Both normalized SAE-AISI and SAE-AISI M steel are iron alloys. There are 10 material properties with values for both materials. Properties with values. M is a low alloy, vacuum melted, steel of very high strength and toughness. It is a modified steel with silicon, vanadium and slightly greater carbon and. M high strength low alloy steel. M (M) is a through hardened low- alloyed with very high strength. It is a modified AISI with silicon, vanadium.
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Corrosion pitting also can lead to sheel crack initiation depending on the component, the location of pitting, and cyclic loading conditions. Overheating affects components to various degrees; in some instances, only finish durability is degraded.
Contact Boeing for assistance with questions about repairing or salvaging high-strength alloy steel components that appear to have been damaged by overheating.
4340M / 300M VAR Cr-Ni-Mo-V Aircraft Quality Alloy Steel
Although these guidelines apply directly to landing gear components, they can strel used to plan the overhaul rework of all high-strength steel components.
When properly maintained and overhauled, high-strength alloy steel components demonstrate high levels of service reliability. Boeing can assist in this determination. In general, the best practice is to initiate baking as soon as possible following a plating operation. Proper use of special plating techniques, such as conforming anodes and robbers, can control plating thicknesses and 4430m. Boeing also is developing supplemental, specialized techniques, such as the Barkhausen inspection, to detect base metal heat damage under chrome plating or other protective finishes.
The elevated temperatures reached during hydrogen embrittlement relief baking, which is performed directly after stripping stwel plating operations during overhaul, effectively remove hydrogen generated during these operations.
This can reduce the possibility of chrome chicken-wire cracking and poor runout details. Refer to the Aircraft Maintenance Manual for materials specified for aircraft cleaning and deicing.
There are few options to restore these machined depressions to meet stewl requirements. When the entire face of a lug must be machined to remove damage, stel new lug transition radii should be shaped and positioned in accordance with CMM requirements. The planning flowcharts in CMMs, and are value-added guidelines for planning the rework of any high-strength alloy steel component on a Boeing airplane.
For example, if an axle fractures as a result of chrome-grinding heat damage during manufacture or overhaul, the Barkhausen inspection allows other suspect components to be screened without first performing a chrome strip and temper etch e. This damage often is caused by improper maintenance practices such as jacking adjacent to a jack pad or an inadvertent impact with tools or ground-support equipment e.
Stress concentrations can lead to initiation of cracking by fatigue, stress corrosion, or hydrogen-assisted stress corrosion.
M Alloy Steel (M) | TW Metals
Heat damage generally is removed by carefully machining the base metal. The microstructural anomalies resulting from cadmium embrittlement can lead to component fractures in service.
The heat damage led to cracking through the cylinder wall. However, if high-temperature exposure was short and discoloration of the enamel or primer was minimal, the component may be a candidate for salvage. These parts often are selected for placement in limited-space eteel e.
Overheating damage can be caused by. Figures 14 and 15 show a fracture resulting from an arc burn that developed during LHE stylus cadmium plating. Operators also will benefit from the enhanced reliability and durability of high-strength alloy steel components on their airplanes. Similar grinding burns also have led to the fracture of flap carriage spindle journals figs.
Some heat damage is so severe that the heat-treat condition of material is altered in adjacent areas.
Components made of high-strength alloy steel generally weigh less and require less space to house than components made of lower strength alloys. Operators usually recognize the benefits of using these steels; however, certain characteristics of the steels are not always given proper consideration during component maintenance or overhaul. These cracks may syeel in a fracture or scrap of a component when found while in service or during overhaul.
Xteel should reflect the same careful, detailed review that occurred during the original design. Some tseel and chemicals may accelerate finish degradation and lead to corrosion.
However, the component still may require special consideration or rework because. Testing to these requirements will determine whether a cleaner or chemical is detrimental to protective finishes or base metal. They need to understand the importance of maintaining component finishes while in service, follow proper rework practices, and use Boeing provided maintenance procedures, planning guidelines, and checklists during scheduled maintenance and overhaul processes.
These components provide structural benefits e. In most instances, these repairs involve rework of the base metal. These situations often occur when components are Inadvertently overheated in an oven.
If the damage is local and widespread deformations are not evident, repair may be similar to that required for corrosion and pitting. When grinding chrome to finish dimensions, overheating the base metal can create UTM and OTM formations under the chrome. Organic coatings or sealants may crack or become brittle or discolored wide range of temperatures. Maintenance efforts focus on corrosion prevention and removal in addition to normal checks for wear and free play.
When removing damaged material from part surfaces during rework, the new transitions or radii should not cause an unacceptable increase in stress concentration at the location or degrade the original design features. If the plating runouts are blended or machined to remove the abrupt plating edge, the techniques must be well controlled to avoid damaging the adjacent base metal.
Improper blending can remove the required shot-peened layer or zteel undercuts or grooves at the edge of the plating that can cause cracking in service.