SAE 4130 steel

Identity and purchasing basis

EMJ's normalized 4130 sheet/plate table gives 95 ksi minimum tensile and 75 ksi yield through 0.062 in, versus 90 ksi minimum tensile and 70 ksi yield over 0.249 through 0.749 in. The separate annealed entry gives 85 ksi maximum tensile. Select by original stock thickness, form and delivery condition. EMJ normalized and annealed table

4130 is a chromium-molybdenum low-alloy steel identified in E. M. Jorgensen's aircraft-alloy catalogue as UNS G41300. Its sheet/plate analysis lists carbon 0.28–0.33%, chromium 0.80–1.10% and molybdenum 0.15–0.25%, with additional controlled elements. Keep those supplier/product entries separate from the complete chemistry requirements of an order. EMJ aircraft-alloy catalogue, 4130 sheet and plate

SAE's J404_200901 covers alloy-steel chemical compositions and distinguishes ladle/heat analysis from check-analysis variations under J409. Its publisher record is dated 27 January 2009. The designation identifies chemistry; it does not specify one universal yield strength, finished hardness or product tolerance. SAE J404 publisher record

Supplied condition matters

Pacific Machinery & Tool Steel describes its 4130 as available annealed or normalized depending on mill availability. Its listed cold-drawn rounds distinguish annealed 1/2–3/4 inch diameters from normalized 7/8–1-1/2 inch diameters. These are supplier offerings, not a statement that all 4130 stock in those sizes has those conditions. Pacific 4130 product page

Record the actual route and condition on the certificate and drawing. A bright surface does not establish a particular thermal treatment or amount of cold work. When replacing a qualified supply, compare the complete condition, dimensional and inspection requirements rather than matching only chemistry.

Bounded sheet-property example

EMJ's catalogue associates AMS 6351 with annealed Condition A, AMS 6345 with normalized Condition N, and AMS 6350 with Condition MA for its 4130 sheets/plates. These are the catalogue's specification associations; current editions and order applicability require separate confirmation.

Its normalized sheet/plate table gives:

The annealed entry separately gives 85 ksi maximum tensile strength. That maximum is not a yield requirement or the strength of normalized stock. Retain the full product, condition, thickness and test basis; these rows are not a universal table for 4130 bar, tubing or forgings. EMJ 4130 sheet/plate specification and mechanical table

For a preliminary original arithmetic example, a uniform 1.0 in² section under 10 kip has nominal stress 10 ksi. Its ratio to the thin normalized row's 75 ksi yield entry is 10 / 75 = 0.133. This is not a safety factor or allowable load: it excludes actual certified properties, local stresses, connections, fatigue, buckling, temperature and design factors.

Heat treatment and hardenability

Pacific describes 4130 as having lower hardenability than 4140 and reports approximately 52 HRC maximum achievable by furnace hardening for its product description. That is a screening statement, not a guarantee throughout an arbitrary section or a required finished condition. Pacific 4130 hardenability description

Distinguish hardness from the ability to develop a hardened structure through a section under a cooling condition. Define core and surface requirements, sampling locations and any hardness traverse when the distribution matters. A surface reading cannot demonstrate adequate core response in a thick feature.

Establish the required property balance before choosing the thermal route. Record prior condition, preheating, equalization, austenitizing, quench, tempering and final verification. Qualify the actual geometry and equipment. A treatment setpoint alone cannot establish cooling behavior, distortion or the resulting properties.

Welding and final fabrication

EMJ describes its 4130 sheet/plate offering as intended for applications involving welding and moderate tensile properties. This is a material-selection description, not a qualified procedure for a particular joint. EMJ application scope

For a welded assembly, resolve base-metal condition, section, restraint, filler, hydrogen controls, thermal sequence and inspection through the applicable procedure. Review dissimilar joints, repairs and attachments separately. Where properties depend on prior heat treatment, assess the final weld and heat-affected region instead of assigning the starting stock's values to the whole assembly.

Plan cutting, forming, welding, thermal processing and finishing as a sequence. Define dimensions and surface acceptance after operations that can change them. Specify corrosion protection and cleaning for the actual exposure independently of the alloy name. No universal cutting speed, bend radius, preheat exemption or service-temperature rating follows from “4130.”

Release record and source versions

Retain producer, heat/lot, chemistry and product specifications/editions, dimensions, supplied/final condition, certificate, processing record and final inspections. Approve substitutions against the complete requirement, including any quality and toughness provisions.

SAE's cited record identifies J404_200901, revised January 2009. The EMJ aircraft-alloy section was retrieved from the search index; its direct PDF URL returned 404 during review. No independent printed issue date was verified for that section or the Pacific webpage; search-engine dates are not treated as technical revisions. The catalogue's historical specification labels do not establish current contractual editions.

See grades, tempers and conditions.