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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Chicken-wire cracking noted in SOPM indicates that the chrome should be stripped and replated.

These situations often occur when components are Inadvertently overheated in an oven. The best safeguard against corrosion is to ensure that finishes conform to the design and that design improvements are incorporated as minor changes whenever possible. Discontinuous shot-peening can lead to crack initiation at the tensile surface stresses adjacent to edges of abrupt compressive layer runouts no fadeout.

When locally machining out corrosion or damage during overhaul, a gradual transition into the reworked depression is necessary. All portions of a component that are to be shot-peened should first be completely stripped; no cadmium residue should remain on the surface.

This section provides guidelines for reworking high-strength alloy steel components and describes some of the implications of improper rework procedures. One type of rework or overhaul, sulfamate-nickel plating, is common on shock strut cylinder diameters and is used to repair lug faces to design dimensions as follows: 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.

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 part is then stripped of all cadmium and replated near the end of overhaul. In addition, airline personnel need to understand the importance of maintaining component finishes while in service in situor on the airplane.


Landing gear truck fractures have occurred in service because of corrosion on the inner diameter of the steeel gear truck beam figs.

Aero 22 – Maintenance of High-Stregth Alloy Steel Components

Common techniques include detailed visual inspections and other nondestructive inspection methods, such as magnetic particle inspection MPI and fluorescent penetrant inspection FPI.

For stewl, when a coating such as chrome or nickel plating is applied stewl surfaces to prevent wear or corrosion, the coating must exhibit proper runouts that terminate before the tangent of fillet radii, edges, or other shape changes.

See SOPMs and Unusual conditions such as refused takeoffs and local fires. After hydrogen-generating operations, relief bake delay time limits must be observed to ensure complete hydrogen removal. Corrosion pitting also can lead to fatigue crack initiation depending on the component, the location of pitting, and cyclic loading conditions. Components manufactured from steel alloys heat-treated above ksipsi should be reworked in accordance with guidelines in Component Maintenance Manuals CMM, and Discoloration of the enamel, primer, or chrome or evidence of cadmium damage on the inner diameter of the axle may require the heat-damaged component be removed from service.

Wheel bearing fractures or high-energy refused takeoffs often result in high local heat 43440m an axle. During overhaul, many landing gear components are completely stripped to replace nickel and chrome plating. Many landing gear, flap track, flap carriage, and other flap actuating components on Boeing airplanes are made of high-strength alloy steels, such as M, Hy-Tuf, M, and M. When grinding chrome to finish dimensions, overheating the base metal can create UTM and OTM formations under the chrome.

These high-strength materials provide significant structural benefits and can result in a weight savings.

300M/4340M UNS K44220

Therefore, surface damage detection is important during overhaul stele on components in service. These characteristics, including sensitivity to corrosion pitting, susceptibility to microstructural damage resulting from embrittlement, and notch sensitivity, can lead to rapid crack growth in some load environments.


This technique can be used successfully to screen components with suspect damage. Refer to the Aircraft Maintenance Manual for materials specified for aircraft cleaning and deicing. Figures 8 and 9 show a severe grinding burn on a main landing gear axle that resulted in a fracture.

This type of cracking most often occurs on surfaces that are both prone to corrosion and exposed sterl sustained tensile stresses while in service, such as the lower surface of landing gear trucks, axles, and the surfaces of forward and aft trunnions.

Organic coatings or sealants may crack or become brittle or discolored wide range of temperatures. Solid-metal embrittlement by cadmium can occur at temperatures below the cadmium melting point. This damage, which occurs on a more frequent basis, is seel by vertical motion against the lower bearing surfaces. 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.

Aircraft Alloy Steel 300M / AISI E4340 Mod (AMS 6417 / AMS 6419)

To prevent excessive corrosion, thorough visual inspections should be performed on a regular basis to evaluate the condition of the protective finishes. Through-thickness cracking also can lead to fatigue or stress corrosion 43340m of the base metal beneath the plating.

High-strength alloy steel components should be stripped completely during overhaul including removal of bushings and bearings in all structural components. Operators should ensure that cleaners and chemicals are tested before use in accordance with Boeing document D6Evaluation of Airplane Maintenance Materials.

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