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Purchase Lists

Dimension Inspection of Bolts and Nuts

Bolts size:

Nominal diameter (d): calipers or micrometers to measure the thread diameter, the error needs to be within the standard allowable range.

Length (L): measure the distance from the top of the head of the bolt to the end of the screw (all-thread bolts to measure the length of the thread), the tolerance needs to be in line with the requirements;

head size: the head of the opposite side of the width (s), the thickness (k), measured by calipers, to ensure that the nut or wrench with the match.

Nuts size:

Nominal Diameter (D): Measure the small diameter of the thread, and the bolt thread match;

Thickness (m): the height of the nut, affecting the length of the thread engagement, need to meet the standard;

Width of the opposite side of the (s): the size of the wrench with the allowable error in the range.

Thread accuracy inspection:

Use thread pass/stop gauge (plug gauge to measure bolt external threads, ring gauge to measure nut internal threads) to detect: the pass gauge should be able to be screwed in smoothly, and the stop gauge should be screwed in at a length of not more than 1-2 threads (according to the standard);

If necessary, use the thread micrometer to measure the thread center diameter to ensure that it is in the tolerance range (the center diameter has a direct impact on the looseness or tightness of the thread fit).

ASTM A193 Grade B7 Stud Bolts 

ASTM A193 is a standard specification covering alloy steel and stainless steel bolting materials for pressure vessels, valves, flanges, and fittings used in high temperature or high pressure service conditions. Among them, B7 is the most commonly used grade.

ASTM A193 Grade B7 Stud Bolts Specification

ASTM A193 Grade B7 Chemical Composition

ASTM A193 B7 Mechanical Property

ASTM A354 Nuts

The STM A354 standard mainly defines the chemical and mechanical property requirements for quenched and tempered alloy steel bolts, studs and other externally threaded fasteners, which are generally 4 inches in diameter and below and are used in services requiring high strength and limited high-temperature applications. The standard itself does not directly specify the brand of nuts, but recommends specific nut brands under the ASTM A563 standard for use with A354 bolts to ensure that the expected load-bearing capacity and reliability can be achieved when the bolt and nut are combined.

ASTM A354 Grades

ASTM A354 Nuts Chemical Composition

ASTM A354 Nuts Mechanical Property

Application Scenarios

Industrial manufacturing: mechanical machine tools, automobiles, ships, aerospace and other equipment parts fixed (such as engine block, chassis frame);

Construction: steel bridge, housing frame, pipeline bracket connection

Daily necessities: furniture assembly, home appliances, bicycles, medical equipment, etc.

Special environments: chemical pipelines, nuclear power equipment, marine platforms, etc., the need for corrosion-resistant, high-temperature-resistant special materials Bolts and Nuts

Installation and Maintenance Precautions

Matching: The specifications  and strength level of bolts and nuts must be matched exactly to avoid fracture due to mismatch of strength (e.g., high-strength bolts with low-strength nuts may lead to nut slippage).

Pre-tightening force control: When tightening, the pre-tightening force should be controlled according to the design requirements, too loose may lead to loosening of the connection, and too tight may cause the bolt to fracture or deformation of the connected parts (torque wrenches should be used on important occasions).

Anti-loosening measures: In the vibration environment, anti-loosening nuts, spring washers, spot welding and other ways to prevent loosening.

Corrosion protection: In wet or corrosive environments, it is necessary to choose stainless steel materials or surface treatment of bolts and nuts (such as galvanized, chrome-plated, coated with antirust paint).

The post Alloy Steel Stud Bolts and Nuts Order appeared first on Supplier of Quality Forged Fittings-Flanges.

ASTM A193 Grade B7 Stud Bolts Specification

ASTM A193 Standard

This specification” covers alloy and stainless steel bolting for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications. See Specification A962/A962M for the definition of bolting. Bars and wire shall be hot-wrought and may be further processed by center less grinding or by cold drawing. Austenitic stainless steel may be carbide solution treated or carbide solution treated and strain-hardened.When strain hardened austenitic steel is ordered, the purchaser should take special care to ensure that Appendix X1 is thoroughly under-stood.

High Temperature Tests

Tests to determine high temperature properties shall be made in accordance with Test Methods E21, E139, and E292, and Practices E150 andE151.

Charpy Impact Tests

Charpy impact tests based on the requirements of specification A320/A320M, shall be made as agreed between the manufacturer and the purchaser. When testing temperatures are as low as those specified in specification A320/A320M, bolting should be ordered to that specification in preference to this specification

100 % Hardness Testing of Grade B7M

Each Grade B7M bolt or stud shall be tested for hardness by indentation method and shall meet the requirements specified in tables

 Length Tolerances for Bolts

ASTM A193 Grade B7 Stud Bolts Material

ASTM A193 Grade B7 Chemical Composition

Manganese is usually between 0.65 and 1.10%. Manganese helps to improve the strength, hardness and toughness of steel, and can improve the deoxidation and desulfurization effects of steel, enhancing the overall performance of steel.

ASTM A193 B7 Mechanical Property

The minimum elongation of ASTM A193 Grade B7 stud bolts is 16%. A certain elongation indicates that the bolt has a certain plastic deformation capacity, which is very important when subjected to dynamic loads or uneven loads. It can adapt to stress changes through plastic deformation and prevent the bolt from breaking suddenly.

ASTM A193 Grade B7 Recommended Hardware

Difference Between A193 Grade B7 & A193 Grade B7M Stud bolts

Hardness is probably the most important difference between A193 B7M & A193 B7. The maximum hardness of ASTM A193 B7M is 235 HB or 99 HRB, while the maximum hardness of ASTM A193 Grade B7 stud bolts are 321 HB or 35 HRC. The most notable difference from a manufacturing perspective is that when supplying A193 B7M bolts, each individual bolt or stud in the batch must be tested for hardness. A193 B7M fasteners also require a different type of heavy-duty hex nut than A193 B7, namely ASTM A194 Grade 2HM.

While A193 B7 is specified relatively often in the construction industry, A193 B7M is a specification not seen as regularly. This makes it important to understand the differences between the two specifications so that the right material is ultimately supplied.

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