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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The heat damage led to cracking through the cylinder wall. Figures 6 and 7 show service-induced heat damage on the inside diameter of a main gear outer cylinder. If the damage is local and widespread deformations are not evident, repair may be similar to that required for corrosion and pitting.
For example, embrittlement relief baking must begin 10 hr after sulfamate-nickel plating is completed or within 24 hr after plating begins, whichever results in the shortest overall bake delay. Common techniques include detailed visual inspections and other nondestructive inspection methods, such as magnetic particle inspection MPI and fluorescent penetrant inspection FPI.
The infused hydrogen migrates to areas of high stress e. Transitions or radii that are sharper than original design. The delay time between plating completion and baking start typically is observed.
4340M / 300M VAR Cr-Ni-Mo-V Aircraft Quality Alloy Steel
Maintenance efforts focus on corrosion prevention and removal in addition to normal checks for wear and free play. Damage should be repaired soon after it is found. Possible mechanical damage to a high-strength alloy steel component should be evaluated by the operator and repaired as needed.
Operators should ensure that cleaners and chemicals are tested before use in accordance with Boeing document D6Evaluation of Airplane Maintenance Materials.
Operators should ensure that proper SOPM and CMM documentation is used during overhaul and rework of high-strength alloy steel components.
M Alloy Steel (M) | TW Metals
In these cases, the cracks can propagate to the critical length and result in ductile fracture of the component. Contact Boeing for assistance, if needed. Slight or no discoloration of the enamel or primer may indicate the cadmium plating was not heated to the extent that cadmium embrittlement would be suspected.
Improper rework and overhaul practices may result in loss of finish, corrosion, and damage 4340j or alteration of the base metal, which may require unscheduled maintenance between overhauls. Design finishes are restored and new bushings with design interferences and dimensions are installed because bushing wear limits do not apply during overhaul. Local blends on inner cylinder outer diameter surfaces and outer cylinder inner diameter surfaces often are filled with sulfamate-nickel plating steel restore them to dimensions that are suitable for subsequent chrome plate application.
The pit then grows through the compressive layer, and the change in residual stress state and the pit geometry initiate stress corrosion cracking.
High-strength alloy steels referenced in this article generally have been heat-treated above ksi [, psi]; most have been heat-treated above ksi. With these benefits comes a need for airline personnel to exercise precise care when reworking high-strength alloy steel components during scheduled maintenance and overhaul. Most can be attributed to a lack of familiarity with high-strength alloy steels. High-strength alloy steels can experience rapid crack propagation from stress corrosion under certain loading conditions.
After overhaul operations are completed, the component is returned to service in accordance with CMM requirements. Plating 43440m a transition radius transition or undercut will create a stress concentration that 434m0 cause crack initiation.
These high-strength materials provide significant structural benefits and can result in a weight savings. Corrosion pits are stress concentrations. Determining whether cadmium has migrated into the grain boundaries of cadmium-plated, high-strength alloy steel components requires destructive testing of the components. Salvage was not possible. SOPM and CMMs, and provide guidelines that indicate when chrome must be removed during overhaul.
This may result in a shorter than planned time between component overhauls. Truck fractures most often occur at maximum ground loads such as after fueling or during preflight taxi. The resulting damage also could precipitate crack initiation and removal of the part from service.
These situations often occur when components are. Touching up damage to accessible enamel and primer in a timely manner can prevent the formation of corrosion pits and reduce the need for excessive rework during overhaul.
These parts often are selected for placement in limited-space envelopes e.
M High Strength Low Alloy Steel,M alloy steel bar suppliers | Shew-E Steel Pipe
The degree to which the mechanical properties are changed depends on the temperature and duration of exposure. The elevated temperatures reached during hydrogen embrittlement relief baking, which is performed directly after stripping or plating operations during overhaul, effectively remove hydrogen generated during these operations.
These fractures may be caused by a combination of degraded protective finishes on the truck inner diameter, poor drainage, and contact with the corrosive chemicals in washing solutions or deicing compounds. Testing to these requirements will determine whether a cleaner or chemical is detrimental to protective finishes or base metal.
These situations often occur when components are Inadvertently overheated in an oven. Axle heat damage caused by a wheel bearing fracture may lead to such a condition.
300M Alloy Steel (4340M)
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. SOPM provides details about the inspection process and interpretation of the results. As a rule, if material removal exceeds 0. This section provides guidelines for reworking high-strength alloy steel components and describes some of the implications of improper rework procedures. This will help operators achieve the benefits associated with high-strength alloy steels and avoid potential safety issues resulting from damage caused by stress concentrations, detrimental surface conditions, corrosion, improper processing, or other factors.
This includes repairing damaged finishes to prevent corrosion and ensuring that solvents and materials that come in contact with the finishes do not result in premature degradation and unscheduled component removal.
Overheating will not alter the heat-treat conditions of the base metal if the temperatures are below the original tempering temperature. Stress concentrations can lead to initiation of cracking by fatigue, stress corrosion, or hydrogen-assisted stress corrosion.
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. The use of high-strength alloy steel parts is economical because it reduces weight, thereby allowing for more efficient aerodynamic surfaces and providing the potential for increased payload and fuel.
Visual evidence of chicken-wire cracking after chrome grinding indicates poor chrome quality and also may indicate the possibility of base metal heat damage.