factories have poor product quality. Not only permanganese steel, ultra-high manganese steel, all metal castings, can never be used too much back furnace material, furnace material should not exceed 25%. So, what about the excess back furnace material? As long as the waste is minimized, there will be no excess material back to the furnace.

Melting：

Here focus on the order of feeding, whether using medium frequency furnace, or arc furnace smelting, always smelt carbon steel first, and all kinds of manganese iron and other valuable alloy materials, to be divided into multiple times, each time a small amount into the furnace, valuable elements in the last addition, to reduce burn damage. Blocks should be as small as possible, 50-80mm is appropriate. After melting, when the furnace temperature reaches 1580-1600 degrees C, deoxygenation, dehydrogenation, nitrogen de nitride, aluminum wire can be used, also can be used Si-Ca alloy or SiC and other materials. The deoxygenator must be pressed deep into the furnace. The metal liquid surface is now covered with a covering agent to separate the outside air. Also calm down for a period of time, so that oxides, debris have enough time to float. However, many enterprises, only aluminum wire or even aluminum chips, sprinkled metal liquid surface, and not covered, it is not wasted! During this period, the content of manganese and carbon is adjusted in time with medium carbon manganese iron.

Before the steel is released, it is necessary to bake the pouring bag above 400 degrees C. The use of V-Fe, Ti-Fe, rare earths and other trace elements to do the desmorization treatment, is a necessary means to make a crystallization refinement, it is essential to the product performance impact.

Furnace materials and moulding materials：

To extend the furnace order, when the properties of the steel species and the furnace lining are clearly divided. Manganese steel is alkaline, furnace lining of course choose magnesium materials. Smashing furnace linings should be rotated and re-positioned. Add furnace lining material should not be too thick, each time about 80 cm is appropriate, mash to low temperature for a long time baking. If the production efficiency is improved, the author suggests the use of molded crucibles (Shenyang Lied plant and Hengfeng factory are also sold), from the dismantling furnace, not 1 hour, can be put into production, at the same time molding crucibles on the anti-wear furnace great benefits. Of course, the length of the furnace order has a lot to do with the operator. Many operators, like athletes throwing lead balls, put the furnace material from three or four meters away into the furnace, neither safe nor injured furnace orders, the furnace material should be placed next to the furnace mouth to preheat, and then slowly with a clip to the furnace material next to the furnace material preheat, and then slowly with a clip to put the furnace material down the furnace wall.

Styling materials and coatings should also be consistent with the properties of the metal liquid, or with ZTE materials (e.g. chromite sands, brown coman jade, etc.). If you want to obtain a crystallization refinement of the collective, the use of large heat storage of chromium iron ore is correct, especially the vanishing mold production plant, with which it will overcome the disadvantages of slow cooling.

Casting process design：

Manganese steel is characterized by large solidification contraction, poor heat dissipation, according to which the casting shrinkage rate in the process design to take 2.5%-2.7%, the older the casting, the higher the upper limit should be taken. The relinching of sand and core must be good. The pouring system is open. Multiple scattered ingates are introduced from the thin walls of the casting, and are flat and wide horn-shaped, and the cross-sectional area near the casting is greater than the cross-sectional area associated with the cross-casting channel, allowing the metal liquid to be injected quickly and smoothly into the casting, preventing the temperature difference in the entire casting from being too large. The diameter of the port should be greater than the diameter of the hot joint, close to the hot section, the height is 2.5-3.0 times the diameter, must use the hot port or even pour the port in one, so that sufficient high temperature metal liquid to fill the casting in the solidification contraction space. Place the straight runner and the port high (the sand box is 5-8). slope) is also correct. Pour as low as possible when pouring. Once solidified, loosen the sand box in time. Smart designers are always good at using cold iron, including inner iron in the outer cold iron, it not only refines a crystallization, eliminates shrink holes, shrinks, but also improves the yield of the process, of course, the appropriate amount and specifications should be considered. Internal cold iron should be clean, easy to melt, the amount of use to be less appropriate. The three-dimensional size of the outer cold iron is related to the function of 0.6-0.7 times the three-dimensional size of the coolant. Too small does not work, too large to cause the casting to crack. Castings are expected to remain warm for a long time in the type until they are below 200 degrees C before opening the box.

Heat treatment：

It is usually carried out using a high-temperature bench-type electric furnace. Heat treatment cracking is caused by excessive heating in the low temperature phase. Therefore, the correct operation is below 350 degrees C, the heating speed <80 degrees C/h, 750 degrees C below, <100 degrees C/h, and there are different periods of insulation. By > 750 degrees C, the casting is plastic and can heat up quickly. The insulation time (usually 1 hour/25mm) is determined according to the thickness of the casting at 1050 degrees C; Then quickly rise to about 1100 degrees C to keep warm for half an hour. Castings must be released as soon as possible into the water, out of the water time can not exceed 45 seconds, winter time should be shorter. Heating is too slow at high temperatures, insulation time is too short, and the interval between coming out to water is too long (should not >0.5min), all of which affect the quality of the casting. The inlet water temperature should < 30 degrees C, and after quenching, the water temperature should <50 degrees C, and the water quantity should not be less than 8 times the casting weight. Cold water enters from the lower part of the pool and warm water flows from the top of the pool. Castings move in three directions in the pool.

Cutting and welding：

Because of the poor thermal conductivity of manganese steel, great care should be paid when cutting the pouring port. It is best to put the casting in water, the cut part exposed to the water, cutting a certain amount of molyser left, heat treatment after grinding off.

Many factories, welding and welding become inevitable. The selection of Austrinal-based manganese nickel welding rod (D256 or D266 type), the specification is slender, 3.2mm×350mm, the outer skin is alkaline. The operation uses small current, weak arc, small welding channel multi-weld layer, always maintain low temperature and less heat operation method. Hit while welding to eliminate stress. Important castings must be probed.

Performance characteristics：

After anti-grinding technology treatment, the surface of the material can reach 500-550 cloth hardness, continue to maintain internal flexibility, surface friction minimization, can be welded with permanganese steel or similar materials, can be cut by acetylene oxygen torch, non-magnetic.